65 lines
1.5 KiB
C++
65 lines
1.5 KiB
C++
#include "hash.h"
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inline uint32_t ROTL32(uint32_t x, int8_t r)
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{
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return (x << r) | (x >> (32 - r));
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}
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unsigned int MurmurHash3(unsigned int nHashSeed, const std::vector<unsigned char>& vDataToHash)
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{
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// The following is MurmurHash3 (x86_32), see http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp
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uint32_t h1 = nHashSeed;
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if (vDataToHash.size() > 0)
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{
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const uint32_t c1 = 0xcc9e2d51;
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const uint32_t c2 = 0x1b873593;
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const int nblocks = vDataToHash.size() / 4;
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//----------
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// body
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const uint32_t* blocks = (const uint32_t*)(&vDataToHash[0] + nblocks * 4);
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for (int i = -nblocks; i; i++) {
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uint32_t k1 = blocks[i];
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k1 *= c1;
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k1 = ROTL32(k1, 15);
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k1 *= c2;
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h1 ^= k1;
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h1 = ROTL32(h1, 13);
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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_t* tail = (const uint8_t*)(&vDataToHash[0] + nblocks * 4);
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uint32_t k1 = 0;
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switch (vDataToHash.size() & 3) {
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case 3:
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k1 ^= tail[2] << 16;
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case 2:
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k1 ^= tail[1] << 8;
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case 1:
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k1 ^= tail[0];
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k1 *= c1;
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k1 = ROTL32(k1, 15);
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k1 *= c2;
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h1 ^= k1;
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};
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}
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//----------
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// finalization
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h1 ^= vDataToHash.size();
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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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