Me@2: //-----------------------------------------------------------------------------
Me@2: // MurmurHash2, by Austin Appleby
Me@2: 
Me@2: // Note - This code makes a few assumptions about how your machine behaves -
Me@2: 
Me@2: // 1. We can read a 4-byte value from any address without crashing
Me@2: // 2. sizeof(int) == 4
Me@2: 
Me@2: // And it has a few limitations -
Me@2: 
Me@2: // 1. It will not work incrementally.
Me@2: // 2. It will not produce the same results on little-endian and big-endian
Me@2: //    machines.
Me@2: 
Me@2: unsigned int MurmurHash2 ( const void * key, int len, unsigned int seed )
Me@2: {
Me@2: 	// 'm' and 'r' are mixing constants generated offline.
Me@2: 	// They're not really 'magic', they just happen to work well.
Me@2: 
Me@2: 	const unsigned int m = 0x5bd1e995;
Me@2: 	const int r = 24;
Me@2: 
Me@2: 	// Initialize the hash to a 'random' value
Me@2: 
Me@2: 	unsigned int h = seed ^ len;
Me@2: 
Me@2: 	// Mix 4 bytes at a time into the hash
Me@2: 
Me@2: 	const unsigned char * data = (const unsigned char *)key;
Me@2: 
Me@2: 	while(len >= 4)
Me@2: 	{
Me@2: 		unsigned int k = *(unsigned int *)data;
Me@2: 
Me@2: 		k *= m; 
Me@2: 		k ^= k >> r; 
Me@2: 		k *= m; 
Me@2: 		
Me@2: 		h *= m; 
Me@2: 		h ^= k;
Me@2: 
Me@2: 		data += 4;
Me@2: 		len -= 4;
Me@2: 	}
Me@2: 	
Me@2: 	// Handle the last few bytes of the input array
Me@2: 
Me@2: 	switch(len)
Me@2: 	{
Me@2: 	case 3: h ^= data[2] << 16;
Me@2: 	case 2: h ^= data[1] << 8;
Me@2: 	case 1: h ^= data[0];
Me@2: 	        h *= m;
Me@2: 	};
Me@2: 
Me@2: 	// Do a few final mixes of the hash to ensure the last few
Me@2: 	// bytes are well-incorporated.
Me@2: 
Me@2: 	h ^= h >> 13;
Me@2: 	h *= m;
Me@2: 	h ^= h >> 15;
Me@2: 
Me@2: 	return h;
Me@2: }