Source

bitsquid / foundation / murmur_hash.cpp

#include "murmur_hash.h"

uint64_t murmur_hash_64(const void * key, uint32_t len, uint64_t seed)
{
	const uint64_t m = 0xc6a4a7935bd1e995ULL;
	const uint32_t r = 47;

	uint64_t h = seed ^ (len * m);

	const uint64_t * data = (const uint64_t *)key;
	const uint64_t * end = data + (len/8);

	while(data != end)
	{
		#ifdef PLATFORM_BIG_ENDIAN
			uint64 k = *data++;
			char *p = (char *)&k;
			char c;
			c = p[0]; p[0] = p[7]; p[7] = c;
			c = p[1]; p[1] = p[6]; p[6] = c;
			c = p[2]; p[2] = p[5]; p[5] = c;
			c = p[3]; p[3] = p[4]; p[4] = c;
		#else
			uint64_t k = *data++;
		#endif

		k *= m;
		k ^= k >> r;
		k *= m;
		
		h ^= k;
		h *= m;
	}

	const unsigned char * data2 = (const unsigned char*)data;

	switch(len & 7)
	{
	case 7: h ^= uint64_t(data2[6]) << 48;
	case 6: h ^= uint64_t(data2[5]) << 40;
	case 5: h ^= uint64_t(data2[4]) << 32;
	case 4: h ^= uint64_t(data2[3]) << 24;
	case 3: h ^= uint64_t(data2[2]) << 16;
	case 2: h ^= uint64_t(data2[1]) << 8;
	case 1: h ^= uint64_t(data2[0]);
			h *= m;
	};
	
	h ^= h >> r;
	h *= m;
	h ^= h >> r;

	return h;
}