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/* hash-pjw-bare.c -- compute a hash value from a provided buffer.
Copyright (C) 2012-2019 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published
by the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
#include <config.h>
#include "hash-pjw-bare.h"
#include <limits.h>
#define SIZE_BITS (sizeof (size_t) * CHAR_BIT)
/* Return a hash of the N bytes of X using the method described by
Bruno Haible in https://www.haible.de/bruno/hashfunc.html.
Note that while many hash functions reduce their result via modulo
to a 0..table_size-1 range, this function does not do that. */
size_t
hash_pjw_bare (const void *x, size_t n)
{
const unsigned char *s = x;
size_t h = 0;
unsigned i;
for (i = 0; i < n; i++)
h = s[i] + ((h << 9) | (h >> (SIZE_BITS - 9)));
return h;
}
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