MurmurHash3.cpp

#include "MurmurHash3.h"
#include <stdlib.h>    // for _rotl

// 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.


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

inline uint32_t getblock ( const uint32_t * p, int i )
{
	return p[i];
}

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

inline void bmix32 ( uint32_t & h1, uint32_t & k1, uint32_t & c1, uint32_t & c2 )
{
	c1 = c1*5+0x7b7d159c;
	c2 = c2*5+0x6bce6396;

	k1 *= c1; 
	k1 = _rotl(k1,11); 
	k1 *= c2;

	h1 = _rotl(h1,13);
	h1 = h1*5+0x52dce729;
	h1 ^= k1;
}

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

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 = 0x971e137b ^ seed;

	uint32_t c1 = 0x95543787;
	uint32_t c2 = 0x2ad7eb25;

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

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

	for(int i = -nblocks; i; i++)
	{
		uint32_t k1 = getblock(blocks,i);

		bmix32(h1,k1,c1,c2);
	}

	//----------
	// 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];
			bmix32(h1,k1,c1,c2);
	};

	//----------
	// finalization

	h1 ^= len;

	h1 *= 0x85ebca6b;
	h1 ^= h1 >> 13;
	h1 *= 0xc2b2ae35;
	h1 ^= h1 >> 16;

	h1 ^= seed;

	*(uint32_t*)out = h1;
} 

//-----------------------------------------------------------------------------
// This mix is large enough that VC++ refuses to inline it unless we use
// __forceinline. It's also not all that fast due to register spillage.

__forceinline void bmix32 ( uint32_t & h1, uint32_t & h2, uint32_t & h3, uint32_t & h4, 
						    uint32_t & k1, uint32_t & k2, uint32_t & k3, uint32_t & k4, 
						    uint32_t & c1, uint32_t & c2 )
{
	k1 *= c1; 
	k1  = _rotl(k1,11); 
	k1 *= c2;
	h1 ^= k1;
	h1 += h2;
	h1 += h3;
	h1 += h4;

	h1 = _rotl(h1,17);

	k2 *= c2; 
	k2  = _rotl(k2,11);
	k2 *= c1;
	h2 ^= k2;
	h2 += h1;

	h1 = h1*3+0x52dce729;
	h2 = h2*3+0x38495ab5;

	c1 = c1*5+0x7b7d159c;
	c2 = c2*5+0x6bce6396;

	k3 *= c1; 
	k3  = _rotl(k3,11); 
	k3 *= c2;
	h3 ^= k3;
	h3 += h1;

	k4 *= c2; 
	k4  = _rotl(k4,11);
	k4 *= c1;
	h4 ^= k4;
	h4 += h1;

	h3 = h3*3+0x52dce729;
	h4 = h4*3+0x38495ab5;

	c1 = c1*5+0x7b7d159c;
	c2 = c2*5+0x6bce6396;
}

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

// avalanches all bits to within 0.25% bias

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

	return h;
}

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;

	uint32_t h1 = 0x8de1c3ac ^ seed;
	uint32_t h2 = 0xbab98226 ^ seed;
	uint32_t h3 = 0xfcba5b2d ^ seed;
	uint32_t h4 = 0x32452e3e ^ seed;

	uint32_t c1 = 0x95543787;
	uint32_t c2 = 0x2ad7eb25;

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

	const uint32_t * blocks = (const uint32_t *)(data);

	for(int i = 0; i < nblocks; 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);

		bmix32(h1,h2,h3,h4, k1,k2,k3,k4, c1,c2);
	}

	//----------
	// 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;

	case 12: k3 ^= tail[11] << 24;
	case 11: k3 ^= tail[10] << 16;
	case 10: k3 ^= tail[ 9] << 8;
	case  9: k3 ^= tail[ 8] << 0;

	case  8: k2 ^= tail[ 7] << 24;
	case  7: k2 ^= tail[ 6] << 16;
	case  6: k2 ^= tail[ 5] << 8;
	case  5: k2 ^= tail[ 4] << 0;

	case  4: k1 ^= tail[ 3] << 24;
	case  3: k1 ^= tail[ 2] << 16;
	case  2: k1 ^= tail[ 1] << 8;
	case  1: k1 ^= tail[ 0] << 0;
	         bmix32(h1,h2,h3,h4, k1,k2,k3,k4, c1,c2);
	};

	//----------
	// finalization

	h4 ^= len;

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

	h1 = fmix32(h1);
	h2 = fmix32(h2);
	h3 = fmix32(h3);
	h4 = fmix32(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;
}

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

inline uint64_t getblock ( const uint64_t * p, int i )
{
	return p[i];
}

//----------
// Block mix - combine the key bits with the hash bits and scramble everything

inline void bmix64 ( uint64_t & h1, uint64_t & h2, uint64_t & k1, uint64_t & k2, uint64_t & c1, uint64_t & c2 )
{
	k1 *= c1; 
	k1  = _rotl64(k1,23); 
	k1 *= c2;

	k2 *= c2; 
	k2  = _rotl64(k2,23);
	k2 *= c1;

	h1 = _rotl64(h1,17);
	h1 += h2;
	h1 ^= k1;

	h2 = _rotl64(h2,41);
	h2 += h1;
	h2 ^= k2;

	h1 = h1*3+0x52dce729;
	h2 = h2*3+0x38495ab5;

	c1 = c1*5+0x7b7d159c;
	c2 = c2*5+0x6bce6396;
}

//----------
// Finalization mix - avalanches all bits to within 0.05% bias

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

	return k;
}

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

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;

	uint64_t h1 = 0x9368e53c2f6af274 ^ seed;
	uint64_t h2 = 0x586dcd208f7cd3fd ^ seed;

	uint64_t c1 = 0x87c37b91114253d5;
	uint64_t c2 = 0x4cf5ad432745937f;

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

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

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

		bmix64(h1,h2,k1,k2,c1,c2);
	}

	//----------
	// 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;

	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;
	         bmix64(h1,h2,k1,k2,c1,c2);
	};

	//----------
	// finalization

	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;
}

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