分享一个生成哈希值的C代码

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