mirror of
https://github.com/nillerusr/source-engine.git
synced 2024-12-23 14:46:53 +00:00
75 lines
1.6 KiB
C++
75 lines
1.6 KiB
C++
//======= Copyright © Valve Corporation, All rights reserved. =================
|
|
//
|
|
// Public domain MurmurHash3 by Austin Appleby is a very solid general-purpose
|
|
// hash with a 32-bit output. References:
|
|
// http://code.google.com/p/smhasher/ (home of MurmurHash3)
|
|
// https://sites.google.com/site/murmurhash/avalanche
|
|
// http://www.strchr.com/hash_functions
|
|
//
|
|
//=============================================================================
|
|
|
|
#include <stdafx.h>
|
|
#include "murmurhash3.h"
|
|
|
|
//-----------------------------------------------------------------------------
|
|
|
|
uint32 MurmurHash3_32( const void * key, size_t len, uint32 seed, bool bCaselessStringVariant )
|
|
{
|
|
const uint8 * data = (const uint8*)key;
|
|
const ptrdiff_t nblocks = len / 4;
|
|
uint32 uSourceBitwiseAndMask = 0xDFDFDFDF | ((uint32)bCaselessStringVariant - 1);
|
|
|
|
uint32 h1 = seed;
|
|
|
|
//----------
|
|
// body
|
|
|
|
const uint32 * blocks = (const uint32 *)(data + nblocks*4);
|
|
|
|
for(ptrdiff_t i = -nblocks; i; i++)
|
|
{
|
|
uint32 k1 = LittleDWord(blocks[i]);
|
|
k1 &= uSourceBitwiseAndMask;
|
|
|
|
k1 *= 0xcc9e2d51;
|
|
k1 = (k1 << 15) | (k1 >> 17);
|
|
k1 *= 0x1b873593;
|
|
|
|
h1 ^= k1;
|
|
h1 = (h1 << 13) | (h1 >> 19);
|
|
h1 = h1*5+0xe6546b64;
|
|
}
|
|
|
|
//----------
|
|
// tail
|
|
|
|
const uint8 * tail = (const uint8*)(data + nblocks*4);
|
|
|
|
uint32 k1 = 0;
|
|
|
|
switch(len & 3)
|
|
{
|
|
case 3: k1 ^= tail[2] << 16;
|
|
case 2: k1 ^= tail[1] << 8;
|
|
case 1: k1 ^= tail[0];
|
|
k1 &= uSourceBitwiseAndMask;
|
|
k1 *= 0xcc9e2d51;
|
|
k1 = (k1 << 15) | (k1 >> 17);
|
|
k1 *= 0x1b873593;
|
|
h1 ^= k1;
|
|
};
|
|
|
|
//----------
|
|
// finalization
|
|
|
|
h1 ^= len;
|
|
|
|
h1 ^= h1 >> 16;
|
|
h1 *= 0x85ebca6b;
|
|
h1 ^= h1 >> 13;
|
|
h1 *= 0xc2b2ae35;
|
|
h1 ^= h1 >> 16;
|
|
|
|
return h1;
|
|
}
|