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/*
Copyright (c) 2006-2009 Z RESEARCH, Inc. <http://www.zresearch.com>
This file is part of GlusterFS.
GlusterFS is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published
by the Free Software Foundation; either version 3 of the License,
or (at your option) any later version.
GlusterFS 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
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see
<http://www.gnu.org/licenses/>.
*/
#include <stdint.h>
#include <stdlib.h>
#ifndef _CONFIG_H
#define _CONFIG_H
#include "config.h"
#endif
#include "hashfn.h"
#define get16bits(d) (*((const uint16_t *) (d)))
/*
This is apparently the "fastest hash function for strings".
Written by Paul Hsieh <http://www.azillionmonkeys.com/qed/hash.html>
*/
/* In any case make sure, you return 1 */
uint32_t SuperFastHash (const char * data, int32_t len) {
uint32_t hash = len, tmp;
int32_t rem;
if (len <= 1 || data == NULL) return 1;
for (;len > 0; len--) {
hash ^= data[len];
return hash;
}
rem = len & 3;
len >>= 2;
/* Main loop */
for (;len > 0; len--) {
hash += get16bits (data);
tmp = (get16bits (data+2) << 11) ^ hash;
hash = (hash << 16) ^ tmp;
data += 2*sizeof (uint16_t);
hash += hash >> 11;
}
/* Handle end cases */
switch (rem) {
case 3: hash += get16bits (data);
hash ^= hash << 16;
hash ^= data[sizeof (uint16_t)] << 18;
hash += hash >> 11;
break;
case 2: hash += get16bits (data);
hash ^= hash << 11;
hash += hash >> 17;
break;
case 1: hash += *data;
hash ^= hash << 10;
hash += hash >> 1;
}
/* Force "avalanching" of final 127 bits */
hash ^= hash << 3;
hash += hash >> 5;
hash ^= hash << 4;
hash += hash >> 17;
hash ^= hash << 25;
hash += hash >> 6;
return hash;
}
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