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strhash.c
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strhash.c
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/* strhash.c string hashing
*
* Copyright (c) 1994-2008 Carnegie Mellon University. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The name "Carnegie Mellon University" must not be used to
* endorse or promote products derived from this software without
* prior written permission. For permission or any legal
* details, please contact
* Carnegie Mellon University
* Center for Technology Transfer and Enterprise Creation
* 4615 Forbes Avenue
* Suite 302
* Pittsburgh, PA 15213
* (412) 268-7393, fax: (412) 268-7395
* innovation@andrew.cmu.edu
*
* 4. Redistributions of any form whatsoever must retain the following
* acknowledgment:
* "This product includes software developed by Computing Services
* at Carnegie Mellon University (http://www.cmu.edu/computing/)."
*
* CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
* THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
* FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
* AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
* OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include "config.h"
#include "lib/strhash.h"
/* The well-known djb2 algorithm (e.g. http://www.cse.yorku.ca/~oz/hash.html),
* with the addition of an optional seed to limit predictability.
*
* XXX return type 'unsigned' for back-compat to previous version, but
* XXX ought to be 'uint32_t'
*/
EXPORTED unsigned strhash_seeded_djb2(uint32_t seed, const char *string)
{
const unsigned char *ustr = (const unsigned char *) string;
unsigned hash = 5381;
int c;
if (seed) {
/* treat the bytes of the seed as a prefix to the string */
unsigned i;
for (i = 0; i < sizeof seed; i++) {
c = seed & 0xff;
hash = ((hash << 5) + hash) ^ c;
seed >>= 8;
}
}
while ((c = *ustr++))
hash = ((hash << 5) + hash) ^ c;
return hash;
}
EXPORTED unsigned strhash_legacy(const char *string)
{
unsigned ret_val = 0;
int i;
while (*string)
{
i = (int) *string;
ret_val ^= i;
ret_val <<= 1;
string ++;
}
return ret_val;
}

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