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20397 lines
600 KiB
20397 lines
600 KiB
<html>
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HDF5 File Format Specification Version 3.0
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</style>
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<!-- #BeginLibraryItem "/ed_libs/styles_Format.lbi" -->
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<!--
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* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
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* Copyright by The HDF Group. *
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* All rights reserved. *
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* *
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* This file is part of HDF5. The full HDF5 copyright notice, including *
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* terms governing use, modification, and redistribution, is contained in *
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* the COPYING file, which can be found at the root of the source code *
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* distribution tree, or in https://www.hdfgroup.org/licenses. *
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* If you do not have access to either file, you may request a copy from *
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* help@hdfgroup.org. *
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* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
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-->
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<!-- #EndLibraryItem --><!-- #BeginLibraryItem "/ed_libs/NavBar_ADevG.lbi" -->
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</head>
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<body>
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<!-- #EndLibraryItem -->
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<center>
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<table border="0" width="90%">
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<tr>
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<td valign="top">
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<ol type="I">
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<li><a href="#Intro">Introduction</a></li>
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<font size="-1">
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<ol type="A">
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<li><a href="#ThisDocument">This Document</a></li>
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<li><a href="#ChangesForHdf5_1_12">Changes for HDF5 1.12</a></li>
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<li><a href="#ChangesForHdf5_1_10">Changes for HDF5 1.10</a></li>
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</ol>
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</font>
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<li><a href="#FileMetaData">Disk Format: Level 0 - File Metadata</a></li>
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<font size="-1">
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<ol type="A">
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<li><a href="#Superblock">Disk Format: Level 0A - Format Signature
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and Superblock</a></li>
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<li><a href="#DriverInfo">Disk Format: Level 0B - File Driver
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Info</a></li>
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<li><a href="#SuperblockExt">Disk Format: Level 0C - Superblock
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Extension</a></li>
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</ol>
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</font>
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<li><a href="#FileInfra">Disk Format: Level 1 - File Infrastructure</a></li>
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<font size="-1">
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<ol type="A">
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<li><a href="#Btrees">Disk Format: Level 1A - B-trees and B-tree
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Nodes</a>
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<ol type="1">
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<li><a href="#V1Btrees">Disk Format: Level 1A1 - Version 1
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B-trees</a></li>
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<li><a href="#V2Btrees">Disk Format: Level 1A2 - Version 2
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B-trees</a></li>
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</ol>
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</li>
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<li><a href="#SymbolTable">Disk Format: Level 1B - Group Symbol
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Table Nodes</a></li>
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<li><a href="#SymbolTableEntry">Disk Format: Level 1C - Symbol
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Table Entry</a></li>
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<li><a href="#LocalHeap">Disk Format: Level 1D - Local Heaps</a></li>
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<li><a href="#GlobalHeap">Disk Format: Level 1E - Global Heap</a></li>
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<li><a href="#GlobalHeapVDS">Disk Format: Level 1F - Global Heap
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Block for Virtual Datasets</a></li>
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<li><a href="#FractalHeap">Disk Format: Level 1G - Fractal Heap</a></li>
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<li><a href="#FreeSpaceManager">Disk Format: Level 1H - Free-space
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Manager</a></li>
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<li><a href="#SOHMTable">Disk Format: Level 1I - Shared Object
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Header Message Table</a></li>
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</ol>
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</font>
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<li><a href="#DataObject">Disk Format: Level 2 - Data Objects</a></li>
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<font size="-1">
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<ol type="A">
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<li><a href="#ObjectHeader">Disk Format: Level 2A - Data Object Headers</a></li>
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<ol type="1">
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<li><a href="#ObjectHeaderPrefix">Disk Format: Level 2A1 -
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Data Object Header Prefix</a>
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<ol type="a">
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<li><a href="#V1ObjectHeaderPrefix">Version 1 Data
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Object Header Prefix</a></li>
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<li><a href="#V2ObjectHeaderPrefix">Version 2 Data
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Object Header Prefix</a></li>
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</ol>
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</li>
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<li><a href="#ObjectHeaderMessages">Disk Format: Level 2A2 -
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Data Object Header Messages</a></li>
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<ol type="a">
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<li><a href="#NILMessage">The NIL Message</a></li> <!-- 0x0000 -->
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<li><a href="#DataspaceMessage">The Dataspace Message</a></li> <!-- 0x0001 -->
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<li><a href="#LinkInfoMessage">The Link Info Message</a></li> <!-- 0x0002 -->
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<li><a href="#DatatypeMessage">The Datatype Message</a></li> <!-- 0x0003 -->
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<li><a href="#OldFillValueMessage">The Data Storage -
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Fill Value (Old) Message</a></li> <!-- 0x0004 -->
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</ol>
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</ol>
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</ol>
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</font>
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</ol>
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</td>
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|
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<td> </td>
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<td valign="top">
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<ol type="I" start="4">
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<li><a href="#DataObject">Disk Format: Level 2 - Data
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Objects</a><font size="-1"><i> (Continued)</i></li>
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<ol type="A">
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<li><a href="#ObjectHeader">Disk Format: Level 2A - Data Object
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Headers</a><i> (Continued)</i>
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<ol type="1" start="2">
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<li><a href="#ObjectHeaderMessages">Disk Format: Level 2A2 -
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Data Object Header Messages</a><i> (Continued)</i></li>
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<ol type="a" start="6">
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<li><a href="#FillValueMessage">The Data Storage -
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Fill Value Message</a></li> <!-- 0x0005 -->
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<li><a href="#LinkMessage">The Link Message</a></li> <!-- 0x0006 -->
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<li><a href="#ExternalFileListMessage">The Data Storage -
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External Data Files Message</a></li> <!-- 0x0007 -->
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<li><a href="#LayoutMessage">The Data Layout Message</a></li> <!-- 0x0008 -->
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<li><a href="#BogusMessage">The Bogus Message</a></li> <!-- 0x0009 -->
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<li><a href="#GroupInfoMessage">The Group Info
|
|
Message</a></li> <!-- 0x000a -->
|
|
<li><a href="#FilterMessage">The Data Storage -
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|
Filter Pipeline Message</a></li> <!-- 0x000b -->
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<li><a href="#AttributeMessage">The Attribute
|
|
Message</a></li> <!-- 0x000c -->
|
|
<li><a href="#CommentMessage">The Object Comment
|
|
Message</a></li> <!-- 0x000d -->
|
|
<li><a href="#OldModificationTimeMessage">The Object
|
|
Modification Time (Old) Message</a></li> <!-- 0x000e -->
|
|
<li><a href="#SOHMTableMessage">The Shared Message
|
|
Table Message</a></li> <!-- 0x000f -->
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|
<li><a href="#ContinuationMessage">The Object Header
|
|
Continuation Message</a></li> <!-- 0x0010 -->
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|
<li><a href="#SymbolTableMessage">The Symbol
|
|
Table Message</a></li> <!-- 0x0011 -->
|
|
<li><a href="#ModificationTimeMessage">The Object
|
|
Modification Time Message</a></li> <!-- 0x0012 -->
|
|
<li><a href="#BtreeKValuesMessage">The B-tree
|
|
‘K’ Values Message</a></li> <!-- 0x0013 -->
|
|
<li><a href="#DrvInfoMessage">The Driver Info
|
|
Message</a></li> <!-- 0x0014 -->
|
|
<li><a href="#AinfoMessage">The Attribute Info
|
|
Message</a></li> <!-- 0x0015 -->
|
|
<li><a href="#RefCountMessage">The Object Reference
|
|
Count Message</a></li> <!-- 0x0016 -->
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|
<li><a href="#FsinfoMessage">The File Space Info
|
|
Message</a></li> <!-- 0x0017 -->
|
|
</ol>
|
|
</ol>
|
|
</li>
|
|
<li><a href="#DataStorage">Disk Format: Level 2B - Data Object Data Storage</a></li>
|
|
</ol>
|
|
</font>
|
|
<li><a href="#AppendixA">Appendix A: Definitions</a></li>
|
|
<li><a href="#AppendixB">Appendix B: File Space Allocation
|
|
Types</a></li>
|
|
<li><a href="#AppendixC">
|
|
Appendix C: Types of Indexes for Dataset Chunks</a></li>
|
|
<font size="-1">
|
|
<ol type="A">
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|
<li><a href="#SingleChunk">The Single Chunk Index</a></li>
|
|
<li><a href="#Implicit">The Implicit Index</a></li>
|
|
<li><a href="#FixedArray">The Fixed Array Index</a></li>
|
|
<li><a href="#ExtensibleArray">The Extensible Array Index</a></li>
|
|
<li><a href="#AppendV2Btrees">The Version 2 B-trees Index</a></li>
|
|
</ol>
|
|
</font>
|
|
<li><a href="#AppendixD">
|
|
Appendix D: Encoding for Dataspace and Reference</a></li>
|
|
<font size="-1">
|
|
<ol type="A">
|
|
<li><a href="#DataspaceEncode">Dataspace Encoding</a></li>
|
|
<li><a href="#ReferenceEncodeRV">Reference Encoding (Revised)</a></li>
|
|
<li><a href="#ReferenceEncodeDP">Reference Encoding (Backward Compatibility)</a></li>
|
|
</ol>
|
|
</font>
|
|
</ol>
|
|
</td></tr>
|
|
</table>
|
|
</center>
|
|
|
|
|
|
<a name="Intro"><h2>I. Introduction</h2></a>
|
|
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|
<table align="right" width="100">
|
|
<tr><td> </td><td align="center">
|
|
<hr />
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|
<img src="FF-IH_FileGroup.gif" alt="HDF5 Groups" hspace="15" vspace="15">
|
|
</td><td> </td></tr>
|
|
<tr><td> </td><td align="center">
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|
<strong>Figure 1:</strong> Relationships among the HDF5 root group, other groups, and objects
|
|
<hr />
|
|
</td><td> </td></tr>
|
|
|
|
<tr><td> </td><td align="center">
|
|
<img src="FF-IH_FileObject.gif" alt="HDF5 Objects" hspace="15" vspace="15">
|
|
</td><td> </td></tr>
|
|
<tr><td> </td><td align="center">
|
|
<strong>Figure 2:</strong> HDF5 objects -- datasets, datatypes, or dataspaces
|
|
<hr />
|
|
</td><td> </td></tr>
|
|
</table>
|
|
|
|
|
|
<p>The format of an HDF5 file on disk encompasses several
|
|
key ideas of the HDF4 and AIO file formats as well as
|
|
addressing some shortcomings therein. The new format is
|
|
more self-describing than the HDF4 format and is more
|
|
uniformly applied to data objects in the file.</p>
|
|
|
|
<p>An HDF5 file appears to the user as a directed graph.
|
|
The nodes of this graph are the higher-level HDF5 objects
|
|
that are exposed by the HDF5 APIs:</p>
|
|
|
|
<ul>
|
|
<li>Groups</li>
|
|
<li>Datasets</li>
|
|
<li>Committed (formerly Named) datatypes</li>
|
|
</ul>
|
|
|
|
<p>At the lowest level, as information is actually written to the disk,
|
|
an HDF5 file is made up of the following objects:</p>
|
|
<ul>
|
|
<li>A superblock</li>
|
|
<li>B-tree nodes</li>
|
|
<li>Heap blocks</li>
|
|
<li>Object headers</li>
|
|
<li>Object data</li>
|
|
<li>Free space</li>
|
|
</ul>
|
|
|
|
<p>The HDF5 Library uses these low-level objects to represent the
|
|
higher-level objects that are then presented to the user or
|
|
to applications through the APIs. For instance, a group is an
|
|
object header that contains a message that points to a local
|
|
heap (for storing the links to objects in the group) and to a
|
|
B-tree (which indexes the links). A dataset is an object header
|
|
that contains messages that describe the datatype, dataspace,
|
|
layout, filters, external files, fill value, and other elements
|
|
with the layout message pointing to either a raw data chunk or
|
|
to a B-tree that points to raw data chunks.</p>
|
|
|
|
|
|
<a name="ThisDocument"><h3>I.A. This Document</h3></a>
|
|
|
|
<p>This document describes the lower-level data objects;
|
|
the higher-level objects and their properties are described
|
|
in the <a href="UG/HDF5_User_Guide-Responsive HTML5/index.html"><cite>HDF5 User Guide</cite></a>.</p>
|
|
|
|
<p>Three levels of information comprise the file format.
|
|
Level 0 contains basic information for identifying and
|
|
defining information about the file. Level 1 information contains
|
|
the information about the pieces of a file shared by many objects
|
|
in the file (such as B-trees and heaps). Level 2 is the rest
|
|
of the file and contains all of the data objects with each object
|
|
partitioned into header information, also known as
|
|
<em>metadata</em>, and data.</p>
|
|
|
|
<p>The various components of the lower-level data objects are
|
|
described in pairs of tables. The first table shows the format
|
|
layout, and the second table describes the fields. The titles
|
|
of format layout tables begin with “Layout”. The
|
|
titles of the tables where the fields are described begin with
|
|
“Fields”. For example, the table that describes the
|
|
format of the <a href="#V2Btrees">version 2 B-tree header</a> has
|
|
a title of “Layout: Version 2 B-tree Header”, and the
|
|
fields in the version 2 B-tree header are described in the table
|
|
titled “Fields: Version 2 B-tree Header”.
|
|
|
|
<p>The sizes of various fields in the following layout tables are
|
|
determined by looking at the number of columns the field spans
|
|
in the table. There are exceptions: </p>
|
|
<ul>
|
|
<li> The size may be overridden by specifying a size in
|
|
parentheses</li>
|
|
<li> The size of addresses is determined by the
|
|
<em><a href="#SizeOfOffsetsV0">Size of Offsets</a></em> field
|
|
in the superblock and is indicated in this document with a
|
|
superscripted ‘O’</li>
|
|
<li> The size of length fields is determined by the
|
|
<em><a href="#SizeOfLengthsV0">Size of Lengths</a></em> field in
|
|
the superblock and is indicated in this document with a
|
|
superscripted ‘L’</li>
|
|
</ul>
|
|
|
|
<p>Values for all fields in this document should be treated as unsigned
|
|
integers, unless otherwise noted in the description of a field.
|
|
Additionally, all metadata fields are stored in little-endian byte
|
|
order.
|
|
</p>
|
|
|
|
<p>All checksums used in the format are computed with the
|
|
<a href="http://www.burtleburtle.net/bob/hash/doobs.html">Jenkins’
|
|
lookup3</a> algorithm.
|
|
</p>
|
|
|
|
<p>Whenever a bit flag or field is mentioned for an entry, bits are
|
|
numbered from the lowest bit position in the entry.
|
|
</p>
|
|
|
|
<p>Various format tables in this document have cells with
|
|
“This space inserted only to align table nicely”. These
|
|
entries in the table are just to make the table presentation nicer
|
|
and do not represent any values or padding in the file.
|
|
</p>
|
|
|
|
<a name="ChangesForHdf5_1_12">
|
|
<h3>I.B. Changes for HDF5 1.12</h3></a>
|
|
<p>The following sections have been
|
|
changed or added for the 1.12 release:</p>
|
|
<ul>
|
|
<li>Under <a href="#DatatypeMessage">“The Datatype Message”</a>,
|
|
in the Description for “Fields:Datatype Message”,
|
|
version 4 was added and Reference class (7) of the datatype was updated to describe version 4.</li>
|
|
<li><a href="#AppendixD">
|
|
“Appendix D: Encoding for Dataspace and Reference”</a>
|
|
was added. </li>
|
|
</ul>
|
|
|
|
|
|
<a name="ChangesForHdf5_1_10">
|
|
<h3>I.C. Changes for HDF5 1.10</h3></a>
|
|
|
|
<p>The following sections have been
|
|
changed or added for the 1.10 release:</p>
|
|
<ul>
|
|
<li>In the <a href="#Superblock">
|
|
“Disk Format: Level 0A - Format Signature and
|
|
Superblock”</a> section, version 3 of the superblock was
|
|
added. </li>
|
|
<li>In the <a href="#SuperblockExt">
|
|
“Disk Format: Level 0C - Superblock Extension”</a>
|
|
section, a link to the Data Storage message was added. </li>
|
|
<li>In the <a href="#V2Btrees">
|
|
“Disk Format: Level 1A2 - Version 2 B-trees”</a>
|
|
section, additional B-tree types were added. Tables that
|
|
describe the <a href="#V2BtreesType10">type 10</a> and
|
|
<a href="#V2BtreesType11">11</a> record layouts were added at
|
|
the end of the section.</li>
|
|
<li>The <a href="#GlobalHeapVDS">“Disk Format: Level 1F -
|
|
Global Heap Block for Virtual Datasets”</a> was added.
|
|
</li>
|
|
<li><a href="#LayoutMessage">
|
|
“The Data Layout Message”</a> section was changed.
|
|
The name was changed, and <a href="#DataLayoutV4">version 4</a>
|
|
of the data layout message was added for the virtual type.</li>
|
|
<li>The <a href="#FsinfoMessage">
|
|
“The File Space Info Message”</a> header message
|
|
type was added.</li>
|
|
<li><a href="#AppendixC">
|
|
“Appendix C: Types of Indexes for Dataset Chunks”</a>
|
|
was added. Five indexing types were added.</li>
|
|
</ul>
|
|
|
|
|
|
|
|
<h2><a name="FileMetaData">
|
|
II. Disk Format: Level 0 - File Metadata</a></h2>
|
|
|
|
|
|
|
|
<h3><a name="Superblock">
|
|
II.A. Disk Format: Level 0A - Format Signature and Superblock</a></h3>
|
|
|
|
<p>The superblock may begin at certain predefined offsets within
|
|
the HDF5 file, allowing a block of unspecified content for
|
|
users to place additional information at the beginning (and
|
|
end) of the HDF5 file without limiting the HDF5 Library’s
|
|
ability to manage the objects within the file itself. This
|
|
feature was designed to accommodate wrapping an HDF5 file in
|
|
another file format or adding descriptive information to an HDF5
|
|
file without requiring the modification of the actual file’s
|
|
information. The superblock is located by searching for the
|
|
HDF5 format signature at byte offset 0, byte offset 512, and at
|
|
successive locations in the file, each a multiple of two of
|
|
the previous location; in other words, at these byte offsets:
|
|
0, 512, 1024, 2048, and so on.</p>
|
|
|
|
<p>The superblock is composed of the format signature, followed by a
|
|
superblock version number and information that is specific to each
|
|
version of the superblock.
|
|
|
|
<p>Currently, there are four versions of the superblock format:
|
|
<ul>
|
|
<li>Version 0 is the default format.</li>
|
|
<li>Version 1 is the same as version 0 but with the
|
|
“<em>Indexed Storage Internal Node K</em>” field
|
|
for storing non-default B-tree ‘K’ value.</li>
|
|
<li>Version 2 has some fields eliminated and compressed from
|
|
superblock format versions 0 and 1. It has added checksum support
|
|
and superblock extension to store additional superblock
|
|
metadata.</li>
|
|
<li>Version 3 is the same as version 2 except that the field
|
|
“<em>File Consistency Flags</em>” is used for file
|
|
locking. This format version will enable support for the latest
|
|
version.</li>
|
|
</ul>
|
|
|
|
<p>Versions 0 and 1 of the superblock are described below:</p>
|
|
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Superblock (Versions 0 and 1)
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Format Signature
|
|
<em>(8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version # of Superblock</td>
|
|
<td>Version # of File’s Free Space Storage</td>
|
|
<td>Version # of Root Group Symbol Table Entry</td>
|
|
<td>Reserved <em>(zero)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version Number of Shared Header Message Format</td>
|
|
<td>Size of Offsets</td>
|
|
<td>Size of Lengths</td>
|
|
<td>Reserved <em>(zero)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Group Leaf Node K</td>
|
|
<td colspan="2">Group Internal Node K</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">File Consistency Flags</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2" style="border:dotted;">Indexed Storage Internal Node K<sup>1</sup></td>
|
|
<td colspan="2" style="border:dotted;">Reserved
|
|
<em>(zero)</em><sup>1</sup></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Base Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address of File Free space Info<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />End of File Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Driver Information Block Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Root Group Symbol Table Entry</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with a ‘1’ in the above table are
|
|
new in version 1 of the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Superblock (Versions 0 and 1)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Format Signature</p></td>
|
|
<td><p>This field contains a constant value and can be used to
|
|
quickly identify a file as being an HDF5 file. The
|
|
constant value is designed to allow easy identification of
|
|
an HDF5 file and to allow certain types of data corruption
|
|
to be detected. The file signature of an HDF5 file always
|
|
contains the following values:</p>
|
|
<center>
|
|
<table border align="center" cellpadding="4">
|
|
<tr align="center">
|
|
<td align="right">Decimal:</td>
|
|
<td width="8%">137</td>
|
|
<td width="8%">72</td>
|
|
<td width="8%">68</td>
|
|
<td width="8%">70</td>
|
|
<td width="8%">13</td>
|
|
<td width="8%">10</td>
|
|
<td width="8%">26</td>
|
|
<td width="8%">10</td>
|
|
</tr>
|
|
|
|
<tr align="center">
|
|
<td align="right">Hexadecimal:</td>
|
|
<td>89</td>
|
|
<td>48</td>
|
|
<td>44</td>
|
|
<td>46</td>
|
|
<td>0d</td>
|
|
<td>0a</td>
|
|
<td>1a</td>
|
|
<td>0a</td>
|
|
</tr>
|
|
|
|
<tr align="center">
|
|
<td align="right">ASCII C Notation:</td>
|
|
<td>\211</td>
|
|
<td>H</td>
|
|
<td>D</td>
|
|
<td>F</td>
|
|
<td>\r</td>
|
|
<td>\n</td>
|
|
<td>\032</td>
|
|
<td>\n</td>
|
|
</tr>
|
|
</table>
|
|
</center>
|
|
<p>This signature both identifies the file as an HDF5 file
|
|
and provides for immediate detection of common
|
|
file-transfer problems. The first two bytes distinguish
|
|
HDF5 files on systems that expect the first two bytes to
|
|
identify the file type uniquely. The first byte is
|
|
chosen as a non-ASCII value to reduce the probability
|
|
that a text file may be misrecognized as an HDF5 file;
|
|
also, it catches bad file transfers that clear bit
|
|
7. Bytes two through four name the format. The CR-LF
|
|
sequence catches bad file transfers that alter newline
|
|
sequences. The control-Z character stops file display
|
|
under MS-DOS. The final line feed checks for the inverse
|
|
of the CR-LF translation problem. (This is a direct
|
|
descendent of the
|
|
<a href="http://www.libpng.org/pub/png/spec/iso/index-object.html#5PNG-file-signature">PNG</a> file
|
|
signature.)</p>
|
|
<p><em>This field is present in version 0+ of the superblock.</em>
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version Number of the Superblock</p></td>
|
|
<td><p>This value is used to determine the format of the
|
|
information in the superblock. When the format of the
|
|
information in the superblock is changed, the version number
|
|
is incremented to the next integer and can be used to
|
|
determine how the information in the superblock is
|
|
formatted.</p>
|
|
|
|
<p>Values of 0, 1 and 2 are defined for this field (the
|
|
format of version 2 is described below, not here).
|
|
</p>
|
|
|
|
<p><em>This field is present in version 0+ of the superblock.</em>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version Number of the File’s Free Space
|
|
Information</p></td>
|
|
<td>
|
|
<p>This value is used to determine the format of the
|
|
file’s free space information.
|
|
</p>
|
|
<p>The only value currently valid in this field is ‘0’, which
|
|
indicates that the file’s free space is as described
|
|
<a href="#FreeSpaceManager">below</a>.
|
|
</p>
|
|
|
|
<p><em>This field is present in versions 0 and 1 of the
|
|
superblock.</em>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version Number of the Root Group Symbol Table
|
|
Entry</p></td>
|
|
<td><p>This value is used to determine the format of the
|
|
information in the Root Group Symbol Table Entry. When the
|
|
format of the information in that field is changed, the
|
|
version number is incremented to the next integer and can be
|
|
used to determine how the information in the field
|
|
is formatted.</p>
|
|
<p>The only value currently valid in this field is ‘0’,
|
|
which indicates that the root group symbol table entry is
|
|
formatted as described <a href="#SymbolTableEntry">below</a>.</p>
|
|
<p><em>This field is present in version 0 and 1 of the
|
|
superblock.</em></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version Number of the Shared Header Message Format</p></td>
|
|
<td><p>This value is used to determine the format of the
|
|
information in a shared object header message. Since the format
|
|
of the shared header messages differs from the other private
|
|
header messages, a version number is used to identify changes
|
|
in the format.
|
|
</p>
|
|
<p>The only value currently valid in this field is ‘0’, which
|
|
indicates that shared header messages are formatted as
|
|
described <a href="#ObjectHeaderMessages">below</a>.
|
|
</p>
|
|
|
|
<p><em>This field is present in version 0 and 1 of the superblock.</em>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p><a name="SizeOfOffsetsV0">Size of Offsets</a></p></td>
|
|
<td><p>This value contains the number of bytes used to store
|
|
addresses in the file. The values for the addresses of
|
|
objects in the file are offsets relative to a base address,
|
|
usually the address of the superblock signature. This
|
|
allows a wrapper to be added after the file is created
|
|
without invalidating the internal offset locations.
|
|
</p>
|
|
|
|
<p><em>This field is present in version 0+ of the superblock.</em>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p><a name="SizeOfLengthsV0">Size of Lengths</a></p></td>
|
|
<td><p>This value contains the number of bytes used to store
|
|
the size of an object.
|
|
</p>
|
|
<p><em>This field is present in version 0+ of the superblock.</em>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Group Leaf Node K</p></td>
|
|
<td>
|
|
<p>Each leaf node of a group B-tree will have at
|
|
least this many entries but not more than twice this
|
|
many. If a group has a single leaf node then it
|
|
may have fewer entries.
|
|
</p>
|
|
<p>This value must be greater than zero.
|
|
</p>
|
|
<p>See the <a href="#Btrees">description</a> of B-trees below.
|
|
</p>
|
|
|
|
<p><em>This field is present in version 0 and 1 of the superblock.</em>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Group Internal Node K</p></td>
|
|
<td>
|
|
<p>Each internal node of a group B-tree will have at
|
|
least this many entries but not more than twice this
|
|
many. If the group has only one internal
|
|
node then it might have fewer entries.
|
|
</p>
|
|
<p>This value must be greater than zero.
|
|
</p>
|
|
<p>See the <a href="#Btrees">description</a> of B-trees below.
|
|
</p>
|
|
|
|
<p><em>This field is present in version 0 and 1 of the superblock.</em>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>File Consistency Flags</p></td>
|
|
<td>
|
|
<p>This field is unused and should be ignored.
|
|
</p>
|
|
<p><em>This field is present in version 0+ of the superblock.</em>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Indexed Storage Internal Node K</p></td>
|
|
<td>
|
|
<p>Each internal node of an indexed storage B-tree will have at
|
|
least this many entries but not more than twice this
|
|
many. If the index storage B-tree has only one internal
|
|
node then it might have fewer entries.
|
|
</p>
|
|
<p>This value must be greater than zero.
|
|
</p>
|
|
<p>See the <a href="#Btrees">description</a> of B-trees below.
|
|
</p>
|
|
|
|
<p><em>This field is present in version 1 of the superblock.</em>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Base Address</p></td>
|
|
<td>
|
|
<p>This is the absolute file address of the first byte of
|
|
the HDF5 data within the file. The library currently
|
|
constrains this value to be the absolute file address
|
|
of the superblock itself when creating new files;
|
|
future versions of the library may provide greater
|
|
flexibility. When opening an existing file and this address does
|
|
not match the offset of the superblock, the library assumes
|
|
that the entire contents of the HDF5 file have been adjusted in
|
|
the file and adjusts the base address and end of file address to
|
|
reflect their new positions in the file. Unless otherwise noted,
|
|
all other file addresses are relative to this base
|
|
address.
|
|
</p>
|
|
|
|
<p><em>This field is present in version 0+ of the superblock.</em>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address of Global Free-space Index</p></td>
|
|
<td>
|
|
<p>The file’s free space is not persistent for version 0 and 1 of
|
|
the superblock.
|
|
Currently this field always contains the
|
|
<a href="#UndefinedAddress">undefined address</a>.
|
|
</p>
|
|
|
|
<p><em>This field is present in version 0 and 1 of the superblock.</em>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>End of File Address</p></td>
|
|
<td>
|
|
<p>This is the absolute file address of the first byte past
|
|
the end of all HDF5 data. It is used to determine whether a
|
|
file has been accidentally truncated and as an address where
|
|
file data allocation can occur if space from the free list is
|
|
not used.
|
|
</p>
|
|
|
|
<p><em>This field is present in version 0+ of the superblock.</em>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Driver Information Block Address</p></td>
|
|
<td>
|
|
<p>This is the relative file address of the file driver
|
|
information block which contains driver-specific
|
|
information needed to reopen the file. If there is no
|
|
driver information block then this entry should be the
|
|
<a href="#UndefinedAddress">undefined address</a>.
|
|
</p>
|
|
|
|
<p><em>This field is present in version 0 and 1 of the superblock.</em>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Root Group Symbol Table Entry</p></td>
|
|
<td>
|
|
<p>This is the <a href="#SymbolTableEntry">symbol table entry</a>
|
|
of the root group, which serves as the entry point into
|
|
the group graph for the file.
|
|
</p>
|
|
|
|
<p><em>This field is present in version 0 and 1 of the superblock.</em>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<p>Versions 2 and 3 of the superblock are described below:</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Superblock (Versions 2 and 3)
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Format Signature
|
|
<em>(8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version # of Superblock</td>
|
|
<td>Size of Offsets</td>
|
|
<td>Size of Lengths</td>
|
|
<td>File Consistency Flags</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Base Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Superblock Extension Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />End of File Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Root Group Object Header Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Superblock Checksum</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Superblock (Versions 2 and 3)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Format Signature</p></td>
|
|
<td>
|
|
<p>This field is the same as described for versions 0 and 1 of the
|
|
superblock.
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version Number of the Superblock</p></td>
|
|
<td>
|
|
<p>This field has a value of 2 and has the same meaning as for
|
|
versions 0 and 1.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size of Offsets</p></td>
|
|
<td>
|
|
<p>This field is the same as described for
|
|
<a href="#SizeOfOffsetsV0">versions 0 and 1</a> of the
|
|
superblock.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size of Lengths</p></td>
|
|
<td>
|
|
<p>This field is the same as described for
|
|
<a href="#SizeOfLengthsV0">versions 0 and 1</a> of the
|
|
superblock.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>File Consistency Flags</p></td>
|
|
|
|
<td>
|
|
<p>For superblock version
|
|
2: This field is unused and should be ignored.</p>
|
|
<p>For superblock version
|
|
3: This value contains flags to ensure file consistency for
|
|
file locking. Currently, the following bit flags are defined:
|
|
<ul>
|
|
<li>Bit 0 if set indicates that the file has been opened for
|
|
write access.</li>
|
|
<li>Bit 1 is reserved for future use.</li>
|
|
<li>Bit 2 if set indicates that the file has been opened for
|
|
single-writer/multiple-reader (SWMR) write access.</li>
|
|
<li>Bits 3-7 are reserved for future use.</li>
|
|
</ul>
|
|
<p>
|
|
Bit 0 should be set as the first action when a file has been
|
|
opened for write access. Bit 2 should be set when a file
|
|
has been opened for SWMR write access. These two bits should
|
|
be cleared only as the final action when closing a file.
|
|
</p>
|
|
<p><em>This field is present in version 0+ of the superblock.</em>
|
|
</p>
|
|
<p><em>The size of this
|
|
field has been reduced from 4 bytes in superblock format
|
|
versions 0 and 1 to 1 byte.</em>
|
|
</p>
|
|
</td>
|
|
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Base Address</p></td>
|
|
<td>
|
|
<p>This field is the same as described for versions 0 and
|
|
1 of the superblock.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Superblock Extension Address</p></td>
|
|
<td>
|
|
<p>The field is the address of the object header for the
|
|
<a href="#SuperblockExt">superblock extension</a>.
|
|
If there is no extension then this entry should be the
|
|
<a href="#UndefinedAddress">undefined address</a>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>End of File Address</p></td>
|
|
<td>
|
|
<p>This field is the same as described for versions 0 and 1 of the
|
|
superblock.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Root Group Object Header Address</p></td>
|
|
<td>
|
|
<p>This is the address of
|
|
the <a href="#DataObject">root group object header</a>,
|
|
which serves as the entry point into the group graph for the file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Superblock Checksum</p></td>
|
|
<td>
|
|
<p>The checksum for the superblock.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
|
|
<h3><a name="DriverInfo">
|
|
II.B. Disk Format: Level 0B - File Driver Info</a></h3>
|
|
|
|
<p>The <b>driver information block</b> is an optional region of the
|
|
file which contains information needed by the file driver
|
|
to reopen a file. The format is described below:</p>
|
|
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Driver Information Block
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td colspan="3">Reserved</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Driver Information Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Driver Identification
|
|
<em>(8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br /><br />Driver Information
|
|
<em>(variable size)</em><br /><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Driver Information Block
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>The version number of the Driver Information Block.
|
|
This document describes version 0.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Driver Information Size</p></td>
|
|
<td>
|
|
<p>The size in bytes of the <em>Driver Information</em> field.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Driver Identification</p></td>
|
|
<td>
|
|
<p>This is an eight-byte ASCII string without null
|
|
termination which identifies the driver and/or version number
|
|
of the Driver Information Block. The predefined driver encoded
|
|
in this field by the HDF5 Library is identified by the
|
|
letters <code>NCSA</code> followed by the first four characters of
|
|
the driver name. If the Driver Information block is not
|
|
the original version then the last letter(s) of the
|
|
identification will be replaced by a version number in
|
|
ASCII, starting with 0.
|
|
</p>
|
|
<p>
|
|
Identification for user-defined drivers is also eight-byte long.
|
|
It can be arbitrary but should be unique to avoid
|
|
the four character prefix “NCSA”.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr valign="top">
|
|
<td><p>Driver Information</p></td>
|
|
<td>Driver information is stored in a format defined by the
|
|
file driver (see description below).</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<p>The two drivers encoded in the <em>Driver Identification</em>
|
|
field are as follows:</p>
|
|
<ul>
|
|
<li>
|
|
Multi driver:
|
|
<p>
|
|
The identifier for this driver is “NCSAmulti”.
|
|
This driver provides a mechanism for segregating raw data and different types of metadata
|
|
into multiple files.
|
|
These files are viewed by the library as a single virtual HDF5 file with a single file address.
|
|
A maximum of 6 files will be created for the following data:
|
|
superblock, B-tree, raw data, global heap, local heap, and object header.
|
|
More than one type of data can be written to the same file.
|
|
</p></li>
|
|
<li>
|
|
Family driver
|
|
<p>
|
|
The identifier for this driver is “NCSAfami” and is encoded in this field for library version 1.8 and after.
|
|
This driver is designed for systems that do not support files larger than 2 gigabytes
|
|
by splitting the HDF5 file address space across several smaller files.
|
|
It does nothing to segregate metadata and raw data;
|
|
they are mixed in the address space just as they would be in a single contiguous file.
|
|
</p></li>
|
|
</ul>
|
|
<p>The format of the <em>Driver Information</em> field for the
|
|
above two drivers are described below:</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Multi Driver Information
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Member Mapping</td>
|
|
<td>Member Mapping</td>
|
|
<td>Member Mapping</td>
|
|
<td>Member Mapping</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Member Mapping</td>
|
|
<td>Member Mapping</td>
|
|
<td>Reserved</td>
|
|
<td>Reserved</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address of Member File 1<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />End of Address for Member File 1<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address of Member File 2<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />End of Address for Member File 2<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />... ...<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address of Member File N<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />End of Address for Member File N<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Name of Member File 1
|
|
<em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Name of Member File 2
|
|
<em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />... ...<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Name of Member File N
|
|
<em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Multi Driver Information
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Member Mapping</p></td>
|
|
<td><p>These fields are integer values from 1 to 6
|
|
indicating how the data can be mapped to or merged with another type of
|
|
data.
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Member Mapping</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">1</td>
|
|
<td>The superblock data.</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">2</td>
|
|
<td>The B-tree data.</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">3</td>
|
|
<td>The raw data.</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">4</td>
|
|
<td>The global heap data.</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">5</td>
|
|
<td>The local heap data.</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">6</td>
|
|
<td>The object header data.</td>
|
|
</tr>
|
|
</table></p>
|
|
<p>For example, if the third field has the value 3 and all the rest have the
|
|
value 1, it means there are two files: one for raw data, and one for superblock,
|
|
B-tree, global heap, local heap, and object header.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Reserved</p></td>
|
|
<td><p>These fields are reserved and should always be zero.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address of Member File N</p></td>
|
|
<td><p>This field Specifies the virtual address at which the member file starts.</p>
|
|
<p>N is the number of member files.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>End of Address for Member File N</p></td>
|
|
<td><p>This field is the end of the allocated address for the member file.
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Name of Member File N</p></td>
|
|
<td><p>This field is the null-terminated name of the member file and
|
|
its length should be multiples of 8 bytes.
|
|
Additional bytes will be padded with <em>NULL</em>s. The default naming
|
|
convention is <em>%s-X.h5</em>, where <em>X</em> is one of the letters
|
|
<em>s</em> (for superblock), <em>b</em> (for B-tree), <em>r</em> (for raw data),
|
|
<em>g</em> (for global heap), <em>l</em> (for local heap), and <em>o</em> (for
|
|
object header). The name of the whole HDF5 file will substitute the <em>%s</em>
|
|
in the string.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Family Driver Information
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="8"><br />Size of Member File<br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Family Driver Information
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size of Member File</p></td>
|
|
<td><p>This field is the size of the member file in the family of files.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h3><a name="SuperblockExt">
|
|
II.C. Disk Format: Level 0C - Superblock Extension</a></h3>
|
|
|
|
<p>The <em>superblock extension</em> is used to store superblock metadata
|
|
which is either optional, or added after the version of the superblock
|
|
was defined. Superblock extensions may only exist when version 2
|
|
or later of the superblock is used. A superblock extension is an object
|
|
header which may hold the following messages:</p>
|
|
<ul>
|
|
<li>
|
|
<a href="#SOHMTableMessage">Shared Message Table message</a> containing
|
|
information to locate the master table of shared object header message
|
|
indices.</li>
|
|
<li>
|
|
<a href="#BtreeKValuesMessage">B-tree ‘K’ Values message</a> containing
|
|
non-default B-tree ‘K’ values.</li>
|
|
<li>
|
|
<a href="#DrvInfoMessage">Driver Info message</a> containing information
|
|
needed by the file driver in order to reopen a file.
|
|
See also the
|
|
<a href="#DriverInfo">“Disk Format: Level 0B - File Driver
|
|
Info”</a> section above.</li>
|
|
<li>
|
|
<a href="#FsinfoMessage">File Space Info message</a> containing
|
|
information about file space handling in the file.</li>
|
|
</ul>
|
|
|
|
|
|
|
|
<h2><a name="FileInfra">
|
|
III. Disk Format: Level 1 - File Infrastructure</a></h2>
|
|
|
|
<h3><a name="Btrees">
|
|
III.A. Disk Format: Level 1A - B-trees and B-tree Nodes</a></h3>
|
|
|
|
<p>B-trees allow flexible storage for objects which tend to grow
|
|
in ways that cause the object to be stored discontiguously. B-trees
|
|
are described in various algorithms books including “Introduction to
|
|
Algorithms” by Thomas H. Cormen, Charles E. Leiserson, and Ronald
|
|
L. Rivest. B-trees are used in several places in the HDF5 file format,
|
|
when an index is needed for another data structure.</p>
|
|
|
|
<p>The version 1 B-tree structure described below is the original
|
|
index structure. The version 1 B-trees are being phased out in
|
|
favor of the version 2 B-trees described below. Note that both
|
|
types of structures may be found in the same file depending on
|
|
the application settings when creating the file.</p>
|
|
|
|
<h4><a name="V1Btrees">
|
|
III.A.1. Disk Format: Level 1A1 - Version 1 B-trees</a></h4>
|
|
|
|
<p>Version 1 B-trees in HDF5 files are an implementation of the
|
|
B-link tree. The sibling nodes at a particular level in
|
|
the tree are stored in a doubly-linked list. See the
|
|
“Efficient Locking for Concurrent Operations on B-trees”
|
|
paper by Phillip Lehman and S. Bing Yao as published in the
|
|
<cite>ACM Transactions on Database Systems</cite>, Vol. 6, No. 4,
|
|
December 1981.</p>
|
|
|
|
<p>The B-trees implemented by the file format contain one more
|
|
key than the number of children. In other words, each child
|
|
pointer out of a B-tree node has a left key and a right key.
|
|
The pointers out of internal nodes point to sub-trees while
|
|
the pointers out of leaf nodes point to symbol nodes and
|
|
raw data chunks.
|
|
Aside from that difference, internal nodes and leaf nodes
|
|
are identical.</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: B-tree Nodes
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Node Type</td>
|
|
<td>Node Level</td>
|
|
<td colspan="2">Entries Used</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address of Left Sibling<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address of Right Sibling<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Key 1 <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address of Child 1<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Key 2 <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address of Child 2<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">...</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Key 2<em>K</em> <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address of Child 2<em>K</em><sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Key 2<em>K</em>+1
|
|
<em>(variable size)</em></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: B-tree Nodes
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>TREE</code>”
|
|
is used to indicate the beginning of a B-tree node. This
|
|
gives file consistency checking utilities a better chance
|
|
of reconstructing a damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Node Type</p></td>
|
|
<td>
|
|
<p>Each B-tree points to a particular type of data.
|
|
This field indicates the type of data as well as
|
|
implying the maximum degree <em>K</em> of the tree and
|
|
the size of each Key field.
|
|
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Node Type</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">0</td>
|
|
<td>This tree points to group nodes.</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">1</td>
|
|
<td>This tree points to raw data chunk nodes.</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Node Level</p></td>
|
|
<td>
|
|
<p>The node level indicates the level at which this node
|
|
appears in the tree (leaf nodes are at level zero). Not
|
|
only does the level indicate whether child pointers
|
|
point to sub-trees or to data, but it can also be used
|
|
to help file consistency checking utilities reconstruct
|
|
damaged trees.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr valign="top">
|
|
<td><p>Entries Used</p></td>
|
|
<td>
|
|
<p>This determines the number of children to which this
|
|
node points. All nodes of a particular type of tree
|
|
have the same maximum degree, but most nodes will point
|
|
to less than that number of children. The valid child
|
|
pointers and keys appear at the beginning of the node
|
|
and the unused pointers and keys appear at the end of
|
|
the node. The unused pointers and keys have undefined
|
|
values.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr valign="top">
|
|
<td><p>Address of Left Sibling</p></td>
|
|
<td>
|
|
<p>This is the relative file address of the left sibling of
|
|
the current node. If the current
|
|
node is the left-most node at this level then this field
|
|
is the <a href="#UndefinedAddress">undefined address</a>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr valign="top">
|
|
<td><p>Address of Right Sibling</p></td>
|
|
<td>
|
|
<p>This is the relative file address of the right sibling of
|
|
the current node. If the current
|
|
node is the right-most node at this level then this
|
|
field is the <a href="#UndefinedAddress">undefined address</a>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr valign="top">
|
|
<td><p>Keys and Child Pointers</p></td>
|
|
<td>
|
|
<p>Each tree has 2<em>K</em>+1 keys with 2<em>K</em>
|
|
child pointers interleaved between the keys. The number
|
|
of keys and child pointers actually containing valid
|
|
values is determined by the node’s <em>Entries
|
|
Used</em> field. If that field is <em>N</em>, then the
|
|
B-tree contains <em>N</em> child pointers and
|
|
<em>N</em>+1 keys.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr valign="top">
|
|
<td><p>Key</p></td>
|
|
<td>
|
|
<p>The format and size of the key values is determined by
|
|
the type of data to which this tree points. The keys are
|
|
ordered and are boundaries for the contents of the child
|
|
pointer; that is, the key values represented by child
|
|
<em>N</em> fall between Key <em>N</em> and Key
|
|
<em>N</em>+1. Whether the interval is open or closed on
|
|
each end is determined by the type of data to which the
|
|
tree points.
|
|
</p>
|
|
|
|
<p>
|
|
The format of the key depends on the node type.
|
|
For nodes of node type 0 (group nodes), the key is formatted as
|
|
follows:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<td width="20%">A single field of
|
|
<i><a href="#SizeOfLengthsV0">Size of Lengths</a></i>
|
|
bytes:</td>
|
|
<td width="80%">Indicates the byte offset into the local heap
|
|
for the first object name in the subtree which
|
|
that key describes.
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
|
|
|
|
<p>
|
|
For nodes of node type 1 (chunked raw data nodes), the key is
|
|
formatted as follows:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<td width="20%">Bytes 1-4:</td>
|
|
<td width="80%">Size of chunk in bytes.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Bytes 4-8:</td>
|
|
<td>Filter mask, a 32-bit bit field indicating which
|
|
filters have been skipped for this chunk. Each filter
|
|
has an index number in the pipeline (starting at 0, with
|
|
the first filter to apply) and if that filter is skipped,
|
|
the bit corresponding to its index is set.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>(<em>D + 1</em>) 64-bit fields:</td>
|
|
<td>The offset of the
|
|
chunk within the dataset where <i>D</i> is the number
|
|
of dimensions of the dataset, and the last value is the
|
|
offset within the dataset’s datatype and should
|
|
always be zero. For example, if
|
|
a chunk in a 3-dimensional dataset begins at the
|
|
position <code>[5,5,5]</code>, there will be three
|
|
such 64-bit values, each with the value of
|
|
<code>5</code>, followed by a <code>0</code> value.</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr valign="top">
|
|
<td><p>Child Pointer</p></td>
|
|
<td>
|
|
<p>The tree node contains file addresses of subtrees or
|
|
data depending on the node level. Nodes at Level 0 point
|
|
to data addresses, either raw data chunks or group nodes.
|
|
Nodes at non-zero levels point to other nodes of the
|
|
same B-tree.
|
|
</p>
|
|
<p>For raw data chunk nodes, the child pointer is the address
|
|
of a single raw data chunk. For group nodes, the child pointer
|
|
points to a <a href="#SymbolTable">symbol table</a>, which contains
|
|
information for multiple symbol table entries.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<p>
|
|
Conceptually, each B-tree node looks like this:</p>
|
|
<center>
|
|
<table>
|
|
<tr valign="top" align="center">
|
|
<td>key[0]</td><td> </td>
|
|
<td>child[0]</td><td> </td>
|
|
<td>key[1]</td><td> </td>
|
|
<td>child[1]</td><td> </td>
|
|
<td>key[2]</td><td> </td>
|
|
<td>...</td><td> </td>
|
|
<td>...</td><td> </td>
|
|
<td>key[<i>N</i>-1]</td><td> </td>
|
|
<td>child[<i>N</i>-1]</td><td> </td>
|
|
<td>key[<i>N</i>]</td>
|
|
</tr>
|
|
</table>
|
|
</center>
|
|
<br />
|
|
|
|
where child[<i>i</i>] is a pointer to a sub-tree (at a level
|
|
above Level 0) or to data (at Level 0).
|
|
Each key[<i>i</i>] describes an <i>item</i> stored by the B-tree
|
|
(a chunk or an object of a group node). The range of values
|
|
represented by child[<i>i</i>] is indicated by key[<i>i</i>]
|
|
and key[<i>i</i>+1].
|
|
|
|
|
|
<p>The following question must next be answered:
|
|
“Is the value described by key[<i>i</i>] contained in
|
|
child[<i>i</i>-1] or in child[<i>i</i>]?”
|
|
The answer depends on the type of tree.
|
|
In trees for groups (node type 0), the object described by
|
|
key[<i>i</i>] is the greatest object contained in
|
|
child[<i>i</i>-1] while in chunk trees (node type 1) the
|
|
chunk described by key[<i>i</i>] is the least chunk in
|
|
child[<i>i</i>].</p>
|
|
|
|
<p>That means that key[0] for group trees is sometimes unused;
|
|
it points to offset zero in the heap, which is always the
|
|
empty string and compares as “less-than” any valid
|
|
object name.</p>
|
|
|
|
<p>And key[<i>N</i>] for chunk trees is sometimes unused;
|
|
it contains a chunk offset which compares as “greater-than”
|
|
any other chunk offset and has a chunk byte size of zero
|
|
to indicate that it is not actually allocated.</p>
|
|
|
|
<h4><a name="V2Btrees">
|
|
III.A.2. Disk Format: Level 1A2 - Version 2 B-trees</a></h4>
|
|
|
|
<p>Version 2 (v2) B-trees are “traditional” B-trees
|
|
with one major difference. Instead of just using a simple pointer
|
|
(or address in the file) to a child of an internal node, the pointer
|
|
to the child node contains two additional pieces of information:
|
|
the number of records in the child node itself, and the total number
|
|
of records in the child node and all its descendants. Storing this
|
|
additional information allows fast array-like indexing to locate
|
|
the n<sup>th</sup> record in the B-tree.</p>
|
|
|
|
<p>The entry into a version 2 B-tree is a header which contains global
|
|
information about the structure of the B-tree. The <em>root node
|
|
address</em>
|
|
field in the header points to the B-tree root node, which is either an
|
|
internal or leaf node, depending on the value in the header’s
|
|
<em>depth</em> field. An internal node consists of records plus
|
|
pointers to further leaf or internal nodes in the tree. A leaf node
|
|
consists of solely of records. The format of the records depends on
|
|
the B-tree type (stored in the header).</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 B-tree Header
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Type</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Node Size</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="2">Record Size</td>
|
|
<td colspan="2">Depth</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Split Percent</td>
|
|
<td>Merge Percent</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Root Node Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="2">Number of Records in Root Node</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Total Number of Records in B-tree<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 B-tree Header
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>BTHD</code>”
|
|
is used to indicate the header of a version 2 (v2) B-tree
|
|
node.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>The version number for this B-tree header. This document
|
|
describes version 0.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Type</p></td>
|
|
<td>
|
|
<p>This field indicates the type of B-tree:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">0</td>
|
|
<td>This B-tree is used for testing only. This
|
|
value should <em>not</em> be used for storing
|
|
records in actual HDF5 files.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">1</td>
|
|
<td>This B-tree is used for indexing indirectly accessed,
|
|
non-filtered ‘huge’ fractal heap objects.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">2</td>
|
|
<td>This B-tree is used for indexing indirectly accessed,
|
|
filtered ‘huge’ fractal heap objects.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">3</td>
|
|
<td>This B-tree is used for indexing directly accessed,
|
|
non-filtered ‘huge’ fractal heap objects.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">4</td>
|
|
<td>This B-tree is used for indexing directly accessed,
|
|
filtered ‘huge’ fractal heap objects.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">5</td>
|
|
<td>This B-tree is used for indexing the ‘name’ field for
|
|
links in indexed groups.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">6</td>
|
|
<td>This B-tree is used for indexing the ‘creation order’
|
|
field for links in indexed groups.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">7</td>
|
|
<td>This B-tree is used for indexing shared object header
|
|
messages.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">8</td>
|
|
<td>This B-tree is used for indexing the ‘name’ field for
|
|
indexed attributes.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">9</td>
|
|
<td>This B-tree is used for indexing the ‘creation order’
|
|
field for indexed attributes.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center">10</td>
|
|
<td>This B-tree is used for indexing chunks of
|
|
datasets with no filters and with more than one
|
|
dimension of unlimited extent.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center">11</td>
|
|
<td>This B-tree is used for indexing chunks of
|
|
datasets with filters and more than one dimension
|
|
of unlimited extent.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
<p>The format of records for each type is described below.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr valign="top">
|
|
<td><p>Node Size</p></td>
|
|
<td>
|
|
<p>This is the size in bytes of all B-tree nodes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr valign="top">
|
|
<td><p>Record Size</p></td>
|
|
<td>
|
|
<p>This field is the size in bytes of the B-tree record.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr valign="top">
|
|
<td><p>Depth</p></td>
|
|
<td>
|
|
<p>This is the depth of the B-tree.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr valign="top">
|
|
<td><p>Split Percent</p></td>
|
|
<td>
|
|
<p>The percent full that a node needs to increase above before it
|
|
is split.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr valign="top">
|
|
<td><p>Merge Percent</p></td>
|
|
<td>
|
|
<p>The percent full that a node needs to be decrease below before it
|
|
is split.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr valign="top">
|
|
<td><p>Root Node Address</p></td>
|
|
<td>
|
|
<p>This is the address of the root B-tree node. A B-tree with
|
|
no records will have the <a href="#UndefinedAddress">undefined
|
|
address</a> in this field.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr valign="top">
|
|
<td><p>Number of Records in Root Node</p></td>
|
|
<td>
|
|
<p>This is the number of records in the root node.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr valign="top">
|
|
<td><p>Total Number of Records in B-tree</p></td>
|
|
<td>
|
|
<p>This is the total number of records in the entire B-tree.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr valign="top">
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>This is the checksum for the B-tree header.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 B-tree Internal Node
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Type</td>
|
|
<td colspan="2">Records 0, 1, 2...N-1 <em>(variable size)</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Child Node Pointer 0<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Number of Records N<sub>0</sub> for Child
|
|
Node 0 <em>(variable size)</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Total Number of Records for Child Node 0
|
|
<em>(optional, variable size)</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Child Node Pointer 1<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
<td colspan="4"><br />Number of Records N<sub>1</sub> for
|
|
Child Node 1 <em>(variable size)</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Total Number of Records for Child Node 1
|
|
<em>(optional, variable size)</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">...</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Child Node Pointer N<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Number of Records N<sub>n</sub> for
|
|
Child Node N <em>(variable size)</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Total Number of Records for Child Node N
|
|
<em>(optional, variable size)</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 B-tree Internal Node
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>BTIN</code>” is
|
|
used to indicate the internal node of a B-tree.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>The version number for this B-tree internal node.
|
|
This document describes version 0.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Type</p></td>
|
|
<td>
|
|
<p>This field is the type of the B-tree node. It should always
|
|
be the same as the B-tree type in the header.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Records</p></td>
|
|
<td>
|
|
<p>The size of this field is determined by the number of records
|
|
for this node and the record size (from the header). The format
|
|
of records depends on the type of B-tree.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Child Node Pointer</p></td>
|
|
<td>
|
|
<p>This field is the address of the child node pointed to by the
|
|
internal node.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Number of Records in Child Node</p></td>
|
|
<td>
|
|
<p>This is the number of records in the child node pointed to by
|
|
the corresponding <em>Node Pointer</em>.
|
|
</p>
|
|
<p>The number of bytes used to store this field is determined by
|
|
the maximum possible number of records able to be stored in the
|
|
child node.
|
|
</p>
|
|
<p>
|
|
The maximum number of records in a child node is computed
|
|
in the following way:
|
|
|
|
<ul>
|
|
<li>Subtract the fixed size overhead for
|
|
the child node (for example, its signature, version,
|
|
checksum, and so on and <em>one</em> pointer triplet
|
|
of information for the child node (because there is one
|
|
more pointer triplet than records in each internal node))
|
|
from the size of nodes for the B-tree. </li>
|
|
<li>Divide that result by the size of a record plus the
|
|
pointer triplet of information stored to reach each
|
|
child node from this node.</li>
|
|
</ul>
|
|
|
|
</p>
|
|
<p>
|
|
Note that leaf nodes do not encode any
|
|
child pointer triplets, so the maximum number of records in a
|
|
leaf node is just the node size minus the leaf node overhead,
|
|
divided by the record size.
|
|
</p>
|
|
<p>
|
|
Also note that the first level of internal nodes above the
|
|
leaf nodes do not encode the <em>Total Number of Records in Child
|
|
Node</em> value in the child pointer triplets (since it is the
|
|
same as the <em>Number of Records in Child Node</em>), so the
|
|
maximum number of records in these nodes is computed with the
|
|
equation above, but using (<em>Child Pointer</em>, <em>Number of
|
|
Records in Child Node</em>) pairs instead of triplets.
|
|
</p>
|
|
<p>
|
|
The number of
|
|
bytes used to encode this field is the least number of bytes
|
|
required to encode the maximum number of records in a child
|
|
node value for the child nodes below this level
|
|
in the B-tree.
|
|
</p>
|
|
<p>
|
|
For example, if the maximum number of child records is
|
|
123, one byte will be used to encode these values in this
|
|
node; if the maximum number of child records is
|
|
20000, two bytes will be used to encode these values in this
|
|
node; and so on. The maximum number of bytes used to
|
|
encode these values is 8 (in other words, an unsigned
|
|
64-bit integer).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Total Number of Records in Child Node</p></td>
|
|
<td>
|
|
<p>This is the total number of records for the node pointed to by
|
|
the corresponding <em>Node Pointer</em> and all its children.
|
|
This field exists only in nodes whose depth in the B-tree node
|
|
is greater than 1 (in other words, the “twig”
|
|
internal nodes, just above leaf nodes, do not store this
|
|
field in their child node pointers).
|
|
</p>
|
|
<p>The number of bytes used to store this field is determined by
|
|
the maximum possible number of records able to be stored in the
|
|
child node and its descendants.
|
|
</p>
|
|
<p>
|
|
The maximum possible number of records able to be stored in a
|
|
child node and its descendants is computed iteratively, in the
|
|
following way: The maximum number of records in a leaf node
|
|
is computed, then that value is used to compute the maximum
|
|
possible number of records in the first level of internal nodes
|
|
above the leaf nodes. Multiplying these two values together
|
|
determines the maximum possible number of records in child node
|
|
pointers for the level of nodes two levels above leaf nodes.
|
|
This process is continued up to any level in the B-tree.
|
|
</p>
|
|
<p>
|
|
The number of bytes used to encode this value is computed in
|
|
the same way as for the <em>Number of Records in Child Node</em>
|
|
field.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>This is the checksum for this node.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 B-tree Leaf Node
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Type</td>
|
|
<td colspan="2">Record 0, 1, 2...N-1 <em>(variable size)</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 B-tree Leaf Node
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>BTLF</code>“
|
|
is used to indicate the leaf node of a version 2 (v2) B-tree.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>The version number for this B-tree leaf node.
|
|
This document describes version 0.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Type</p></td>
|
|
<td>
|
|
<p>This field is the type of the B-tree node. It should always
|
|
be the same as the B-tree type in the header.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Records</p></td>
|
|
<td>
|
|
<p>The size of this field is determined by the number of records
|
|
for this node and the record size (from the header). The format
|
|
of records depends on the type of B-tree.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>This is the checksum for this node.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<p>The record layout for each stored (in other words, non-testing)
|
|
B-tree type is as follows:</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 B-tree, Type 1 Record Layout - Indirectly
|
|
Accessed, Non-filtered, ‘Huge’ Fractal Heap Objects
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Huge Object Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Huge Object Length<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Huge Object ID<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 B-tree, Type 1 Record Layout - Indirectly
|
|
Accessed, Non-filtered, ‘Huge’ Fractal Heap Objects
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Huge Object Address</p></td>
|
|
<td>
|
|
<p>The address of the huge object in the file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Huge Object Length</p></td>
|
|
<td>
|
|
<p>The length of the huge object in the file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Huge Object ID</p></td>
|
|
<td>
|
|
<p>The heap ID for the huge object.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 B-tree, Type 2 Record Layout - Indirectly
|
|
Accessed, Filtered, ‘Huge’ Fractal Heap Objects
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Filtered Huge Object Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Filtered Huge Object Length<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Filter Mask</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Filtered Huge Object Memory Size<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Huge Object ID<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 B-tree, Type 2 Record Layout - Indirectly
|
|
Accessed, Filtered, ‘Huge’ Fractal Heap Objects
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filtered Huge Object Address</p></td>
|
|
<td>
|
|
<p>The address of the filtered huge object in the file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filtered Huge Object Length</p></td>
|
|
<td>
|
|
<p>The length of the filtered huge object in the file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filter Mask</p></td>
|
|
<td>
|
|
<p>A 32-bit bit field indicating which filters have been skipped for
|
|
this chunk. Each filter has an index number in the pipeline
|
|
(starting at 0, with the first filter to apply) and if that
|
|
filter is skipped, the bit corresponding to its index is set.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filtered Huge Object Memory Size</p></td>
|
|
<td>
|
|
<p>The size of the de-filtered huge object in memory.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Huge Object ID</p></td>
|
|
<td>
|
|
<p>The heap ID for the huge object.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 B-tree, Type 3 Record Layout - Directly
|
|
Accessed, Non-filtered, ‘Huge’ Fractal Heap Objects
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Huge Object Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Huge Object Length<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 B-tree, Type 3 Record Layout - Directly
|
|
Accessed, Non-filtered, ‘Huge’ Fractal Heap Objects
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Huge Object Address</p></td>
|
|
<td>
|
|
<p>The address of the huge object in the file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Huge Object Length</p></td>
|
|
<td>
|
|
<p>The length of the huge object in the file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 B-tree, Type 4 Record Layout - Directly
|
|
Accessed, Filtered, ‘Huge’ Fractal Heap Objects
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Filtered Huge Object Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Filtered Huge Object Length<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Filter Mask</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Filtered Huge Object Memory Size<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 B-tree, Type 4 Record Layout - Directly
|
|
Accessed, Filtered, ‘Huge’ Fractal Heap Objects
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filtered Huge Object Address</p></td>
|
|
<td>
|
|
<p>The address of the filtered huge object in the file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filtered Huge Object Length</p></td>
|
|
<td>
|
|
<p>The length of the filtered huge object in the file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filter Mask</p></td>
|
|
<td>
|
|
<p>A 32-bit bit field indicating which filters have been skipped for
|
|
this chunk. Each filter has an index number in the pipeline
|
|
(starting at 0, with the first filter to apply) and if that
|
|
filter is skipped, the bit corresponding to its index is set.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filtered Huge Object Memory Size</p></td>
|
|
<td>
|
|
<p>The size of the de-filtered huge object in memory.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 B-tree, Type 5 Record Layout - Link Name
|
|
for Indexed Group
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Hash of Name</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">ID <em>(bytes 1-4)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="3">ID <em>(bytes 5-7)</em></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 B-tree, Type 5 Record Layout - Link Name
|
|
for Indexed Group
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Hash</p></td>
|
|
<td>
|
|
<p>This field is hash value of the name for the link. The hash
|
|
value is the Jenkins’ lookup3 checksum algorithm applied to
|
|
the link’s name.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>ID</p></td>
|
|
<td>
|
|
<p>This is a 7-byte sequence of bytes and is the heap ID for the
|
|
link record in the group’s fractal heap.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 B-tree, Type 6 Record Layout - Creation
|
|
Order for Indexed Group
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Creation Order
|
|
<em>(8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">ID <em>(bytes 1-4)</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="3">ID <em>(bytes 5-7)</em></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 B-tree, Type 6 Record Layout - Creation
|
|
Order for Indexed Group
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Creation Order</p></td>
|
|
<td>
|
|
<p>This field is the creation order value for the link.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>ID</p></td>
|
|
<td>
|
|
<p>This is a 7-byte sequence of bytes and is the heap ID for the
|
|
link record in the group’s fractal heap.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 B-tree, Type 7 Record Layout - Shared
|
|
Object Header Messages (Sub-type 0 - Message in Heap)
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan>Message Location</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Hash</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Reference Count</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Heap ID <em>(8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 B-tree, Type 7 Record Layout - Shared
|
|
Object Header Messages (Sub-type 0 - Message in Heap)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Message Location</p></td>
|
|
<td>
|
|
<p>This field Indicates the location where the message is stored:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">0</td>
|
|
<td>Shared message is stored in shared message index heap.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">1</td>
|
|
<td>Shared message is stored in object header.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Hash</p></td>
|
|
<td>
|
|
<p>This field is hash value of the shared message. The hash
|
|
value is the Jenkins’ lookup3 checksum algorithm applied to
|
|
the shared message.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Reference Count</p></td>
|
|
<td>
|
|
<p>The number of objects which reference this message.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Heap ID</p></td>
|
|
<td>
|
|
<p>This is an 8-byte sequence of bytes and is the heap ID for the
|
|
shared message in the shared message index’s fractal heap.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 B-tree, Type 7 Record Layout - Shared
|
|
Object Header Messages (Sub-type 1 - Message in Object Header)
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan>Message Location</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Hash</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Reserved (zero)</td>
|
|
<td>Message Type</td>
|
|
<td colspan="2">Object Header Index</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Object Header Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 B-tree, Type 7 Record Layout - Shared
|
|
Object Header Messages (Sub-type 1 - Message in Object Header)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Message Location</p></td>
|
|
<td>
|
|
<p>This field Indicates the location where the message is stored:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">0</td>
|
|
<td>Shared message is stored in shared message index heap.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">1</td>
|
|
<td>Shared message is stored in object header.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Hash</p></td>
|
|
<td>
|
|
<p>This field is hash value of the shared message. The hash
|
|
value is the Jenkins’ lookup3 checksum algorithm applied to
|
|
the shared message.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Message Type</p></td>
|
|
<td>
|
|
<p>The object header message type of the shared message.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Object Header Index</p></td>
|
|
<td>
|
|
<p>This field indicates that the shared message is the n<sup>th</sup> message
|
|
of its type in the specified object header.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Object Header Address</p></td>
|
|
<td>
|
|
<p>The address of the object header containing the shared message.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 B-tree, Type 8 Record Layout - Attribute
|
|
Name for Indexed Attributes
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Heap ID <em>(8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan>Message Flags</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Creation Order</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Hash of Name</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 B-tree, Type 8 Record Layout - Attribute
|
|
Name for Indexed Attributes
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Heap ID</p></td>
|
|
<td>
|
|
<p>This is an 8-byte sequence of bytes and is the heap ID for the
|
|
attribute in the object’s attribute fractal heap.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Message Flags</p></td>
|
|
<td><p>The object header message flags for the attribute message.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Creation Order</p></td>
|
|
<td>
|
|
<p>This field is the creation order value for the attribute.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Hash</p></td>
|
|
<td>
|
|
<p>This field is hash value of the name for the attribute. The hash
|
|
value is the Jenkins’ lookup3 checksum algorithm applied to
|
|
the attribute’s name.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 B-tree, Type 9 Record Layout - Creation
|
|
Order for Indexed Attributes
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Heap ID <em>(8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan>Message Flags</td>
|
|
<td colspan="3" bgcolor="#DDDDDD">
|
|
<em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Creation Order</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 B-tree, Type 9 Record Layout - Creation
|
|
Order for Indexed Attributes
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Heap ID</p></td>
|
|
<td>
|
|
<p>This is an 8-byte sequence of bytes and is the heap ID for the
|
|
attribute in the object’s attribute fractal heap.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Message Flags</p></td>
|
|
<td>
|
|
<p>The object header message flags for the attribute message.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Creation Order</p></td>
|
|
<td>
|
|
<p>This field is the creation order value for the attribute.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<a name="V2BtType10"></a>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
<a name="V2BtreesType10"></a>
|
|
Layout: Version 2 B-tree, Type 10 Record Layout -
|
|
Non-filtered Dataset Chunks
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Dimension 0 Scaled Offset
|
|
<em>(8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Dimension 1 Scaled Offset
|
|
<em>(8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />...<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Dimension #n Scaled Offset
|
|
<em>(8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 B-tree, Type 10 Record Layout -
|
|
Non-filtered Dataset Chunks
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address</p></td>
|
|
<td>
|
|
<p>This field is the address of the dataset chunk in the file.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimension #n Scaled Offset</p></td>
|
|
<td>
|
|
<p>This field is the scaled offset of the chunk within the
|
|
dataset. <em>n</em> is the number of dimensions for the
|
|
dataset. The first scaled offset stored in the list is for
|
|
the slowest changing dimension, and the last scaled offset
|
|
stored is for the fastest changing dimension. Scaled offset
|
|
is calculated by dividing the chunk dimension sizes into
|
|
the chunk offsets.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
<a name="V2BtreesType11"></a>
|
|
Layout: Version 2 B-tree, Type 11 Record Layout - Filtered
|
|
Dataset Chunks
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Chunk Size
|
|
<em>(variable size; at most 8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Filter Mask</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Dimension 0 Scaled Offset
|
|
<em>(8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Dimension 1 Scaled Offset
|
|
<em>(8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />...<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Dimension #n Scaled Offset
|
|
<em>(8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 B-tree, Type 11 Record Layout - Filtered
|
|
Dataset Chunks
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address</p></td>
|
|
<td>
|
|
<p>This field is the address of the dataset chunk in the file.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Chunk Size</p></td>
|
|
<td>
|
|
<p>This field is the size of the dataset chunk in bytes.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filter Mask</p></td>
|
|
<td>
|
|
<p>This field is the filter mask which indicates the filter
|
|
to skip for the dataset chunk. Each filter has an index
|
|
number in the pipeline and if that filter is skipped,
|
|
the bit corresponding to its index is set.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimension #n Scaled Offset</p></td>
|
|
<td>
|
|
<p>This field is the scaled offset of the chunk within
|
|
the dataset. <em>n</em> is the number of dimensions for
|
|
the dataset. The first scaled offset stored in the list
|
|
is for the slowest changing dimension, and the last scaled
|
|
offset stored is for the fastest changing dimension.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<h3><a name="SymbolTable">
|
|
III.B. Disk Format: Level 1B - Group Symbol Table Nodes</a></h3>
|
|
|
|
<p>A group is an object internal to the file that allows
|
|
arbitrary nesting of objects within the file (including other
|
|
groups). A group maps a set of link names in the group to a set
|
|
of relative file addresses of objects in the file. Certain metadata
|
|
for an object to which the group points can be cached in the
|
|
group’s symbol table entry in addition to being in the
|
|
object’s header.</p>
|
|
|
|
<p>An HDF5 object name space can be stored hierarchically by
|
|
partitioning the name into components and storing each
|
|
component as a link in a group. The link for a
|
|
non-ultimate component points to the group containing
|
|
the next component. The link for the last
|
|
component points to the object being named.</p>
|
|
|
|
<p>One implementation of a group is a collection of symbol table
|
|
nodes indexed by a B-tree. Each symbol table node contains entries
|
|
for one or more links. If an attempt is made to add a link to an
|
|
already full symbol table node containing 2<em>K</em> entries, then
|
|
the node is split and one node contains <em>K</em> symbols and the
|
|
other contains <em>K</em>+1 symbols.</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Symbol Table Node (A Leaf of a B-tree)
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version Number</td>
|
|
<td>Reserved <em>(zero)</em></td>
|
|
<td colspan="2">Number of Symbols</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br /><br />Group Entries<br /><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Symbol Table Node (A Leaf of a B-tree)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>SNOD</code>” is
|
|
used to indicate the
|
|
beginning of a symbol table node. This gives file
|
|
consistency checking utilities a better chance of
|
|
reconstructing a damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version Number</p></td>
|
|
<td>
|
|
<p>The version number for the symbol table node. This
|
|
document describes version 1. (There is no version ‘0’
|
|
of the symbol table node)
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Number of Entries</p></td>
|
|
<td>
|
|
<p>Although all symbol table nodes have the same length,
|
|
most contain fewer than the maximum possible number of
|
|
link entries. This field indicates how many entries
|
|
contain valid data. The valid entries are packed at the
|
|
beginning of the symbol table node while the remaining
|
|
entries contain undefined values.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Symbol Table Entries</p></td>
|
|
<td>
|
|
<p>Each link has an entry in the symbol table node.
|
|
The format of the entry is described below.
|
|
There are 2<em>K</em> entries in each group node, where
|
|
<em>K</em> is the “Group Leaf Node K” value from the
|
|
<a href="#Superblock">superblock</a>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h3><a name="SymbolTableEntry">
|
|
III.C. Disk Format: Level 1C - Symbol Table Entry </a></h3>
|
|
|
|
<p>Each symbol table entry in a symbol table node is designed
|
|
to allow for very fast browsing of stored objects.
|
|
Toward that design goal, the symbol table entries
|
|
include space for caching certain constant metadata from the
|
|
object header.</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Symbol Table Entry
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Link Name Offset<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Object Header Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Cache Type</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Reserved <em>(zero)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br /><br />Scratch-pad Space
|
|
<em>(16 bytes)</em><br /><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Symbol Table Entry
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Link Name Offset</p></td>
|
|
<td>
|
|
<p>This is the byte offset into the group’s local
|
|
heap for the name of the link. The name is null
|
|
terminated.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Object Header Address</p></td>
|
|
<td>
|
|
<p>Every object has an object header which serves as a
|
|
permanent location for the object’s metadata. In addition
|
|
to appearing in the object header, some of the object’s metadata
|
|
can be cached in the scratch-pad space.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Cache Type</p></td>
|
|
<td>
|
|
<p>The cache type is determined from the object header.
|
|
It also determines the format for the scratch-pad space:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Type</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">0</td>
|
|
<td>No data is cached by the group entry. This
|
|
is guaranteed to be the case when an object header
|
|
has a link count greater than one.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">1</td>
|
|
<td>Group object header metadata is cached in the
|
|
scratch-pad space. This implies that the symbol table
|
|
entry refers to another group.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center">2</td>
|
|
<td>The entry is a symbolic link. The first four bytes
|
|
of the scratch-pad space are the offset into the local
|
|
heap for the link value. The object header address
|
|
will be undefined.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Reserved</p></td>
|
|
<td>
|
|
<p>These four bytes are present so that the scratch-pad
|
|
space is aligned on an eight-byte boundary. They are
|
|
always set to zero.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Scratch-pad Space</p></td>
|
|
<td>
|
|
<p>This space is used for different purposes, depending
|
|
on the value of the Cache Type field. Any metadata
|
|
about an object represented in the scratch-pad
|
|
space is duplicated in the object header for that
|
|
object.
|
|
</p>
|
|
<p>
|
|
Furthermore, no data is cached in the group
|
|
entry scratch-pad space if the object header for
|
|
the object has a link count greater than one.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h4>Format of the Scratch-pad Space</h4>
|
|
|
|
<p>The symbol table entry scratch-pad space is formatted
|
|
according to the value in the Cache Type field.</p>
|
|
|
|
<p>If the Cache Type field contains the value zero
|
|
<code>(0)</code> then no information is
|
|
stored in the scratch-pad space.</p>
|
|
|
|
<p>If the Cache Type field contains the value one
|
|
<code>(1)</code>, then the scratch-pad space
|
|
contains cached metadata for another object header
|
|
in the following format:</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Object Header Scratch-pad Format
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address of B-tree<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address of Name Heap<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Object Header Scratch-pad Format
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address of B-tree</p></td>
|
|
<td>
|
|
<p>This is the file address for the root of the
|
|
group’s B-tree.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address of Name Heap</p></td>
|
|
<td>
|
|
<p>This is the file address for the group’s local
|
|
heap, in which are stored the group’s symbol names.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<p>If the Cache Type field contains the value two
|
|
<code>(2)</code>, then the scratch-pad space
|
|
contains cached metadata for a symbolic link
|
|
in the following format:</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Symbolic Link Scratch-pad Format
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Offset to Link Value</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Symbolic Link Scratch-pad Format
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Offset to Link Value</p></td>
|
|
<td>
|
|
<p>The value of a symbolic link (that is, the name of the
|
|
thing to which it points) is stored in the local heap.
|
|
This field is the 4-byte offset into the local heap for
|
|
the start of the link value, which is null terminated.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h3><a name="LocalHeap">
|
|
III.D. Disk Format: Level 1D - Local Heaps</a></h3>
|
|
|
|
<p>A local heap is a collection of small pieces of data that are particular
|
|
to a single object in the HDF5 file. Objects can be
|
|
inserted and removed from the heap at any time.
|
|
The address of a heap does not change once the heap is created.
|
|
For example, a group stores addresses of objects in symbol table nodes
|
|
with the names of links stored in the group’s local heap.
|
|
</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Local Heap
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td colspan="3">Reserved <em>(zero)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Data Segment Size<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Offset to Head of Free-list<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address of Data Segment<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Local Heap
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>HEAP</code>”
|
|
is used to indicate the
|
|
beginning of a heap. This gives file consistency
|
|
checking utilities a better chance of reconstructing a
|
|
damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>Each local heap has its own version number so that new
|
|
heaps can be added to old files. This document
|
|
describes version zero (0) of the local heap.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Data Segment Size</p></td>
|
|
<td>
|
|
<p>The total amount of disk memory allocated for the heap
|
|
data. This may be larger than the amount of space
|
|
required by the objects stored in the heap. The extra
|
|
unused space in the heap holds a linked list of free blocks.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Offset to Head of Free-list</p></td>
|
|
<td>
|
|
<p>This is the offset within the heap data segment of the
|
|
first free block (or the
|
|
<a href="#UndefinedAddress">undefined address</a> if there is no
|
|
free block). The free block contains
|
|
<a href="#SizeOfLengthsV0">Size of Lengths</a> bytes that
|
|
are the offset of the next free block (or the
|
|
value ‘1’ if this is the
|
|
last free block) followed by Size of Lengths bytes that store
|
|
the size of this free block. The size of the free block includes
|
|
the space used to store the offset of the next free block and
|
|
the size of the current block, making the minimum size of a free
|
|
block 2 * Size of Lengths.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address of Data Segment</p></td>
|
|
<td>
|
|
<p>The data segment originally starts immediately after
|
|
the heap header, but if the data segment must grow as a
|
|
result of adding more objects, then the data segment may
|
|
be relocated, in its entirety, to another part of the
|
|
file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<p>Objects within a local heap should be aligned on an 8-byte boundary.</p>
|
|
|
|
<h3><a name="GlobalHeap">
|
|
III.E. Disk Format: Level 1E - Global Heap</a></h3>
|
|
|
|
<p>Each HDF5 file has a global heap which stores various types of
|
|
information which is typically shared between datasets. The
|
|
global heap was designed to satisfy these goals:</p>
|
|
|
|
<ol type="A">
|
|
<li>Repeated access to a heap object must be efficient without
|
|
resulting in repeated file I/O requests. Since global heap
|
|
objects will typically be shared among several datasets, it is
|
|
probable that the object will be accessed repeatedly.</li>
|
|
<li>Collections of related global heap objects should result in
|
|
fewer and larger I/O requests. For instance, a dataset of
|
|
object references will have a global heap object for each
|
|
reference. Reading the entire set of object references
|
|
should result in a few large I/O requests instead of one small
|
|
I/O request for each reference.</li>
|
|
<li>It should be possible to remove objects from the global heap
|
|
and the resulting file hole should be eligible to be reclaimed
|
|
for other uses.</li>
|
|
</ol>
|
|
|
|
|
|
<p>The implementation of the heap makes use of the memory management
|
|
already available at the file level and combines that with a new
|
|
object called a <em>collection</em> to achieve goal B. The global heap
|
|
is the set of all collections. Each global heap object belongs to
|
|
exactly one collection, and each collection contains one or more global
|
|
heap objects. For the purposes of disk I/O and caching, a collection is
|
|
treated as an atomic object, addressing goal A.
|
|
</p>
|
|
|
|
<p>When a global heap object is deleted from a collection (which
|
|
occurs when its reference count falls to zero), objects located
|
|
after the deleted object in the collection are packed down toward
|
|
the beginning of the collection, and the collection’s
|
|
global heap object 0 is created (if possible), or its size is
|
|
increased to account for the recently freed space. There are
|
|
no gaps between objects in each collection, with the possible
|
|
exception of the final space in the collection, if it is not
|
|
large enough to hold the header for the collection’s
|
|
global heap object 0. These features address goal C.
|
|
</p>
|
|
|
|
<p>The HDF5 Library creates global heap collections as needed, so there may
|
|
be multiple collections throughout the file. The set of all of them is
|
|
abstractly called the “global heap”, although they do not actually link
|
|
to each other, and there is no global place in the file where you can
|
|
discover all of the collections. The collections are found simply by
|
|
finding a reference to one through another object in the file. For
|
|
example, data of variable-length datatype elements is stored in the
|
|
global heap and is accessed via a global heap ID. The format for
|
|
global heap IDs is described at the end of this section.
|
|
</p>
|
|
|
|
<p>For more information on global heaps for virtual datasets, see
|
|
<a href="#GlobalHeapVDS">“Disk Format: Level 1F - Global Heap
|
|
Block for Virtual Datasets.”</a></p>
|
|
<br />
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: A Global Heap Collection
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td colspan="3">Reserved (zero)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Collection Size<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Global Heap Object 1<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Global Heap Object 2<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />...<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Global Heap Object <em>N</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Global Heap Object 0 (free space)<br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: A Global Heap Collection
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>GCOL</code>”
|
|
is used to indicate the
|
|
beginning of a collection. This gives file consistency
|
|
checking utilities a better chance of reconstructing a
|
|
damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>Each collection has its own version number so that new
|
|
collections can be added to old files. This document
|
|
describes version one (1) of the collections (there is no
|
|
version zero (0)).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Collection Size</p></td>
|
|
<td>
|
|
<p>This is the size in bytes of the entire collection
|
|
including this field. The default (and minimum)
|
|
collection size is 4096 bytes which is a typical file
|
|
system block size. This allows for 127 16-byte heap
|
|
objects plus their overhead (the collection header of 16 bytes
|
|
and the 16 bytes of information about each heap object).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Global Heap Object 1 through <em>N</em></p></td>
|
|
<td>
|
|
<p>The objects are stored in any order with no
|
|
intervening unused space.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Global Heap Object 0</p></td>
|
|
<td>
|
|
<p>Global Heap Object 0 (zero), when present, represents the free
|
|
space in the collection. Free space always appears at the end of
|
|
the collection. If the free space is too small to store the header
|
|
for Object 0 (described below) then the header is implied and is not
|
|
written.
|
|
<p>
|
|
The field <em>Object Size</em> for Object 0 indicates the
|
|
amount of possible free space in the collection including the 16-byte
|
|
header size of Object 0.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Global Heap Object
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Heap Object Index</td>
|
|
<td colspan="2">Reference Count</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Reserved (zero)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Object Size<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Object Data<br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Global Heap Object
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Heap Object Index</p></td>
|
|
<td>
|
|
<p>Each object has a unique identification number within a
|
|
collection. The identification numbers are chosen so that
|
|
new objects have the smallest value possible with the
|
|
exception that the identifier <code>0</code> always refers to the
|
|
object which represents all free space within the
|
|
collection.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Reference Count</p></td>
|
|
<td>
|
|
<p>All heap objects have a reference count field. An
|
|
object which is referenced from some other part of the
|
|
file will have a positive reference count. The reference
|
|
count for Object 0 is always zero.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Reserved</p></td>
|
|
<td>
|
|
<p>Zero padding to align next field on an 8-byte boundary.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Object Size</p></td>
|
|
<td>
|
|
<p>This is the size of the object data stored for the object.
|
|
The actual storage space allocated for the object data is rounded
|
|
up to a multiple of eight.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Object Data</p></td>
|
|
<td>
|
|
<p>The object data is treated as a one-dimensional array
|
|
of bytes to be interpreted by the caller.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<p>
|
|
<a name="GlobalHeapID"></a>
|
|
The format for the ID used to locate an object in the global heap is
|
|
described here:</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Global Heap ID
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Collection Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Object Index</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Global Heap ID
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Collection Address</p></td>
|
|
<td>
|
|
<p>This field is the address of the global heap collection
|
|
where the data object is stored.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>ID</p></td>
|
|
<td>
|
|
<p>This field is the index of the data object within the
|
|
global heap collection.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
|
|
|
|
<h3><a name="GlobalHeapVDS"> III.F. Disk Format: Level 1F - Global
|
|
Heap Block for Virtual Datasets</a></h3>
|
|
|
|
<p>The layout for the global heap block used with virtual datasets is
|
|
described below. For more information on global heaps, see
|
|
<a href="#GlobalHeap"></a>“Disk Format: Level 1E - Global Heap.”</p>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Global Heap Block for Virtual Dataset
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted
|
|
only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Num Entries<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Source Filename #1 <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Source Dataset #1 <em>(variable
|
|
size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Source Selection #1 <em>(variable
|
|
size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Virtual Selection #1 <em>(variable
|
|
size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Source Filename #n <em>(variable
|
|
size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Source Dataset #n <em>(variable
|
|
size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Source Selection #n <em>(variable
|
|
size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Virtual Selection #n <em>(variable
|
|
size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Global Heap Block for Virtual Dataset
|
|
</caption>
|
|
<tr>
|
|
<th width="40%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>The version number for the block; the value is 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Num Entries</p></td>
|
|
<td><p>The number of entries in the block.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Source Filename #n</p></td>
|
|
<td>
|
|
<p>The source file name where the source dataset is located.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Source Dataset #n</p></td>
|
|
<td><p>The source dataset name that is mapped to the
|
|
virtual dataset.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Source Selection #n</p></td>
|
|
<td>
|
|
<p>The <a href="#DataspaceSEL">dataspace selection</a> in the
|
|
source dataset that is mapped to the virtual selection.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Virtual Selection #n</p></td>
|
|
<td>
|
|
<p>This is the <a href="#DataspaceSEL">dataspace selection</a> in the virtual dataset that is
|
|
mapped to the source selection.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>This is the checksum for the block.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
<br>
|
|
|
|
<h3><a name="FractalHeap">
|
|
III.G. Disk Format: Level 1G - Fractal Heap</a></h3>
|
|
|
|
<p>
|
|
Each fractal heap consists of a header and zero or more direct and
|
|
indirect blocks (described below). The header contains general
|
|
information as well as
|
|
initialization parameters for the doubling table. The <em>Address
|
|
of Root Block</em> field in the header points to the first direct or
|
|
indirect block in the heap.
|
|
</p>
|
|
|
|
<p>
|
|
Fractal heaps are based on a data structure called a <em>doubling
|
|
table</em>. A doubling table provides a mechanism for quickly
|
|
extending an array-like data structure that minimizes the number of
|
|
empty blocks in the heap, while retaining very fast lookup of any
|
|
element within the array. More information on fractal heaps and
|
|
doubling tables can be found in the RFC
|
|
“<a href="Supplements/FractalHeap/PrivateHeap.pdf">Private
|
|
Heaps in HDF5</a>.”
|
|
</p>
|
|
|
|
<p>
|
|
The fractal heap implements the doubling table structure with
|
|
indirect and direct blocks.
|
|
Indirect blocks in the heap do not actually contain data for
|
|
objects in the heap, their “size” is abstract -
|
|
they represent the indexing structure for locating the
|
|
direct blocks in the doubling table.
|
|
Direct blocks
|
|
contain the actual data for objects stored in the heap.
|
|
</p>
|
|
|
|
<p>
|
|
All indirect blocks have a constant number of block entries in each
|
|
row, called the <em>width</em> of the doubling table
|
|
(see <em>Table Width</em> field in the header).
|
|
|
|
The number
|
|
of rows for each indirect block in the heap is determined by the
|
|
size of the block that the indirect block represents in the
|
|
doubling table (calculation of this is shown below) and is
|
|
constant, except for the “root”
|
|
indirect block, which expands and shrinks its number of rows as
|
|
needed.
|
|
</p>
|
|
|
|
<p>
|
|
Blocks in the first <em>two</em> rows of an indirect block
|
|
are <em>Starting Block Size</em> number of bytes in size.
|
|
For example, if the row <em>width</em> of the doubling table is 4,
|
|
then the first eight block entries in the
|
|
indirect block are <em>Starting Block Size</em> number of bytes in size.
|
|
The blocks in each subsequent row are twice the size of
|
|
the blocks in the previous row. In other words, blocks in
|
|
the third row are twice the <em>Starting Block Size</em>,
|
|
blocks in the fourth row are four times the
|
|
<em>Starting Block Size</em>, and so on. Entries for
|
|
blocks up to the <em>Maximum Direct Block Size</em> point to
|
|
direct blocks, and entries for blocks greater than that size
|
|
point to further indirect blocks (which have their own
|
|
entries for direct and indirect blocks).
|
|
<em>Starting Block Size</em> and
|
|
<em>Maximum Direct Block Size</em> are fields
|
|
stored in the header.
|
|
</p>
|
|
|
|
<p>
|
|
The number of rows of blocks, <em>nrows</em>, in an
|
|
indirect block is calculated by the following expression:
|
|
<br /> <br />
|
|
<em>nrows</em> = (log<sub>2</sub>(<em>block_size</em>) -
|
|
log<sub>2</sub>(<em><Starting Block Size></em>)) + 1
|
|
</p>
|
|
where <em>block_size</em> is the size of the block that the indirect block
|
|
represents in the doubling table.
|
|
For example, to represent a block with <em>block_size</em> equals to 1024,
|
|
and <em>Starting Block Size</em> equals to 256,
|
|
three rows are needed.
|
|
<p>
|
|
The maximum number of rows of direct blocks, <em>max_dblock_rows</em>,
|
|
in any indirect block of a fractal heap is given by the
|
|
following expression:
|
|
<br /> <br />
|
|
<em>max_dblock_rows</em> =
|
|
(log<sub>2</sub>(<em><Maximum Direct Block Size></em>) -
|
|
log<sub>2</sub>(<em><Starting Block Size></em>)) + 2
|
|
</p>
|
|
<p>
|
|
Using the computed values for <em>nrows</em> and
|
|
<em>max_dblock_rows</em>, along with the <em>width</em> of the
|
|
doubling table, the number of direct and indirect block entries
|
|
(<em>K</em> and <em>N</em> in the indirect block description, below)
|
|
in an indirect block can be computed:
|
|
<br /> <br />
|
|
<em>K</em> = MIN(<em>nrows</em>, <em>max_dblock_rows</em>) *
|
|
<em><Table Width></em>
|
|
|
|
<br /> <br />
|
|
If <em>nrows</em> is less than or equal to <em>max_dblock_rows</em>,
|
|
<em>N</em> is 0. Otherwise, <em>N</em> is simply computed:
|
|
<br /> <br />
|
|
<em>N</em> = <em>K</em> - (<em>max_dblock_rows</em> *
|
|
<em><Table Width></em>)
|
|
</p>
|
|
|
|
<p>
|
|
The size of indirect blocks on disk is determined by the number
|
|
of rows in the indirect block (computed above). The size of direct
|
|
blocks on disk is exactly the size of the block in the doubling
|
|
table.
|
|
</p>
|
|
<br>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fractal Heap Header
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Heap ID Length</td>
|
|
<td colspan="2">I/O Filters’ Encoded Length</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Flags</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Maximum Size of Managed Objects</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Next Huge Object ID<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />v2 B-tree Address of Huge Objects<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Amount of Free Space in Managed Blocks<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address of Managed Block Free Space Manager<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Amount of Managed Space in Heap<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Amount of Allocated Managed Space in Heap<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Offset of Direct Block Allocation Iterator in Managed Space<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Number of Managed Objects in Heap<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Size of Huge Objects in Heap<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Number of Huge Objects in Heap<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Size of Tiny Objects in Heap<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Number of Tiny Objects in Heap<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Table Width</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Starting Block Size<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Maximum Direct Block Size<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Maximum Heap Size</td>
|
|
<td colspan="2">Starting # of Rows in Root Indirect Block</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address of Root Block<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Current # of Rows in Root Indirect Block</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Size of Filtered Root Direct Block <em>(optional)</em><sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">I/O Filter Mask<em> (optional)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">I/O Filter Information<em> (optional, variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fractal Heap Header
|
|
</caption>
|
|
<tr>
|
|
<th width="40%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>FRHP</code>”
|
|
is used to indicate the
|
|
beginning of a fractal heap header. This gives file consistency
|
|
checking utilities a better chance of reconstructing a
|
|
damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>This document describes version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Heap ID Length</p></td>
|
|
<td>
|
|
<p>This is the length in bytes of heap object IDs for this heap.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>I/O Filters’ Encoded Length</p></td>
|
|
<td>
|
|
<p>This is the size in bytes of the encoded <em>I/O Filter Information</em>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Flags</p></td>
|
|
<td>
|
|
<p>This field is the heap status flag and is a bit field
|
|
indicating additional information about the fractal heap.
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit(s)</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>If set, the ID value to use for huge object has wrapped
|
|
around. If the value for the <em>Next Huge Object ID</em>
|
|
has wrapped around, each new huge object inserted into the
|
|
heap will require a search for an ID value.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>If set, the direct blocks in the heap are checksummed.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2-7</code></td>
|
|
<td>Reserved</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Maximum Size of Managed Objects</p></td>
|
|
<td>
|
|
<p>This is the maximum size of managed objects allowed in the heap.
|
|
Objects greater than this this are ‘huge’ objects and will be
|
|
stored in the file directly, rather than in a direct block for
|
|
the heap.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Next Huge Object ID</p></td>
|
|
<td>
|
|
<p>This is the next ID value to use for a huge object in the heap.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>v2 B-tree Address of Huge Objects</p></td>
|
|
<td>
|
|
<p>This is the address of the <a href="#V2Btrees">v2 B-tree</a>
|
|
used to track huge objects in the heap. The type of records
|
|
stored in the <em>v2 B-tree</em> will
|
|
be determined by whether the address and length of a huge object
|
|
can fit into a heap ID (if yes, it is a “directly” accessed
|
|
huge object) and whether there is a filter used on objects
|
|
in the heap.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Amount of Free Space in Managed Blocks</p></td>
|
|
<td>
|
|
<p>This is the total amount of free space in managed direct blocks
|
|
(in bytes).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address of Managed Block Free Space Manager</p></td>
|
|
<td>
|
|
<p>This is the address of the
|
|
<em><a href="#FreeSpaceManager">Free-space Manager</a></em> for
|
|
managed blocks.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Amount of Managed Space in Heap</p></td>
|
|
<td>
|
|
<p>This is the total amount of managed space in the heap (in bytes),
|
|
essentially the upper bound of the heap’s linear address space.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Amount of Allocated Managed Space in Heap</p></td>
|
|
<td>
|
|
<p>This is the total amount of managed space (in bytes) actually
|
|
allocated in
|
|
the heap. This can be less than the <em>Amount of Managed Space
|
|
in Heap</em> field, if some direct blocks in the heap’s linear
|
|
address space are not allocated.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Offset of Direct Block Allocation Iterator in Managed Space</p></td>
|
|
<td>
|
|
<p>This is the linear heap offset where the next direct
|
|
block should be allocated at (in bytes). This may be less than
|
|
the <em>Amount of Managed Space in Heap</em> value because the
|
|
heap’s address space is increased by a “row” of direct blocks
|
|
at a time, rather than by single direct block increments.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Number of Managed Objects in Heap</p></td>
|
|
<td>
|
|
<p>This is the number of managed objects in the heap.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size of Huge Objects in Heap</p></td>
|
|
<td>
|
|
<p>This is the total size of huge objects in the heap (in bytes).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Number of Huge Objects in Heap</p></td>
|
|
<td>
|
|
<p>This is the number of huge objects in the heap.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size of Tiny Objects in Heap</p></td>
|
|
<td>
|
|
<p>This is the total size of tiny objects that are packed in heap
|
|
IDs (in bytes).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Number of Tiny Objects in Heap</p></td>
|
|
<td>
|
|
<p>This is the number of tiny objects that are packed in heap IDs.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Table Width</p></td>
|
|
<td>
|
|
<p>This is the number of columns in the doubling table for managed
|
|
blocks. This value must be a power of two.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Starting Block Size</p></td>
|
|
<td>
|
|
<p>This is the starting block size to use in the doubling table for
|
|
managed blocks (in bytes). This value must be a power of two.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Maximum Direct Block Size</p></td>
|
|
<td>
|
|
<p>This is the maximum size allowed for a managed direct block.
|
|
Objects inserted into the heap that are larger than this value
|
|
(less the number of bytes of direct block prefix/suffix)
|
|
are stored as ‘huge’ objects. This value must be a power of
|
|
two.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Maximum Heap Size</p></td>
|
|
<td>
|
|
<p>This is the maximum size of the heap’s linear address space for
|
|
managed objects (in bytes). The value stored is the log2 of
|
|
the actual value, that is: the number of bits of the address space.
|
|
‘Huge’ and ‘tiny’ objects are not counted in this value, since
|
|
they do not store objects in the linear address space of the
|
|
heap.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Starting # of Rows in Root Indirect Block</p></td>
|
|
<td>
|
|
<p>This is the starting number of rows for the root indirect block.
|
|
A value of 0 indicates that the root indirect block will have
|
|
the maximum number of rows needed to address the heap’s <em>Maximum
|
|
Heap Size</em>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address of Root Block</p></td>
|
|
<td>
|
|
<p>This is the address of the root block for the heap. It can
|
|
be the <a href="#UndefinedAddress">undefined address</a> if
|
|
there is no data in the heap. It either points to a direct
|
|
block (if the <em>Current # of Rows in the Root Indirect
|
|
Block</em> value is 0), or an indirect block.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Current # of Rows in Root Indirect Block</p></td>
|
|
<td>
|
|
<p>This is the current number of rows in the root indirect block.
|
|
A value of 0 indicates that <em>Address of Root Block</em>
|
|
points to direct block instead of indirect block.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size of Filtered Root Direct Block</p></td>
|
|
<td>
|
|
<p>This is the size of the root direct block, if filters are
|
|
applied to heap objects (in bytes). This field is only
|
|
stored in the header if the <em>I/O Filters’ Encoded Length</em>
|
|
is greater than 0.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>I/O Filter Mask</p></td>
|
|
<td>
|
|
<p>This is the filter mask for the root direct block, if filters
|
|
are applied to heap objects. This mask has the same format as
|
|
that used for the filter mask in chunked raw data records in a
|
|
<a href="#V1Btrees">v1 B-tree</a>.
|
|
This field is only
|
|
stored in the header if the <em>I/O Filters’ Encoded Length</em>
|
|
is greater than 0.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>I/O Filter Information</p></td>
|
|
<td>
|
|
<p>This is the I/O filter information encoding direct blocks and
|
|
huge objects, if filters are applied to heap objects. This
|
|
field is encoded as a <a href="#FilterMessage">Filter Pipeline</a>
|
|
message.
|
|
The size of this field is determined by <em>I/O Filters’
|
|
Encoded Length</em>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>This is the checksum for the header.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fractal Heap Direct Block
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Heap Header Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Block Offset <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum <em>(optional)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Object Data <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fractal Heap Direct Block
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>FHDB</code>”
|
|
is used to indicate the
|
|
beginning of a fractal heap direct block. This gives file consistency
|
|
checking utilities a better chance of reconstructing a
|
|
damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>This document describes version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Heap Header Address</p></td>
|
|
<td>
|
|
<p>This is the address for the fractal heap header that this
|
|
block belongs to. This field is principally used for file
|
|
integrity checking.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Block Offset</p></td>
|
|
<td>
|
|
<p>This is the offset of the block within the fractal heap’s
|
|
address space (in bytes). The number of bytes used to encode
|
|
this field is the <em>Maximum Heap Size</em> (in the heap’s
|
|
header) divided by 8 and rounded up to the next highest integer,
|
|
for values that are not a multiple of 8. This value is
|
|
principally used for file integrity checking.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>This is the checksum for the direct block.</p>
|
|
<p>This field is only present if bit 1 of <em>Flags</em> in the
|
|
heap’s header is set.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Object Data</p></td>
|
|
<td>
|
|
<p>This section of the direct block stores the actual data for
|
|
objects in the heap. The size of this section is determined by
|
|
the direct block’s size minus the size of the other fields
|
|
stored in the direct block (for example, the <em>Signature</em>,
|
|
<em>Version</em>, and others including the <em>Checksum</em> if it is
|
|
present).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fractal Heap Indirect Block
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Heap Header Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Block Offset <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Child Direct Block #0 Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Size of Filtered Direct Block #0 <em>(optional)</em> <sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Filter Mask for Direct Block #0 <em>(optional)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Child Direct Block #1 Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Size of Filtered Direct Block #1 <em>(optional)</em><sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Filter Mask for Direct Block #1 <em>(optional)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">...</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Child Direct Block #K-1 Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Size of Filtered Direct Block #K-1 <em>(optional)</em><sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Filter Mask for Direct Block #K-1 <em>(optional)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Child Indirect Block #0 Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Child Indirect Block #1 Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">...</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Child Indirect Block #N-1 Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fractal Heap Indirect Block
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>FHIB</code>” is used to
|
|
indicate the beginning of a fractal heap indirect block. This
|
|
gives file consistency checking utilities a better chance of
|
|
reconstructing a damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>This document describes version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Heap Header Address</p></td>
|
|
<td>
|
|
<p>This is the address for the fractal heap header that this
|
|
block belongs to. This field is principally used for file
|
|
integrity checking.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Block Offset</p></td>
|
|
<td>
|
|
<p>This is the offset of the block within the fractal heap’s
|
|
address space (in bytes). The number of bytes used to encode
|
|
this field is the <em>Maximum Heap Size</em> (in the heap’s
|
|
header) divided by 8 and rounded up to the next highest integer,
|
|
for values that are not a multiple of 8. This value is
|
|
principally used for file integrity checking.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Child Direct Block #K Address</p></td>
|
|
<td>
|
|
<p>This field is the address of the child direct block.
|
|
The size of the [uncompressed] direct block can be computed by
|
|
its offset in the heap’s linear address space.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size of Filtered Direct Block #K</p></td>
|
|
<td>
|
|
<p>This is the size of the child direct block after passing through
|
|
the I/O filters defined for this heap (in bytes). If no I/O
|
|
filters are present for this heap, this field is not present.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td><p>Filter Mask for Direct Block #K</p></td>
|
|
<td>
|
|
<p>This is the I/O filter mask for the filtered direct block.
|
|
This mask has the same format as that used for the filter mask
|
|
in chunked raw data records in a <a href="#V1Btrees">v1 B-tree</a>.
|
|
If no I/O filters are present for this heap, this field is not
|
|
present.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Child Indirect Block #N Address</p></td>
|
|
<td>
|
|
<p>This field is the address of the child indirect block.
|
|
The size of the indirect block can be computed by
|
|
its offset in the heap’s linear address space.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>This is the checksum for the indirect block.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<p>An object in the fractal heap is identified by means of a fractal heap ID,
|
|
which encodes information to locate the object in the heap.
|
|
Currently, the fractal heap stores an object in one of three ways,
|
|
depending on the object’s size:</p>
|
|
|
|
<div align="center">
|
|
<table class="list80">
|
|
<tr>
|
|
<th width="20%">Type</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center">Tiny</td>
|
|
<td>
|
|
<p>When an object is small enough to be encoded in the
|
|
heap ID, the object’s data is embedded in the fractal
|
|
heap ID itself. There are two sub-types for this type of
|
|
object: normal and extended. The sub-type for tiny heap
|
|
IDs depends on whether the heap ID is large enough to
|
|
store objects greater than 16 bytes or not. If the
|
|
heap ID length is 18 bytes or smaller, the
|
|
‘normal’ tiny heap ID form is used. If the
|
|
heap ID length is greater than 18 bytes in length, the
|
|
“extended” form is used. See the format
|
|
description below for both sub-types.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center">Huge</td>
|
|
<td>
|
|
<p>When the size of an object is larger than <em>Maximum Size of
|
|
Managed Objects</em> in the <em>Fractal Heap Header</em>, the
|
|
object’s data is stored on its own in the file and the object
|
|
is tracked/indexed via a version 2 B-tree. All huge objects
|
|
for a particular fractal heap use the same v2 B-tree. All huge
|
|
objects for a particular fractal heap use the same format for
|
|
their huge object IDs.
|
|
</p>
|
|
|
|
<p>Depending on whether the IDs for a heap are large enough to hold
|
|
the object’s retrieval information and whether I/O pipeline filters
|
|
are applied to the heap’s objects, 4 sub-types are derived for
|
|
huge object IDs for this heap:</p>
|
|
|
|
<div align="center">
|
|
<table class="list">
|
|
<tr>
|
|
<th align="left" width="35%">Sub-type</th>
|
|
<th align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left">Directly accessed, non-filtered</td>
|
|
<td>
|
|
<p>The object’s address and length are embedded in the
|
|
fractal heap ID itself and the object is directly accessed
|
|
from them. This allows the object to be accessed without
|
|
resorting to the B-tree.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left">Directly accessed, filtered</td>
|
|
<td>
|
|
<p>The filtered object’s address, length, filter mask and
|
|
de-filtered size are embedded in the fractal heap ID itself
|
|
and the object is accessed directly with them. This allows
|
|
the object to be accessed without resorting to the B-tree.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left">Indirectly accessed, non-filtered</td>
|
|
<td>
|
|
<p>The object is located by using a B-tree key embedded in
|
|
the fractal heap ID to retrieve the address and length from
|
|
the version 2 B-tree for huge objects. Then, the address
|
|
and length are used to access the object.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left">Indirectly accessed, filtered</td>
|
|
<td>
|
|
<p>The object is located by using a B-tree key embedded in
|
|
the fractal heap ID to retrieve the filtered object’s
|
|
address, length, filter mask and de-filtered size from the
|
|
version 2 B-tree for huge objects. Then, this information
|
|
is used to access the object.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center">Managed</td>
|
|
<td>
|
|
<p>When the size of an object does not meet the above two
|
|
conditions, the object is stored and managed via the direct and
|
|
indirect blocks based on the doubling table.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<p>The specific format for each type of heap ID is described below:
|
|
</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fractal Heap ID for Tiny Objects (Sub-type 1 -
|
|
‘Normal’)
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version, Type, and Length</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Data <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fractal Heap ID for Tiny Objects (Sub-type 1 -
|
|
‘Normal’)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version, Type, and Length</p></td>
|
|
<td>
|
|
<p>This is a bit field with the following definition:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>6-7</code></td>
|
|
<td>The current version of ID format. This document
|
|
describes version 0.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>4-5</code></td>
|
|
<td>The ID type. Tiny objects have a value of <code>2</code>.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>0-3</code></td>
|
|
<td>The length of the tiny object. The value stored
|
|
is one less than the actual length (since zero-length
|
|
objects are not allowed to be stored in the heap).
|
|
For example, an object of actual length 1 has an
|
|
encoded length of 0, an object of actual length 2
|
|
has an encoded length of 1, and so on.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Data</p></td>
|
|
<td>
|
|
<p>This is the data for the object.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fractal Heap ID for Tiny Objects (Sub-type 2 -
|
|
‘Extended’)
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version, Type, and Length</td>
|
|
<td>Extended Length</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Data <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fractal Heap ID for Tiny Objects (Sub-type 2 -
|
|
‘Extended’)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version, Type, and Length</p></td>
|
|
<td>
|
|
<p>This is a bit field with the following definition:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>6-7</code></td>
|
|
<td>The current version of ID format. This document
|
|
describes version 0.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>4-5</code></td>
|
|
<td>The ID type. Tiny objects have a value of <code>2</code>.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>0-3</code></td>
|
|
<td>These 4 bits, together with the next byte, form an
|
|
unsigned 12-bit integer for holding the length of the
|
|
object. These 4-bits are bits 8-11 of the 12-bit integer.
|
|
See description for the <em>Extended Length</em> field below.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Extended Length</p></td>
|
|
<td>
|
|
<p>This byte, together with the 4 bits in the previous byte,
|
|
forms an unsigned 12-bit integer for holding the length of
|
|
the tiny object. These 8 bits are bits 0-7 of the 12-bit
|
|
integer formed. The value stored is one less than the actual
|
|
length (since zero-length objects are not allowed to be
|
|
stored in the heap). For example, an object of actual length
|
|
1 has an encoded length of 0, an object of actual length
|
|
2 has an encoded length of 1, and so on.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Data</p></td>
|
|
<td>
|
|
<p>This is the data for the object.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fractal Heap ID for Huge Objects (Sub-types 1 and 2):
|
|
Indirectly Accessed, Non-filtered/Filtered
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version and Type</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted
|
|
only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />v2 B-tree Key<sup>L</sup><em> (variable size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fractal Heap ID for Huge Objects (Sub-types 1 and 2):
|
|
Indirectly Accessed, Non-filtered/Filtered
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version and Type</p></td>
|
|
<td>
|
|
<p>This is a bit field with the following definition:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>6-7</code></td>
|
|
<td>The current version of ID format. This document
|
|
describes version 0.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>4-5</code></td>
|
|
<td>The ID type. Huge objects have a value of <code>1</code>.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>0-3</code></td>
|
|
<td>Reserved.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>v2 B-tree Key</p></td>
|
|
<td><p>This field is the B-tree key for retrieving the information
|
|
from the version 2 B-tree for huge objects needed to access the
|
|
object. See the description of <a href="#V2Btrees">v2 B-tree</a>
|
|
records sub-types 1 and 2 for a description of the fields. New key
|
|
values are derived from <em>Next Huge Object ID</em> in the
|
|
<em>Fractal Heap Header</em>.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fractal Heap ID for Huge Objects (Sub-type 3):
|
|
Directly Accessed, Non-filtered
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version and Type</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address <sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Length <sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fractal Heap ID for Huge Objects (Sub-type 3):
|
|
Directly Accessed, Non-filtered
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version and Type</p></td>
|
|
<td>
|
|
<p>This is a bit field with the following definition:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>6-7</code></td>
|
|
<td>The current version of ID format. This document
|
|
describes version 0.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>4-5</code></td>
|
|
<td>The ID type. Huge objects have a value of <code>1</code>.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>0-3</code></td>
|
|
<td>Reserved.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address</p></td>
|
|
<td><p>This field is the address of the object in the file.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Length</p></td>
|
|
<td><p>This field is the length of the object in the file.</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fractal Heap ID for Huge Objects (Sub-type 4):
|
|
Directly Accessed, Filtered
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version and Type</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address <sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Length <sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Filter Mask</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />De-filtered Size <sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fractal Heap ID for Huge Objects (Sub-type 4):
|
|
Directly Accessed, Filtered
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version and Type</p></td>
|
|
<td>
|
|
<p>This is a bit field with the following definition:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>6-7</code></td>
|
|
<td>The current version of ID format. This document
|
|
describes version 0.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>4-5</code></td>
|
|
<td>The ID type. Huge objects have a value of <code>1</code>.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>0-3</code></td>
|
|
<td>Reserved.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address</p></td>
|
|
<td><p>This field is the address of the filtered object in the file.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Length</p></td>
|
|
<td><p>This field is the length of the filtered object in the file.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filter Mask</p></td>
|
|
<td><p>This field is the I/O pipeline filter mask for the
|
|
filtered object in the file.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filtered Size</p></td>
|
|
<td><p>This field is the size of the de-filtered object in the file.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fractal Heap ID for Managed Objects
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version and Type</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Offset <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Length <em>(variable size)</em></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fractal Heap ID for Managed Objects
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version and Type</p></td>
|
|
<td><p>This is a bit field with the following definition:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>6-7</code></td>
|
|
<td>The current version of ID format. This document
|
|
describes version 0.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>4-5</code></td>
|
|
<td>The ID type. Managed objects have a value of <code>0</code>.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>0-3</code></td>
|
|
<td>Reserved.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Offset</p></td>
|
|
<td><p>This field is the offset of the object in the heap.
|
|
This field’s size is the minimum number of bytes
|
|
necessary to encode the <em>Maximum Heap Size</em> value
|
|
(from the <em>Fractal Heap Header</em>). For example, if the
|
|
value of the <em>Maximum Heap Size</em> is less than 256 bytes,
|
|
this field is 1 byte in length, a <em>Maximum Heap Size</em>
|
|
of 256-65535 bytes uses a 2 byte length, and so on.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Length</p></td>
|
|
<td><p>This field is the length of the object in the heap. It
|
|
is determined by taking the minimum value of <em>Maximum
|
|
Direct Block Size</em> and <em>Maximum Size of Managed
|
|
Objects</em> in the <em>Fractal Heap Header</em>. Again,
|
|
the minimum number of bytes needed to encode that value is
|
|
used for the size of this field.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h3><a name="FreeSpaceManager">
|
|
III.H. Disk Format: Level 1H - Free-space Manager</a></h3>
|
|
|
|
<p>
|
|
Free-space managers are used to describe space within a heap or
|
|
the entire HDF5 file that is not currently used for that heap or
|
|
file.
|
|
</p>
|
|
|
|
<p>
|
|
The <em>free-space manager header</em> contains metadata information
|
|
about the space being tracked, along with the address of the list
|
|
of <em>free space sections</em> which actually describes the free
|
|
space. The header records information about free-space sections being
|
|
tracked, creation parameters for handling free-space sections of a
|
|
client, and section information used to locate the collection of
|
|
free-space sections.
|
|
</p>
|
|
|
|
<p>
|
|
The <em>free-space section list</em> stores a collection of
|
|
free-space sections that is specific to each <em>client</em> of the
|
|
free-space manager.
|
|
|
|
For example, the fractal heap is a client of the free space manager
|
|
and uses it to track unused space within the heap. There are 4
|
|
types of section records for the fractal heap, each of which has
|
|
its own format, listed below.
|
|
</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Free-space Manager Header
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Client ID</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Total Space Tracked<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Total Number of Sections<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Number of Serialized Sections<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Number of Un-Serialized Sections<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Number of Section Classes</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Shrink Percent</td>
|
|
<td colspan="2">Expand Percent</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Size of Address Space</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Maximum Section Size <sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address of Serialized Section List<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Size of Serialized Section List Used<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Allocated Size of Serialized Section List<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Free-space Manager Header
|
|
</caption>
|
|
<tr>
|
|
<th width="35%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>FSHD</code>”
|
|
is used to indicate the beginning of the Free-space Manager
|
|
Header. This gives file consistency checking utilities a
|
|
better chance of reconstructing a damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>This is the version number for the Free-space Manager Header
|
|
and this document describes version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Client ID</p></td>
|
|
<td>
|
|
<p>This is the client ID for identifying the user of this
|
|
free-space manager:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">ID</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Fractal heap
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>File
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2+</code></td>
|
|
<td>Reserved.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Total Space Tracked</p></td>
|
|
<td>
|
|
<p>This is the total amount of free space being tracked, in bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Total Number of Sections</p></td>
|
|
<td>
|
|
<p>This is the total number of free-space sections being tracked.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Number of Serialized Sections</p></td>
|
|
<td>
|
|
<p>This is the number of serialized free-space sections being
|
|
tracked.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td><p>Number of Un-Serialized Sections</p></td>
|
|
<td>
|
|
<p>This is the number of un-serialized free-space sections being
|
|
managed. Un-serialized sections are created by the free-space
|
|
client when the list of sections is read in.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Number of Section Classes</p></td>
|
|
<td>
|
|
<p>This is the number of section classes handled by this free space
|
|
manager for the free-space client.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Shrink Percent</p></td>
|
|
<td>
|
|
<p>This is the percent of current size to shrink the allocated
|
|
serialized free-space section list.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Expand Percent</p></td>
|
|
<td>
|
|
<p>This is the percent of current size to expand the allocated
|
|
serialized free-space section list.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size of Address Space</p></td>
|
|
<td>
|
|
<p>This is the size of the address space that free-space sections
|
|
are within. This is stored as the log<sub>2</sub> of the
|
|
actual value (in other words, the number of bits required
|
|
to store values within that address space).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Maximum Section Size</p></td>
|
|
<td>
|
|
<p>This is the maximum size of a section to be tracked.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address of Serialized Section List</p></td>
|
|
<td>
|
|
<p>This is the address where the serialized free-space section
|
|
list is stored.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size of Serialized Section List Used</p></td>
|
|
<td>
|
|
<p>This is the size of the serialized free-space section
|
|
list used (in bytes). This value must be less than
|
|
or equal to the <em>allocated size of serialized section
|
|
list</em>, below.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Allocated Size of Serialized Section List</p></td>
|
|
<td>
|
|
<p>This is the size of serialized free-space section list
|
|
actually allocated (in bytes).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>This is the checksum for the free-space manager header.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<p>The free-space sections being managed are stored in a
|
|
<em>free-space section list</em>, described below. The sections
|
|
in the free-space section list are stored in the following way:
|
|
a count of the number of sections describing a particular size of
|
|
free space and the size of the free-space described (in bytes),
|
|
followed by a list of section description records; then another
|
|
section count and size, followed by the list of section
|
|
descriptions for that size; and so on.</p>
|
|
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Free-space Section List
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Free-space Manager Header Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Number of Section Records in Set #0 <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Size of Free-space Section Described in Record Set #0 <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Record Set #0 Section Record #0 Offset<em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="1">Record Set #0 Section Record #0 Type</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Record Set #0 Section Record #0 Data <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">...</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Record Set #0 Section Record #K-1 Offset<em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="1">Record Set #0 Section Record #K-1 Type</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Record Set #0 Section Record #K-1 Data <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Number of Section Records in Set #1 <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Size of Free-space Section Described in Record Set #1 <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Record Set #1 Section Record #0 Offset<em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="1">Record Set #1 Section Record #0 Type</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Record Set #1 Section Record #0 Data <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">...</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Record Set #1 Section Record #K-1 Offset<em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="1">Record Set #1 Section Record #K-1 Type</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Record Set #1 Section Record #K-1 Data <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><strong>...</strong></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><strong>...</strong></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Number of Section Records in Set #N-1 <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Size of Free-space Section Described in Record Set #N-1 <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Record Set #N-1 Section Record #0 Offset<em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="1">Record Set #N-1 Section Record #0 Type</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Record Set #N-1 Section Record #0 Data <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">...</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Record Set #N-1 Section Record #K-1 Offset<em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="1">Record Set #N-1 Section Record #K-1 Type</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Record Set #N-1 Section Record #K-1 Data <em>(variable size)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Free-space Section List
|
|
</caption>
|
|
<tr>
|
|
<th width="35%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>FSSE</code>”
|
|
is used to indicate the beginning of the Free-space Section
|
|
Information. This gives file consistency checking utilities
|
|
a better chance of reconstructing a damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>This is the version number for the Free-space Section List
|
|
and this document describes version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Free-space Manager Header Address</p></td>
|
|
<td>
|
|
<p>This is the address of the <em>Free-space Manager Header</em>.
|
|
This field is principally used for file
|
|
integrity checking.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Number of Section Records for Set #N</p></td>
|
|
<td>
|
|
<p>This is the number of free-space section records for set #N.
|
|
The length of this field is the minimum number of bytes needed
|
|
to store the <em>number of serialized sections</em> (from the
|
|
<em>free-space manager header</em>).
|
|
</p>
|
|
|
|
<p>
|
|
The number of sets of free-space section records is
|
|
determined by the <em>size of serialized section list</em> in
|
|
the <em>free-space manager header</em>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Section Size for Record Set #N</p></td>
|
|
<td>
|
|
<p>This is the size (in bytes) of the free-space section described
|
|
for <em>all</em> the section records in set #N.
|
|
</p>
|
|
|
|
<p>
|
|
The length of this field is the minimum number of bytes needed
|
|
to store the <em>maximum section size</em> (from the
|
|
<em>free-space manager header</em>).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Record Set #N Section #K Offset</p></td>
|
|
<td>
|
|
<p>This is the offset (in bytes) of the free-space section within
|
|
the client for the free-space manager.
|
|
</p>
|
|
|
|
<p>
|
|
The length of this field is the minimum number of bytes needed
|
|
to store the <em>size of address space</em> (from the
|
|
<em>free-space manager header</em>).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Record Set #N Section #K Type</p></td>
|
|
<td>
|
|
<p>This is the type of the section record, used to decode the
|
|
<em>record set #N section #K data</em> information. The defined
|
|
record type for <em>file</em> client is:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Type</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>File’s section (a range of actual bytes in file)
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1+</code></td>
|
|
<td>Reserved.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
<p>The defined record types for a <em>fractal heap</em> client are:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Type</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Fractal heap “single” section
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Fractal heap “first row” section
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>Fractal heap “normal row” section
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>Fractal heap “indirect” section
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>4+</code></td>
|
|
<td>Reserved.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Record Set #N Section #K Data</p></td>
|
|
<td>
|
|
<p>This is the section-type specific information for each record
|
|
in the record set, described below.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>This is the checksum for the <em>Free-space Section List</em>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<p>
|
|
The section-type specific data for each free-space section record is
|
|
described below:
|
|
</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: File’s Section Data Record
|
|
</caption>
|
|
|
|
<tr>
|
|
<td colspan="4"><em>No additional record data stored</em></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fractal Heap “Single” Section Data Record
|
|
</caption>
|
|
|
|
<tr>
|
|
<td colspan="4"><em>No additional record data stored</em></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fractal Heap “First Row” Section Data
|
|
Record
|
|
</caption>
|
|
|
|
<tr>
|
|
<td colspan="4"><em>Same format as “indirect”
|
|
section data</em></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fractal Heap “Normal Row” Section Data
|
|
Record
|
|
</caption>
|
|
|
|
<tr>
|
|
<td colspan="4"><em>No additional record data stored</em></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fractal Heap “Indirect” Section
|
|
Data Record
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Fractal Heap Indirect Block Offset <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Block Start Row</td>
|
|
<td colspan="2">Block Start Column</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Number of Blocks</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fractal Heap “Indirect” Section
|
|
Data Record
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Fractal Heap Block Offset</p></td>
|
|
<td>
|
|
<p>The offset of the indirect block in the fractal heap’s address
|
|
space containing the empty blocks.
|
|
</p>
|
|
<p>
|
|
The number of bytes used to encode this field is the minimum
|
|
number of bytes needed to encode values for the <em>Maximum
|
|
Heap Size</em> (in the fractal heap’s header).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Block Start Row</p></td>
|
|
<td>
|
|
<p>This is the row that the empty blocks start in.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Block Start Column</p></td>
|
|
<td>
|
|
<p>This is the column that the empty blocks start in.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Number of Blocks</p></td>
|
|
<td>
|
|
<p>This is the number of empty blocks covered by the section.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h3><a name="SOHMTable">
|
|
III.I. Disk Format: Level 1I - Shared Object Header Message Table</a></h3>
|
|
|
|
<p>
|
|
The <em>shared object header message table</em> is used to locate
|
|
object
|
|
header messages that are shared between two or more object headers
|
|
in the file. Shared object header messages are stored and indexed
|
|
in the file in one of two ways: indexed sequentially in a
|
|
<em>shared header message list</em> or indexed with a v2 B-tree.
|
|
The shared messages themselves are either stored in a fractal
|
|
heap (when two or more objects share the message), or remain in an
|
|
object’s header (when only one object uses the message currently,
|
|
but the message can be shared in the future).
|
|
</p>
|
|
|
|
<p>
|
|
The <em>shared object header message table</em>
|
|
contains a list of shared message index headers. Each index header
|
|
records information about the version of the index format, the index
|
|
storage type, flags for the message types indexed, the number of
|
|
messages in the index, the address where the index resides,
|
|
and the fractal heap address if shared messages are stored there.
|
|
</p>
|
|
|
|
<p>
|
|
Each index can be either a list or a v2 B-tree and may transition
|
|
between those two forms as the number of messages in the index
|
|
varies. Each shared message record contains information used to
|
|
locate the shared message from either a fractal heap or an object
|
|
header. The types of messages that can be shared are: <em>Dataspace,
|
|
Datatype, Fill Value, Filter Pipeline and Attribute</em>.
|
|
</p>
|
|
|
|
<p>
|
|
The <em>shared object header message table</em> is pointed to
|
|
from a <a href="#SOHMTableMessage">shared message table</a> message
|
|
in the superblock extension for a file. This message stores the
|
|
version of the table format, along with the number of index headers
|
|
in the table.
|
|
</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Shared Object Header Message Table
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version for index #0</td>
|
|
<td>Index Type for index #0</td>
|
|
<td colspan="2">Message Type Flags for index #0</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Minimum Message Size for index #0</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">List Cutoff for index #0</td>
|
|
<td colspan="2">v2 B-tree Cutoff for index #0</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Number of Messages for index #0</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Index Address<sup>O</sup> for index #0<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Fractal Heap Address<sup>O</sup> for index #0<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">...</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">...</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version for index #N-1</td>
|
|
<td>Index Type for index #N-1</td>
|
|
<td colspan="2">Message Type Flags for index #N-1</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Minimum Message Size for index #N-1</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">List Cutoff for index #N-1</td>
|
|
<td colspan="2">v2 B-tree Cutoff for index #N-1</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Number of Messages for index #N-1</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Index Address<sup>O</sup> for index #N-1<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Fractal Heap Address<sup>O</sup> for index #N-1<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Shared Object Header Message Table
|
|
</caption>
|
|
<tr>
|
|
<th width="35%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>SMTB</code>”
|
|
is used to indicate the beginning of the Shared Object
|
|
Header Message table. This gives file consistency checking
|
|
utilities a better chance of reconstructing a damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version for index #N</p></td>
|
|
<td>
|
|
<p>This is the version number for the list of shared object header message
|
|
indexes and this document describes version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Index Type for index #N</p></td>
|
|
<td>
|
|
<p>The type of index can be an unsorted list or a v2 B-tree.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Message Type Flags for index #N</p></td>
|
|
<td>
|
|
<p>This field indicates the type of messages tracked in the index,
|
|
as follows:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bits</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>If set, the index tracks <em>Dataspace Messages</em>.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>If set, the message tracks <em>Datatype Messages</em>.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>If set, the message tracks <em>Fill Value Messages</em>.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>If set, the message tracks <em>Filter Pipeline Messages</em>.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>4</code></td>
|
|
<td>If set, the message tracks <em>Attribute Messages</em>.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>5-15</code></td>
|
|
<td>Reserved (zero).
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
|
|
<p>
|
|
An index can track more than one type of message, but each type
|
|
of message can only by in one index.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Minimum Message Size for index #N</p></td>
|
|
<td>
|
|
<p>This is the message size sharing threshold for the index.
|
|
If the encoded size of the message is less than this value, the
|
|
message is not shared.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>List Cutoff for index #N</p></td>
|
|
<td>
|
|
<p>This is the cutoff value for the indexing of messages to
|
|
switch from a list to a v2 B-tree. If the number of messages
|
|
is greater than this value, the index should be a v2 B-tree.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td><p>v2 B-tree Cutoff for index #N</p></td>
|
|
<td>
|
|
<p>This is the cutoff value for the indexing of messages
|
|
to switch from a v2 B-tree back to a list. If the number
|
|
of messages is less than this value, the index should be
|
|
a list.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Number of Messages for index #N</p></td>
|
|
<td>
|
|
<p>The number of shared messages being tracked for the index.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Index Address for index #N</p></td>
|
|
<td>
|
|
<p>This field is the address of the list or v2 B-tree where the
|
|
index nodes reside.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Fractal Heap Address for index #N</p></td>
|
|
<td>
|
|
<p>This field is the address of the fractal heap if shared messages
|
|
are stored there.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>This is the checksum for the table.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<p>
|
|
Shared messages are indexed either with a <em>shared message record
|
|
list</em>, described below, or using a v2 B-tree (using record type 7).
|
|
The number of records in the <em>shared message record list</em> is
|
|
determined in the index’s entry in the <em>shared object header message
|
|
table</em>.
|
|
</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Shared Message Record List
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Shared Message Record #0</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Shared Message Record #1</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">...</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Shared Message Record #N-1</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Shared Message Record List
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>SMLI</code>”
|
|
is used to indicate the beginning of a list of index nodes.
|
|
This gives file consistency checking utilities a better
|
|
chance of reconstructing a damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Shared Message Record #N</p></td>
|
|
<td>
|
|
<p>The record for locating the shared message, either in the
|
|
fractal heap for the index, or an object header (see format for
|
|
<em>index nodes</em> below).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>This is the checksum for the list.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<p>
|
|
The record for each shared message in an index is stored in one
|
|
of the following forms:
|
|
</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Shared Message Record for Messages Stored in a
|
|
Fractal Heap
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Message Location</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Hash Value</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Reference Count</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Fractal Heap ID<br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Shared Message Record for Messages Stored in a
|
|
Fractal Heap
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Message Location</p></td>
|
|
<td>
|
|
<p>This has a value of 0 indicating that the message is stored in
|
|
the heap.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Hash Value</p></td>
|
|
<td>
|
|
<p>This is the hash value for the message.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Reference Count</p></td>
|
|
<td>
|
|
<p>This is the number of times the message is used in the file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Fractal Heap ID</p></td>
|
|
<td>
|
|
<p>This is an 8-byte fractal heap ID for the message as stored in
|
|
the fractal heap for the index.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Shared Message Record for Messages Stored in an
|
|
Object Header
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Message Location</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Hash Value</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Reserved</td>
|
|
<td>Message Type</td>
|
|
<td colspan="2">Creation Index</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Object Header Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Shared Message Record for Messages Stored in an
|
|
Object Header
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Message Location</p></td>
|
|
<td>
|
|
<p>This has a value of 1 indicating that the message is stored in
|
|
an object header.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Hash Value</p></td>
|
|
<td>
|
|
<p>This is the hash value for the message.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Message Type</p></td>
|
|
<td>
|
|
<p>This is the message type in the object header.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Creation Index</p></td>
|
|
<td>
|
|
<p>This is the creation index of the message within the object
|
|
header.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Object Header Address</p></td>
|
|
<td>
|
|
<p>This is the address of the object header where the message is
|
|
located.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h2><a name="DataObject">
|
|
IV. Disk Format: Level 2 - Data Objects </a></h2>
|
|
|
|
<p>Data objects contain the “real” user-visible information in the file.
|
|
These objects compose the scientific data and other information which
|
|
are generally thought of as “data” by the end-user. All the
|
|
other information in the file is provided as a framework for
|
|
storing and accessing these data objects.
|
|
</p>
|
|
|
|
<p>A data object is composed of header and data
|
|
information. The header information contains the information
|
|
needed to interpret the data information for the object as
|
|
well as additional “metadata” or pointers to additional
|
|
“metadata” used to describe or annotate each object.
|
|
</p>
|
|
|
|
<h3><a name="ObjectHeader">
|
|
IV.A. Disk Format: Level 2A - Data Object Headers</a></h3>
|
|
|
|
<p>The header information of an object is designed to encompass
|
|
all of the information about an object, except for the data itself.
|
|
This information includes the dataspace, the datatype, information
|
|
about how the data is stored on disk (in external files, compressed,
|
|
broken up in blocks, and so on), as well as other information used
|
|
by the library to speed up access to the data objects or maintain
|
|
a file’s integrity. Information stored by user applications
|
|
as attributes is also stored in the object’s header. The header
|
|
of each object is not necessarily located immediately prior to the
|
|
object’s data in the file and in fact may be located in any
|
|
position in the file. The order of the messages in an object header
|
|
is not significant.</p>
|
|
|
|
<p>Object headers are composed of a prefix and a set of messages. The
|
|
prefix contains the information needed to interpret the messages and
|
|
a small amount of metadata about the object, and the messages contain
|
|
the majority of the metadata about the object.
|
|
</p>
|
|
|
|
<h3><a name="ObjectHeaderPrefix">
|
|
IV.A.1. Disk Format: Level 2A1 - Data Object Header Prefix</a></h3>
|
|
|
|
|
|
|
|
<h4><a name="V1ObjectHeaderPrefix">
|
|
IV.A.1.a. Version 1 Data Object Header Prefix</a></h4>
|
|
|
|
<p>Header messages are aligned on 8-byte boundaries for version 1
|
|
object headers.
|
|
</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 1 Object Header
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Reserved (zero)</td>
|
|
<td colspan="2">Total Number of Header Messages</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Object Reference Count</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Object Header Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Reserved (zero)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Header Message Type #1</td>
|
|
<td colspan="2">Size of Header Message Data #1</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Header Message #1 Flags</td>
|
|
<td colspan="3">Reserved (zero)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Header Message Data #1<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Header Message Type #n</td>
|
|
<td colspan="2">Size of Header Message Data #n</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Header Message #n Flags</td>
|
|
<td colspan="3">Reserved (zero)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Header Message Data #n<br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 1 Object Header
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>This value is used to determine the format of the
|
|
information in the object header. When the format of the
|
|
object header is changed, the version number
|
|
is incremented and can be used to determine how the
|
|
information in the object header is formatted. This
|
|
is version one (1) (there was no version zero (0)) of the
|
|
object header.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Total Number of Header Messages</p></td>
|
|
<td>
|
|
<p>This value determines the total number of messages listed in
|
|
object headers for this object. This value includes the messages
|
|
in continuation messages for this object.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Object Reference Count</p></td>
|
|
<td>
|
|
<p>This value specifies the number of “hard links” to this object
|
|
within the current file. References to the object from external
|
|
files, “soft links” in this file and object references in this
|
|
file are not tracked.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Object Header Size</p></td>
|
|
<td>
|
|
<p>This value specifies the number of bytes of header message data
|
|
following this length field that contain object header messages
|
|
for this object header. This value does not include the size of
|
|
object header continuation blocks for this object elsewhere in the
|
|
file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Header Message #n Type</p></td>
|
|
<td>
|
|
<p>This value specifies the type of information included in the
|
|
following header message data. The message types for
|
|
header messages are defined in sections below.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size of Header Message #n Data</p></td>
|
|
<td>
|
|
<p>This value specifies the number of bytes of header
|
|
message data following the header message type and length
|
|
information for the current message. The size includes
|
|
padding bytes to make the message a multiple of eight
|
|
bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Header Message #n Flags</p></td>
|
|
<td>
|
|
<p>This is a bit field with the following definition:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>If set, the message data is constant. This is used
|
|
for messages like the datatype message of a dataset.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>If set, the message is <em>shared</em> and stored
|
|
in another location than the object header. The Header
|
|
Message Data field contains a Shared Message
|
|
(described in the <a href="#ObjectHeaderMessages">Data Object Header Messages</a>
|
|
section below)
|
|
and the Size of Header Message Data field
|
|
contains the size of that Shared Message.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>If set, the message should not be shared.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>If set, the HDF5 decoder should fail to open this object
|
|
if it does not understand the message’s type and the file
|
|
is open with permissions allowing write access to the file.
|
|
(Normally, unknown messages can just be ignored by HDF5
|
|
decoders)
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>4</code></td>
|
|
<td>If set, the HDF5 decoder should set bit 5 of this
|
|
message’s flags (in other words, this bit field)
|
|
if it does not understand the message’s type
|
|
and the object is modified in any way. (Normally,
|
|
unknown messages can just be ignored by HDF5
|
|
decoders)
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>5</code></td>
|
|
<td>If set, this object was modified by software that did not
|
|
understand this message.
|
|
(Normally, unknown messages should just be ignored by HDF5
|
|
decoders) (Can be used to invalidate an index or a similar
|
|
feature)
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>6</code></td>
|
|
<td>If set, this message is shareable.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>7</code></td>
|
|
<td>If set, the HDF5 decoder should always fail to open this
|
|
object if it does not understand the message’s type (whether
|
|
it is open for read-only or read-write access). (Normally,
|
|
unknown messages can just be ignored by HDF5 decoders)
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Header Message #n Data</p></td>
|
|
<td>
|
|
<p>The format and length of this field is determined by the
|
|
header message type and size respectively. Some header
|
|
message types do not require any data and this information
|
|
can be eliminated by setting the length of the message to
|
|
zero. The data is padded with enough zeroes to make the
|
|
size a multiple of eight.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h4><a name="V2ObjectHeaderPrefix">
|
|
IV.A.1.b. Version 2 Data Object Header Prefix</a></h4>
|
|
|
|
<p>Note that the “total number of messages” field has been dropped from
|
|
the data object header prefix in this version. The number of messages
|
|
in the data object header is just determined by the messages encountered
|
|
in all the object header blocks.</p>
|
|
|
|
<p>Note also that the fields and messages in this version of data object
|
|
headers have <em>no</em> alignment or padding bytes inserted - they are
|
|
stored packed together.</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 Object Header
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Flags</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Access time <em>(optional)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Modification Time <em>(optional)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Change Time <em>(optional)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Birth Time <em>(optional)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Maximum # of compact attributes <em>(optional)</em></td>
|
|
<td colspan="2">Minimum # of dense attributes <em>(optional)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Size of Chunk #0 <em>(variable size)</em></td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Header Message Type #1</td>
|
|
<td colspan="2">Size of Header Message Data #1</td>
|
|
<td>Header Message #1 Flags</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Header Message #1 Creation Order <em>(optional)</em></td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Header Message Data #1<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Header Message Type #n</td>
|
|
<td colspan="2">Size of Header Message Data #n</td>
|
|
<td>Header Message #n Flags</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Header Message #n Creation Order <em>(optional)</em></td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Header Message Data #n<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Gap <em>(optional, variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 Object Header
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>OHDR</code>”
|
|
is used to indicate the beginning of an object header. This
|
|
gives file consistency checking utilities a better chance
|
|
of reconstructing a damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>This field has a value of 2 indicating version 2 of the object header.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Flags</p></td>
|
|
<td>
|
|
<p>This field is a bit field indicating additional information
|
|
about the object header.
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit(s)</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0-1</code></td>
|
|
<td>This two bit field determines the size of the
|
|
<em>Size of Chunk #0</em> field. The values are:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>The <em>Size of Chunk #0</em> field is 1 byte.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>The <em>Size of Chunk #0</em> field is 2 bytes.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>The <em>Size of Chunk #0</em> field is 4 bytes.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>The <em>Size of Chunk #0</em> field is 8 bytes.
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>If set, attribute creation order is tracked.</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>If set, attribute creation order is indexed.</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>4</code></td>
|
|
<td>If set, non-default attribute storage phase change
|
|
values are stored.</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>5</code></td>
|
|
<td>If set, access, modification, change and birth times
|
|
are stored.</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>6-7</code></td>
|
|
<td>Reserved</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Access Time</p></td>
|
|
<td>
|
|
<p>This 32-bit value represents the number of seconds after the
|
|
UNIX epoch when the object’s raw data was last accessed
|
|
(in other words, read or written).
|
|
</p>
|
|
<p>This field is present if bit 5 of <em>flags</em> is set.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Modification Time</p></td>
|
|
<td>
|
|
<p>This 32-bit value represents the number of seconds after
|
|
the UNIX epoch when the object’s raw data was last
|
|
modified (in other words, written).
|
|
</p>
|
|
<p>This field is present if bit 5 of <em>flags</em> is set.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Change Time</p></td>
|
|
<td>
|
|
<p>This 32-bit value represents the number of seconds after the
|
|
UNIX epoch when the object’s metadata was last changed.
|
|
</p>
|
|
<p>This field is present if bit 5 of <em>flags</em> is set.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Birth Time</p></td>
|
|
<td>
|
|
<p>This 32-bit value represents the number of seconds after the
|
|
UNIX epoch when the object was created.
|
|
</p>
|
|
<p>This field is present if bit 5 of <em>flags</em> is set.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Maximum # of compact attributes</p></td>
|
|
<td>
|
|
<p>This is the maximum number of attributes to store in the compact
|
|
format before switching to the indexed format.
|
|
</p>
|
|
<p>This field is present if bit 4 of <em>flags</em> is set.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Minimum # of dense attributes</p></td>
|
|
<td>
|
|
<p>This is the minimum number of attributes to store in the indexed
|
|
format before switching to the compact format.
|
|
</p>
|
|
<p>This field is present if bit 4 of <em>flags</em> is set.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size of Chunk #0</p></td>
|
|
<td>
|
|
<p>
|
|
This unsigned value specifies the number of bytes of header
|
|
message data following this field that contain object header
|
|
information.
|
|
</p>
|
|
<p>
|
|
This value does not include the size of object header
|
|
continuation blocks for this object elsewhere in the file.
|
|
</p>
|
|
<p>
|
|
The length of this field varies depending on bits 0 and 1 of
|
|
the <em>flags</em> field.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Header Message #n Type</p></td>
|
|
<td>
|
|
<p>Same format as version 1 of the object header, described above.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size of Header Message #n Data</p></td>
|
|
<td>
|
|
<p>This value specifies the number of bytes of header
|
|
message data following the header message type and length
|
|
information for the current message. The size of messages
|
|
in this version does <em>not</em> include any padding bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Header Message #n Flags</p></td>
|
|
<td>
|
|
<p>Same format as version 1 of the object header, described above.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Header Message #n Creation Order</p></td>
|
|
<td>
|
|
<p>This field stores the order that a message of a given type
|
|
was created in.
|
|
</p>
|
|
<p>This field is present if bit 2 of <em>flags</em> is set.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Header Message #n Data</p></td>
|
|
<td>
|
|
<p>Same format as version 1 of the object header, described above.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Gap</p></td>
|
|
<td>
|
|
<p>A gap in an object header chunk is inferred by the end of the
|
|
messages for the chunk before the beginning of the chunk’s
|
|
checksum. Gaps are always smaller than the size of an
|
|
object header message prefix (message type + message size +
|
|
message flags).
|
|
</p>
|
|
<p>Gaps are formed when a message (typically an attribute message)
|
|
in an earlier chunk is deleted and a message from a later
|
|
chunk that does not quite fit into the free space is moved
|
|
into the earlier chunk.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>This is the checksum for the object header chunk.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<p>The header message types and the message data associated with
|
|
them compose the critical “metadata” about each object. Some
|
|
header messages are required for each object while others are
|
|
optional. Some optional header messages may also be repeated
|
|
several times in the header itself, the requirements and number
|
|
of times allowed in the header will be noted in each header
|
|
message description below.
|
|
</p>
|
|
|
|
|
|
<h3><a name="ObjectHeaderMessages">
|
|
IV.A.2. Disk Format: Level 2A2 - Data Object Header Messages</a></h3>
|
|
|
|
<p>Data object header messages are small pieces of metadata that are
|
|
stored in the data object header for each object in an HDF5 file.
|
|
Data object header messages provide the metadata required to describe
|
|
an object and its contents, as well as optional pieces of metadata
|
|
that annotate the meaning or purpose of the object.
|
|
</p>
|
|
|
|
<p>Data object header messages are either stored directly in the data
|
|
object header for the object or are shared between multiple objects
|
|
in the file. When a message is shared, a flag in the <em>Message Flags</em>
|
|
indicates that the actual <em>Message Data</em>
|
|
portion of that message is stored in another location (such as another
|
|
data object header, or a heap in the file) and the <em>Message Data</em>
|
|
field contains the information needed to locate the actual information
|
|
for the message.
|
|
</p>
|
|
|
|
<p>
|
|
The format of shared message data is described here:</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Shared Message (Version 1)
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Type</td>
|
|
<td colspan="2">Reserved (zero)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Reserved (zero)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Shared Message (Version 1)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number is used when there are changes in the format
|
|
of a shared object message and is described here:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Version</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Never used.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Used by the library before version 1.6.1.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Type</p></td>
|
|
<td><p>The type of shared message location:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Message stored in another object’s header (a <em>committed</em>
|
|
message).
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address</p></td>
|
|
<td><p>The address of the object header
|
|
containing the message to be shared.</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
|
|
<caption>
|
|
Layout: Shared Message (Version 2)
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Type</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Shared Message (Version 2)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number is used when there are changes in the format
|
|
of a shared object message and is described here:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Version</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>Used by the library of version 1.6.1 and after.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Type</p></td>
|
|
<td><p>The type of shared message location:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Message stored in another object’s header (a <em>committed</em>
|
|
message).
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address</p></td>
|
|
<td><p>The address of the object header
|
|
containing the message to be shared.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Shared Message (Version 3)
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Type</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Location <em>(variable size)</em></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Shared Message (Version 3)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number indicates changes in the format of shared
|
|
object message and is described here:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Version</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>Used by the library of version 1.8 and after. In this
|
|
version, the <em>Type</em> field can indicate that
|
|
the message is stored in the fractal heap.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Type</p></td>
|
|
<td><p>The type of shared message location:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Message is not shared and is not shareable.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Message stored in file’s <em>shared object header message</em>
|
|
heap (a <em>shared</em> message).
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>Message stored in another object’s header (a <em>committed</em>
|
|
message).
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>Message stored is not shared, but is shareable.
|
|
</td>
|
|
</tr>
|
|
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Location</p></td>
|
|
<td><p>This field contains either a <a href="#SizeOfOffsetsV0">
|
|
<em>Size of Offsets</em></a>-bytes address of the object header
|
|
containing the message to be shared, or an 8-byte fractal heap
|
|
ID for the message in the file’s <em>shared object header
|
|
message</em> heap.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<p>The following is a list of currently defined header messages:
|
|
</p>
|
|
|
|
<h4><a name="NILMessage">IV.A.2.a. The NIL Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> NIL</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x0000</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Varies</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may be repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td>The NIL message is used to indicate a message which is to be
|
|
ignored when reading the header messages for a data object.
|
|
[Possibly one which has been deleted for some reason.]
|
|
</td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> Unspecified</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
|
|
<h4><a name="DataspaceMessage">IV.A.2.b. The Dataspace Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Dataspace</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x0001</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Varies according to the number of
|
|
dimensions, as described in the following table.</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Required for dataset objects;
|
|
may not be repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td>The dataspace message describes the number of dimensions (in
|
|
other words, “rank”) and size of each dimension that
|
|
the data object has. This message is only used for datasets which
|
|
have a simple, rectilinear, array-like layout; datasets requiring
|
|
a more complex layout are not yet supported.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Dataspace Message - Version 1
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Dimensionality</td>
|
|
<td>Flags</td>
|
|
<td>Reserved</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Reserved</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Dimension #1 Size<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Dimension #n Size<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Dimension #1 Maximum Size<sup>L</sup> <em>(optional)</em><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Dimension #n Maximum Size<sup>L</sup> <em>(optional)</em><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Permutation Index #1<sup>L</sup> <em>(optional)</em><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Permutation Index #n<sup>L</sup> <em>(optional)</em><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Dataspace Message - Version 1
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>This value is used to determine the format of the
|
|
Dataspace Message. When the format of the
|
|
information in the message is changed, the version number
|
|
is incremented and can be used to determine how the
|
|
information in the object header is formatted. This
|
|
document describes version one (1) (there was no version
|
|
zero (0)).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimensionality</p></td>
|
|
<td>
|
|
<p>This value is the number of dimensions that the data
|
|
object has.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Flags</p></td>
|
|
<td>
|
|
<p>This field is used to store flags to indicate the
|
|
presence of parts of this message. Bit 0 (the least
|
|
significant bit) is used to indicate that maximum
|
|
dimensions are present. Bit 1 is used to indicate that
|
|
permutation indices are present.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimension #n Size</p></td>
|
|
<td>
|
|
<p>This value is the current size of the dimension of the
|
|
data as stored in the file. The first dimension stored in
|
|
the list of dimensions is the slowest changing dimension
|
|
and the last dimension stored is the fastest changing
|
|
dimension.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimension #n Maximum Size</p></td>
|
|
<td>
|
|
<p>This value is the maximum size of the dimension of the
|
|
data as stored in the file. This value may be the special
|
|
“<a href="#UnlimitedDim">unlimited</a>” size which indicates
|
|
that the data may expand along this dimension indefinitely.
|
|
If these values are not stored, the maximum size of each
|
|
dimension is assumed to be the dimension’s current size.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Permutation Index #n</p></td>
|
|
<td>
|
|
<p>This value is the index permutation used to map
|
|
each dimension from the canonical representation to an
|
|
alternate axis for each dimension. If these values are
|
|
not stored, the first dimension stored in the list of
|
|
dimensions is the slowest changing dimension and the last
|
|
dimension stored is the fastest changing dimension.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
|
|
<br />
|
|
<p>Version 2 of the dataspace message dropped the optional
|
|
permutation index value support, as it was never implemented in the
|
|
HDF5 Library:</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Dataspace Message - Version 2
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Dimensionality</td>
|
|
<td>Flags</td>
|
|
<td>Type</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Dimension #1 Size<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Dimension #n Size<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Dimension #1 Maximum Size<sup>L</sup> <em>(optional)</em><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Dimension #n Maximum Size<sup>L</sup> <em>(optional)</em><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Dataspace Message - Version 2
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>This value is used to determine the format of the
|
|
Dataspace Message. This field should be ‘2’ for version 2
|
|
format messages.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimensionality</p></td>
|
|
<td>
|
|
<p>This value is the number of dimensions that the data object has.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Flags</p></td>
|
|
<td>
|
|
<p>This field is used to store flags to indicate the
|
|
presence of parts of this message. Bit 0 (the least
|
|
significant bit) is used to indicate that maximum
|
|
dimensions are present.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Type</p></td>
|
|
<td>
|
|
<p>This field indicates the type of the dataspace:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>A <em>scalar</em> dataspace; in other words,
|
|
a dataspace with a single, dimensionless element.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>A <em>simple</em> dataspace; in other words,
|
|
a dataspace with a rank greater than 0 and an
|
|
appropriate number of dimensions.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>A <em>null</em> dataspace; in other words,
|
|
a dataspace with no elements.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimension #n Size</p></td>
|
|
<td>
|
|
<p>This value is the current size of the dimension of the
|
|
data as stored in the file. The first dimension stored in
|
|
the list of dimensions is the slowest changing dimension
|
|
and the last dimension stored is the fastest changing
|
|
dimension.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimension #n Maximum Size</p></td>
|
|
<td>
|
|
<p>This value is the maximum size of the dimension of the
|
|
data as stored in the file. This value may be the special
|
|
“<a href="#UnlimitedDim">unlimited</a>” size which indicates
|
|
that the data may expand along this dimension indefinitely.
|
|
If these values are not stored, the maximum size of each
|
|
dimension is assumed to be the dimension’s current size.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
|
|
|
|
<!--
|
|
<h4><a name="DataSpaceMessage">Header Message Name: Complex Dataspace (Fiber Bundle?)</a></h4>
|
|
|
|
<!-- start msgdesc table --
|
|
<center>
|
|
<table class="msgdesc">
|
|
<p><b>Header Message Name: ???????</b></td></tr>
|
|
<b>Header Message Type: </b>0x0002<br />
|
|
<b>Length:</b> Varies</td></tr>
|
|
|
|
<b>Status:</b> One of the <em>Simple Dataspace</em> or
|
|
<em>Complex Dataspace</em> messages is required (but not both) and may
|
|
not be repeated.<br /> <b>Description:</b> The
|
|
<em>Dataspace</em> message describes space that the dataset is
|
|
mapped onto in a more comprehensive way than the <em>Simple
|
|
Dimensionality</em> message is capable of handling. The
|
|
dataspace of a dataset encompasses the type of coordinate system
|
|
used to locate the dataset’s elements as well as the structure and
|
|
regularity of the coordinate system. The dataspace also
|
|
describes the number of dimensions which the dataset inhabits as
|
|
well as a possible higher dimensional space in which the dataset
|
|
is located within.
|
|
|
|
<br />
|
|
<p><b>Format of Data:</b></p>
|
|
|
|
<center>
|
|
<table border cellpadding="4" width="80%">
|
|
<caption align="bottom">
|
|
<b>HDF5 Dataspace Message Layout</b>
|
|
</caption>
|
|
|
|
<tr align="center">
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr align="center">
|
|
<td colspan="4">Mesh Type</td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">Logical Dimensionality</td>
|
|
</tr>
|
|
</table>
|
|
</center>
|
|
|
|
<br />
|
|
<dl>
|
|
<dt>The elements of the dimensionality message are described below:
|
|
<dd>
|
|
<dl>
|
|
<dt>Mesh Type: (unsigned 32-bit integer)
|
|
<dd>This value indicates whether the grid is
|
|
polar/spherical/cartesion,
|
|
structured/unstructured and regular/irregular. <br />
|
|
The mesh type value is broken up as follows: <br />
|
|
|
|
<br />
|
|
<center>
|
|
<table border cellpadding="4" width="80%">
|
|
<caption align="bottom">
|
|
<b>HDF5 Mesh-type Layout</b>
|
|
</caption>
|
|
|
|
<tr align="center">
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr align="center">
|
|
<td colspan="1">Mesh Embedding</td>
|
|
<td colspan="1">Coordinate System</td>
|
|
<td colspan="1">Structure</td>
|
|
<td colspan="1">Regularity</td>
|
|
</tr>
|
|
</table>
|
|
</center>
|
|
The following are the definitions of mesh-type bytes:
|
|
<dl>
|
|
<dt>Mesh Embedding
|
|
<dd>This value indicates whether the dataset dataspace
|
|
is located within
|
|
another dataspace or not:
|
|
<dl> <dl>
|
|
<dt><STANDALONE>
|
|
<dd>The dataset mesh is self-contained and is not
|
|
embedded in another mesh.
|
|
<dt><EMBEDDED>
|
|
<dd>The dataset’s dataspace is located within
|
|
another dataspace, as
|
|
described in information below.
|
|
</dl> </dl>
|
|
<dt>Coordinate System
|
|
<dd>This value defines the type of coordinate system
|
|
used for the mesh:
|
|
<dl> <dl>
|
|
<dt><POLAR>
|
|
<dd>The last two dimensions are in polar
|
|
coordinates, higher dimensions are
|
|
cartesian.
|
|
<dt><SPHERICAL>
|
|
<dd>The last three dimensions are in spherical
|
|
coordinates, higher dimensions
|
|
are cartesian.
|
|
<dt><CARTESIAN>
|
|
<dd>All dimensions are in cartesian coordinates.
|
|
</dl> </dl>
|
|
<dt>Structure
|
|
<dd>This value defines the locations of the grid-points
|
|
on the axes:
|
|
<dl> <dl>
|
|
<dt><STRUCTURED>
|
|
<dd>All grid-points are on integral, sequential
|
|
locations, starting from 0.
|
|
<dt><UNSTRUCTURED>
|
|
<dd>Grid-points locations in each dimension are
|
|
explicitly defined and
|
|
may be of any numeric datatype.
|
|
</dl> </dl>
|
|
<dt>Regularity
|
|
<dd>This value defines the locations of the dataset
|
|
points on the grid:
|
|
<dl> <dl>
|
|
<dt><REGULAR>
|
|
<dd>All dataset elements are located at the
|
|
grid-points defined.
|
|
<dt><IRREGULAR>
|
|
<dd>Each dataset element has a particular
|
|
grid-location defined.
|
|
</dl> </dl>
|
|
</dl>
|
|
<p>The following grid combinations are currently allowed:</p>
|
|
<dl> <dl>
|
|
<dt><POLAR-STRUCTURED-REGULAR>
|
|
<dt><SPHERICAL-STRUCTURED-REGULAR>
|
|
<dt><CARTESIAN-STRUCTURED-REGULAR>
|
|
<dt><POLAR-UNSTRUCTURED-REGULAR>
|
|
<dt><SPHERICAL-UNSTRUCTURED-REGULAR>
|
|
<dt><CARTESIAN-UNSTRUCTURED-REGULAR>
|
|
<dt><CARTESIAN-UNSTRUCTURED-IRREGULAR>
|
|
</dl> </dl>
|
|
All of the above grid types can be embedded within another
|
|
dataspace.
|
|
<br /> <br />
|
|
<dt>Logical Dimensionality: (unsigned 32-bit integer)
|
|
<dd>This value is the number of dimensions that the dataset occupies.
|
|
|
|
<br />
|
|
<center>
|
|
<table border cellpadding="4" width="80%">
|
|
<caption align="bottom">
|
|
<b>HDF5 Dataspace Embedded Dimensionality Information</b>
|
|
</caption>
|
|
|
|
<tr align="center">
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr align="center">
|
|
<td colspan="4">Embedded Dimensionality</td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">Embedded Dimension Size #1</td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">Embedded Dimension Size #n</td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">Embedded Origin Location #1</td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">Embedded Origin Location #n</td>
|
|
</tr>
|
|
</table>
|
|
</center>
|
|
|
|
<dt>Embedded Dimensionality: (unsigned 32-bit integer)
|
|
<dd>This value is the number of dimensions of the space the
|
|
dataset is located within: in other words, a planar dataset
|
|
located within a 3-D space, a 3-D dataset
|
|
which is a subset of another 3-D space, and so on.
|
|
<dt>Embedded Dimension Size: (unsigned 32-bit integer)
|
|
<dd>These values are the sizes of the dimensions of the
|
|
embedded dataspace
|
|
that the dataset is located within.
|
|
<dt>Embedded Origin Location: (unsigned 32-bit integer)
|
|
<dd>These values comprise the location of the dataset’s
|
|
origin within the embedded dataspace.
|
|
</dl>
|
|
</dl>
|
|
[Comment: need some way to handle different orientations of the
|
|
dataset dataspace
|
|
within the embedded dataspace]<br />
|
|
|
|
<br />
|
|
<center>
|
|
<table border cellpadding="4" width="80%">
|
|
<caption align="bottom">
|
|
<b>HDF5 Dataspace Structured/Regular Grid Information</b>
|
|
</caption>
|
|
|
|
<tr align="center">
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr align="center">
|
|
<td colspan="4">Logical Dimension Size #1</td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">Logical Dimension Maximum #1</td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">Logical Dimension Size #n</td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">Logical Dimension Maximum #n</td>
|
|
</tr>
|
|
</table>
|
|
</center>
|
|
|
|
<br />
|
|
<dl>
|
|
<dt>The elements of the dimensionality message are described below:
|
|
<dd>
|
|
<dl>
|
|
<dt>Logical Dimension Size #n: (unsigned 32-bit integer)
|
|
<dd>This value is the current size of the dimension of the
|
|
data as stored in
|
|
the file. The first dimension stored in the list of
|
|
dimensions is the slowest
|
|
changing dimension and the last dimension stored is the
|
|
fastest changing
|
|
dimension.
|
|
<dt>Logical Dimension Maximum #n: (unsigned 32-bit integer)
|
|
<dd>This value is the maximum size of the dimension of the
|
|
data as stored in
|
|
the file. This value may be the special value
|
|
<UNLIMITED> which
|
|
indicates that the data may expand along this dimension
|
|
indefinitely.
|
|
</dl>
|
|
</dl>
|
|
<br />
|
|
<center>
|
|
<table border cellpadding="4" width="80%">
|
|
<caption align="bottom">
|
|
<b>HDF5 Dataspace Structured/Irregular Grid Information</b>
|
|
</caption>
|
|
|
|
<tr align="center">
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr align="center">
|
|
<td colspan="4"># of Grid Points in Dimension #1</td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4"># of Grid Points in Dimension #n</td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">Datatype of Grid Point Locations</td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">Location of Grid Points in Dimension #1</td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">Location of Grid Points in Dimension #n</td>
|
|
</tr>
|
|
</table>
|
|
</center>
|
|
|
|
<br />
|
|
<center>
|
|
<table border cellpadding="4" width="80%">
|
|
<caption align="bottom">
|
|
<b>HDF5 Dataspace Unstructured Grid Information</b>
|
|
</caption>
|
|
|
|
<tr align="center">
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr align="center">
|
|
<td colspan="4"># of Grid Points</td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">Datatype of Grid Point Locations</td>
|
|
</tr>
|
|
<tr align="center">
|
|
<td colspan="4">Grid Point Locations<br />.<br />.<br /></td>
|
|
</tr>
|
|
</table>
|
|
</center>
|
|
-->
|
|
|
|
<h4><a name="LinkInfoMessage">IV.A.2.c. The Link Info Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Link Info</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x002 </td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Varies </td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may not be
|
|
repeated. </td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td>The link info message tracks variable information about the
|
|
current state of the links for a “new style”
|
|
group’s behavior. Variable information will be stored in
|
|
this message and constant information will be stored in the
|
|
<a href="#GroupInfoMessage">Group Info</a> message.
|
|
</td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Link Info
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Flags</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Maximum Creation Index <em>(8 bytes, optional)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Fractal Heap Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address of v2 B-tree for Name Index<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address of v2 B-tree for Creation Order Index<sup>O</sup> <em>(optional)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Link Info
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>The version number for this message. This document describes
|
|
version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Flags</p></td>
|
|
<td><p>This field determines various optional aspects of the link
|
|
info message:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>If set, creation order for the links is tracked.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>If set, creation order for the links is indexed.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2-7</code></td>
|
|
<td>Reserved</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Maximum Creation Index</p></td>
|
|
<td><p>This 64-bit value is the maximum creation order index value
|
|
stored for a link in this group.</p>
|
|
<p>This field is present if bit 0 of <em>flags</em> is set.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Fractal Heap Address</p></td>
|
|
<td>
|
|
<p>
|
|
This is the address of the fractal heap to store dense links.
|
|
Each link stored in the fractal heap is stored as a
|
|
<a href="#LinkMessage">Link Message</a>.
|
|
</p>
|
|
<p>
|
|
If there are no links in the group, or the group’s links
|
|
are stored “compactly” (as object header messages), this
|
|
value will be the <a href="#UndefinedAddress">undefined
|
|
address</a>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address of v2 B-tree for Name Index</p></td>
|
|
<td><p>This is the address of the version 2 B-tree to index names of links.</p>
|
|
<p>If there are no links in the group, or the group’s links
|
|
are stored “compactly” (as object header messages), this
|
|
value will be the <a href="#UndefinedAddress">undefined
|
|
address</a>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address of v2 B-tree for Creation Order Index</p></td>
|
|
<td><p>This is the address of the version 2 B-tree to index creation order of links.</p>
|
|
<p>If there are no links in the group, or the group’s links
|
|
are stored “compactly” (as object header messages), this
|
|
value will be the <a href="#UndefinedAddress">undefined
|
|
address</a>.
|
|
</p>
|
|
<p>This field exists if bit 1 of <em>flags</em> is set.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<h4><a name="DatatypeMessage">IV.A.2.d. The Datatype Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Datatype</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x0003
|
|
</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Variable</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Required for dataset or committed
|
|
datatype (formerly named datatype) objects; may not be repeated.
|
|
</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td><p>The datatype message defines the datatype for each element
|
|
of a dataset or a common datatype for sharing between multiple
|
|
datasets. A datatype can describe an atomic type like a fixed-
|
|
or floating-point type or more complex types like a C struct
|
|
(compound datatype), array (array datatype), or C++ vector
|
|
(variable-length datatype).</p>
|
|
<p>Datatype messages that are part of a dataset object do not
|
|
describe how elements are related to one another; the dataspace
|
|
message is used for that purpose. Datatype messages that are part of
|
|
a committed datatype (formerly named datatype) message describe
|
|
a common datatype that can be shared by multiple datasets in the
|
|
file.</p>
|
|
</td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Datatype Message
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Class and Version</td>
|
|
<td>Class Bit Field, Bits 0-7</td>
|
|
<td>Class Bit Field, Bits 8-15</td>
|
|
<td>Class Bit Field, Bits 16-23</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br /><br />Properties<br /><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Datatype Message
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Class and Version</p></td>
|
|
<td>
|
|
<p>The version of the datatype message and the datatype’s class
|
|
information are packed together in this field. The version
|
|
number is packed in the top 4 bits of the field and the class
|
|
is contained in the bottom 4 bits.
|
|
</p>
|
|
<p>The version number information is used for changes in the
|
|
format of the datatype message and is described here:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Version</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Never used
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Used by early versions of the library to encode
|
|
compound datatypes with explicit array fields.
|
|
See the compound datatype description below for
|
|
further details.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>Used when an array datatype needs to be encoded.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>Used when a VAX byte-ordered type needs to be
|
|
encoded. Packs various other datatype classes more
|
|
efficiently also.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>4</code></td>
|
|
<td>Used to encode the revised reference datatype.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
<p>The class of the datatype determines the format for the class
|
|
bit field and properties portion of the datatype message, which
|
|
are described below. The
|
|
following classes are currently defined:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td><a href="#ClassFixedPoint">Fixed-Point</a></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td><a href="#ClassFloatingPoint">Floating-Point</a></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td> <a href="#ClassTime">Time</a></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td><a href="#ClassString">String</a></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>4</code></td>
|
|
<td><a href="#ClassBitField">Bit field</a></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>5</code></td>
|
|
<td><a href="#ClassOpaque">Opaque</a></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>6</code></td>
|
|
<td><a href="#ClassCompound">Compound</a></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>7</code></td>
|
|
<td><a href="#ClassReference">Reference</a></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>8</code></td>
|
|
<td><a href="#ClassEnum">Enumerated</a></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>9</code></td>
|
|
<td><a href="#ClassVarLen">Variable-Length</a></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>10</code></td>
|
|
<td><a href="#ClassArray">Array</a></td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Class Bit Fields</p></td>
|
|
<td>
|
|
<p>The information in these bit fields is specific to each datatype
|
|
class and is described below. All bits not defined for a
|
|
datatype class are set to zero.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size</p></td>
|
|
<td>
|
|
<p>The size of a datatype element in bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Properties</p></td>
|
|
<td>
|
|
<p>This variable-sized sequence of bytes encodes information
|
|
specific to each datatype class and is described for each class
|
|
below. If there is no property information specified for a
|
|
datatype class, the size of this field is zero bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<a name="ClassFixedPoint"></a>
|
|
<p>Class specific information for the Fixed-point Numbers class
|
|
(Class 0):</p>
|
|
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Bits: Fixed-point Bit Field Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="10%">Bits</th>
|
|
<th>Meaning</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>0</p></td>
|
|
<td><p><b>Byte Order.</b> If zero, byte order is little-endian;
|
|
otherwise, byte order is big endian.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>1, 2</p></td>
|
|
<td><p><b>Padding type.</b> Bit 1 is the lo_pad bit and bit 2
|
|
is the hi_pad bit. If a datum has unused bits at either
|
|
end, then the lo_pad or hi_pad bit is copied to those
|
|
locations.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>3</p></td>
|
|
<td><p><b>Signed.</b> If this bit is set then the fixed-point
|
|
number is in 2’s complement form.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>4-23</p></td>
|
|
<td><p>Reserved (zero).</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fixed-point Property Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Bit Offset</td>
|
|
<td colspan="2">Bit Precision</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fixed-point Property Description
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Bit Offset</p></td>
|
|
<td>
|
|
<p>The bit offset of the first significant bit of the fixed-point
|
|
value within the datatype. The bit offset specifies the number
|
|
of bits “to the right of” the value (which are set to the
|
|
lo_pad bit value).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Bit Precision</p></td>
|
|
<td>
|
|
<p>The number of bits of precision of the fixed-point value
|
|
within the datatype. This value, combined with the datatype
|
|
element’s size and the Bit Offset field specifies the number
|
|
of bits “to the left of” the value (which are set to the
|
|
hi_pad bit value).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<a name="ClassFloatingPoint"></a>
|
|
<p>Class specific information for the Floating-point Numbers class
|
|
(Class 1):</p>
|
|
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Bits: Floating-point Bit Field Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="10%">Bits</th>
|
|
<th>Meaning</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>0, 6</p></td>
|
|
<td><p><b>Byte Order.</b> These two non-contiguous bits specify the
|
|
“endianness” of the bytes in the datatype element.
|
|
<table class="list">
|
|
<tr>
|
|
<th width="10%" align="center">Bit 6</th>
|
|
<th width="10%" align="center">Bit 0</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Byte order is little-endian
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Byte order is big-endian
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Reserved
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Byte order is VAX-endian
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>1, 2, 3</p></td>
|
|
<td><p><b>Padding type.</b> Bit 1 is the low bits pad type, bit 2
|
|
is the high bits pad type, and bit 3 is the internal bits
|
|
pad type. If a datum has unused bits at either end or between
|
|
the sign bit, exponent, or mantissa, then the value of bit
|
|
1, 2, or 3 is copied to those locations.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>4-5</p></td>
|
|
<td><p><b>Mantissa Normalization.</b> This 2-bit bit field specifies
|
|
how the most significant bit of the mantissa is managed.
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>No normalization
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>The most significant bit of the mantissa is always set
|
|
(except for 0.0).
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>The most significant bit of the mantissa is not stored,
|
|
but is implied to be set.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>Reserved.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>7</p></td>
|
|
<td><p>Reserved (zero).</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>8-15</p></td>
|
|
<td><p><b>Sign Location.</b> This is the bit position of the sign
|
|
bit. Bits are numbered with the least significant bit zero.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>16-23</p></td>
|
|
<td><p>Reserved (zero).</p></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Floating-point Property Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Bit Offset</td>
|
|
<td colspan="2">Bit Precision</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Exponent Location</td>
|
|
<td>Exponent Size</td>
|
|
<td>Mantissa Location</td>
|
|
<td>Mantissa Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Exponent Bias</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Floating-point Property Description
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Bit Offset</p></td>
|
|
<td>
|
|
<p>The bit offset of the first significant bit of the floating-point
|
|
value within the datatype. The bit offset specifies the number
|
|
of bits “to the right of” the value.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Bit Precision</p></td>
|
|
<td>
|
|
<p>The number of bits of precision of the floating-point value
|
|
within the datatype.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Exponent Location</p></td>
|
|
<td>
|
|
<p>The bit position of the exponent field. Bits are numbered with
|
|
the least significant bit number zero.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Exponent Size</p></td>
|
|
<td>
|
|
<p>The size of the exponent field in bits.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Mantissa Location</p></td>
|
|
<td>
|
|
<p>The bit position of the mantissa field. Bits are numbered with
|
|
the least significant bit number zero.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Mantissa Size</p></td>
|
|
<td>
|
|
<p>The size of the mantissa field in bits.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Exponent Bias</p></td>
|
|
<td>
|
|
<p>The bias of the exponent field.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<a name="ClassTime"></a>
|
|
<p>Class specific information for the Time class (Class 2):</p>
|
|
|
|
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Bits: Time Bit Field Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="10%">Bits</th>
|
|
<th>Meaning</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>0</p></td>
|
|
<td><p><b>Byte Order.</b> If zero, byte order is little-endian;
|
|
otherwise, byte order is big endian.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>1-23</p></td>
|
|
<td><p>Reserved (zero).</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Time Property Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Bit Precision</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Time Property Description
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Bit Precision</p></td>
|
|
<td>
|
|
<p>The number of bits of precision of the time value.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<a name="ClassString"></a>
|
|
<p>Class specific information for the Strings class (Class 3):</p>
|
|
|
|
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Bits: String Bit Field Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="10%">Bits</th>
|
|
<th>Meaning</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>0-3</p></td>
|
|
<td><p><b>Padding type.</b> This four-bit value determines the
|
|
type of padding to use for the string. The values are:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Null Terminate: A zero byte marks the end of the
|
|
string and is guaranteed to be present after
|
|
converting a long string to a short string. When
|
|
converting a short string to a long string the value is
|
|
padded with additional null characters as necessary.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Null Pad: Null characters are added to the end of
|
|
the value during conversions from short values to long
|
|
values but conversion in the opposite direction simply
|
|
truncates the value.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>Space Pad: Space characters are added to the end of
|
|
the value during conversions from short values to long
|
|
values but conversion in the opposite direction simply
|
|
truncates the value. This is the Fortran
|
|
representation of the string.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>3-15</code></td>
|
|
<td>Reserved
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>4-7</p></td>
|
|
<td><p><b>Character Set.</b> The character set used to
|
|
encode the string.
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>ASCII character set encoding
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>UTF-8 character set encoding
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2-15</code></td>
|
|
<td>Reserved
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>8-23</p></td>
|
|
<td><p>Reserved (zero).</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<p>There are no properties defined for the string class.
|
|
</p>
|
|
|
|
<br />
|
|
<br />
|
|
<a name="ClassBitField"></a>
|
|
<p>Class specific information for the Bit Fields class (Class 4):</p>
|
|
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Bits: Bitfield Bit Field Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="10%">Bits</th>
|
|
<th>Meaning</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>0</p></td>
|
|
<td><p><b>Byte Order.</b> If zero, byte order is little-endian;
|
|
otherwise, byte order is big endian.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>1, 2</p></td>
|
|
<td><p><b>Padding type.</b> Bit 1 is the lo_pad type and bit 2
|
|
is the hi_pad type. If a datum has unused bits at either
|
|
end, then the lo_pad or hi_pad bit is copied to those
|
|
locations.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>3-23</p></td>
|
|
<td><p>Reserved (zero).</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Bit Field Property Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Bit Offset</td>
|
|
<td colspan="2">Bit Precision</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Bit Field Property Description
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Bit Offset</p></td>
|
|
<td>
|
|
<p>The bit offset of the first significant bit of the bit field
|
|
within the datatype. The bit offset specifies the number
|
|
of bits “to the right of” the value.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Bit Precision</p></td>
|
|
<td>
|
|
<p>The number of bits of precision of the bit field
|
|
within the datatype.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<a name="ClassOpaque"></a>
|
|
<p>Class specific information for the Opaque class (Class 5):</p>
|
|
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Bits: Opaque Bit Field Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="10%">Bits</th>
|
|
<th>Meaning</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>0-7</p></td>
|
|
<td><p>Length of ASCII tag in bytes.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>8-23</p></td>
|
|
<td><p>Reserved (zero).</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Opaque Property Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />ASCII Tag<br />
|
|
<br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Opaque Property Description
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>ASCII Tag</p></td>
|
|
<td>
|
|
<p>This NUL-terminated string provides a description for the
|
|
opaque type. It is NUL-padded to a multiple of 8 bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<a name="ClassCompound"></a>
|
|
<p>Class specific information for the Compound class (Class 6):</p>
|
|
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Bits: Compound Bit Field Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="10%">Bits</th>
|
|
<th>Meaning</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>0-15</p></td>
|
|
<td><p><b>Number of Members.</b> This field contains the number
|
|
of members defined for the compound datatype. The member
|
|
definitions are listed in the Properties field of the data
|
|
type message.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>16-23</p></td>
|
|
<td><p>Reserved (zero).</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<p>The Properties field of a compound datatype is a list of the
|
|
member definitions of the compound datatype. The member
|
|
definitions appear one after another with no intervening bytes.
|
|
The member types are described with a (recursively) encoded datatype
|
|
message.</p>
|
|
|
|
<p>Note that the property descriptions are different for different
|
|
versions of the datatype version. Additionally note that the version
|
|
0 datatype encoding is deprecated and has been replaced with later
|
|
encodings in versions of the HDF5 Library from the 1.4 release
|
|
onward.</p>
|
|
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Compound Properties Description for Datatype Version 1
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Name<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Byte Offset of Member</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Dimensionality</td>
|
|
<td colspan="3">Reserved (zero)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dimension Permutation</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Reserved (zero)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dimension #1 Size (required)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dimension #2 Size (required)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dimension #3 Size (required)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dimension #4 Size (required)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Member Type Message<br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Compound Properties Description for Datatype Version 1
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Name</p></td>
|
|
<td>
|
|
<p>This NUL-terminated string provides a description for the
|
|
opaque type. It is NUL-padded to a multiple of 8 bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Byte Offset of Member</p></td>
|
|
<td>
|
|
<p>This is the byte offset of the member within the datatype.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimensionality</p></td>
|
|
<td>
|
|
<p>If set to zero, this field indicates a scalar member. If set
|
|
to a value greater than zero, this field indicates that the
|
|
member is an array of values. For array members, the size of
|
|
the array is indicated by the ‘Size of Dimension n’ field in
|
|
this message.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimension Permutation</p></td>
|
|
<td>
|
|
<p>This field was intended to allow an array field to have
|
|
its dimensions permuted, but this was never implemented.
|
|
This field should always be set to zero.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimension #n Size</p></td>
|
|
<td>
|
|
<p>This field is the size of a dimension of the array field as
|
|
stored in the file. The first dimension stored in the list of
|
|
dimensions is the slowest changing dimension and the last
|
|
dimension stored is the fastest changing dimension.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Member Type Message</p></td>
|
|
<td>
|
|
<p>This field is a datatype message describing the datatype of
|
|
the member.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Compound Properties Description for Datatype Version 2
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Name<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Byte Offset of Member</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Member Type Message<br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Compound Properties Description for Datatype Version 2
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Name</p></td>
|
|
<td>
|
|
<p>This NUL-terminated string provides a description for the
|
|
opaque type. It is NUL-padded to a multiple of 8 bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Byte Offset of Member</p></td>
|
|
<td>
|
|
<p>This is the byte offset of the member within the datatype.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Member Type Message</p></td>
|
|
<td>
|
|
<p>This field is a datatype message describing the datatype of
|
|
the member.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Compound Properties Description for Datatype Version 3
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Name<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Byte Offset of Member <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Member Type Message<br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Compound Properties Description for Datatype Version 3
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Name</p></td>
|
|
<td><p>This NUL-terminated string provides a description for the
|
|
opaque type. It is <em>not</em> NUL-padded to a multiple of 8
|
|
bytes.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Byte Offset of Member</p></td>
|
|
<td><p>This is the byte offset of the member within the datatype.
|
|
The field size is the minimum number of bytes necessary,
|
|
based on the size of the datatype element. For example, a
|
|
datatype element size of less than 256 bytes uses a 1 byte
|
|
length, a datatype element size of 256-65535 bytes uses a
|
|
2 byte length, and so on.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Member Type Message</p></td>
|
|
<td><p>This field is a datatype message describing the datatype of
|
|
the member.</p></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<a name="ClassReference"></a>
|
|
<p>Class specific information for the Reference class (Class 7):</p>
|
|
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Bits: Reference Bit Field Description for Datatype Version < 4
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="10%">Bits</th>
|
|
<th>Meaning</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>0-3</p></td>
|
|
<td><p><b>Type.</b> This four-bit value contains the reference types which are supported for
|
|
backward compatibility. The values defined are:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Object Reference (H5R_OBJECT1): A reference to another object in this
|
|
HDF5 file.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Dataset Region Reference (H5R_DATASET_REGION1): A reference to a region within
|
|
a dataset in this HDF5 file.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2-15</code></td>
|
|
<td>Reserved
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>4-23</p></td>
|
|
<td><p>Reserved (zero).</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Bits: Reference Bit Field Description for Datatype Version 4
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="10%">Bits</th>
|
|
<th>Meaning</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>0-3</p></td>
|
|
<td><p><b>Type.</b> This four-bit value contains the revised reference types.
|
|
The values defined are:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>Object Reference (H5R_OBJECT2): A reference to another object
|
|
in this file or an external file.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>Dataset Region Reference (H5R_DATASET_REGION2): A reference to a region within
|
|
a dataset in this file or an external file.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>4</code></td>
|
|
<td>Attribute Reference (H5R_ATTR): A reference to an attribute attached to an
|
|
object in this file or an external file.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>5-15</code></td>
|
|
<td>Reserved
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>4-7</p></td>
|
|
<td><p><b>Version.</b> This four-bit value contains the version for encoding
|
|
the revised reference types. The values defined are:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Unused
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>The version for encoding the revised reference types: Object Reference (2),
|
|
Dataset Region Reference (3) and Attribute Reference (4).
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2-15</code></td>
|
|
<td>Reserved
|
|
</td>
|
|
</tr>
|
|
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>8-23</p></td>
|
|
<td><p>Reserved (zero).</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<p>There are no properties defined for the reference class.
|
|
</p>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<a name="ClassEnum"></a>
|
|
<p>Class specific information for the Enumeration class (Class 8):</p>
|
|
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Bits: Enumeration Bit Field Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="10%">Bits</th>
|
|
<th>Meaning</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>0-15</p></td>
|
|
<td><p><b>Number of Members.</b> The number of name/value
|
|
pairs defined for the enumeration type.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>16-23</p></td>
|
|
<td><p>Reserved (zero).</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Enumeration Property Description for Datatype Versions
|
|
1 and 2
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Base Type<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Names<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Values<br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Enumeration Property Description for Datatype Versions
|
|
1 and 2
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Base Type</p></td>
|
|
<td>
|
|
<p>Each enumeration type is based on some parent type, usually an
|
|
integer. The information for that parent type is described
|
|
recursively by this field.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Names</p></td>
|
|
<td>
|
|
<p>The name for each name/value pair. Each name is stored as a null
|
|
terminated ASCII string in a multiple of eight bytes. The names
|
|
are in no particular order.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Values</p></td>
|
|
<td>
|
|
<p>The list of values in the same order as the names. The values
|
|
are packed (no inter-value padding) and the size of each value
|
|
is determined by the parent type.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Enumeration Property Description for Datatype Version 3
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Base Type<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Names<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Values<br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Enumeration Property Description for Datatype Version 3
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Base Type</p></td>
|
|
<td>
|
|
<p>Each enumeration type is based on some parent type, usually an
|
|
integer. The information for that parent type is described
|
|
recursively by this field.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Names</p></td>
|
|
<td>
|
|
<p>The name for each name/value pair. Each name is stored as a null
|
|
terminated ASCII string, <em>not</em> padded to a multiple of
|
|
eight bytes. The names are in no particular order.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Values</p></td>
|
|
<td>
|
|
<p>The list of values in the same order as the names. The values
|
|
are packed (no inter-value padding) and the size of each value
|
|
is determined by the parent type.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
|
|
|
|
<br />
|
|
<a name="ClassVarLen"></a>
|
|
<p>Class specific information for the Variable-length class (Class 9):</p>
|
|
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Bits: Variable-length Bit Field Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="10%">Bits</th>
|
|
<th>Meaning</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>0-3</p></td>
|
|
<td><p><b>Type.</b> This four-bit value contains the type of
|
|
variable-length datatype described. The values defined are:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Sequence: A variable-length sequence of any datatype.
|
|
Variable-length sequences do not have padding or
|
|
character set information.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>String: A variable-length sequence of characters.
|
|
Variable-length strings have padding and character set
|
|
information.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2-15</code></td>
|
|
<td>Reserved
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>4-7</p></td>
|
|
<td><p><b>Padding type.</b> (variable-length string only)
|
|
This four-bit value determines the type of padding
|
|
used for variable-length strings. The values are the same
|
|
as for the string padding type, as follows:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Null terminate: A zero byte marks the end of a string
|
|
and is guaranteed to be present after converting a long
|
|
string to a short string. When converting a short string
|
|
to a long string, the value is padded with additional null
|
|
characters as necessary.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Null pad: Null characters are added to the end of the
|
|
value during conversion from a short string to a longer
|
|
string. Conversion from a long string to a shorter string
|
|
simply truncates the value.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>Space pad: Space characters are added to the end of the
|
|
value during conversion from a short string to a longer
|
|
string. Conversion from a long string to a shorter string
|
|
simply truncates the value. This is the Fortran
|
|
representation of the string.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>3-15</code></td>
|
|
<td>Reserved
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
<p>This value is set to zero for variable-length sequences.</p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>8-11</p></td>
|
|
<td><p><b>Character Set.</b> (variable-length string only)
|
|
This four-bit value specifies the character set
|
|
to be used for encoding the string:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>ASCII character set encoding
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>UTF-8 character set encoding
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2-15</code></td>
|
|
<td>Reserved
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
<p>This value is set to zero for variable-length sequences.</p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>12-23</p></td>
|
|
<td><p>Reserved (zero).</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Variable-length Property Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Base Type<br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Variable-length Property Description
|
|
</caption>
|
|
<tr>
|
|
<th width="10%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Base Type</p></td>
|
|
<td>
|
|
<p>Each variable-length type is based on some parent type. The
|
|
information for that parent type is described recursively by
|
|
this field.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<a name="ClassArray"></a>
|
|
<p>Class specific information for the Array class (Class 10):</p>
|
|
|
|
<p>There are no bit fields defined for the array class.
|
|
</p>
|
|
|
|
<p>Note that the dimension information defined in the property for this
|
|
datatype class is independent of dataspace information for a dataset.
|
|
The dimension information here describes the dimensionality of the
|
|
information within a data element (or a component of an element, if the
|
|
array datatype is nested within another datatype) and the dataspace for a
|
|
dataset describes the size and locations of the elements in a dataset.
|
|
</p>
|
|
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Array Property Description for Datatype Version 2
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Dimensionality</td>
|
|
<td colspan="3">Reserved (zero)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dimension #1 Size</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Dimension #n Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Permutation Index #1</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Permutation Index #n</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Base Type<br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Array Property Description for Datatype Version 2
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimensionality</p></td>
|
|
<td>
|
|
<p>This value is the number of dimensions that the array has.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimension #n Size</p></td>
|
|
<td>
|
|
<p>This value is the size of the dimension of the array
|
|
as stored in the file. The first dimension stored in
|
|
the list of dimensions is the slowest changing dimension
|
|
and the last dimension stored is the fastest changing
|
|
dimension.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Permutation Index #n</p></td>
|
|
<td>
|
|
<p>This value is the index permutation used to map
|
|
each dimension from the canonical representation to an
|
|
alternate axis for each dimension. Currently, dimension
|
|
permutations are not supported, and these indices should
|
|
be set to the index position minus one. In other words,
|
|
the first dimension should be set to 0, the second dimension
|
|
should be set to 1, and so on.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Base Type</p></td>
|
|
<td>
|
|
<p>Each array type is based on some parent type. The
|
|
information for that parent type is described recursively by
|
|
this field.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Array Property Description for Datatype Version 3
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
<th width="25%">Byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Dimensionality</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dimension #1 Size</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Dimension #n Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Base Type<br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Array Property Description for Datatype Version 3
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimensionality</p></td>
|
|
<td>
|
|
<p>This value is the number of dimensions that the array has.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimension #n Size</p></td>
|
|
<td>
|
|
<p>This value is the size of the dimension of the array
|
|
as stored in the file. The first dimension stored in
|
|
the list of dimensions is the slowest changing dimension
|
|
and the last dimension stored is the fastest changing
|
|
dimension.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Base Type</p></td>
|
|
<td>
|
|
<p>Each array type is based on some parent type. The
|
|
information for that parent type is described recursively by
|
|
this field.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
|
|
|
|
<h4><a name="OldFillValueMessage">IV.A.2.e. The Data Storage -
|
|
Fill Value (Old) Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Fill Value
|
|
(old)</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x0004</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Varies</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may not be
|
|
repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td><p>The fill value message stores a single data value which
|
|
is returned to the application when an uninitialized data element
|
|
is read from a dataset. The fill value is interpreted with the
|
|
same datatype as the dataset. If no fill value message is present
|
|
then a fill value of all zero bytes is assumed.</p>
|
|
<p>This fill value message is deprecated in favor of the
|
|
“new” fill value message (Message Type 0x0005) and
|
|
is only written to the file for forward compatibility with
|
|
versions of the HDF5 Library before the 1.6.0 version.
|
|
Additionally, it only appears for datasets with a user-defined
|
|
fill value (as opposed to the library default fill value or an
|
|
explicitly set “undefined” fill value).</p>
|
|
</td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fill Value Message (Old)
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Fill Value <em>(optional, variable size)</em><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fill Value Message (Old)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size</p></td>
|
|
<td>
|
|
<p>This is the size of the Fill Value field in bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Fill Value</p></td>
|
|
<td>
|
|
<p>The fill value. The bytes of the fill value are interpreted
|
|
using the same datatype as for the dataset.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<h4><a name="FillValueMessage">IV.A.2.f. The Data Storage -
|
|
Fill Value Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Fill
|
|
Value</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x0005</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Varies</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Required for dataset objects;
|
|
may not be repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td>The fill value message stores a single data value which is
|
|
returned to the application when an uninitialized data element
|
|
is read from a dataset. The fill value is interpreted with the
|
|
same datatype as the dataset.</td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fill Value Message - Versions 1 and 2
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Space Allocation Time</td>
|
|
<td>Fill Value Write Time</td>
|
|
<td>Fill Value Defined</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Size <em>(optional)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Fill Value <em>(optional, variable size)</em><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fill Value Message - Versions 1 and 2
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>The version number information is used for changes in the
|
|
format of the fill value message and is described here:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Version</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Never used
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Initial version of this message.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>In this version, the Size and Fill Value fields are
|
|
only present if the Fill Value Defined field is set
|
|
to 1.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>This version packs the other fields in the message
|
|
more efficiently than version 2.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Space Allocation Time</p></td>
|
|
<td>
|
|
<p>When the storage space for the dataset’s raw data will be
|
|
allocated. The allowed values are:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Not used.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Early allocation. Storage space for the entire dataset
|
|
should be allocated in the file when the dataset is
|
|
created.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>Late allocation. Storage space for the entire dataset
|
|
should not be allocated until the dataset is written
|
|
to.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>Incremental allocation. Storage space for the
|
|
dataset should not be allocated until the portion
|
|
of the dataset is written to. This is currently
|
|
used in conjunction with chunked data storage for
|
|
datasets.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Fill Value Write Time</p></td>
|
|
<td>
|
|
<p>At the time that storage space for the dataset’s raw data is
|
|
allocated, this value indicates whether the fill value should
|
|
be written to the raw data storage elements. The allowed values
|
|
are:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>On allocation. The fill value is always written to
|
|
the raw data storage when the storage space is allocated.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Never. The fill value should never be written to
|
|
the raw data storage.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>Fill value written if set by user. The fill value
|
|
will be written to the raw data storage when the storage
|
|
space is allocated only if the user explicitly set
|
|
the fill value. If the fill value is the library
|
|
default or is undefined, it will not be written to
|
|
the raw data storage.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Fill Value Defined</p></td>
|
|
<td>
|
|
<p>This value indicates if a fill value is defined for this
|
|
dataset. If this value is 0, the fill value is undefined.
|
|
If this value is 1, a fill value is defined for this dataset.
|
|
For version 2 or later of the fill value message, this value
|
|
controls the presence of the Size and Fill Value fields.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size</p></td>
|
|
<td>
|
|
<p>This is the size of the Fill Value field in bytes. This field
|
|
is not present if the Version field is greater than 1,
|
|
and the Fill Value Defined field is set to 0.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Fill Value</p></td>
|
|
<td>
|
|
<p>The fill value. The bytes of the fill value are interpreted
|
|
using the same datatype as for the dataset. This field is
|
|
not present if the Version field is greater than 1,
|
|
and the Fill Value Defined field is set to 0.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fill Value Message - Version 3
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Flags</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Size <em>(optional)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Fill Value <em>(optional, variable size)</em><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fill Value Message - Version 3
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>The version number information is used for changes in the
|
|
format of the fill value message and is described here:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Version</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Never used
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Initial version of this message.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>In this version, the Size and Fill Value fields are
|
|
only present if the Fill Value Defined field is set
|
|
to 1.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>This version packs the other fields in the message
|
|
more efficiently than version 2.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Flags</p></td>
|
|
<td>
|
|
<p>When the storage space for the dataset’s raw data will be
|
|
allocated. The allowed values are:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bits</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0-1</code></td>
|
|
<td>Space Allocation Time, with the same
|
|
values as versions 1 and 2 of the message.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2-3</code></td>
|
|
<td>Fill Value Write Time, with the same
|
|
values as versions 1 and 2 of the message.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>4</code></td>
|
|
<td>Fill Value Undefined, indicating that the fill
|
|
value has been marked as “undefined” for this dataset.
|
|
Bits 4 and 5 cannot both be set.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>5</code></td>
|
|
<td>Fill Value Defined, with the same values as
|
|
versions 1 and 2 of the message.
|
|
Bits 4 and 5 cannot both be set.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>6-7</code></td>
|
|
<td>Reserved (zero).
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size</p></td>
|
|
<td>
|
|
<p>This is the size of the Fill Value field in bytes. This field
|
|
is not present if the Version field is greater than 1,
|
|
and the Fill Value Defined flag is set to 0.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Fill Value</p></td>
|
|
<td>
|
|
<p>The fill value. The bytes of the fill value are interpreted
|
|
using the same datatype as for the dataset. This field is
|
|
not present if the Version field is greater than 1,
|
|
and the Fill Value Defined flag is set to 0.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<h4><a name="LinkMessage">IV.A.2.g. The Link Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Link</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x0006</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Varies </td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may be
|
|
repeated. </td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td><p>This message encodes the information for a link in a
|
|
group’s object header, when the group is storing its links
|
|
“compactly”, or in the group’s fractal heap,
|
|
when the group is storing its links “densely”.</p>
|
|
<p>A group is storing its links compactly when the fractal heap
|
|
address in the <em><a href="#LinkInfoMessage">Link Info
|
|
Message</a></em> is set to the “undefined address”
|
|
value.</p></td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Link Message
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Flags</td>
|
|
<td>Link type <em>(optional)</em></td>
|
|
<td bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Creation Order <em>(8 bytes, optional)</em><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td>Link Name Character Set <em>(optional)</em></td>
|
|
<td>Length of Link Name (variable size)</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Link Name (variable size)</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Link Information (variable size)<br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Link Message
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number for this message. This document describes version 1.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Flags</p></td>
|
|
<td><p>This field contains information about the link and controls
|
|
the presence of other fields below.
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bits</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0-1</code></td>
|
|
<td>Determines the size of the <em>Length of Link Name</em>
|
|
field.
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>The size of the <em>Length of Link Name</em>
|
|
field is 1 byte.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>The size of the <em>Length of Link Name</em>
|
|
field is 2 bytes.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>The size of the <em>Length of Link Name</em>
|
|
field is 4 bytes.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>The size of the <em>Length of Link Name</em>
|
|
field is 8 bytes.
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>Creation Order Field Present: if set, the <em>Creation
|
|
Order</em> field is present. If not set, creation order
|
|
information is not stored for links in this group.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>Link Type Field Present: if set, the link is not
|
|
a hard link and the <em>Link Type</em> field is present.
|
|
If not set, the link is a hard link.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>4</code></td>
|
|
<td>Link Name Character Set Field Present: if set, the
|
|
link name is not represented with the ASCII character
|
|
set and the <em>Link Name Character Set</em> field is
|
|
present. If not set, the link name is represented with
|
|
the ASCII character set.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>5-7</code></td>
|
|
<td>Reserved (zero).
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Link type</p></td>
|
|
<td><p>This is the link class type and can be one of the following
|
|
values:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>A hard link (should never be stored in the file)
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>A soft link.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2-63</code></td>
|
|
<td>Reserved for future HDF5 internal use.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>64</code></td>
|
|
<td>An external link.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>65-255</code></td>
|
|
<td>Reserved, but available for user-defined link types.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
<p>This field is present if bit 3 of <em>Flags</em> is set.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Creation Order</p></td>
|
|
<td><p>This 64-bit value is an index of the link’s creation time within
|
|
the group. Values start at 0 when the group is created an increment
|
|
by one for each link added to the group. Removing a link from a
|
|
group does not change existing links’ creation order field.
|
|
</p>
|
|
<p>This field is present if bit 2 of <em>Flags</em> is set.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Link Name Character Set</p></td>
|
|
<td><p>This is the character set for encoding the link’s name:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>ASCII character set encoding (this should never be stored
|
|
in the file)
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>UTF-8 character set encoding
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
<p>This field is present if bit 4 of <em>Flags</em> is set.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Length of link name</p></td>
|
|
<td><p>This is the length of the link’s name. The size of this field
|
|
depends on bits 0 and 1 of <em>Flags</em>.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Link name</p></td>
|
|
<td><p>This is the name of the link, non-NULL terminated.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Link information</p></td>
|
|
<td><p>The format of this field depends on the <em>link type</em>.</p>
|
|
<p>For <b>hard</b> links, the field is formatted as follows:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<td width="20%"><i><a href="#SizeOfOffsetsV0">
|
|
Size of Offsets</a></i> bytes:</td>
|
|
<td width="80%">The address of the object header for the object that the
|
|
link points to.
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
|
|
<p>
|
|
For <b>soft</b> links, the field is formatted as follows:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<td width="20%">Bytes 1-2:</td>
|
|
<td width="80%">Length of soft link value.</td>
|
|
</tr>
|
|
<tr>
|
|
<td><em>Length of soft link value</em> bytes:</td>
|
|
<td>A non-NULL-terminated string storing the value of the
|
|
soft link.
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
|
|
<p>
|
|
For <b>external</b> links, the field is formatted as follows:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<td width="20%">Bytes 1-2:</td>
|
|
<td width="80%">Length of external link value.</td>
|
|
</tr>
|
|
<tr>
|
|
<td><em>Length of external link value</em> bytes:</td>
|
|
<td>The first byte contains the version number in the
|
|
upper 4 bits and flags in the lower 4 bits for the external
|
|
link. Both version and flags are defined to be zero in
|
|
this document. The remaining bytes consist of two
|
|
NULL-terminated strings, with no padding between them.
|
|
The first string is the name of the HDF5 file containing
|
|
the object linked to and the second string is the full path
|
|
to the object linked to, within the HDF5 file’s
|
|
group hierarchy.
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
|
|
<p>
|
|
For <b>user-defined</b> links, the field is formatted as follows:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<td width="20%">Bytes 1-2:</td>
|
|
<td width="80%">Length of user-defined data.</td>
|
|
</tr>
|
|
<tr>
|
|
<td><em>Length of user-defined link value</em> bytes:</td>
|
|
<td>The data supplied for the user-defined link type.</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h4><a name="ExternalFileListMessage">IV.A.2.h. The Data Storage -
|
|
External Data Files Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> External
|
|
Data Files</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x0007</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Varies</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may not be
|
|
repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td>The external data storage message indicates that the data
|
|
for an object is stored outside the HDF5 file. The filename of
|
|
the object is stored as a Universal Resource Location (URL) of
|
|
the actual filename containing the data. An external file list
|
|
record also contains the byte offset of the start of the data
|
|
within the file and the amount of space reserved in the file
|
|
for that data.</td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: External File List Message
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td colspan="3">Reserved (zero)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Allocated Slots</td>
|
|
<td colspan="2">Used Slots</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Heap Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Slot Definitions...<br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: External File List Message
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>The version number information is used for changes in the format of
|
|
External Data Storage Message and is described here:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Version</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Never used.</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>The current version used by the library.</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Allocated Slots</p></td>
|
|
<td>
|
|
<p>The total number of slots allocated in the message. Its value must be at least as
|
|
large as the value contained in the Used Slots field. (The current library simply
|
|
uses the number of Used Slots for this message)</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Used Slots</p></td>
|
|
<td>
|
|
<p>The number of initial slots which contains valid information.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Heap Address</p></td>
|
|
<td>
|
|
<p>This is the address of a local heap which contains the names for the external
|
|
files (The local heap information can be found in Disk Format Level 1D in this
|
|
document). The name at offset zero in the heap is always the empty string.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Slot Definitions</p></td>
|
|
<td>
|
|
<p>The slot definitions are stored in order according to the array addresses they
|
|
represent.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: External File List Slot
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Name Offset in Local Heap<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Offset in External Data File<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Data Size in External File<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: External File List Slot
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Name Offset in Local Heap</p></td>
|
|
<td>
|
|
<p>The byte offset within the local name heap for the name
|
|
of the file. File names are stored as a URL which has a
|
|
protocol name, a host name, a port number, and a file
|
|
name:
|
|
<code><em>protocol</em>:<em>port</em>//<em>host</em>/<em>file</em></code>.
|
|
If the protocol is omitted then “file:” is assumed. If
|
|
the port number is omitted then a default port for that
|
|
protocol is used. If both the protocol and the port
|
|
number are omitted then the colon can also be omitted. If
|
|
the double slash and host name are omitted then
|
|
“localhost” is assumed. The file name is the only
|
|
mandatory part, and if the leading slash is missing then
|
|
it is relative to the application’s current working
|
|
directory (the use of relative names is not
|
|
recommended).
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Offset in External Data File</p></td>
|
|
<td>
|
|
<p>This is the byte offset to the start of the data in the
|
|
specified file. For files that contain data for a single
|
|
dataset this will usually be zero.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Data Size in External File</p></td>
|
|
<td>
|
|
<p>This is the total number of bytes reserved in the
|
|
specified file for raw data storage. For a file that
|
|
contains exactly one complete dataset which is not
|
|
extendable, the size will usually be the exact size of the
|
|
dataset. However, by making the size larger one allows
|
|
HDF5 to extend the dataset. The size can be set to a value
|
|
larger than the entire file since HDF5 will read zeroes
|
|
past the end of the file without failing.</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<h4><a name="LayoutMessage">IV.A.2.i. The Data Layout Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Data Layout</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x0008</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Varies</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Required for datasets; may not
|
|
be repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td>The Data Layout message
|
|
describes how the elements of a multi-dimensional array are stored
|
|
in the HDF5 file. Four types of data layout are supported:
|
|
<ol>
|
|
<li>Contiguous: The array is stored in one contiguous area of
|
|
the file. This layout requires that the size of the array be
|
|
constant: data manipulations such as chunking, compression,
|
|
checksums, or encryption are not permitted. The message stores
|
|
the total storage size of the array. The offset of an element
|
|
from the beginning of the storage area is computed as in a C
|
|
array.</li>
|
|
<li>Chunked: The array domain is regularly decomposed into
|
|
chunks, and each chunk is allocated and stored separately. This
|
|
layout supports arbitrary element traversals, compression,
|
|
encryption, and checksums (these features are described
|
|
in other messages). The message stores the size of a chunk
|
|
instead of the size of the entire array; the storage size of
|
|
the entire array can be calculated by traversing the chunk index
|
|
that stores the chunk addresses.</li>
|
|
<li>Compact: The array is stored in one contiguous block as
|
|
part of this object header message.</li>
|
|
<li>Virtual: This is only supported for version 4 of the Data
|
|
Layout message. The message stores information that is used to
|
|
locate the global heap collection containing the Virtual Dataset
|
|
(VDS) mapping information. The mapping associates the VDS to
|
|
the source dataset elements that are stored across a collection
|
|
of HDF5 files.</li>
|
|
</ol></td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Data Layout Message (Versions 1 and 2)
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Dimensionality</td>
|
|
<td>Layout Class</td>
|
|
<td>Reserved <em>(zero)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Reserved <em>(zero)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Data Address<sup>O</sup> <em>(optional)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dimension 1 Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dimension 2 Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">...</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dimension #n Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dataset Element Size <em>(optional)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Compact Data Size <em>(optional)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Compact Data... <em>(variable size, optional)</em><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Data Layout Message (Versions 1 and 2)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>The version number information is used for changes in the format of the data
|
|
layout message and is described here:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Version</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Never used.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Used by version 1.4 and before of the library to encode layout information.
|
|
Data space is always allocated when the data set is created.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>Used by version 1.6.[0,1,2] of the library to encode layout information.
|
|
Data space is allocated only when it is necessary.</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimensionality</p></td>
|
|
<td><p>An array has a fixed dimensionality. This field
|
|
specifies the number of dimension size fields later in the
|
|
message. The value stored for chunked storage is 1 greater than
|
|
the number of dimensions in the dataset’s dataspace.
|
|
For example, 2 is stored for a 1 dimensional dataset.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Layout Class</p></td>
|
|
<td><p>The layout class specifies the type of storage for the data
|
|
and how the other fields of the layout message are to be
|
|
interpreted.
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Compact Storage
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Contiguous Storage
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>Chunked Storage
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Data Address</p></td>
|
|
<td><p>For contiguous storage, this is the address of the raw
|
|
data in the file. For chunked storage this is the address
|
|
of the <a href="#V1Btrees">v1 B-tree</a> that is used to look up the addresses of the
|
|
chunks. This field is not present for compact storage.
|
|
If the version for this message is greater than 1, the address
|
|
may have the “undefined address” value, to indicate that
|
|
storage has not yet been allocated for this array.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimension #n Size</p></td>
|
|
<td><p>For contiguous and compact storage the dimensions define
|
|
the entire size of the array while for chunked storage they define
|
|
the size of a single chunk. In all cases, they are in units of
|
|
array elements (not bytes). The first dimension stored in the list
|
|
of dimensions is the slowest changing dimension and the last
|
|
dimension stored is the fastest changing dimension.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dataset Element Size</p></td>
|
|
<td><p>The size of a dataset element, in bytes. This field is only
|
|
present for chunked storage.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Compact Data Size</p></td>
|
|
<td><p>This field is only present for compact data storage.
|
|
It contains the size of the raw data for the dataset array, in
|
|
bytes.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Compact Data</p></td>
|
|
<td><p>This field is only present for compact data storage.
|
|
It contains the raw data for the dataset array.</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<p>Version 3 of this message re-structured the format into specific
|
|
properties that are required for each layout class.</p>
|
|
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Data Layout Message (Version 3)
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Layout Class</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Properties <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Data Layout Message (Version 3)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>The version number information is used for changes in the format of layout message
|
|
and is described here:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Version</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>Used by the version 1.6.3 and later of the library to store properties
|
|
for each layout class.</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Layout Class</p></td>
|
|
<td><p>The layout class specifies the type of storage for the data
|
|
and how the other fields of the layout message are to be
|
|
interpreted.
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Compact Storage
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Contiguous Storage
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>Chunked Storage
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Properties</p></td>
|
|
<td><p>This variable-sized field encodes information specific to each
|
|
layout class and is described below. If there is no property
|
|
information specified for a layout class, the size of this field
|
|
is zero bytes.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<a name="CompactStorage"></a>
|
|
<p>Class-specific information for compact storage (layout class 0): (Note: The dimensionality information
|
|
is in the Dataspace message)</p>
|
|
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Compact Storage Property Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Size</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Raw Data... <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Compact Storage Property Description
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size</p></td>
|
|
<td><p>This field contains the size of the raw data for the dataset
|
|
array, in bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Raw Data</p></td>
|
|
<td><p>This field contains the raw data for the dataset array.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<a name="ContiguousStorage"></a>
|
|
<p>Class-specific information for contiguous storage (layout class 1):
|
|
(Note: The dimensionality information is in the Dataspace message)</p>
|
|
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Contiguous Storage Property Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Size<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Contiguous Storage Property Description
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address</p></td>
|
|
<td><p>This is the address of the raw data in the file.
|
|
The address may have the “undefined address” value, to indicate
|
|
that storage has not yet been allocated for this array.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size</p></td>
|
|
<td><p>This field contains the size allocated to store the raw data,
|
|
in bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<p>Class-specific information for chunked storage (layout class 2):</p>
|
|
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Chunked Storage Property Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Dimensionality</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dimension 0 Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dimension 1 Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">...</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dimension #n Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dataset Element Size</td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Chunked Storage Property Description
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimensionality</p></td>
|
|
<td><p>A chunk has a fixed dimensionality. This field specifies
|
|
the number of dimension size fields later in the message.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address</p></td>
|
|
<td><p>This is the address of the <a href="#V1Btrees">v1 B-tree</a>
|
|
that is used to look up the
|
|
addresses of the chunks that actually store portions of the array
|
|
data. The address may have the “undefined address” value, to
|
|
indicate that storage has not yet been allocated for this array.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimension #n Size</p></td>
|
|
<td><p>These values define the dimension size of a single chunk, in
|
|
units of array elements (not bytes). The first dimension stored in
|
|
the list of dimensions is the slowest changing dimension and the
|
|
last dimension stored is the fastest changing dimension.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dataset Element Size</p></td>
|
|
<td><p>The size of a dataset element, in bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
|
|
<p><a name="DataLayoutV4">
|
|
Version 4</a> of this message is similar to version 3 but has
|
|
additional information for the virtual layout class as well as
|
|
indexing information for the chunked layout class.</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Data Layout Message (Version 4)
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Layout Class</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted
|
|
only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Properties <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Data Layout Message (Version 4)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>The value for this field is 4 and is used by version 1.10.0
|
|
and later of the library to store properties for each layout
|
|
class and indexing information for the chunked layout.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Layout Class</p></td>
|
|
<td><p>The layout class specifies the type of storage for the data
|
|
and how the other fields of the layout message are to be
|
|
interpreted.
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Compact Storage
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Contiguous Storage
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>Chunked Storage
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>Virtual Storage
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Properties</p></td>
|
|
<td><p>This variable-sized field encodes information specific to a
|
|
layout class as follows:
|
|
<table class="list">
|
|
<tr>
|
|
<th align="left" width="20%">Layout Class</th>
|
|
<th align="left" width="80%">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left">Compact Storage</td>
|
|
<td>See <a href="#CompactStorage">Compact Storage
|
|
Property Description</i></a> for the version 3
|
|
Data Layout message.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left">Contiguous Storage</td>
|
|
<td>See <a href="#ContiguousStorage">Contiguous Storage
|
|
Property Description</i></a> for the version 3
|
|
Data Layout message.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left">Chunked Storage</td>
|
|
<td>See <a href="#ChunkedStorage">Chunked Storage
|
|
Property Description</i></a> below.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left">Virtual Storage</td>
|
|
<td>See <a href="#VirtualStorage">Virtual Storage
|
|
Property Description</i></a> below.
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
|
|
</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<a name="ChunkedStorage"></a>
|
|
<p>Class-specific information for chunked storage (layout
|
|
class 2):</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Chunked Storage Property Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Flags</td>
|
|
<td>Dimensionality</td>
|
|
<td>Dimension Size Encoded Length</td>
|
|
<td colspan="1" bgcolor="#DDDDDD"><em>This space inserted to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dimension 0 Size <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dimension 1 Size <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">...</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Dimension #n Size <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Chunk Indexing Type</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Indexing Type Information <em>(variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Chunked Storage Property Description
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Flags</p></td>
|
|
<td><p>This is the chunked layout feature flag:</p>
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="55%" align="left">Value</th>
|
|
<th width="45%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left"><code>DONT_FILTER_PARTIAL_BOUND_CHUNKS (bit 0)</code></td>
|
|
<td>Do not apply filter to a partial edge chunk.
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left"><code>SINGLE_INDEX_WITH_FILTER (bit 1)</code></td>
|
|
<td>A filtered chunk for <i>Single Chunk</i> indexing.
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
</td>
|
|
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimensionality</p></td>
|
|
<td><p>A chunk has fixed dimension. This field specifies
|
|
the number of <em>Dimension Size</em> fields later in the message.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimension Size Encoded Length</p></td>
|
|
<td>
|
|
<p>This is the size in bytes used to encode <em>Dimension Size</em>.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dimension #n Size</p></td>
|
|
<td><p>These values define the dimension size of a single chunk, in
|
|
units of array elements (not bytes). The first dimension stored in
|
|
the list of dimensions is the slowest changing dimension and the
|
|
last dimension stored is the fastest changing dimension.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Chunk Indexing Type</p></td>
|
|
<td><p>There are five indexing types used to look up addresses
|
|
of the chunks. For more information on each type, see
|
|
<a href="#AppendixC">“Appendix C: Types of Indexes for
|
|
Dataset Chunks.”</a>
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td><a href="#SingleChunk"><i>Single Chunk</i></a> indexing type.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td><a href="#Implicit"><i>Implicit</i></a> indexing type.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td><a href="#FixedArray"><i>Fixed Array</i></a> indexing type.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>4</code></td>
|
|
<td><a href="#ExtensibleArray"><i>Extensible Array</i></a> indexing type.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>5</code></td>
|
|
<td><a href="#V2Btrees"><i>Version 2 B-tree</i></a> indexing type.
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Indexing Type Information</p></td>
|
|
<td><p>This variable-sized field encodes information specific to
|
|
an indexing type. More information on what is encoded with
|
|
each type can be found below this table.
|
|
<ul>
|
|
<li>See <a href="#IndexInfoSingle"><i>Single Chunk</i></a> below.</li>
|
|
<li>See <a href="#IndexInfoImplicit"><i>Implicit</i></a> below.</li>
|
|
<li>See <a href="#IndexInfoFixed"><i>Fixed Array</i></a> below.</li>
|
|
<li>See <a href="#IndexInfoExtensible"><i>Extensible Array</i></a> below.</li>
|
|
<li>See <a href="#IndexInfoV2Btrees"><i>Version 2 B-tree</i></a> below.</li>
|
|
</ul>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address</p></td>
|
|
<td><p>This is the address specific to an indexing type.
|
|
The address may be undefined if the chunk or index storage is not allocated yet.
|
|
<table class="list">
|
|
<tr>
|
|
<th width="40%" align="left">Value</th>
|
|
<th width="60%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left"><i>Single Chunk index</i></td>
|
|
<td align="left">Address of the single chunk.</td>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left"><i>Implicit index</i></td>
|
|
<td align="left">Address of the array of dataset chunks.</td>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left"><i>Fixed Array index</i></td>
|
|
<td align="left">Address of the index.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left"><i>Extensible Array index</i></td>
|
|
<td align="left">Address of the index.</td>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="left"><i>Version 2 B-tree index</i></td>
|
|
<td align="left">Address of the index.</td>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
|
|
<ol>
|
|
<li>
|
|
<a name="IndexInfoSingle"></a>
|
|
Index-specific information for <i>Single Chunk</i>:
|
|
</li>
|
|
|
|
<p>The following information exists only when the chunk is filtered.
|
|
In other words, when <code>DONT_FILTER_PARTIAL_BOUND_CHUNKS</code>
|
|
(bit 0) is enabled in the field <em>flags</em>.</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Single Chunk Indexing Information
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Size of filtered chunk<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Filters for chunk</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="55%"> </td>
|
|
<td width="45%"> <!-- width is slightly different: these
|
|
tables are part of an ordered list; see <ol> tags. -->
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Single Chunk Indexing Information
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size of filtered chunk</p></td>
|
|
<td><p>This field is the size of a filtered chunk.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filters for chunk</p></td>
|
|
<td><p>This field contains filters for the chunk.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
</p>
|
|
|
|
<br />
|
|
|
|
<li>
|
|
<a name="IndexInfoImplicit"></a>
|
|
Index-specific information for <i>Implicit</i>:
|
|
</li>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Implicit Indexing Information
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4" bgcolor="#DDDDDD">
|
|
<em>No specific indexing information</em></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<li>
|
|
<a name="IndexInfoFixed"></a>
|
|
Index-specific information for <i>Fixed Array</i>:
|
|
</li>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fixed Array Indexing Information
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="1">Page Bits</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fixed Array Indexing Information
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Page Bits</p></td>
|
|
<td><p>This field contains the number of bits needed to store the
|
|
maximum number of elements in a data block page.</p></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
</p>
|
|
|
|
<br />
|
|
<li>
|
|
<a name="IndexInfoExtensible"></a>
|
|
Index-specific information for <i>Extensible Array</i>:
|
|
</li>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Extensible Array Indexing Information
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Max Bits</td>
|
|
<td>Index Elements</td>
|
|
<td>Min Pointers</td>
|
|
<td>Min Elements</td>
|
|
</tr>
|
|
|
|
<td colspan="2">Page Bits</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Extensible Array Indexing Information
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Max Bits</p></td>
|
|
<td><p>This field contains the number of bits needed to store the maximum number of elements
|
|
in the array.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Index Elements</p></td>
|
|
<td><p>This field contains the number of elements to store in the
|
|
index block.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Min Pointers</p></td>
|
|
<td><p>This field contains the minimum number of data block pointers
|
|
for a superblock.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Min Elements</p></td>
|
|
<td><p>This field contains the minimum number of elements per data block.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Page Bits</p></td>
|
|
<td><p>This field contains the number of bits needed to store the
|
|
maximum number of elements in a data block page.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
</p>
|
|
<br />
|
|
|
|
<li>
|
|
<a name="IndexInfoV2Btrees"></a>
|
|
Index-specific information for <i>Version 2 B-tree</i>:
|
|
</li>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 B-tree Indexing Information
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Node Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Split Percent</td>
|
|
<td>Merge Percent</td>
|
|
<td colspan="2" bgcolor="#DDDDDD">
|
|
<em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 B-tree Indexing Information
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Node Size</p></td>
|
|
<td><p>This field is the size in bytes of a B-tree node.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Split Percent</p></td>
|
|
<td><p>This field is the percentage full of a B-tree node at which to split the node.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Merge Percent</p></td>
|
|
<td><p>This field is the percentage full of a B-tree node at which to merge the node.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
</ol>
|
|
|
|
|
|
|
|
<br />
|
|
<a name="VirtualStorage"></a>
|
|
<p>
|
|
Class-specific information for virtual storage (layout class 3):</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Virtual Storage Property Description
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Index</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Virtual Storage Property Description
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address</p></td>
|
|
<td><p>This is the address of the global heap collection where
|
|
the VDS mapping entries are stored.
|
|
See <a href="#GlobalHeapVDS">“Disk Format: Level 1F -
|
|
Global Heap Block for Virtual Datasets.”</a>
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Index</p></td>
|
|
<td><p>This is the index of the data object within the global heap collection.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h4><a name="BogusMessage">IV.A.2.j. The Bogus Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Bogus</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x0009</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> 4 bytes</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> For testing only; should never
|
|
be stored in a valid file.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td>This message is used for testing the HDF5 Library’s
|
|
response to an “unknown” message type and should
|
|
never be encountered in a valid HDF5 file.</td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Bogus Message
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Bogus Value</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Bogus Message
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Bogus Value</p></td>
|
|
<td>
|
|
<p>This value should always be: <code>0xdeadbeef</code>.</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h4><a name="GroupInfoMessage">IV.A.2.k. The Group Info Message
|
|
</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Group Info</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x000A</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Varies</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may not be
|
|
repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td><p>This message stores information for the constants defining
|
|
a “new style” group’s behavior. Constant
|
|
information will be stored in this message and variable
|
|
information will be stored in the
|
|
<a href="#LinkInfoMessage">Link Info</a> message.</p>
|
|
<p>Note: the “estimated entry” information below is
|
|
used when determining the size of the object header for the
|
|
group when it is created.</p></td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Group Info Message
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Flags</td>
|
|
<td colspan="2">Link Phase Change: Maximum Compact Value <em>(optional)</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="2">Link Phase Change: Minimum Dense Value <em>(optional)</em></td>
|
|
<td colspan="2">Estimated Number of Entries <em>(optional)</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="2">Estimated Link Name Length of Entries <em>(optional)</em></td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Group Info Message
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number for this message. This document describes version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Flags</p></td>
|
|
<td><p>This is the group information flag with the following definition:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>If set, link phase change values are stored.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>If set, the estimated entry information is non-default
|
|
and is stored.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2-7</code></td>
|
|
<td>Reserved</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Link Phase Change: Maximum Compact Value</p></td>
|
|
<td><p>The is the maximum number of links to store “compactly” (in
|
|
the group’s object header).</p>
|
|
<p>This field is present if bit 0 of <em>Flags</em> is set.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Link Phase Change: Minimum Dense Value</p></td>
|
|
<td><p>This is the minimum number of links to store “densely” (in
|
|
the group’s fractal heap). The fractal heap’s address is
|
|
located in the <a href="#LinkInfoMessage">Link Info</a>
|
|
message.</p>
|
|
<p>This field is present if bit 0 of <em>Flags</em> is set.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Estimated Number of Entries</p></td>
|
|
<td><p>This is the estimated number of entries in groups.</p>
|
|
<p>If this field is not present, the default value of <code>4</code>
|
|
will be used for the estimated number of group entries.</p>
|
|
<p>This field is present if bit 1 of <em>Flags</em> is set.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Estimated Link Name Length of Entries</p></td>
|
|
<td><p>This is the estimated length of entry name.</p>
|
|
<p>If this field is not present, the default value of <code>8</code>
|
|
will be used for the estimated link name length of group entries.</p>
|
|
<p>This field is present if bit 1 of <em>Flags</em> is set.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
<!-- </p> -->
|
|
|
|
<h4><a name="FilterMessage">IV.A.2.l. The Data Storage - Filter
|
|
Pipeline Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b>
|
|
Data Storage - Filter Pipeline</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x000B</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Varies</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may not be
|
|
repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td><p>This message describes the filter pipeline which should
|
|
be applied to the data stream by providing filter identification
|
|
numbers, flags, a name, and client data.</p>
|
|
<p>This message may be present in the object headers of both
|
|
dataset and group objects. For datasets, it specifies the
|
|
filters to apply to raw data. For groups, it specifies the
|
|
filters to apply to the group’s fractal heap. Currently,
|
|
only datasets using chunked data storage use the filter
|
|
pipeline on their raw data.</p></td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Filter Pipeline Message - Version 1
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Number of Filters</td>
|
|
<td colspan="2">Reserved (zero)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Reserved (zero)</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Filter Description List <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Filter Pipeline Message - Version 1
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number for this message. This table
|
|
describes version 1.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Number of Filters</p></td>
|
|
<td><p>The total number of filters described in this
|
|
message. The maximum possible number of filters in a
|
|
message is 32.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filter Description List</p></td>
|
|
<td><p>A description of each filter. A filter description
|
|
appears in the next table.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Filter Description - Version 1
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Filter Identification Value</td>
|
|
<td colspan="2">Name Length</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Flags</td>
|
|
<td colspan="2">Number Client Data Values</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Name <em>(variable size, optional)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Client Data <em>(variable size, optional)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Padding <em>(variable size, optional)</em></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Filter Description - Version 1
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filter Identification Value</p></td>
|
|
<td>
|
|
<p>
|
|
This value, often referred to as a filter identifier,
|
|
is designed to be a unique identifier for the filter.
|
|
Values from zero through 32,767 are reserved for filters
|
|
supported by The HDF Group in the HDF5 Library and for
|
|
filters requested and supported by third parties.
|
|
Filters supported by The HDF Group are documented immediately
|
|
below. Information on 3rd-party filters can be found at
|
|
The HDF Group’s
|
|
<a href="http://www.hdfgroup.org/services/contributions.html">
|
|
Contributions</a> page.</p>
|
|
|
|
<p>
|
|
To request a filter identifier, please contact
|
|
The HDF Group’s Help Desk at
|
|
<img src="Graphics/help.png" valign="middle" height="14"
|
|
alt="The HDF Group Help Desk">.
|
|
You will be asked to provide the following information:</p>
|
|
<ol>
|
|
<li>Contact information for the developer requesting the
|
|
new identifier</li>
|
|
<li>A short description of the new filter</li>
|
|
<li>Links to any relevant information, including licensing
|
|
information</li>
|
|
</ol>
|
|
<p>
|
|
Values from 32768 to 65535 are reserved for non-distributed uses
|
|
(for example, internal company usage) or for application usage
|
|
when testing a feature. The HDF Group does not track or document
|
|
the use of the filters with identifiers from this range.</p>
|
|
|
|
<p>
|
|
The filters currently in library version 1.8.0 are
|
|
listed below:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Identification</th>
|
|
<th width="15%" align="left">Name</th>
|
|
<th width="65%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>N/A</td>
|
|
<td>Reserved</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>deflate</td>
|
|
<td>GZIP deflate compression</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>shuffle</td>
|
|
<td>Data element shuffling</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>fletcher32</td>
|
|
<td>Fletcher32 checksum</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>4</code></td>
|
|
<td>szip</td>
|
|
<td>SZIP compression</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>5</code></td>
|
|
<td>nbit</td>
|
|
<td>N-bit packing</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>6</code></td>
|
|
<td>scaleoffset</td>
|
|
<td>Scale and offset encoded values</td>
|
|
</tr>
|
|
</table>
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Name Length</p></td>
|
|
<td><p>Each filter has an optional null-terminated ASCII name
|
|
and this field holds the length of the name including the
|
|
null termination padded with nulls to be a multiple of
|
|
eight. If the filter has no name then a value of zero is
|
|
stored in this field.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Flags</p></td>
|
|
<td><p>The flags indicate certain properties for a filter. The
|
|
bit values defined so far are:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>If set then the filter is an optional filter.
|
|
During output, if an optional filter fails it will be
|
|
silently skipped in the pipeline.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1-15</code></td>
|
|
<td>Reserved (zero)</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Number of Client Data Values</p></td>
|
|
<td><p>Each filter can store integer values to control
|
|
how the filter operates. The number of entries in the
|
|
<em>Client Data</em> array is stored in this field.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Name</p></td>
|
|
<td><p>If the <em>Name Length</em> field is non-zero then it will
|
|
contain the size of this field, padded to a multiple of eight. This
|
|
field contains a null-terminated, ASCII character string to serve
|
|
as a comment/name for the filter.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Client Data</p></td>
|
|
<td><p>This is an array of four-byte integers which will be
|
|
passed to the filter function. The <em>Client Data Number</em> of
|
|
Values determines the number of elements in the array.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Padding</p></td>
|
|
<td><p>Four bytes of zeroes are added to the message at this
|
|
point if the Client Data Number of Values field contains
|
|
an odd number.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Filter Pipeline Message - Version 2
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Number of Filters</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Filter Description List <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Filter Pipeline Message - Version 2
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number for this message. This table
|
|
describes version 2.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Number of Filters</p></td>
|
|
<td><p>The total number of filters described in this
|
|
message. The maximum possible number of filters in a
|
|
message is 32.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filter Description List</p></td>
|
|
<td><p>A description of each filter. A filter description
|
|
appears in the next table.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Filter Description - Version 2
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Filter Identification Value</td>
|
|
<td colspan="2">Name Length <em>(optional)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Flags</td>
|
|
<td colspan="2">Number Client Data Values</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Name <em>(variable size, optional)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Client Data <em>(variable size, optional)</em><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Filter Description - Version 2
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filter Identification Value</p></td>
|
|
<td>
|
|
<p>
|
|
This value, often referred to as a filter identifier,
|
|
is designed to be a unique identifier for the filter.
|
|
Values from zero through 32,767 are reserved for filters
|
|
supported by The HDF Group in the HDF5 Library and for
|
|
filters requested and supported by third parties.
|
|
Filters supported by The HDF Group are documented immediately
|
|
below. Information on 3rd-party filters can be found at
|
|
The HDF Group’s
|
|
<a href="http://www.hdfgroup.org/services/contributions.html">
|
|
Contributions</a> page.</p>
|
|
|
|
<p>
|
|
To request a filter identifier, please contact
|
|
The HDF Group’s Help Desk at
|
|
<img src="Graphics/help.png" valign="middle" height="14"
|
|
alt="The HDF Group Help Desk">.
|
|
You will be asked to provide the following information:</p>
|
|
<ol>
|
|
<li>Contact information for the developer requesting the
|
|
new identifier</li>
|
|
<li>A short description of the new filter</li>
|
|
<li>Links to any relevant information, including licensing
|
|
information</li>
|
|
</ol>
|
|
<p>
|
|
Values from 32768 to 65535 are reserved for non-distributed uses
|
|
(for example, internal company usage) or for application usage
|
|
when testing a feature. The HDF Group does not track or document
|
|
the use of the filters with identifiers from this range.</p>
|
|
|
|
<p>
|
|
The filters currently in library version 1.8.0 are
|
|
listed below:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Identification</th>
|
|
<th width="15%" align="left">Name</th>
|
|
<th width="65%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>N/A</td>
|
|
<td>Reserved</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>deflate</td>
|
|
<td>GZIP deflate compression</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>shuffle</td>
|
|
<td>Data element shuffling</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>fletcher32</td>
|
|
<td>Fletcher32 checksum</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>4</code></td>
|
|
<td>szip</td>
|
|
<td>SZIP compression</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>5</code></td>
|
|
<td>nbit</td>
|
|
<td>N-bit packing</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>6</code></td>
|
|
<td>scaleoffset</td>
|
|
<td>Scale and offset encoded values</td>
|
|
</tr>
|
|
</table>
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Name Length</p></td>
|
|
<td><p>Each filter has an optional null-terminated ASCII name
|
|
and this field holds the length of the name including the
|
|
null termination padded with nulls to be a multiple of
|
|
eight. If the filter has no name then a value of zero is
|
|
stored in this field.</p>
|
|
<p>Filters with IDs less than 256 (in other words, filters
|
|
that are defined in this format documentation) do not store
|
|
the <em>Name Length</em> or <em>Name</em> fields.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Flags</p></td>
|
|
<td><p>The flags indicate certain properties for a filter. The
|
|
bit values defined so far are:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>If set then the filter is an optional filter.
|
|
During output, if an optional filter fails it will be
|
|
silently skipped in the pipeline.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1-15</code></td>
|
|
<td>Reserved (zero)</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Number of Client Data Values</p></td>
|
|
<td><p>Each filter can store integer values to control
|
|
how the filter operates. The number of entries in the
|
|
<em>Client Data</em> array is stored in this field.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Name</p></td>
|
|
<td><p>If the <em>Name Length</em> field is non-zero, then it will
|
|
contain the size of this field, <em>not</em> padded to a multiple
|
|
of eight. This field contains a <em>non-</em>null-terminated,
|
|
ASCII character string to serve as a comment/name for the filter.
|
|
</p>
|
|
<p>Filters that are defined in this format documentation
|
|
such as deflate and shuffle do not store the <em>Name
|
|
Length</em> or <em>Name</em> fields.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Client Data</p></td>
|
|
<td><p>This is an array of four-byte integers which will be
|
|
passed to the filter function. The Client Data Number of
|
|
Values</em> determines the number of elements in the array.</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h4><a name="AttributeMessage">IV.A.2.m. The Attribute Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Attribute</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x000C</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Varies</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may be
|
|
repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td><p>The <em>Attribute</em> message is used to store objects
|
|
in the HDF5 file which are used as attributes, or
|
|
“metadata” about the current object. An attribute
|
|
is a small dataset; it has a name, a datatype, a dataspace, and
|
|
raw data. Since attributes are stored in the object header, they
|
|
should be relatively small (in other words, less than 64KB).
|
|
They can be associated with any type of object which has an
|
|
object header (groups, datasets, or committed (named)
|
|
datatypes).</p>
|
|
<p>In 1.8.x versions of the library, attributes can be larger
|
|
than 64KB. See the
|
|
<a href="UG/HDF5_Users_Guide-Responsive%20HTML5/index.html#t=HDF5_Users_Guide%2FAttributes%2FHDF5_Attributes.htm%3Frhtocid%3Dtoc8.2_1%23TOC_8_5_Special_Issuesbc-13">
|
|
“Special Issues”</a> section of the Attributes chapter
|
|
in the <cite>HDF5 User’s Guide</cite> for more information.</p>
|
|
<p>Note: Attributes on an object must have unique names:
|
|
the HDF5 Library currently enforces this by causing the
|
|
creation of an attribute with a duplicate name to fail.
|
|
Attributes on different objects may have the same name,
|
|
however.</p></td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Attribute Message (Version 1)
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Reserved (zero)</td>
|
|
<td colspan="2">Name Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Datatype Size</td>
|
|
<td colspan="2">Dataspace Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Name <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Datatype <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Dataspace <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Data <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Attribute Message (Version 1)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number information is used for changes in the format of the
|
|
attribute message and is described here:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Version</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Never used.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Used by the library before version 1.6 to encode attribute message.
|
|
This version does not support shared datatypes.</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Name Size</p></td>
|
|
<td><p>The length of the attribute name in bytes including the
|
|
null terminator. Note that the <em>Name</em> field below may
|
|
contain additional padding not represented by this
|
|
field.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Datatype Size</p></td>
|
|
<td><p>The length of the datatype description in the <em>Datatype</em>
|
|
field below. Note that the <em>Datatype</em> field may contain
|
|
additional padding not represented by this field.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dataspace Size</p></td>
|
|
<td><p>The length of the dataspace description in the <em>Dataspace</em>
|
|
field below. Note that the <em>Dataspace</em> field may contain
|
|
additional padding not represented by this field.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Name</p></td>
|
|
<td><p>The null-terminated attribute name. This field is
|
|
padded with additional null characters to make it a
|
|
multiple of eight bytes.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Datatype</p></td>
|
|
<td><p>The datatype description follows the same format as
|
|
described for the datatype object header message. This
|
|
field is padded with additional zero bytes to make it a
|
|
multiple of eight bytes.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dataspace</p></td>
|
|
<td><p>The dataspace description follows the same format as
|
|
described for the dataspace object header message. This
|
|
field is padded with additional zero bytes to make it a
|
|
multiple of eight bytes.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Data</p></td>
|
|
<td><p>The raw data for the attribute. The size is determined
|
|
from the datatype and dataspace descriptions. This
|
|
field is <em>not</em> padded with additional bytes.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Attribute Message (Version 2)
|
|
</caption>
|
|
|
|
<tr align="center">
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Flags</td>
|
|
<td colspan="2">Name Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Datatype Size</td>
|
|
<td colspan="2">Dataspace Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Name <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Datatype <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Dataspace <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Data <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Attribute Message (Version 2)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number information is used for changes in the
|
|
format of the attribute message and is described here:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Version</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>Used by the library of version 1.6.x and after to encode
|
|
attribute messages.
|
|
This version supports shared datatypes. The fields of
|
|
name, datatype, and dataspace are not padded with
|
|
additional bytes of zero.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Flags</p></td>
|
|
<td><p>This bit field contains extra information about
|
|
interpreting the attribute message:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>If set, datatype is shared.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>If set, dataspace is shared.</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Name Size</p></td>
|
|
<td><p>The length of the attribute name in bytes including the
|
|
null terminator.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Datatype Size</p></td>
|
|
<td><p>The length of the datatype description in the <em>Datatype</em>
|
|
field below.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dataspace Size</p></td>
|
|
<td><p>The length of the dataspace description in the <em>Dataspace</em>
|
|
field below.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Name</p></td>
|
|
<td><p>The null-terminated attribute name. This field is <em>not</em>
|
|
padded with additional bytes.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Datatype</p></td>
|
|
<td><p>The datatype description follows the same format as
|
|
described for the datatype object header message.
|
|
</p>
|
|
<p>If the
|
|
<em>Flag</em> field indicates this attribute’s datatype is
|
|
shared, this field will contain a “shared message” encoding
|
|
instead of the datatype encoding.
|
|
</p>
|
|
<p>This field is <em>not</em> padded with additional bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dataspace</p></td>
|
|
<td><p>The dataspace description follows the same format as
|
|
described for the dataspace object header message.
|
|
</p>
|
|
<p>If the
|
|
<em>Flag</em> field indicates this attribute’s dataspace is
|
|
shared, this field will contain a “shared message” encoding
|
|
instead of the dataspace encoding.
|
|
</p>
|
|
<p>This field is <em>not</em> padded with additional bytes.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Data</p></td>
|
|
<td><p>The raw data for the attribute. The size is determined
|
|
from the datatype and dataspace descriptions.
|
|
</p>
|
|
<p>This field is <em>not</em> padded with additional zero bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Attribute Message (Version 3)
|
|
</caption>
|
|
|
|
<tr align="center">
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Flags</td>
|
|
<td colspan="2">Name Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Datatype Size</td>
|
|
<td colspan="2">Dataspace Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Name Character Set Encoding</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Name <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Datatype <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Dataspace <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Data <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Attribute Message (Version 3)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number information is used for changes in the
|
|
format of the attribute message and is described here:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Version</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>Used by the library of version 1.8.x and after to
|
|
encode attribute messages.
|
|
This version supports attributes with non-ASCII names.
|
|
</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Flags</p></td>
|
|
<td><p>This bit field contains extra information about
|
|
interpreting the attribute message:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>If set, datatype is shared.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>If set, dataspace is shared.</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Name Size</p></td>
|
|
<td><p>The length of the attribute name in bytes including the
|
|
null terminator.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Datatype Size</p></td>
|
|
<td><p>The length of the datatype description in the <em>Datatype</em>
|
|
field below.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dataspace Size</p></td>
|
|
<td><p>The length of the dataspace description in the <em>Dataspace</em>
|
|
field below.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Name Character Set Encoding</p></td>
|
|
<td><p>The character set encoding for the attribute’s name:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>ASCII character set encoding
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>UTF-8 character set encoding
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Name</p></td>
|
|
<td><p>The null-terminated attribute name. This field is <em>not</em>
|
|
padded with additional bytes.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Datatype</p></td>
|
|
<td><p>The datatype description follows the same format as
|
|
described for the datatype object header message.
|
|
</p>
|
|
<p>If the
|
|
<em>Flag</em> field indicates this attribute’s datatype is
|
|
shared, this field will contain a “shared message” encoding
|
|
instead of the datatype encoding.
|
|
</p>
|
|
<p>This field is <em>not</em> padded with additional bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dataspace</p></td>
|
|
<td><p>The dataspace description follows the same format as
|
|
described for the dataspace object header message.
|
|
</p>
|
|
<p>If the
|
|
<em>Flag</em> field indicates this attribute’s dataspace is
|
|
shared, this field will contain a “shared message” encoding
|
|
instead of the dataspace encoding.
|
|
</p>
|
|
<p>This field is <em>not</em> padded with additional bytes.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Data</p></td>
|
|
<td><p>The raw data for the attribute. The size is determined
|
|
from the datatype and dataspace descriptions.
|
|
</p>
|
|
<p>This field is <em>not</em> padded with additional zero bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h4><a name="CommentMessage">IV.A.2.n. The Object Comment
|
|
Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Object
|
|
Comment</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x000D</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Varies</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may not be
|
|
repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td>The object comment is designed to be a short description of
|
|
an object. An object comment is a sequence of non-zero
|
|
(<code>\0</code>) ASCII characters with no other formatting
|
|
included by the library.</td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Object Comment Message
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Comment <em>(variable size)</em><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Object Comment Message
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Name</p></td>
|
|
<td><p>A null terminated ASCII character string.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h4><a name="OldModificationTimeMessage">IV.A.2.o. The Object
|
|
Modification Time (Old) Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Object
|
|
Modification Time (Old)</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x000E</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Fixed</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may not be
|
|
repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td><p>The object modification date and time is a timestamp
|
|
which indicates (using ISO-8601 date and time format) the last
|
|
modification of an object. The time is updated when any object
|
|
header message changes according to the system clock where the
|
|
change was posted. All fields of this message should be
|
|
interpreted as coordinated universal time (UTC).</p>
|
|
<p>This modification time message is deprecated in favor of
|
|
the “new” <a href="#ModificationTimeMessage">Object
|
|
Modification Time</a> message and is no longer written to the
|
|
file in versions of the HDF5 Library after the 1.6.0
|
|
version.</p></td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Modification Time Message (Old)
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Year</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Month</td>
|
|
<td colspan="2">Day of Month</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Hour</td>
|
|
<td colspan="2">Minute</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Second</td>
|
|
<td colspan="2">Reserved</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Modification Time Message (Old)
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Year</p></td>
|
|
<td><p>The four-digit year as an ASCII string. For example,
|
|
<code>1998</code>.
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Month</p></td>
|
|
<td><p>The month number as a two digit ASCII string where
|
|
January is <code>01</code> and December is <code>12</code>.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Day of Month</p></td>
|
|
<td><p>The day number within the month as a two digit ASCII
|
|
string. The first day of the month is <code>01</code>.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Hour</p></td>
|
|
<td><p>The hour of the day as a two digit ASCII string where
|
|
midnight is <code>00</code> and 11:00pm is <code>23</code>.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Minute</p></td>
|
|
<td><p>The minute of the hour as a two digit ASCII string where
|
|
the first minute of the hour is <code>00</code> and
|
|
the last is <code>59</code>.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Second</p></td>
|
|
<td><p>The second of the minute as a two digit ASCII string
|
|
where the first second of the minute is <code>00</code>
|
|
and the last is <code>59</code>.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Reserved</p></td>
|
|
<td><p>This field is reserved and should always be zero.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h4><a name="SOHMTableMessage">IV.A.2.p. The Shared Message Table
|
|
Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Shared Message
|
|
Table</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x000F</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Fixed</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may not be
|
|
repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td>This message is used to locate the table of shared object
|
|
header message (SOHM) indexes. Each index consists of information
|
|
to find the shared messages from either the heap or object header.
|
|
This message is <em>only</em> found in the superblock
|
|
extension.</td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Shared Message Table Message
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Shared Object Header Message Table Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Number of Indices</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Shared Message Table Message
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number for this message. This document describes version 0.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Shared Object Header Message Table Address</p></td>
|
|
<td><p>This field is the address of the master table for shared
|
|
object header message indexes.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Number of Indices</p></td>
|
|
<td><p>This field is the number of indices in the master table.
|
|
</p></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<h4><a name="ContinuationMessage">IV.A.2.q. The Object Header
|
|
Continuation Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Object Header
|
|
Continuation</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x0010</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Fixed</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may be
|
|
repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td>The object header continuation is the location in the file
|
|
of a block containing more header messages for the current data
|
|
object. This can be used when header blocks become too large or
|
|
are likely to change over time.</td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Object Header Continuation Message
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Offset<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Length<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Object Header Continuation Message
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Offset</p></td>
|
|
<td><p>This value is the address in the file where the
|
|
header continuation block is located.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Length</p></td>
|
|
<td><p>This value is the length in bytes of the header continuation
|
|
block in the file.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
<br />
|
|
|
|
<p>The format of the header continuation block that this message points
|
|
to depends on the version of the object header that the message is
|
|
contained within.
|
|
</p>
|
|
|
|
<p>
|
|
Continuation blocks for version 1 object headers have no special
|
|
formatting information; they are merely a list of object header
|
|
message info sequences (type, size, flags, reserved bytes and data
|
|
for each message sequence). See the description
|
|
of <a href="#V1ObjectHeaderPrefix">Version 1 Data Object Header Prefix.</a>
|
|
</p>
|
|
|
|
<p>Continuation blocks for version 2 object headers <em>do</em> have
|
|
special formatting information as described here
|
|
(see also the description of
|
|
<a href="#V2ObjectHeaderPrefix">Version 2 Data Object Header Prefix.</a>):
|
|
</p>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 Object Header Continuation Block
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
<tr>
|
|
<td>Header Message Type #1</td>
|
|
<td colspan="2">Size of Header Message Data #1</td>
|
|
<td>Header Message #1 Flags</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Header Message #1 Creation Order <em>(optional)</em></td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Header Message Data #1<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Header Message Type #n</td>
|
|
<td colspan="2">Size of Header Message Data #n</td>
|
|
<td>Header Message #n Flags</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Header Message #n Creation Order <em>(optional)</em></td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Header Message Data #n<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Gap <em>(optional, variable size)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 Object Header Continuation Block
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>OCHK</code>”
|
|
is used to indicate the beginning of an object header
|
|
continuation block. This gives file consistency checking
|
|
utilities a better chance of reconstructing a damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Header Message #n Type</p></td>
|
|
<td>
|
|
<p>Same format as version 1 of the object header, described above.
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size of Header Message #n Data</p></td>
|
|
<td>
|
|
<p>Same format as version 1 of the object header, described above.
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Header Message #n Flags</p></td>
|
|
<td>
|
|
<p>Same format as version 1 of the object header, described above.
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Header Message #n Creation Order</p></td>
|
|
<td>
|
|
<p>This field stores the order that a message of a given type
|
|
was created in.</p>
|
|
<p>This field is present if bit 2 of <em>flags</em> is set.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Header Message #n Data</p></td>
|
|
<td>
|
|
<p>Same format as version 1 of the object header, described above.
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Gap</p></td>
|
|
<td>
|
|
<p>A gap in an object header chunk is inferred by the end of the
|
|
messages for the chunk before the beginning of the chunk’s
|
|
checksum. Gaps are always smaller than the size of an
|
|
object header message prefix (message type + message size +
|
|
message flags).</p>
|
|
<p>Gaps are formed when a message (typically an attribute message)
|
|
in an earlier chunk is deleted and a message from a later
|
|
chunk that does not quite fit into the free space is moved
|
|
into the earlier chunk.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>This is the checksum for the object header chunk.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h4><a name="SymbolTableMessage">IV.A.2.r. The Symbol Table
|
|
Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Symbol Table
|
|
Message</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x0011</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Fixed</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Required for
|
|
“old style” groups; may not be repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td>Each “old style” group has a v1 B-tree and a
|
|
local heap for storing symbol table entries, which are located
|
|
with this message.</td></tr>
|
|
<tr><td colspan="2"><b>Format of data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Symbol Table Message
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />v1 B-tree Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Local Heap Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Symbol Table Message
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>v1 B-tree Address</p></td>
|
|
<td><p>This value is the address of the v1 B-tree containing the
|
|
symbol table entries for the group.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Local Heap Address</p></td>
|
|
<td><p>This value is the address of the local heap containing
|
|
the link names for the symbol table entries for the group.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h4><a name="ModificationTimeMessage">IV.A.2.s. The Object
|
|
Modification Time Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Object
|
|
Modification Time</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x0012</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Fixed</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may not be
|
|
repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td>The object modification time is a timestamp which indicates
|
|
the time of the last modification of an object. The time is
|
|
updated when any object header message changes according to
|
|
the system clock where the change was posted.</td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Modification Time Message
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td colspan="3">Reserved <em>(zero)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Seconds After UNIX Epoch</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Modification Time Message
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number is used for changes in the format of Object Modification Time
|
|
and is described here:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Version</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Never used.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Used by Version 1.6.1 and after of the library to encode time. In
|
|
this version, the time is the seconds after Epoch.</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Seconds After UNIX Epoch</p></td>
|
|
<td><p>A 32-bit unsigned integer value that stores the number of
|
|
seconds since 0 hours, 0 minutes, 0 seconds, January 1, 1970,
|
|
Coordinated Universal Time.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h4><a name="BtreeKValuesMessage">IV.A.2.t. The B-tree
|
|
‘K’ Values Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> B-tree
|
|
‘K’ Values</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x0013</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Fixed</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may not be
|
|
repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td>This message retrieves non-default ‘K’ values
|
|
for internal and leaf nodes of a group or indexed storage v1
|
|
B-trees. This message is <em>only</em> found in the superblock
|
|
extension.</td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: B-tree ‘K’ Values Message
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td colspan="2">Indexed Storage Internal Node K</td>
|
|
<td bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Group Internal Node K</td>
|
|
<td colspan="2">Group Leaf Node K</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: B-tree ‘K’ Values Message
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number for this message. This document describes
|
|
version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Indexed Storage Internal Node K</p></td>
|
|
<td><p>This is the node ‘K’ value for each internal node of an
|
|
indexed storage v1 B-tree. See the description of this field
|
|
in version 0 and 1 of the superblock as well the section on
|
|
v1 B-trees.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Group Internal Node K</p></td>
|
|
<td><p>This is the node ‘K’ value for each internal node of a group
|
|
v1 B-tree. See the description of this field in version 0 and
|
|
1 of the superblock as well as the section on v1 B-trees.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Group Leaf Node K</p></td>
|
|
<td><p>This is the node ‘K’ value for each leaf node of a group v1
|
|
B-tree. See the description of this field in version 0 and 1
|
|
of the superblock as well as the section on v1 B-trees.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<h4><a name="DrvInfoMessage">IV.A.2.u. The Driver Info
|
|
Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Driver
|
|
Info</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x0014</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Varies</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may not be
|
|
repeated.</td></tr>
|
|
|
|
<tr><td>
|
|
<b>Description:</b></td>
|
|
<td>This message contains information needed by the file driver
|
|
to reopen a file. This message is <em>only</em> found in the
|
|
superblock extension: see the <a href="#SuperblockExt">
|
|
“Disk Format: Level 0C - Superblock Extension”</a>
|
|
section for more information. For more information on the fields
|
|
in the driver info message, see the <a href="#DriverInfo">
|
|
“Disk Format: Level 0B - File Driver Info”</a>
|
|
section; those who use the multi and family file drivers will
|
|
find this section particularly helpful.</td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Driver Info Message
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Driver Identification</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Driver Information Size</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br /><br />Driver Information <em>(variable size)</em><br /><br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Driver Info Message
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number for this message. This document describes
|
|
version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Driver Identification</p></td>
|
|
<td><p>This is an eight-byte ASCII string without null termination which
|
|
identifies the driver.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Driver Information Size</p></td>
|
|
<td><p>The size in bytes of the <em>Driver Information</em> field of this
|
|
message.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Driver Information</p></td>
|
|
<td><p>Driver information is stored in a format defined by the file driver.</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h4><a name="AinfoMessage">IV.A.2.v. The Attribute Info
|
|
Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Attribute
|
|
Info</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x0015</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Varies</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may not be
|
|
repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td>This message stores information about the attributes on an
|
|
object, such as the maximum creation index for the attributes
|
|
created and the location of the attribute storage when the
|
|
attributes are stored “densely”.</td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Attribute Info Message
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Flags</td>
|
|
<td colspan="2">Maximum Creation Index <em>(optional)</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Fractal Heap Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Attribute Name v2 B-tree Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Attribute Creation Order v2 B-tree Address<sup>O</sup> <em>(optional)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Attribute Info Message
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number for this message. This document describes
|
|
version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Flags</p></td>
|
|
<td><p>This is the attribute index information flag with the
|
|
following definition:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>If set, creation order for attributes is tracked.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>If set, creation order for attributes is indexed.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2-7</code></td>
|
|
<td>Reserved</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Maximum Creation Index</p></td>
|
|
<td><p>The is the maximum creation order index value for the
|
|
attributes on the object.</p>
|
|
<p>This field is present if bit 0 of <em>Flags</em> is set.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Fractal Heap Address</p></td>
|
|
<td><p>This is the address of the fractal heap to store dense
|
|
attributes.
|
|
Each attribute stored in the fractal heap is described by
|
|
the <a href="#AttributeMessage">Attribute Message.</a>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Attribute Name v2 B-tree Address</p></td>
|
|
<td><p>This is the address of the version 2 B-tree to index the
|
|
names of densely stored attributes.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Attribute Creation Order v2 B-tree Address</p></td>
|
|
<td><p>This is the address of the version 2 B-tree to index the
|
|
creation order of densely stored attributes.</p>
|
|
<p>This field is present if bit 1 of <em>Flags</em> is set.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<h4><a name="RefCountMessage">IV.A.2.w. The Object Reference
|
|
Count Message</a></h4>
|
|
|
|
<!-- start msgdesc table -->
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> Object Reference
|
|
Count</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x0016</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Fixed</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may not be
|
|
repeated.</td></tr>
|
|
<tr><td><b>Description:</b></td>
|
|
<td>This message stores the number of hard links (in groups or
|
|
objects) pointing to an object: in other words, its
|
|
<em>reference count</em>.</td></tr>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<!-- end msgdesc table -->
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Object Reference Count
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Reference count</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Object Reference Count
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number for this message. This document describes
|
|
version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Reference Count</p></td>
|
|
<td><p>The unsigned 32-bit integer is the reference count for the
|
|
object. This message is only present in “version 2”
|
|
(or later) object headers, and if not present those object
|
|
header versions, the reference count for the object is assumed
|
|
to be 1.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
|
|
<h4><a name="FsinfoMessage">IV.A.2.x. The File Space Info
|
|
Message</a></h4>
|
|
|
|
<center>
|
|
<table class="msgdesc">
|
|
<tr><td colspan="2"><b>Header Message Name:</b> File Space
|
|
Info</td></tr>
|
|
<tr><td colspan="2"><b>Header Message Type:</b> 0x0017</td></tr>
|
|
<tr><td colspan="2"><b>Length:</b> Fixed</td></tr>
|
|
<tr><td colspan="2"><b>Status:</b> Optional; may not be
|
|
repeated.</td></tr>
|
|
<tr><td>
|
|
<b>Description:</b></td>
|
|
<td>This message stores the file space management information
|
|
that the library uses in handling file space
|
|
requests for the file. Version 0 of the message is used for release 1.10.0 only.
|
|
Version 1 of the message is used for release 1.10.1+.
|
|
There is no File Space Info message before release 1.10 as the library does
|
|
not track file space across multiple file opens.
|
|
<p>
|
|
Note that version 0 is deprecated starting release 1.10.1.
|
|
That means when the 1.10.1+ library opens an HDF5 file with a version 0 message,
|
|
the library will decode and map the message to version 1.
|
|
On file close, it will encode the message as a version 1 message.
|
|
<p>
|
|
The library uses the following three mechanisms to manage file space in an HDF5 file:
|
|
<ul>
|
|
<li> Free-space managers
|
|
<br> They track free-space sections of various sizes in the file that are not currently
|
|
allocated. Each free-space manager corresponds to a file space type.
|
|
There are two main groups of file space types: metadata and raw data.
|
|
Metadata is further divided into five types: superblock, B-tree, global heap,
|
|
local heap, and object header.
|
|
See the description of <a href="#FreeSpaceManager">Free-space
|
|
Manager</a> as well the description of file space allocation types in
|
|
<a href="#AppendixB">Appendix B</a>
|
|
</li>
|
|
<li> Aggregators
|
|
<br> The library manages two aggregators, one for metadata and one for raw data.
|
|
Aggregator is a contiguous block of free-space in the file.
|
|
The size of each aggregator is tunable via public routines
|
|
<code>H5Pset_meta_block_size</code> and <code>H5Pset_small_data_block_size</code> respectively.
|
|
</li>
|
|
<li> Virtual file drivers
|
|
<br> The library's virtual file driver interface dispatches requests for additional
|
|
space to the allocation routine of the file driver associated with the file.
|
|
For example, if the sec2 file driver is being used, its allocation routine will
|
|
increase the size of the file to service the requests.
|
|
</li>
|
|
</ul>
|
|
<p>
|
|
For release 1.10.0, the library derives the following four file space strategies
|
|
based on the mechanisms:
|
|
<ul>
|
|
<li>H5F_FILE_SPACE_ALL
|
|
<ul>
|
|
<li>Mechanisms used: free-space managers, aggregators, and virtual file drivers</li>
|
|
<li>Does not persist free-space across file opens</li>
|
|
<li>This strategy is the library default</li>
|
|
</ul>
|
|
</li>
|
|
<li>H5F_FILE_SPACE_ALL_PERSIST</li>
|
|
<ul>
|
|
<li>Mechanisms used: free-space managers, aggregators, and virtual file drivers</li>
|
|
<li>Persist free-space across file opens</li>
|
|
</ul>
|
|
<li>H5F_FILE_SPACE_AGGR_VFD</li>
|
|
<ul>
|
|
<li>Mechanisms used: aggregators and virtual file drivers</li>
|
|
<li>Does not persist free-space across file opens</li>
|
|
</ul>
|
|
<li>H5F_FILE_SPACE_VFD</li>
|
|
<ul>
|
|
<li>Mechanisms used: virtual file drivers</li>
|
|
<li>Does not persist free-space across file opens</li>
|
|
</ul>
|
|
</ul>
|
|
For release 1.10.1+, the free-space manager mechanism is modified to handle paged aggregation
|
|
which aggregates small metadata and raw data allocations into constant-sized well-aligned pages
|
|
to allow efficient I/O accesses.
|
|
With the support of this feature, the library derives the following four file space strategies:
|
|
<ul>
|
|
<li>H5F_FSPACE_STRATEGY_FSM_AGGR </li>
|
|
<ul>
|
|
<li>Mechanisms used: free-space managers, aggregators, and virtual file drivers</li>
|
|
<li>This strategy is the library default</li>
|
|
</ul>
|
|
<li>H5F_FSPACE_STRATEGY_PAGE</li>
|
|
<ul>
|
|
<li>Mechanisms used: free-space managers with embedded paged aggregation and virtual file drivers</li>
|
|
</ul>
|
|
<li>H5F_FSPACE_STRATEGY_AGGR</li>
|
|
<ul>
|
|
<li>Mechanisms used: aggregators and virtual file drivers</li>
|
|
</ul>
|
|
<li>H5F_FSPACE_STRATEGY_NONE</li>
|
|
<ul>
|
|
<li>Mechanisms used: virtual file drivers</li>
|
|
</ul>
|
|
</ul>
|
|
The default is not persisting free-space across file opens for the above four strategies.
|
|
User can use the public routine <code>H5Pset_file_space_strategy</code> to request
|
|
persisting free-space.
|
|
</td></tr>
|
|
<p>
|
|
<tr><td colspan="2"><b>Format of Data:</b> See the tables
|
|
below.</td></tr>
|
|
</table></center>
|
|
<p>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: File Space Info - Version 0
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Strategy</td>
|
|
<td colspan="2">Threshold<sup>L</sup></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Free-space manager address<sup>O</sup> for H5FD_MEM_SUPER<br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Free-space manager address<sup>0</sup> for H5FD_MEM_BTREE<br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Free-space manager address<sup>0</sup> for H5FD_MEM_DRAW<br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Free-space manager address<sup>0</sup> for H5FD_MEM_GHEAP<br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Free-space manager address<sup>0</sup> for H5FD_MEM_LHEAP<br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Free-space manager address<sup>0</sup> for H5FD_MEM_OHDR<br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: File Space Info
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>This is version 0 of this message.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Strategy</p></td>
|
|
<td><p>This is the file space strategy used to manage file space.
|
|
There are four types:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>H5F_FILE_SPACE_ALL_PERSIST</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>H5F_FILE_SPACE_ALL</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>H5F_FILE_SPACE_AGGR_VFD</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>4</code></td>
|
|
<td>H5F_FILE_SPACE_VFD</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Threshold</p></td>
|
|
<td><p>This is the smallest free-space section size that the
|
|
free-space manager will track.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td><p>Free-space manager addresses</p></td>
|
|
<td><p>These are the six free-space manager addresses for the
|
|
six file space allocation types:
|
|
<ul>
|
|
<li>H5FD_MEM_SUPER</li>
|
|
<li>H5FD_MEM_BTREE</li>
|
|
<li>H5FD_MEM_DRAW</li>
|
|
<li>H5FD_MEM_GHEAP</li>
|
|
<li>H5FD_MEM_LHEAP</li>
|
|
<li>H5FD_MEM_OHDR</li>
|
|
</ul>
|
|
Note that these six fields exist only if the value for the field
|
|
“<em>Strategy</em>” is H5F_FILE_SPACE_ALL_PERSIST.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
<br />
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: File Space Info - Version 1
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Strategy</td>
|
|
<td>Persisting free-space</td>
|
|
<td colspan="1" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Free-space Section Threshold<sup>L</sup></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">File Space Page Size</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="2">Page-end Metadata threshold</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />EOA<sup>0</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup> of small-sized free-space manager for H5FD_MEM_SUPER<br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup> of small-sized free-space manager for H5FD_MEM_BTREE<br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup> of small-sized free-space manager for H5FM_MEM_DRAW<br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup> of small-sized free-space manager for H5FD_MEM_GHEAP<br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup> of small-sized free-space manager for H5FD_MEM_LHEAP<br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup> of small-sized free-space manager for H5FD_MEM_OHDR<br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup> of large-sized free-space manager for H5FD_MEM_SUPER<br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup> of large-sized free-space manager for H5FD_MEM_BTREE<br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup> of large-sized free-space manager for H5FM_MEM_DRAW<br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup> of large-sized free-space manager for H5FD_MEM_GHEAP<br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup> of large-sized free-space manager for H5FD_MEM_LHEAP<br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup> of large-sized free-space manager for H5FD_MEM_OHDR<br /><br /></td>
|
|
</tr>
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: File Space Info
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>This is version 1 of this message.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Strategy</p></td>
|
|
<td><p>This is the file space strategy used to manage file space.
|
|
There are four types:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>H5F_FSPACE_STRATEGY_FSM_AGGR</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>H5F_FSPACE_STRATEGY_PAGE</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>H5F_FSPACE_STRATEGY_AGGR</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>H5F_FSPACE_STRATEGY_NONE</td>
|
|
</tr>
|
|
</table></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Persisting free-space</p></td>
|
|
<td><p>True or false in persisting free-space.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Free-space Section Threshold</p></td>
|
|
<td><p>This is the smallest free-space section size that the
|
|
free-space manager will track.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>File space page size</p></td>
|
|
<td><p>This is the file space page size, which is used when the paged aggregation feature
|
|
is enabled.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Page-end metadata threshold</p></td>
|
|
<td><p>This is the smallest free-space section size at the end of a page that
|
|
the free-space manager will track. This is used when the paged aggregation feature
|
|
is enabled.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>EOA</p></td>
|
|
<td><p>The EOA before the allocation of free-space manager header and section info for the
|
|
self-referential free-space managers when persisting free-space.
|
|
<br>
|
|
Note that self-referential free-space managers are managers that involve file space
|
|
allocation for the managers' free-space header and section info.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Addresses of small-sized free-space managers</p></td>
|
|
<td><p>These are the addresses of the six small-sized free-space managers for
|
|
the six file space allocation types:
|
|
</p>
|
|
<ul>
|
|
<li>H5FD_MEM_SUPER</li>
|
|
<li>H5FD_MEM_BTREE</li>
|
|
<li>H5FD_MEM_DRAW</li>
|
|
<li>H5FD_MEM_GHEAP</li>
|
|
<li>H5FD_MEM_LHEAP</li>
|
|
<li>H5FD_MEM_OHDR</li>
|
|
</ul>
|
|
Note that these six fields exist only if the value for the field
|
|
“<em>Persisting free-space</em>” is true.
|
|
</ul>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Addresses of large-sized free-space managers</p></td>
|
|
<td><p>These are the addresses of the six large-sized free-space managers for
|
|
the six file space allocation types:
|
|
</p>
|
|
<ul>
|
|
<li>H5FD_MEM_SUPER</li>
|
|
<li>H5FD_MEM_BTREE</li>
|
|
<li>H5FD_MEM_DRAW</li>
|
|
<li>H5FD_MEM_GHEAP</li>
|
|
<li>H5FD_MEM_LHEAP</li>
|
|
<li>H5FD_MEM_OHDR</li>
|
|
</ul>
|
|
Note that these six fields exist only if the value for the field
|
|
“<em>Persisting free-space</em>” is true.
|
|
</ul>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<h3><a name="DataStorage">
|
|
IV.B. Disk Format: Level 2B - Data Object Data Storage</a></h3>
|
|
|
|
<p>The data for an object is stored separately from its header
|
|
information in the file and may not actually be located in the HDF5 file
|
|
itself if the header indicates that the data is stored externally. The
|
|
information for each record in the object is stored according to the
|
|
dimensionality of the object (indicated in the dataspace header message).
|
|
Multi-dimensional array data is stored in C order; in other words, the
|
|
“last” dimension changes fastest.</p>
|
|
|
|
<p>Data whose elements are composed of atomic datatypes are stored in IEEE
|
|
format, unless they are specifically defined as being stored in a different
|
|
machine format with the architecture-type information from the datatype
|
|
header message. This means that each architecture will need to [potentially]
|
|
byte-swap data values into the internal representation for that particular
|
|
machine.</p>
|
|
|
|
<p> Data with a variable-length datatype is stored in the global heap
|
|
of the HDF5 file. Global heap identifiers are stored in the
|
|
data object storage.</p>
|
|
|
|
<p>Data whose elements are composed of reference datatypes are stored in
|
|
several different ways depending on the particular reference type involved.
|
|
Object pointers are just stored as the offset of the object header being
|
|
pointed to with the size of the pointer being the same number of bytes as
|
|
offsets in the file.</p>
|
|
|
|
<p>Dataset region references are stored as a heap-ID which points to
|
|
the following information within the file-heap: an offset of the object
|
|
pointed to, number-type information (same format as header message),
|
|
dimensionality information (same format as header message), sub-set start
|
|
and end information (in other words, a coordinate location for each),
|
|
and field start and end names (in other words, a [pointer to the] string
|
|
indicating the first field included and a [pointer to the] string name
|
|
for the last field). </p>
|
|
|
|
<p>Data of a compound datatype is stored as a contiguous stream of the items
|
|
in the structure, with each item formatted according to its datatype.
|
|
<p>
|
|
Description of datatypes for variable-length, references and compound classes can be found
|
|
in <a href="#DatatypeMessage">Datatype Message</a>.
|
|
<p>
|
|
Information about global heap and heap ID can be found in <a href="#GlobalHeap">Global Heap</a>.
|
|
<p>
|
|
For reference datatype,
|
|
see also the encoding description for <a href="#ReferenceEncodeRV">Reference Encoding (Revised) </a> and
|
|
<a href="#ReferenceEncodeDP">Reference Encoding (Backward Compatibility)</a> in Appendix D.
|
|
</p>
|
|
|
|
<h2><a name="AppendixA">
|
|
V. Appendix A: Definitions</a></h2>
|
|
|
|
<p>Definitions of various terms used in this document are included in
|
|
this section.</p>
|
|
|
|
<div align="center">
|
|
<table class="glossary">
|
|
<tr>
|
|
<th width="20%">Term</th>
|
|
<th>Definition</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Undefined Address</td>
|
|
<td>The <a name="UndefinedAddress">undefined
|
|
address</a> for a file is a file address with all bits
|
|
set: in other words, <code>0xffff...ff</code>.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Unlimited Size</td>
|
|
<td>The <a name="UnlimitedDim">unlimited size</a>
|
|
for a size is a value with all bits set: in other words,
|
|
<code>0xffff...ff</code>.</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<h2><a name="AppendixB">
|
|
VI. Appendix B: File Space Allocation Types</a></h2>
|
|
|
|
<p>There are six basic types of file space allocation as follows:
|
|
</p>
|
|
<div align="center">
|
|
<table class="desc">
|
|
<tr>
|
|
<th width="30%">Basic Allocation Type</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_SUPER</td>
|
|
<td>File space allocated for <em>Superblock.</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_BTREE</td>
|
|
<td>File space allocated for <em>B-tree.</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_DRAW</td>
|
|
<td>File space allocated for <em>raw data</em>.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_GHEAP</td>
|
|
<td>File space allocated for <em>Global Heap.</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_LHEAP</td>
|
|
<td>File space allocated for <em>Local Heap.</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_OHDR</td>
|
|
<td>File space allocated for <em>Object Header.</em></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<p>There are other file space allocation types that are mapped to the
|
|
above six basic types because they are similar in nature.
|
|
The mapping and the corresponding description are listed in the following two tables:
|
|
</p>
|
|
|
|
<div align="center">
|
|
<table class="desc">
|
|
<tr>
|
|
<th width="30%">Basic Allocation Type</th>
|
|
<th>Mapping of Allocation Types to Basic Allocation Types</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_SUPER</td>
|
|
<td><em>none</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_BTREE</td>
|
|
<td>H5FD_MEM_SOHM_INDEX</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_DRAW</td>
|
|
<td>H5FD_MEM_FHEAP_HUGE_OBJ</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_GHEAP</td>
|
|
<td><em>none</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_LHEAP</td>
|
|
<td>H5FD_MEM_FHEAP_DBLOCK, H5FD_MEM_FSPACE_SINFO</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_OHDR</td>
|
|
<td>H5FD_MEM_FHEAP_HDR, H5FD_MEM_FHEAP_IBLOCK, H5FD_MEM_FSPACE_HDR, H5FD_MEM_SOHM_TABLE</td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
</p>
|
|
|
|
<div align="center">
|
|
<table class="desc">
|
|
<tr>
|
|
<th width="30%">Allocation Type</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_FHEAP_HDR</td>
|
|
<td>File space allocated for <em>Fractal Heap Header.</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_FHEAP_DBLOCK</td>
|
|
<td>File space allocated for <em>Fractal Heap Direct Blocks.</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_FHEAP_IBLOCK</td>
|
|
<td>File space allocated for <em>Fractal Heap Indirect Blocks.</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_FHEAP_HUGE_OBJ</td>
|
|
<td>File space allocated for huge objects in the fractal heap.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_FSPACE_HDR</td>
|
|
<td>File space allocated for <em>Free-space Manager Header.</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>H5FD_MEM_FSPACE_SINFO</td>
|
|
<td>File space allocated for <em>Free-space Section List</em> of the free-space manager.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>H5FD_MEM_SOHM_TABLE</td>
|
|
<td>File space allocated for <em>Shared Object Header Message Table.</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td>H5FD_MEM_SOHM_INDEX</td>
|
|
<td>File space allocated for <em>Shared Message Record List.</em></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<h2><a name="AppendixC"> VII. Appendix C:
|
|
Types of Indexes for Dataset Chunks</a></h2>
|
|
|
|
<p>For an HDF5 file without the latest format enabled, the library
|
|
uses the <a href="#V1Btrees">Version 1 B-tree</a> to index dataset
|
|
chunks.</p>
|
|
|
|
<p>For an HDF5 file with the latest format enabled, the library uses
|
|
one of the following five indexing types depending on a chunked
|
|
dataset’s dimension specification and the way it is extended.
|
|
</p>
|
|
|
|
<a name="SingleChunk">
|
|
<h3>VII.A. The Single Chunk Index</h3></a>
|
|
|
|
<p>The <i>Single Chunk</i> index can be used when the dataset fulfills
|
|
the following condition:</p>
|
|
|
|
<ul>
|
|
<li>the current, maximum, and chunk dimension sizes are all the same</li>
|
|
</ul>
|
|
|
|
<p>The dataset has only one chunk, and the address of the single
|
|
chunk is stored in the version 4 <i>Data Layout</i> message.
|
|
See the <a href="#ChunkedStorage">Chunked Storage Property
|
|
Description</i></a> layout and field description tables.</p>
|
|
|
|
<a name="Implicit">
|
|
<h3>VII.B. The Implicit Index</h3></a>
|
|
|
|
<p>The <i>Implicit</i> index can be used when the dataset fulfills
|
|
the following conditions:</p>
|
|
|
|
<ul>
|
|
<li>fixed maximum dimension sizes</li>
|
|
<li>no filter applied to the dataset</li>
|
|
<li>the timing for the space allocation of the dataset chunks is
|
|
<code>H5P_ALLOC_TIME_EARLY</code></li>
|
|
</ul>
|
|
|
|
<p>Since the dataset’s dimension sizes are known and storage space
|
|
is to be allocated early, an array of dataset chunks are allocated
|
|
based on the maximum dimension sizes when the dataset is created.
|
|
The base address of the array is stored in the version 4
|
|
<i>Data Layout</i> message. See the
|
|
<a href="#ChunkedStorage">Chunked Storage Property
|
|
Description</i></a> layout and field description tables.
|
|
</p>
|
|
|
|
<p>When accessing a dataset chunk with a specified offset, the
|
|
address of the chunk in the array is computed as below:</p>
|
|
|
|
<dir><p><code>base address + (size of a chunk in bytes * chunk index
|
|
associated with the offset)</code></p></dir>
|
|
|
|
<p>A chunk index starts at 0 and increases according to the
|
|
fastest changing dimension, then the next fastest, and so on.
|
|
<a name="ChunkIndex"></a>
|
|
The chunk index for a dataset chunk offset is computed as below:
|
|
<ol>
|
|
<li>Calculate the scaled offset for each dimension in
|
|
<code>scaled_offset</code>:
|
|
<br />
|
|
<pre>
|
|
scaled_offset = chunk_offset/chunk_dims
|
|
</pre></li>
|
|
<li>Calculate the # of chunks for each dimension in
|
|
<code>nchunks</code>:
|
|
<br />
|
|
<pre>
|
|
nchunks = (curr_dims + chunk_dims - 1)/chunk_dims
|
|
</pre></li>
|
|
|
|
<li>Calculate the down chunks for each dimension in
|
|
<code>down_chunks</code>:
|
|
<br />
|
|
<pre>
|
|
/* n is the # of dimensions */
|
|
for(i = (int)(n-1), acc = 1; i >= 0; i--) {
|
|
down_chunks[i] = acc;
|
|
acc *= nchunks[i];
|
|
}
|
|
</pre>
|
|
</li>
|
|
|
|
<li>Calculate the chunk index in <code>chunk_index</code>:
|
|
<br />
|
|
<pre>
|
|
/* n is the # of dimensions */
|
|
for(u = 0, chunk_index = 0; u < n; u++)
|
|
chunk_index += down_chunks[u] * scaled_offset[u];
|
|
</pre>
|
|
</li>
|
|
</ol>
|
|
<p>
|
|
For example, for a 2-dimensional dataset with
|
|
<code>curr_dims[4,5]</code> and <code>chunk_dims[3,2]</code>,
|
|
there will be a total of 6 chunks, with 3 chunks in the fastest
|
|
changing dimension and 2 chunks in the slowest changing dimension.
|
|
See the figure below.
|
|
The chunk index for the chunk offset <code>[3,4]</code>
|
|
is computed as below:
|
|
<ol>
|
|
<code>
|
|
<li>scaled_offset[0] = 1, scaled_offset[1] = 2</li>
|
|
<li>nchunks[0] = 2, nchunks[1] = 3</li>
|
|
<li>down_chunks[0] = 3, down_chunks[1] = 1</li>
|
|
<li>chunk_index = 5</li>
|
|
</code>
|
|
</ol>
|
|
|
|
|
|
<table align="center" width="400" border="0">
|
|
<tr valign="center" align="center">
|
|
<td>
|
|
<hr size="2"/>
|
|
<img height="250" src="FileFormatSpecChunkDiagram.jpg"
|
|
alt="Chunk Diagram"></td>
|
|
</tr>
|
|
<tr valign="top" align="center">
|
|
<td>
|
|
<hr size="1" />
|
|
<b>Figure 3. Implicit index chunk diagram </b>
|
|
<hr size="2"/></td>
|
|
</tr>
|
|
</table>
|
|
|
|
|
|
|
|
|
|
|
|
<a name="FixedArray">
|
|
<h3>VII.C. The Fixed Array Index</h3></a>
|
|
|
|
<p>The <i>Fixed Array</i> index can be used when the dataset fulfills
|
|
the following condition:</p>
|
|
<ul>
|
|
<li>fixed maximum dimension sizes</li>
|
|
</ul>
|
|
|
|
<p>Since the maximum number of chunks is known, an array of
|
|
in-file-on-disk addresses based on the maximum number of chunks is
|
|
allocated when data is written to the dataset. To access a dataset
|
|
chunk with a specified offset, the
|
|
<a href="#ChunkIndex">chunk index</i></a> associated with the offset
|
|
is calculated. The index is mapped into the array to locate the
|
|
disk address for the chunk.</p>
|
|
|
|
<p>The Fixed Array (FA) index structure provides space and speed
|
|
improvements in locating chunks over index structures that handle
|
|
more dynamic data accesses like a
|
|
<a href="#AppendV2Btrees">Version 2 B-tree</a> index.
|
|
The entry into the Fixed Array is the Fixed Array header which
|
|
contains metadata about the entries stored in the array. The
|
|
header contains a pointer to a data block which stores the array
|
|
of entries that describe the dataset chunks. For greater efficiency,
|
|
the array will be divided into multiple pages if the number of
|
|
entries exceeds a threshold value. The space for the data block
|
|
and possibly data block pages are allocated as a single contiguous
|
|
block of space.</p>
|
|
|
|
<p>The content of the data block depends on whether paging is
|
|
activated or not. When paging is not used, elements that describe
|
|
the chunks are stored in the data block. If paging is turned on,
|
|
the data block contains a bitmap indicating which pages are
|
|
initialized. Then subsequent data block pages will contain the
|
|
entries that describe the chunks.</p>
|
|
|
|
<p>An entry describes either a filtered or non-filtered dataset
|
|
chunk. The formats for both element types are described below.
|
|
</p>
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fixed Array Header
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Client ID</td>
|
|
<td>Entry Size</td>
|
|
<td>Page Bits</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Max Num
|
|
Entries<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Data Block
|
|
Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fixed Array Header
|
|
</caption>
|
|
<tr>
|
|
<th width="40%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>FAHD</code>”
|
|
is used to indicate the beginning of a Fixed Array header.
|
|
This gives file consistency checking utilities a better
|
|
chance of reconstructing a damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>This document describes version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Client ID</p></td>
|
|
<td>
|
|
<p>The ID for identifying the client of the
|
|
Fixed Array:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">ID</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Non-filtered dataset chunks
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Filtered dataset chunks
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2+</code></td>
|
|
<td>Reserved
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Entry Size</p></td>
|
|
<td>
|
|
<p>The size in bytes of an entry in the Fixed Array.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Page Bits</p></td>
|
|
<td>
|
|
<p>The number of bits needed to store the maximum
|
|
number of entries in a
|
|
<a href="#FADataBlockPage">data block page.</a></p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Max Num Entries</p></td>
|
|
<td>
|
|
<p>The maximum number of entries in the Fixed
|
|
Array.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Data Block Address</p></td>
|
|
<td>
|
|
<p>The address of the data block in the Fixed Array.
|
|
</p>
|
|
</td>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>The checksum for the header.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Fixed Array Data Block
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Client ID</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted
|
|
only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Header Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Page Bitmap <em>(variable size and
|
|
optional)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Elements <em>(variable size and
|
|
optional)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fixed Array Data Block
|
|
</caption>
|
|
<tr>
|
|
<th width="40%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>FADB</code>”
|
|
is used to indicate the beginning of a Fixed Array data
|
|
block. This gives file consistency checking utilities a
|
|
better chance of reconstructing a damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>This document describes version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Client ID</p></td>
|
|
<td>
|
|
<p>The ID for identifying the client of the
|
|
Fixed Array:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">ID</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Non-filtered dataset chunks
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Filtered dataset chunks
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2+</code></td>
|
|
<td>Reserved.
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Header Address</p></td>
|
|
<td>
|
|
<p>The address of the Fixed Array header. Principally used
|
|
for file integrity checking.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Page Bitmap</p></td>
|
|
<td><p>A bitmap indicating which data block pages are initialized.</p>
|
|
<p>Exists only if the data block is paged.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Elements</p></td>
|
|
<td>
|
|
<p>Contains the elements stored in the data block
|
|
and exists only if the data block is not paged.
|
|
There are two element types:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">ID</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td><a href="#FaNonFilterChunk">Non-filtered
|
|
dataset chunks</i></a>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td><a href="#FaFilterChunk">Filtered dataset
|
|
chunks</i></a>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>The checksum for the Fixed Array data block.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption><a name="FADataBlockPage">
|
|
Layout: Fixed Array Data Block Page</a>
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Elements <em>(variable
|
|
size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Fixed Array Data Block Page
|
|
</caption>
|
|
<tr>
|
|
<th width="40%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Elements</p></td>
|
|
<td>
|
|
<p>Contains the elements stored in the data block page.
|
|
There are two element types:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">ID</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td><a href="#FaNonFilterChunk">Non-filtered dataset chunks</i></a>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td><a href="#FaFilterChunk">Filtered dataset chunks</i></a>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>The checksum for a Fixed Array data block page.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<a name="FaNonFilterChunk"></a>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Data Block Element for Non-filtered Dataset Chunk
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Data Block Element for Non-filtered Dataset Chunk
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address</p></td>
|
|
<td><p>The address of the dataset chunk in the file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
<!-- </p> -->
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<a name="FaFilterChunk"></a>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Data Block Element for Filtered Dataset Chunk
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Chunk Size <em>(variable size; at most
|
|
8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Filter Mask</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Data Block Element for Filtered Dataset Chunk
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address</p></td>
|
|
<td><p>The address of the dataset chunk in the file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Chunk Size</p></td>
|
|
<td><p>The size of the dataset chunk in bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filter Mask</p></td>
|
|
<td><p>Indicates the filter to skip for the dataset chunk. Each
|
|
filter has an index number in the pipeline; if that filter is
|
|
skipped, the bit corresponding to its index is set.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<a name="ExtensibleArray">
|
|
<h3>VII.D. The Extensible Array Index</h3></a>
|
|
|
|
<p>The <i>Extensible Array</i> index can be used when the dataset
|
|
fulfills the following condition:</p>
|
|
|
|
<ul>
|
|
<li>only one dimension of unlimited extent</li>
|
|
</ul>
|
|
|
|
<p>The Extensible Array (EA) is a data structure that is used as a
|
|
chunk index in datasets where the dataspace has a single
|
|
unlimited dimension. In other words, one dimension is set to
|
|
<code>H5S_UNLIMITED</code>, and the other dimensions are any number
|
|
of fixed-size dimensions. The idea behind the extensible array is
|
|
that a particular data object can be located via a lightweight
|
|
indexing structure of fixed depth for a given address space. This
|
|
indexing structure requires only a few (2-3) file operations per
|
|
element lookup and gives good cache performance. Unlike the B-tree
|
|
structure, the extensible array is optimized for appends. Where a
|
|
B-tree would always add at the rightmost node under these
|
|
circumstances, either creating a deep tree (version 1) or requiring
|
|
expensive rebalances to correct (version 2), the extensible array
|
|
has already mapped out a pre-balanced internal structure. This
|
|
optimized internal structure is instantiated as needed when chunk
|
|
records are inserted into the structure.</p>
|
|
|
|
|
|
|
|
<!--
|
|
|
|
<p>A description of the rationale that leads to the present
|
|
implementation of the extensible array can be found at
|
|
<a href="https://svn.hdfgroup.org/hdf5doc/trunk/projects/1_10_alpha/ReviseChunks/skip_lists">
|
|
https://svn.hdfgroup.org/hdf5doc/trunk/projects/1_10_alpha/ReviseChunks/skip_lists</a>.
|
|
</p>
|
|
|
|
<p>The current implementation differs from the data structure
|
|
described in that reference in some ways, but the basic idea is the
|
|
same.</p>
|
|
|
|
-->
|
|
|
|
|
|
|
|
<p>An Extensible Array consists of a header, an index block,
|
|
secondary blocks, data blocks, and (optional) data block pages. The
|
|
general scheme is that the index block is used to reference a
|
|
secondary block, which is, in turn, used to reference the data block
|
|
page where the chunk information is stored. The data blocks will
|
|
be paged for efficiency when their size passes a threshold value.
|
|
These pages are laid out contiguously on the disk after the data
|
|
block, are initialized as needed, and are tracked via bitmaps
|
|
stored in the secondary block. The number of secondary and data
|
|
blocks/pages in a chunk index varies as they are allocated as
|
|
needed and the first few are (conceptually) stored in parent
|
|
elements as an optimization.</p>
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Extensible Array Header
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Client ID</td>
|
|
<td>Element Size</td>
|
|
<td>Max Nelmts Bits</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Index Blk Elmts</td>
|
|
<td>Data Blk Min Elmts</td>
|
|
<td>Secondary Blk Min Data Ptrs</td>
|
|
<td>Max Data Blk Page Nelmts Bits</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Num Secondary Blks<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Secondary Blk Size<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Num Data Blks<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Data Blk Size<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Max Index Set<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Num Elements<sup>L</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Index Block Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘L’ in the above table are
|
|
of the size specified in the <a href="#SizeOfLengthsV0">Size
|
|
of Lengths</a> field in the superblock.)
|
|
</td></tr>
|
|
<tr>
|
|
<td> </td>
|
|
<td>
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Extensible Array Header
|
|
</caption>
|
|
<tr>
|
|
<th width="40%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>EAHD</code>”
|
|
is used to indicate the beginning of an Extensible Array
|
|
header. This gives file consistency checking utilities a
|
|
better chance of reconstructing a damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>This document describes version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Client ID</p></td>
|
|
<td>
|
|
<p>The ID for identifying the client of the
|
|
Fixed Array:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">ID</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Non-filtered dataset chunks
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Filtered dataset chunks
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2+</code></td>
|
|
<td>Reserved.
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Element Size</p></td>
|
|
<td>
|
|
<p>The size in bytes of an element in the Extensible Array.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Max Nelmts Bits</p></td>
|
|
<td>
|
|
<p>The number of bits needed to store the
|
|
maximum number of elements in the Extensible Array.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Index Blk Elmts</p></td>
|
|
<td>
|
|
<p>The number of elements to store in the index block.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Data Blk Min Elmts</p></td>
|
|
<td>
|
|
<p>The minimum number of elements per data block.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Secondary Blk Min Data Ptrs</p></td>
|
|
<td>
|
|
<p>The minimum number of data block pointers for a
|
|
secondary block.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Max Dblk Page Nelmts Bits</p></td>
|
|
<td>
|
|
<p>The number of bits needed to store the maximum number
|
|
of elements in a data block page.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Num Secondary Blks</p></td>
|
|
<td>
|
|
<p>The number of secondary blocks created.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Secondary Blk Size</p></td>
|
|
<td>
|
|
<p>The size of the secondary blocks created.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Num Data Blks</p></td>
|
|
<td>
|
|
<p>The number of data blocks created.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Data Blk Size</p></td>
|
|
<td>
|
|
<p>The size of the data blocks created.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Max Index Set</p></td>
|
|
<td>
|
|
<p>The maximum index set.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Num Elmts</p></td>
|
|
<td>
|
|
<p>The number of elements realized.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Index Block Address</p></td>
|
|
<td>
|
|
<p>The address of the index block.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>The checksum for the header.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Extensible Array Index Block
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Client ID</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted
|
|
only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Header Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Elements <em>(variable size and
|
|
optional)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Data Block Addresses <em>(variable
|
|
size and optional)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Secondary Block Addresses <em>(variable
|
|
size and optional)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Extensible Array Index Block
|
|
</caption>
|
|
<tr>
|
|
<th width="40%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>EAIB</code>”
|
|
is used to indicate the beginning of an Extensible Array
|
|
Index Block. This gives file consistency checking utilities
|
|
a better chance of reconstructing a damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>This document describes version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Client ID</p></td>
|
|
<td>
|
|
<p>The client ID for identifying the user of the
|
|
Extensible Array:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">ID</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Non-filtered dataset chunks
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Filtered dataset chunks
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2+</code></td>
|
|
<td>Reserved.
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Header Address</p></td>
|
|
<td>
|
|
<p>The address of the Extensible Array header. Principally
|
|
used for file integrity checking.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Elements</p></td>
|
|
<td>
|
|
<p>Contains the elements that are stored directly in
|
|
the index block. An optimization to avoid unnecessary
|
|
secondary blocks.
|
|
<br />
|
|
<br />
|
|
There are two element types:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">ID</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td><a href="#EaNonFilterChunk">Non-filtered dataset chunks</i></a>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td><a href="#EaFilterChunk">Filtered dataset chunks</i></a>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Data Block Addresses</p></td>
|
|
<td>
|
|
<p>Contains the addresses of the data blocks
|
|
that are stored directly in the Index Block. An
|
|
optimization to avoid unnecessary secondary blocks.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Secondary Block Addresses</p></td>
|
|
<td>
|
|
<p>Contains the addresses of the secondary
|
|
blocks.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>The checksum for the Extensible Array Index Block.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Extensible Array Secondary Block
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Client ID</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted
|
|
only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Header Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Block Offset <em>(variable
|
|
size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Page Bitmap <em>(variable size and
|
|
optional)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Data Block Addresses <em>(variable
|
|
size and optional)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Extensible Array Secondary Block
|
|
</caption>
|
|
<tr>
|
|
<th width="40%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>EASB</code>”
|
|
is used to indicate the beginning of an Extensible Array
|
|
Secondary Block. This gives file consistency checking utilities
|
|
a better chance of reconstructing a damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>This document describes version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Client ID</p></td>
|
|
<td>
|
|
<p>The ID for identifying the client of the
|
|
Extensible Array:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">ID</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Non-filtered dataset chunks
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Filtered dataset chunks
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2+</code></td>
|
|
<td>Reserved.
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Header Address</p></td>
|
|
<td>
|
|
<p>The address of the Extensible Array header. Principally
|
|
used for file integrity checking.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Block Offset</p></td>
|
|
<td>
|
|
<p>Stores the offset of the block in the array.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Page Bitmap</p></td>
|
|
<td>
|
|
<p>A bitmap indicating which
|
|
data block pages are initialized.
|
|
<p>
|
|
Exists only if the data block is paged.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Data Block Addresses</p></td>
|
|
<td>
|
|
<p>Contains the addresses of the data blocks
|
|
referenced by this secondary block.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>The checksum for the Extensible Array
|
|
Secondary Block.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Extensible Array Data Block
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Signature</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Version</td>
|
|
<td>Client ID</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted
|
|
only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Header Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Block Offset <em>(variable
|
|
size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Elements <em>(variable size and
|
|
optional)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Extensible Array Data Block
|
|
</caption>
|
|
<tr>
|
|
<th width="40%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Signature</p></td>
|
|
<td>
|
|
<p>The ASCII character string “<code>EADB</code>”
|
|
is used to indicate the beginning of an Extensible Array
|
|
data block. This gives file consistency checking utilities
|
|
a better chance of reconstructing a damaged file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td>
|
|
<p>This document describes version 0.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Client ID</p></td>
|
|
<td>
|
|
<p>The ID for identifying the client of the
|
|
Extensible Array:
|
|
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">ID</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Non-filtered dataset chunks
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Filtered dataset chunks
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>2+</code></td>
|
|
<td>Reserved.
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Header Address</p></td>
|
|
<td>
|
|
<p>The address of the Extensible Array header. Principally
|
|
used for file integrity checking.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Block Offset</p></td>
|
|
<td>
|
|
<p>The offset of the block in the array.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Elements</p></td>
|
|
<td>
|
|
<p>Contains the elements stored in the data block and
|
|
exists only if the data block is not paged.
|
|
<br />
|
|
<br />
|
|
There are two element types:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">ID</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td><a href="#EaNonFilterChunk">Non-filtered dataset chunks</i></a>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td><a href="#EaFilterChunk">Filtered dataset chunks</i></a>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>The checksum for the Extensible Array data block.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Extensible Array Data Block Page
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Elements <em>(variable
|
|
size)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Checksum</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Extensible Array Data Block Page
|
|
</caption>
|
|
<tr>
|
|
<th width="40%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Elements</p></td>
|
|
<td>
|
|
<p>Contains the elements stored in the data block
|
|
page.</p>
|
|
<p>
|
|
There are two element types:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">ID</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td><a href="#EaNonFilterChunk">Non-filtered dataset chunks</i></a>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td><a href="#EaFilterChunk">Filtered dataset chunks</i></a>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Checksum</p></td>
|
|
<td>
|
|
<p>The checksum for an Extensible Array data block
|
|
page.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<a name="EaNonFilterChunk"></a>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Data Block Element for Non-filtered Dataset Chunk
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr><td>
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Data Block Element for Non-filtered Dataset Chunk
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address</p></td>
|
|
<td><p>The address of the dataset chunk in the file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
</p>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<a name="EaFilterChunk"></a>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Data Block Element for Filtered Dataset Chunk
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Chunk Size<em> (variable size; at
|
|
most 8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Filter Mask</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Data Block Element for Filtered Dataset Chunk
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Address</p></td>
|
|
<td><p>The address of the dataset chunk in the file.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Chunk Size</p></td>
|
|
<td><p>The size of the dataset chunk in bytes.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Filter Mask</p></td>
|
|
<td><p>Indicates the filter to skip for the dataset chunk.
|
|
Each filter has an index number in the pipeline; if that
|
|
filter is skipped, the bit corresponding to its index is set.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<a name="AppendV2Btrees">
|
|
<h3>VII.E. The Version 2 B-trees Index</h3></a>
|
|
|
|
<p>The <i>Version 2 B-trees</i> index can be used when the dataset
|
|
fulfills the following condition:</p>
|
|
|
|
<ul>
|
|
<li>more than one dimension of unlimited extent</li>
|
|
</ul>
|
|
|
|
<p>Version 2 B-trees can be used to index various objects in the
|
|
library. See <a href="#V2Btrees">“Version 2 B-trees”</a>
|
|
for more information. The B-tree types <a href="#V2BtType10">10</a>
|
|
and <a href="#V2BtreesType11">11</a> record layouts are for
|
|
indexing dataset chunks.</p>
|
|
|
|
<h2><a name="AppendixD"> VIII. Appendix D:
|
|
Encoding for dataspace and reference</a></h2>
|
|
|
|
<a name="DataspaceEncode">
|
|
<h3>VIII.A. Dataspace Encoding </h3></a>
|
|
<i>H5Sencode</i> is a public routine that encodes a dataspace description into a buffer while
|
|
<i>H5Sdecode</i> is the corresponding routine that decodes the description encoded in the buffer.
|
|
<p>
|
|
See the reference manual description for these two public routines.
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Dataspace Description for H5Sencode/H5Sdecode
|
|
</caption>
|
|
|
|
<tr>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
<th>byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Dataspace ID</td>
|
|
<td>Encode Version</td>
|
|
<td>Size of Size</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted
|
|
only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Size of Extent
|
|
<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br /><br />Dataspace Message
|
|
<em>(variable size)</em>
|
|
<br /><br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br /><br />Dataspace Selection
|
|
<em>(variable size)</em>
|
|
<br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Dataspace Description for H5Sencode/H5Sdecode
|
|
</caption>
|
|
<tr>
|
|
<th width="40%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dataspace ID</p></td>
|
|
<td>
|
|
<p>The datspace message ID which is 1.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Encode Version</p></td>
|
|
<td>
|
|
<p>H5S_ENCODE_VERSION which is 0.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size of Size</p></td>
|
|
<td>
|
|
<p>The number of bytes used to store the size of an object.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Size of Extent</p></td>
|
|
<td>
|
|
<p>Size of the dataspace message.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dataspace Message</p></td>
|
|
<td>
|
|
<p>The dataspace message information. See
|
|
<a href="#DataspaceMessage">Dataspace Message.</a></p>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dataspace Selection</p></td>
|
|
<td>
|
|
<p>The dataspace selection information. See
|
|
<a href="#DataspaceSEL">Dataspace Selection.</a></p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<a name="DataspaceSEL"></a>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Dataspace Selection
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Selection Type</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Selection Info (<em>variable
|
|
size</em>)<br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Dataspace Selection
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Selection Type</p></td>
|
|
<td>
|
|
<p>There are 4 types of selection:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>H5S_SEL_NONE: Nothing selected
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>H5S_SEL_POINTS: Sequence of points selected
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>H5S_SEL_HYPER: Hyperslab selected
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>H5S_SEL_ALL: Entire extent selected
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</td>
|
|
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Selection Info</p></td>
|
|
<td>
|
|
<p>There are 4 types of selection info:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>Selection info for <a href="#SelNONE">H5S_SEL_NONE</a>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>Selection info for <a href="#SelPOINTS">H5S_SEL_POINTS</a>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>Selection info for <a href="#SelHYPER">H5S_SEL_HYPER</a>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>Selection for <a href="#SelALL">H5S_SEL_ALL</a>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</td>
|
|
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<a name="SelNONE"/></a>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Selection Info for H5S_SEL_NONE
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Version</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Reserved <em>(zero, 8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Selection Info for H5S_SEL_NONE
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number for the H5S_SEL_NONE Selection Info.
|
|
The value is 1.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<a name="SelPOINTS"></a>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Selection Info for H5S_SEL_POINTS
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Version</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br /><br />Points Selection Info <em>(variable size)</em>
|
|
<br /><br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Selection Info for H5S_SEL_POINTS
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number for the H5S_SEL_POINTS Selection Info.
|
|
The value is either 1 or 2.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Points Selection Info</p></td>
|
|
<td><p>Depending on <em>version</em>:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Version</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>See <a href="#SelPOINTSV1">Version 1 Points Selection Info</a>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>See <a href="#SelPOINTSV2">Version 2 Points Selection Info</a>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<a name="SelPOINTSV1"></a>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 1 Points Selection Info
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Reserved <em>(zero)</em></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Length</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Rank</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Num Points</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Point #1: coordinate #1</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Point #1: coordinate #u</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Point #n: coordinate #1</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Point #n: coordinate #u</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 1 Points Selection Info
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Length</p></td>
|
|
<td><p>The size in bytes from <em>Length</em> to the end of the
|
|
selection info.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Rank</p></td>
|
|
<td><p>The number of dimensions.</p></td>
|
|
</tr>
|
|
<tr>
|
|
<td><p>Num Points</p></td>
|
|
<td><p>The number of points in the selection.</p></td>
|
|
</tr>
|
|
<tr>
|
|
<td><p>Point #n: coordinate #u</p></td>
|
|
<td><p>The array of points in the selection.
|
|
<p>The points selected are #1 to #n where n is <em>Num Points</em>.
|
|
<p>The list of coordinates for each point are #1 to #u where u is
|
|
<em>Rank</em>.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<a name="SelPOINTSV2"></a>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 Points Selection Info
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="1">Encode Size</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted only to align table nicely</em>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Rank</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Num Points<p>(2, 4 or 8 bytes)<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Point #1: coordinate #1<p>(2, 4 or 8 bytes)<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Point #1: coordinate #u<p>(2, 4 or 8 bytes)<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Point #n: coordinate #1 <p>(2, 4 or 8 bytes)<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Point #n: coordinate #u<p>(2, 4 or 8 bytes)<br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 Points Selection Info
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Encode Size</td>
|
|
<td><p>The size for encoding the points selection info which can be 2, 4 or 8 bytes.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Rank</p></td>
|
|
<td><p>The number of dimensions.</p></td>
|
|
</tr>
|
|
<tr>
|
|
<td><p>Num Points</p></td>
|
|
<td><p>The number of points in the selection.
|
|
<p>The field <em>Encode Size</em> indicates the size of this field</p></td>
|
|
</tr>
|
|
<tr>
|
|
<td><p>Point #n: coordinate #u</p></td>
|
|
<td><p>The array of points in the selection.
|
|
<p>The points selected are #1 to #n where n is <em>Num Points</em>.
|
|
<p>The list of coordinates for each point are #1 to #u where u is
|
|
<em>Rank</em>.
|
|
<p>The field <em>Encode Size</em> indicates the size of this field</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<a name="SelHYPER"></a>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Selection Info for H5S_SEL_HYPER
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Version</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Hyperslab Selection Info
|
|
(<em>variable size</em>)<br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Selection Info for H5S_SEL_HYPER
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number for the H5S_SEL_HYPER selection info.
|
|
The value is 1, 2 or 3.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Hyperslab Selection Info</p></td>
|
|
<td><p>Depending on <em>version</em>:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Version</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>1</code></td>
|
|
<td>See <a href="#SelHYPERV1">Version 1 Hyperslab Selection Info</a>.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>See <a href="#SelHYPERV2">Version 2 Hyperslab Selection Info</a>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>See <a href="#SelHYPERV3">Version 3 Hyperslab Selection Info</a>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<a name="SelHYPERV1"></a>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 1 Hyperslab Selection Info
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Reserved</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Length</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Rank</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Num Blocks</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Starting Offset #1 for Block #1</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Starting Offset #n for Block #1</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Ending Offset #1 for Block #1</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Ending Offset #n for Block #1</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Starting Offset #1 for Block #u</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Starting Offset #n for Block #u</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Ending Offset #1 for Block #u</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Ending Offset #n for Block #u</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 1 Hyperslab Selection Info
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Length</p></td>
|
|
<td><p>The size in bytes from the field <em>Rank</em> to the
|
|
end of the Selection Info.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Rank</p></td>
|
|
<td><p>The number of dimensions in the dataspace.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Num Blocks</p></td>
|
|
<td><p>The number of blocks in the selection.</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Starting Offset #n for Block #u</p></td>
|
|
<td><p>The offset #n of the starting element in block #u.
|
|
<p>#n is from 1 to <em>Rank</em>.
|
|
<p>#u is from 1 to <em>Num Blocks</em> moving from the fastest
|
|
changing dimension to the slowest changing dimension.
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Ending Offset #n for Block #u</p></td>
|
|
<td><p>The offset #n of the ending element in block #u.
|
|
<p>#n is from 1 to <em>Rank</em>.
|
|
<p>#u is from 1 to <em>Num Blocks</em> moving from the fastest
|
|
changing dimension to the slowest changing dimension.
|
|
</p></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<a name="SelHYPERV2"></a>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 2 Hyperslab Selection Info
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Flags</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted
|
|
only to align table nicely</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Length</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Rank</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Start #1 <em>(8 bytes)</em><p></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Stride #1 <em>(8 bytes)</em><p></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Count #1 <em>(8 bytes)</em><p></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Block #1 <em>(8 bytes)</em><p></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Start #n <em>(8 bytes)</em><p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Stride #n <em>(8 bytes)</em><p></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Count #n <em>(8 bytes)</em><p></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Block #n <em>(8 bytes)</em><p></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 2 Hyperslab Selection Info
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Flags</p></td>
|
|
<td><p>This is a bit field with the following definition.
|
|
Currently, this is always set to 0x1.
|
|
<p>
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>If set, it is a regular hyperslab, otherwise, irregular.
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</td>
|
|
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Length</p></td>
|
|
<td><p>The size in bytes from the field <em>Rank</em> to the
|
|
end of the Selection Info.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Rank</p></td>
|
|
<td><p>The number of dimensions in the dataspace.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Start #n</p></td>
|
|
<td><p>The offset of the starting element in the block.
|
|
<p>#n is from 1 to <em>Rank</em>.
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Stride #n</p></td>
|
|
<td><p>The number of elements to move in each dimension.
|
|
<p>#n is from 1 to <em>Rank</em>.
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Count #n</p></td>
|
|
<td><p>The number of blocks to select in each dimension.
|
|
<p>#n is from 1 to <em>Rank</em>.
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Block #n</p></td>
|
|
<td><p>The size (in elements) of each block in each dimension.
|
|
<p>#n is from 1 to <em>Rank</em>.
|
|
</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<a name="SelHYPERV3"></a>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 3 Hyperslab Selection Info
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Flags</td>
|
|
<td>Encode Size</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted
|
|
only to align table nicely</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Rank</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Regular/Irregular Hyperslab Selection Info
|
|
<p><em>(variable size)</em><br /><br/></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 3 Hyperslab Selection Info
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Flags</p></td>
|
|
<td><p>This is a bit field with the following definition:
|
|
<p>
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>If set, it is a regular hyperslab, otherwise, irregular.
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Encode Size</p></td>
|
|
<td><p>The size for encoding hyperslab selection info, which can 2, 4 or 8 bytes.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Rank</p></td>
|
|
<td><p>The number of dimensions in the dataspace.</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Regular/Irregular Hyperslab Selection Info</p></td>
|
|
<td><p>This is the selection info for version 3 hyperslab which can be regular or irregular.
|
|
<p>If bit 0 of the field <em>Flags</em> is set,
|
|
See <a href="#SelHYPERV3REG">Version 3 Regular Hyperslab Selection Info</a>
|
|
<p>Otherwise, see <a href="#SelHYPERV3IRREG">Version 3 Irregular Hyperslab Selection Info</a>
|
|
</td>
|
|
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<a name="SelHYPERV3REG"></a>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 3 Regular Hyperslab Selection Info
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Start #1 <p><em>(2, 4 or 8 bytes)</em><p></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Stride #1 <p><em>(2, 4 or 8 bytes)</em><p></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Count #1 <p><em>(2, 4 or 8 bytes)</em><p></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Block #1 <p><em>(2, 4 or 8 bytes)</em><p></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Start #n <p><em>(2, 4 or 8 bytes)</em><p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Stride #n <p><em>(2, 4 or 8 bytes)</em><p></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Count #n <p><em>(2, 4 or 8 bytes)</em><p></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Block #n <p><em>(2, 4 or 8 bytes)</em><p></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 3 Regular Hyperslab Selection Info
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Start #n</p></td>
|
|
<td><p>The offset of the starting element in the block.
|
|
<p>#n is from 1 to <em>Rank</em>.
|
|
<p>The field <em>Encode Size</em> indicates the size of this field.
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Stride #n</p></td>
|
|
<td><p>The number of elements to move in each dimension.
|
|
<p>#n is from 1 to <em>Rank</em>.
|
|
<p>The field <em>Encode Size</em> indicates the size of this field.
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Count #n</p></td>
|
|
<td><p>The number of blocks to select in each dimension.
|
|
<p>#n is from 1 to <em>Rank</em>.
|
|
<p>The field <em>Encode Size</em> indicates the size of this field.
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Block #n</p></td>
|
|
<td><p>The size (in elements) of each block in each dimension.
|
|
<p>#n is from 1 to <em>Rank</em>.
|
|
<p>The field <em>Encode Size</em> indicates the size of this field.
|
|
</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<a name="SelHYPERV3IRREG"></a>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Version 3 Irregular Hyperslab Selection Info
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Num Blocks<p><em>(2, 4 or 8 bytes)</em><p></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Starting Offset #1 for Block #1<p><em>(2, 4 or 8 bytes)</em><p></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Starting Offset #n for Block #1<p><em>(2, 4 or 8 bytes)</em><p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Ending Offset #1 for Block #1<p><em>(2, 4 or 8 bytes)</em><p></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Ending Offset #n for Block #1<p><em>(2, 4 or 8 bytes)</em><p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Starting Offset #1 for Block #u<p><em>(2, 4 or 8 bytes)</em><p></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Starting Offset #n for Block #u<p><em>(2, 4 or 8 bytes)</em><p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Ending Offset #1 for Block #u<p><em>(2, 4 or 8 bytes)</em><p></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">.<br />.<br />.<br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4">Ending Offset #n for Block #u<p><em>(2, 4 or 8 bytes)</em><p></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Version 3 Irregular Hyperslab Selection Info
|
|
</caption>
|
|
|
|
<tr>
|
|
<td><p>Num Blocks</p></td>
|
|
<td><p>The number of blocks in the selection.
|
|
<p>The field <em>Encode Size</em> indicates the size of this field</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Starting Offset #n for Block #u</p></td>
|
|
<td><p>The offset #n of the starting element in block #u.
|
|
<p>#n is from 1 to <em>Rank</em>.
|
|
<p>#u is from 1 to <em>Num Blocks</em> moving from the fastest
|
|
changing dimension to the slowest changing dimension.
|
|
<p>The field <em>Encode Size</em> indicates the size of this field
|
|
</p></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Ending Offset #n for Block #u</p></td>
|
|
<td><p>The offset #n of the ending element in block #u.
|
|
<p>#n is from 1 to <em>Rank</em>.
|
|
<p>#u is from 1 to <em>Num Blocks</em> moving from the fastest
|
|
changing dimension to the slowest changing dimension.
|
|
<p>The field <em>Encode Size</em> indicates the size of this field
|
|
</p></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
<a name="SelALL"></a>
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Selection Info for H5S_SEL_ALL
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4">Version</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan="4"><br />Reserved <em>(zero,
|
|
8 bytes)</em><br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Selection Info for H5S_SEL_ALL
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Version</p></td>
|
|
<td><p>The version number for the H5S_SEL_ALL Selection Info;
|
|
the value is 1.</p></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
|
|
<a name="ReferenceEncodeRV">
|
|
<h3>VIII.B. Reference Encoding (Revised)</h3></a>
|
|
<p>
|
|
<br />
|
|
For the following reference type,
|
|
the Reference Header and Reference Block are stored together as the dataset's raw data:
|
|
<ul>
|
|
<li>Object Reference (H5R_OBJECT2) (without reference to an external file)</li>
|
|
</ul>
|
|
<p>
|
|
For the following reference types,
|
|
the Reference Header plus the <a href="#GlobalHeapID">Global Heap ID</a> are stored
|
|
as the dataset's raw data in the file.
|
|
The global heap ID is used to locate the Reference Block stored in the global heap:
|
|
<ul>
|
|
<li>Object Reference (H5R_OBJECT2) (with reference to an external file)</li>
|
|
<li>Dataset Region Reference (H5R_DATASET_REGION2) (with/without reference to an external file)</li>
|
|
<li>Attribute Reference (H5R_ATTR) (with/without reference to an external file)</li>
|
|
</ul>
|
|
<br />
|
|
<br />
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Reference Header
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Reference Type</td>
|
|
<td>Flags</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted
|
|
only to align table nicely</em></td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Reference Header
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Reference Type</p></td>
|
|
<td>
|
|
<p>There are 3 types of references:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Value</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>2</code></td>
|
|
<td>H5R_OBJECT2: Object Reference
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>3</code></td>
|
|
<td>H5R_DATASET_REGION2: Dataset Region Reference
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>4</code></td>
|
|
<td>H5R_ATTR: Attribute Reference
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Flags</p></td>
|
|
<td><p>This field describes the reference:
|
|
<table class="list">
|
|
<tr>
|
|
<th width="20%" align="center">Bit</th>
|
|
<th width="80%" align="left">Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td align="center"><code>0</code></td>
|
|
<td>If set, the reference is to an external file.
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"><code>1-7</code></td>
|
|
<td>Reserved</td>
|
|
</tr>
|
|
</table></p>
|
|
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Reference Block
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>Token Size</td>
|
|
<td colspan="3" bgcolor="#DDDDDD"><em>This space inserted
|
|
only to align table nicely</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan=4><br /><br />Token
|
|
<em>(variable size)</em><br /> <br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan=2>Length of External File Name</td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted
|
|
only to align table nicely</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan=4><br /><br />External File Name
|
|
<em>(variable size)</em><br /><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan=4>Size of Dataspace Selection</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan=4>Rank of Dataspace Selection</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan=4><br /><br />Dataspace Selection Information
|
|
<em>(variable size)</em><br /><br /> <br /></td>
|
|
</td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan=2>Length of Attribute Name </td>
|
|
<td colspan="2" bgcolor="#DDDDDD"><em>This space inserted
|
|
only to align table nicely</em></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan=4><br /><br />Attribute Name
|
|
<em>(variable size)</em><br /><br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Reference Block
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Token size</p></td>
|
|
<td><p>This is the size of the token for the object.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Token</p></td>
|
|
<td>
|
|
<p>
|
|
This is the token for the object.
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Length of External File Name</p></td>
|
|
<td><p>This is the length for the external file name.
|
|
<p>This field exists if bit 0 of <em>flags</em> is set.</p>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>External File Name</p></td>
|
|
<td><p>This is the name of the external file being referenced.</p>
|
|
</p>
|
|
<p>This field exists if bit 0 of <em>flags</em> is set.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dataspace Selection Information</p></td>
|
|
<td><p>See <a href="#DataspaceSEL">Dataspace Selection.</a></p>
|
|
</p>
|
|
<p>This field exists if the <em>Reference Type</em> is H5R_DATASET_REGION2.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Length of Attribute Name</p></td>
|
|
<td><p>This is the length of the attribute name.
|
|
<p>This field exists if the <em>Reference Type</em> is H5R_ATTRIBUTE.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Attribute Name</p></td>
|
|
<td><p>This is the name of the attribute being referenced.
|
|
<p>This field exists if the <em>Reference Type</em> is H5R_ATTRIBUTE.</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
|
|
|
|
<a name="ReferenceEncodeDP">
|
|
<h3>VIII.C. Reference Encoding (Backward Compatibility)</h3></a>
|
|
<p>
|
|
<br />
|
|
The two references described below are maintained to preserve compatibility with previous versions of the library.
|
|
<p>
|
|
For the following reference type,
|
|
the reference encoding is stored as the dataset's raw data in the file:
|
|
<ul>
|
|
<li>Object Reference (H5R_OBJECT1)</li>
|
|
</ul>
|
|
<p>
|
|
For the following reference type,
|
|
the <a href="#GlobalHeapID">Global Heap ID</a> is stored as the dataset's raw data in the file.
|
|
The global heap ID is used to locate the reference encoding
|
|
stored in the global heap:
|
|
<ul>
|
|
<li>Dataset Region Reference (H5R_DATASET_REGION1)</li>
|
|
</ul>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Reference for H5R_OBJECT1
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Object Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Reference for H5R_OBJECT1
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Object Address</p></td>
|
|
<td>
|
|
<p>Address of the object being referenced
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
|
|
<div align="center">
|
|
<table class="format">
|
|
<caption>
|
|
Layout: Reference for H5R_DATASET_REGION1
|
|
</caption>
|
|
|
|
<tr>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
<th width="25%">byte</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td colspan="4"><br />Object Address<sup>O</sup><br /><br /></td>
|
|
</tr>
|
|
<tr>
|
|
<td colspan=4><br /><br />Dataspace Selection Information
|
|
<em>(variable size)</em><br /><br /> <br /></td>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
|
|
<table class="note">
|
|
<tr>
|
|
<td width="60%"> </td>
|
|
<td width="40%">
|
|
(Items marked with an ‘O’ in the above table are
|
|
of the size specified in the <a href="#SizeOfOffsetsV0">Size
|
|
of Offsets</a> field in the superblock.)
|
|
</td></tr>
|
|
</table>
|
|
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<div align="center">
|
|
<table class="desc">
|
|
<caption>
|
|
Fields: Reference for H5R_DATASET_REGION1
|
|
</caption>
|
|
<tr>
|
|
<th width="30%">Field Name</th>
|
|
<th>Description</th>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Object Address</p></td>
|
|
<td><p>This is the address of the object being referenced.
|
|
</td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td><p>Dataspace Selection Information</p></td>
|
|
<td><p>This is the dataspace selection for the object being referenced.
|
|
See <a href="#DataspaceSEL">Dataspace Selection.</a></p>
|
|
</p>
|
|
</td>
|
|
</tr>
|
|
|
|
</table>
|
|
</div>
|
|
|
|
<br />
|
|
<br />
|
|
<br />
|
|
|
|
|
|
</body>
|
|
</html>
|
|
|