Function MurmurHash3_x86_32

BeefySysLib/util/Hash.cpp:1030–1082

//-----------------------------------------------------------------------------

void MurmurHash3_x86_32(const void * key, int len,
	uint32_t seed, void * out)
{
	const uint8_t * data = (const uint8_t*) key;
	const int nblocks = len / 4;

	uint32_t h1 = seed;

	const uint32_t c1 = 0xcc9e2d51;
	const uint32_t c2 = 0x1b873593;

	//----------
	// body

	const uint32_t * blocks = (const uint32_t *) (data + nblocks * 4);

	for (int i = -nblocks; i; i++)
	{
		uint32_t k1 = getblock32(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*) (data + nblocks * 4);

	uint32_t k1 = 0;

	switch (len & 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 ^= len;

	h1 = fmix32(h1);

	*(uint32_t*) out = h1;
}

//-----------------------------------------------------------------------------