代码是我在阅读assimp源码时看到的,不依赖任何第三方,可直接集成。
#pragma once
#ifndef AI_HASH_H_INCLUDED
#define AI_HASH_H_INCLUDED
#ifdef __GNUC__
# pragma GCC system_header
#endif
#include <stdint.h>
#include <string.h>
#include <cmath>
// ------------------------------------------------------------------------------------------------
// Hashing function taken from
// http://www.azillionmonkeys.com/qed/hash.html
// (incremental version)
//
// This code is Copyright 2004-2008 by Paul Hsieh. It is used here in the belief that
// Assimp's license is considered compatible with Pauls's derivative license as specified
// on his web page.
//
// (stdint.h should have been been included here)
// ------------------------------------------------------------------------------------------------
#undef get16bits
#if (defined(__GNUC__) && defined(__i386__)) || defined(__WATCOMC__) \
|| defined(_MSC_VER) || defined (__BORLANDC__) || defined (__TURBOC__)
#define get16bits(d) (*((const uint16_t *) (d)))
#endif
#if !defined (get16bits)
#define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
+(uint32_t)(((const uint8_t *)(d))[0]) )
#endif
// ------------------------------------------------------------------------------------------------
inline uint32_t SuperFastHash (const char * data, uint32_t len = 0, uint32_t hash = 0) {
uint32_t tmp;
int rem;
if (!data) return 0;
if (!len)len = (uint32_t)::strlen(data);
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 ^= abs(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;
}
#endif // !! AI_HASH_H_INCLUDED