diff options
author | Vikas Gorur <vikas@zresearch.com> | 2009-02-18 17:36:07 +0530 |
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committer | Vikas Gorur <vikas@zresearch.com> | 2009-02-18 17:36:07 +0530 |
commit | 77adf4cd648dce41f89469dd185deec6b6b53a0b (patch) | |
tree | 02e155a5753b398ee572b45793f889b538efab6b /libglusterfs/src/hashfn.c | |
parent | f3b2e6580e5663292ee113c741343c8a43ee133f (diff) |
Added all files
Diffstat (limited to 'libglusterfs/src/hashfn.c')
-rw-r--r-- | libglusterfs/src/hashfn.c | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/libglusterfs/src/hashfn.c b/libglusterfs/src/hashfn.c new file mode 100644 index 00000000000..edc49678fc5 --- /dev/null +++ b/libglusterfs/src/hashfn.c @@ -0,0 +1,89 @@ +/* + Copyright (c) 2006, 2007, 2008 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; +} |