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Collin Funk
43 lines
1.4 KiB
C
43 lines
1.4 KiB
C
/* hashcode-mem.c -- compute a hash value from a provided buffer.
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Copyright (C) 2012-2026 Free Software Foundation, Inc.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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This file is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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#include <config.h>
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/* Specification. */
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#include "hashcode-mem.h"
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#include <limits.h>
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#define SIZE_BITS (sizeof (size_t) * CHAR_BIT)
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/* Return a hash of the N bytes of X using the method described by
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Bruno Haible in https://www.haible.de/bruno/hashfunc.html.
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Note that while many hash functions reduce their result via modulo
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to a 0..table_size-1 range, this function does not do that. */
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size_t
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hash_pjw_bare (const void *x, size_t n)
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{
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const unsigned char *s = x;
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size_t h = 0;
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for (unsigned int i = 0; i < n; i++)
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h = s[i] + ((h << 9) | (h >> (SIZE_BITS - 9)));
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return h;
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}
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