text/plain
•
3.20 KB
•
112 lines
/* The MIT License
Copyright (C) 2012 Zilong Tan (eric.zltan@gmail.com)
Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation
files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use, copy,
modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/
#ifndef _FASTHASH_H
#define _FASTHASH_H
#include <stdint.h>
#include <stdio.h>
// Compression function for Merkle-Damgard construction.
// This function is generated using the framework provided.
#define mix(h) ({ \
(h) ^= (h) >> 23; \
(h) *= 0x2127599bf4325c37ULL; \
(h) ^= (h) >> 47; })
/**
* fasthash64v - 64-bit implementation of fasthash
* @v: data to hash
* @seed: the seed
*/
static inline uint64_t fasthash64v(uint64_t v){
const uint64_t m = 0x880355f21e6d1965ULL;
const uint64_t seed = 0x5b0a159d9eac0381ULL;
uint64_t h = seed ^ (8 * m);
h ^= mix(v);
h *= m;
return mix(h);
}
static inline uint32_t fasthash32v(uint64_t v){
const uint64_t h = fasthash64v(v);
return h - (h >> 32);
}
/**
* fasthash64 - 64-bit implementation of fasthash
* @buf: data buffer
* @len: data size
* @seed: the seed
*/
static inline uint64_t fasthash64(const void *buf, size_t len, uint64_t seed){
const uint64_t m = 0x880355f21e6d1965ULL;
const uint64_t *pos = (const uint64_t *)buf;
const uint64_t *end = pos + (len / 8);
const uint8_t *pos2;
uint64_t h = seed ^ (len * m);
uint64_t v;
while (pos != end) {
v = *pos++;
h ^= mix(v);
h *= m;
}
pos2 = (const uint8_t *)pos;
v = 0;
switch (len & 7) {
case 7: v ^= (uint64_t)pos2[6] << 48; // fall-through
case 6: v ^= (uint64_t)pos2[5] << 40; // fall-through
case 5: v ^= (uint64_t)pos2[4] << 32; // fall-through
case 4: v ^= (uint64_t)pos2[3] << 24; // fall-through
case 3: v ^= (uint64_t)pos2[2] << 16; // fall-through
case 2: v ^= (uint64_t)pos2[1] << 8; // fall-through
case 1: v ^= (uint64_t)pos2[0];
h ^= mix(v);
h *= m;
}
return mix(h);
}
/**
* fasthash32 - 32-bit implementation of fasthash
* @buf: data buffer
* @len: data size
* @seed: the seed
*/
static inline uint32_t fasthash32(const void *buf, size_t len, uint64_t seed){
// the following trick converts the 64-bit hashcode to Fermat
// residue, which shall retain information from both the higher
// and lower parts of hashcode.
const uint64_t h = fasthash64(buf, len, seed);
return h - (h >> 32);
}
#undef mix
#endif
