src/support/murmur3.c

/*-----------------------------------------------------------------------------
 * MurmurHash3 was written by Austin Appleby, and is placed in the public
 * domain. The author hereby disclaims copyright to this source code.
 *
 * Note - The x86 and x64 versions do _not_ produce the same results, as the
 * algorithms are optimized for their respective platforms. You can still
 * compile and run any of them on any platform, but your performance with the
 * non-native version will be less than optimal.
 */

#include "config.h"

#include "murmur3.h"

/*------------------------------------------------------------------------------
 * Platform-specific functions and macros
 */

inline uint32_t rotl32(uint32_t x, int8_t r)
{
	return (x << r) | (x >> (32 - r));
}

inline uint64_t rotl64(uint64_t x, int8_t r)
{
	return (x << r) | (x >> (64 - r));
}

#define	ROTL32(x, y)	rotl32(x, y)
#define ROTL64(x, y)	rotl64(x, y)

#define BIG_CONSTANT(x) (x##LLU)

/*------------------------------------------------------------------------------
 * Block read - if your platform needs to do endian-swapping or can only
 * handle aligned reads, do the conversion here
 */

#define getblock(p, i) (p[i])

/*------------------------------------------------------------------------------
 * Finalization mix - force all bits of a hash block to avalanche
 */

static inline __attribute__((always_inline)) uint32_t fmix32(uint32_t h)
{
	h ^= h >> 16;
	h *= 0x85ebca6b;
	h ^= h >> 13;
	h *= 0xc2b2ae35;
	h ^= h >> 16;

	return h;
}

static inline __attribute__((always_inline)) uint64_t fmix64(uint64_t k)
{
	k ^= k >> 33;
	k *= BIG_CONSTANT(0xff51afd7ed558ccd);
	k ^= k >> 33;
	k *= BIG_CONSTANT(0xc4ceb9fe1a85ec53);
	k ^= k >> 33;

	return k;
}

/*----------------------------------------------------------------------------*/

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;
	int i;

	uint32_t h1 = seed;

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

	/* body */

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

	for (i = -nblocks; i; i++) {
		uint32_t k1 = getblock(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;
}

/*----------------------------------------------------------------------------*/

void MurmurHash3_x86_128(const void *key, const int len, uint32_t seed,
			 void *out)
{
	const uint8_t *data = (const uint8_t *)key;
	const int nblocks = len / 16;
	int i;

	uint32_t h1 = seed;
	uint32_t h2 = seed;
	uint32_t h3 = seed;
	uint32_t h4 = seed;

	uint32_t c1 = 0x239b961b;
	uint32_t c2 = 0xab0e9789;
	uint32_t c3 = 0x38b34ae5;
	uint32_t c4 = 0xa1e38b93;

	/* body */

	const uint32_t *blocks = (const uint32_t *)(data + nblocks * 16);

	for (i = -nblocks; i; i++) {
		uint32_t k1 = getblock(blocks, i * 4 + 0);
		uint32_t k2 = getblock(blocks, i * 4 + 1);
		uint32_t k3 = getblock(blocks, i * 4 + 2);
		uint32_t k4 = getblock(blocks, i * 4 + 3);

		k1 *= c1;
		k1 = ROTL32(k1, 15);
		k1 *= c2;
		h1 ^= k1;

		h1 = ROTL32(h1, 19);
		h1 += h2;
		h1 = h1 * 5 + 0x561ccd1b;

		k2 *= c2;
		k2 = ROTL32(k2, 16);
		k2 *= c3;
		h2 ^= k2;

		h2 = ROTL32(h2, 17);
		h2 += h3;
		h2 = h2 * 5 + 0x0bcaa747;

		k3 *= c3;
		k3 = ROTL32(k3, 17);
		k3 *= c4;
		h3 ^= k3;

		h3 = ROTL32(h3, 15);
		h3 += h4;
		h3 = h3 * 5 + 0x96cd1c35;

		k4 *= c4;
		k4 = ROTL32(k4, 18);
		k4 *= c1;
		h4 ^= k4;

		h4 = ROTL32(h4, 13);
		h4 += h1;
		h4 = h4 * 5 + 0x32ac3b17;
	}

	/* tail */

	const uint8_t *tail = (const uint8_t *)(data + nblocks * 16);

	uint32_t k1 = 0;
	uint32_t k2 = 0;
	uint32_t k3 = 0;
	uint32_t k4 = 0;

	switch (len & 15) {
	case 15:
		k4 ^= tail[14] << 16;
	case 14:
		k4 ^= tail[13] << 8;
	case 13:
		k4 ^= tail[12] << 0;
		k4 *= c4;
		k4 = ROTL32(k4, 18);
		k4 *= c1;
		h4 ^= k4;

	case 12:
		k3 ^= tail[11] << 24;
	case 11:
		k3 ^= tail[10] << 16;
	case 10:
		k3 ^= tail[9] << 8;
	case 9:
		k3 ^= tail[8] << 0;
		k3 *= c3;
		k3 = ROTL32(k3, 17);
		k3 *= c4;
		h3 ^= k3;

	case 8:
		k2 ^= tail[7] << 24;
	case 7:
		k2 ^= tail[6] << 16;
	case 6:
		k2 ^= tail[5] << 8;
	case 5:
		k2 ^= tail[4] << 0;
		k2 *= c2;
		k2 = ROTL32(k2, 16);
		k2 *= c3;
		h2 ^= k2;

	case 4:
		k1 ^= tail[3] << 24;
	case 3:
		k1 ^= tail[2] << 16;
	case 2:
		k1 ^= tail[1] << 8;
	case 1:
		k1 ^= tail[0] << 0;
		k1 *= c1;
		k1 = ROTL32(k1, 15);
		k1 *= c2;
		h1 ^= k1;
	};

	/* finalization */

	h1 ^= len;
	h2 ^= len;
	h3 ^= len;
	h4 ^= len;

	h1 += h2;
	h1 += h3;
	h1 += h4;
	h2 += h1;
	h3 += h1;
	h4 += h1;

	h1 = fmix64(h1);
	h2 = fmix64(h2);
	h3 = fmix64(h3);
	h4 = fmix64(h4);

	h1 += h2;
	h1 += h3;
	h1 += h4;
	h2 += h1;
	h3 += h1;
	h4 += h1;

	((uint32_t *) out)[0] = h1;
	((uint32_t *) out)[1] = h2;
	((uint32_t *) out)[2] = h3;
	((uint32_t *) out)[3] = h4;
}

/*----------------------------------------------------------------------------*/

void MurmurHash3_x64_128(const void *key, const int len, const uint32_t seed,
			 void *out)
{
	const uint8_t *data = (const uint8_t *)key;
	const int nblocks = len / 16;
	int i;

	uint64_t h1 = seed;
	uint64_t h2 = seed;

	uint64_t c1 = BIG_CONSTANT(0x87c37b91114253d5);
	uint64_t c2 = BIG_CONSTANT(0x4cf5ad432745937f);

	/* body */

	const uint64_t *blocks = (const uint64_t *)(data);

	for (i = 0; i < nblocks; i++) {
		uint64_t k1 = getblock(blocks, i * 2 + 0);
		uint64_t k2 = getblock(blocks, i * 2 + 1);

		k1 *= c1;
		k1 = ROTL64(k1, 31);
		k1 *= c2;
		h1 ^= k1;

		h1 = ROTL64(h1, 27);
		h1 += h2;
		h1 = h1 * 5 + 0x52dce729;

		k2 *= c2;
		k2 = ROTL64(k2, 33);
		k2 *= c1;
		h2 ^= k2;

		h2 = ROTL64(h2, 31);
		h2 += h1;
		h2 = h2 * 5 + 0x38495ab5;
	}

	/* tail */

	const uint8_t *tail = (const uint8_t *)(data + nblocks * 16);

	uint64_t k1 = 0;
	uint64_t k2 = 0;

	switch (len & 15) {
	case 15:
		k2 ^= (uint64_t) (tail[14]) << 48;
	case 14:
		k2 ^= (uint64_t) (tail[13]) << 40;
	case 13:
		k2 ^= (uint64_t) (tail[12]) << 32;
	case 12:
		k2 ^= (uint64_t) (tail[11]) << 24;
	case 11:
		k2 ^= (uint64_t) (tail[10]) << 16;
	case 10:
		k2 ^= (uint64_t) (tail[9]) << 8;
	case 9:
		k2 ^= (uint64_t) (tail[8]) << 0;
		k2 *= c2;
		k2 = ROTL64(k2, 33);
		k2 *= c1;
		h2 ^= k2;

	case 8:
		k1 ^= (uint64_t) (tail[7]) << 56;
	case 7:
		k1 ^= (uint64_t) (tail[6]) << 48;
	case 6:
		k1 ^= (uint64_t) (tail[5]) << 40;
	case 5:
		k1 ^= (uint64_t) (tail[4]) << 32;
	case 4:
		k1 ^= (uint64_t) (tail[3]) << 24;
	case 3:
		k1 ^= (uint64_t) (tail[2]) << 16;
	case 2:
		k1 ^= (uint64_t) (tail[1]) << 8;
	case 1:
		k1 ^= (uint64_t) (tail[0]) << 0;
		k1 *= c1;
		k1 = ROTL64(k1, 31);
		k1 *= c2;
		h1 ^= k1;
	};

	/* finalization */

	h1 ^= len;
	h2 ^= len;

	h1 += h2;
	h2 += h1;

	h1 = fmix64(h1);
	h2 = fmix64(h2);

	h1 += h2;
	h2 += h1;

	((uint64_t *) out)[0] = h1;
	((uint64_t *) out)[1] = h2;
}

/*----------------------------------------------------------------------------*/