hash.c

/*
 * Copyright 2013 Google Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */
/*---------------------------------------------------------------------------
 * From public domain code at:
 *  http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp
 */

/*---------------------------------------------------------------------------
 * 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 "hash.h"

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

static __always_inline u32 rotl32(u32 x, s8 r)
{
	return (x << r) | (x >> (32 - r));
}

static __always_inline u64 rotl64(u64 x, s8 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
 */

static __always_inline u32 getblock_32(const u32 *p, int i)
{
	return p[i];
}

static __always_inline u64 getblock_64(const u64 *p, int i)
{
	return p[i];
}

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

static __always_inline u32 fmix_32(u32 h)
{
	h ^= h >> 16;
	h *= 0x85ebca6b;
	h ^= h >> 13;
	h *= 0xc2b2ae35;
	h ^= h >> 16;

	return h;
}

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

static __always_inline u64 fmix_64(u64 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, u32 seed, void *out)
{
	const u8 *data = (const u8 *)key;
	const int nblocks = len / 4;

	u32 h1 = seed;

	u32 c1 = 0xcc9e2d51;
	u32 c2 = 0x1b873593;

	/*---------*/
	/* body */

	const u32 *blocks = (const u32 *)(data + nblocks * 4);

	int i;
	for (i = -nblocks; i; i++) {
		u32 k1 = getblock_32(blocks, i);

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

		h1 ^= k1;
		h1 = ROTL32(h1, 13);
		h1 = h1 * 5 + 0xe6546b64;
	}

	/*---------*/
	/* tail */

	const u8 *tail = (const u8 *)(data + nblocks * 4);

	u32 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 = fmix_32(h1);

	*(u32 *) out = h1;
}

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

void MurmurHash3_x86_128(const void *key, const int len, u32 seed, void *out)
{
	const u8 *data = (const u8 *)key;
	const int nblocks = len / 16;

	u32 h1 = seed;
	u32 h2 = seed;
	u32 h3 = seed;
	u32 h4 = seed;

	u32 c1 = 0x239b961b;
	u32 c2 = 0xab0e9789;
	u32 c3 = 0x38b34ae5;
	u32 c4 = 0xa1e38b93;

	/*---------*/
	/* body */

	const u32 *blocks = (const u32 *)(data + nblocks * 16);

	int i;
	for (i = -nblocks; i; i++) {
		u32 k1 = getblock_32(blocks, i * 4 + 0);
		u32 k2 = getblock_32(blocks, i * 4 + 1);
		u32 k3 = getblock_32(blocks, i * 4 + 2);
		u32 k4 = getblock_32(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 u8 *tail = (const u8 *)(data + nblocks * 16);

	u32 k1 = 0;
	u32 k2 = 0;
	u32 k3 = 0;
	u32 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 = fmix_32(h1);
	h2 = fmix_32(h2);
	h3 = fmix_32(h3);
	h4 = fmix_32(h4);

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

	((u32 *) out)[0] = h1;
	((u32 *) out)[1] = h2;
	((u32 *) out)[2] = h3;
	((u32 *) out)[3] = h4;
}

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

void MurmurHash3_x64_128(const void *key, const int len,
			 const u32 seed, void *out)
{
	const u8 *data = (const u8 *)key;
	const int nblocks = len / 16;

	u64 h1 = seed;
	u64 h2 = seed;

	u64 c1 = BIG_CONSTANT(0x87c37b91114253d5);
	u64 c2 = BIG_CONSTANT(0x4cf5ad432745937f);

	/*---------*/
	/* body */

	const u64 *blocks = (const u64 *)(data);

	int i;
	for (i = 0; i < nblocks; i++) {
		u64 k1 = getblock_64(blocks, i * 2 + 0);
		u64 k2 = getblock_64(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 u8 *tail = (const u8 *)(data + nblocks * 16);

	u64 k1 = 0;
	u64 k2 = 0;

	switch (len & 15) {
	case 15:
		k2 ^= (u64) (tail[14]) << 48;
	case 14:
		k2 ^= (u64) (tail[13]) << 40;
	case 13:
		k2 ^= (u64) (tail[12]) << 32;
	case 12:
		k2 ^= (u64) (tail[11]) << 24;
	case 11:
		k2 ^= (u64) (tail[10]) << 16;
	case 10:
		k2 ^= (u64) (tail[9]) << 8;
	case 9:
		k2 ^= (u64) (tail[8]) << 0;
		k2 *= c2;
		k2 = ROTL64(k2, 33);
		k2 *= c1;
		h2 ^= k2;

	case 8:
		k1 ^= (u64) (tail[7]) << 56;
	case 7:
		k1 ^= (u64) (tail[6]) << 48;
	case 6:
		k1 ^= (u64) (tail[5]) << 40;
	case 5:
		k1 ^= (u64) (tail[4]) << 32;
	case 4:
		k1 ^= (u64) (tail[3]) << 24;
	case 3:
		k1 ^= (u64) (tail[2]) << 16;
	case 2:
		k1 ^= (u64) (tail[1]) << 8;
	case 1:
		k1 ^= (u64) (tail[0]) << 0;
		k1 *= c1;
		k1 = ROTL64(k1, 31);
		k1 *= c2;
		h1 ^= k1;
	};

	/*---------*/
	/* finalization */

	h1 ^= len;
	h2 ^= len;

	h1 += h2;
	h2 += h1;

	h1 = fmix_64(h1);
	h2 = fmix_64(h2);

	h1 += h2;
	h2 += h1;

	((u64 *) out)[0] = h1;
	((u64 *) out)[1] = h2;
}

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