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30 lines
905 B
30 lines
905 B
/*
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* Copyright(C) 1999-2020 National Technology & Engineering Solutions
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* of Sandia, LLC (NTESS). Under the terms of Contract DE-NA0003525 with
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* NTESS, the U.S. Government retains certain rights in this software.
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*
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* See packages/seacas/LICENSE for details
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*/
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/* Reverse the bits of a number. */
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int bit_reverse(int val, int nbits)
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/* value to reverse bits of */
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/* number of significant bits */
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{
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int mask_low, mask_high; /* masks for bits to interchange */
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int bit_low, bit_high; /* values of the bits in question */
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int i; /* loop counter */
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mask_low = 1;
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mask_high = 1 << (nbits - 1);
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for (i = 0; i < nbits / 2; i++) {
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bit_low = (val & mask_low) >> i;
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bit_high = (val & mask_high) >> (nbits - i - 1);
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mask_low <<= 1;
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mask_high >>= 1;
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if (bit_low != bit_high) {
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val ^= (1 << i) ^ (1 << (nbits - i - 1));
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}
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}
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return (val);
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}
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