diff options
Diffstat (limited to 'src/hash.cpp')
-rw-r--r-- | src/hash.cpp | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/src/hash.cpp b/src/hash.cpp new file mode 100644 index 0000000000..bddd8abf38 --- /dev/null +++ b/src/hash.cpp @@ -0,0 +1,58 @@ +#include "hash.h" + +inline uint32_t ROTL32 ( uint32_t x, int8_t r ) +{ + return (x << r) | (x >> (32 - r)); +} + +unsigned int MurmurHash3(unsigned int nHashSeed, const std::vector<unsigned char>& vDataToHash) +{ + // The following is MurmurHash3 (x86_32), see http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp + uint32_t h1 = nHashSeed; + const uint32_t c1 = 0xcc9e2d51; + const uint32_t c2 = 0x1b873593; + + const int nblocks = vDataToHash.size() / 4; + + //---------- + // body + const uint32_t * blocks = (const uint32_t *)(&vDataToHash[0] + nblocks*4); + + for(int i = -nblocks; i; i++) + { + uint32_t k1 = blocks[i]; + + k1 *= c1; + k1 = ROTL32(k1,15); + k1 *= c2; + + h1 ^= k1; + h1 = ROTL32(h1,13); + h1 = h1*5+0xe6546b64; + } + + //---------- + // tail + const uint8_t * tail = (const uint8_t*)(&vDataToHash[0] + nblocks*4); + + uint32_t k1 = 0; + + switch(vDataToHash.size() & 3) + { + case 3: k1 ^= tail[2] << 16; + case 2: k1 ^= tail[1] << 8; + case 1: k1 ^= tail[0]; + k1 *= c1; k1 = ROTL32(k1,15); k1 *= c2; h1 ^= k1; + }; + + //---------- + // finalization + h1 ^= vDataToHash.size(); + h1 ^= h1 >> 16; + h1 *= 0x85ebca6b; + h1 ^= h1 >> 13; + h1 *= 0xc2b2ae35; + h1 ^= h1 >> 16; + + return h1; +} |