diff -r 000000000000 -r 06e7d03fd23e MurmurHash.c --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/MurmurHash.c Tue Jun 24 12:05:24 2008 -0700 @@ -0,0 +1,80 @@ +/* + * MurmurHash.c + * MYUtilities + * + * This file created by Jens Alfke on 3/17/08. + * Algorithm & source code by Austin Appleby, released to public domain. + * + * Downloaded 3/16/2008. + * Modified slightly by Jens Alfke (use standard uint32_t and size_t types; + * change 'm' and 'r' to #defines for better C compatibility.) + * + */ + +#include "MurmurHash.h" + + +//----------------------------------------------------------------------------- +// MurmurHash2, by Austin Appleby + +// Note - This code makes a few assumptions about how your machine behaves - + +// 1. We can read a 4-byte value from any address without crashing +// 2. sizeof(int) == 4 **Jens: I fixed this by changing 'unsigned int' to 'uint32_t'** + +// And it has a few limitations - + +// 1. It will not work incrementally. +// 2. It will not produce the same results on little-endian and big-endian +// machines. + +uint32_t MurmurHash2 ( const void * key, size_t len, uint32_t seed ) +{ + // 'm' and 'r' are mixing constants generated offline. + // They're not really 'magic', they just happen to work well. + + #define m 0x5bd1e995 + #define r 24 + + // Initialize the hash to a 'random' value + + uint32_t h = seed ^ len; + + // Mix 4 bytes at a time into the hash + + const unsigned char * data = (const unsigned char *)key; + + while(len >= 4) + { + uint32_t k = *(uint32_t *)data; + + k *= m; + k ^= k >> r; + k *= m; + + h *= m; + h ^= k; + + data += 4; + len -= 4; + } + + // Handle the last few bytes of the input array + + switch(len) + { + case 3: h ^= data[2] << 16; + case 2: h ^= data[1] << 8; + case 1: h ^= data[0]; + h *= m; + }; + + // Do a few final mixes of the hash to ensure the last few + // bytes are well-incorporated. + + h ^= h >> 13; + h *= m; + h ^= h >> 15; + + return h; +}