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