MurmurHash3.c

// ****************************************************************************
// This file originally from:
// http://web.mit.edu/mmadinot/Desktop/mmadinot/MacData/afs/athena.mit.edu/software/julia_v0.2.0/julia/src/support/MurmurHash3.c
// ****************************************************************************

//-----------------------------------------------------------------------------
// MurmurHash3 was written by Austin Appleby, and is placed in the public
// domain. The author hereby disclaims copyright to this source code.

#include "MurmurHash3.h"

//-----------------------------------------------------------------------------
// Platform-specific functions and macros
// Microsoft Visual Studio

#if defined(_MSC_VER)

#define FORCE_INLINE	__forceinline

#include <stdlib.h>

#define ROTL64(x,y)	_rotl64(x,y)

#define BIG_CONSTANT(x) (x)

// Other compilers

#else	// defined(_MSC_VER)

#define	FORCE_INLINE inline __attribute__((always_inline))

FORCE_INLINE uint64_t getblock64 ( const uint64_t * p, int i );
FORCE_INLINE uint64_t fmix64 ( uint64_t k );

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

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

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

#endif // !defined(_MSC_VER)

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

FORCE_INLINE uint64_t getblock64 ( const uint64_t * p, int i )
{
  return p[i];
}

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

FORCE_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_x64_128 (const void *key, const Size len,
						  const uint64_t seed, void *out)
{
	const uint8_t * data = (const uint8_t*)key;
	const int nblocks = len / 16;

	uint64_t h1 = seed;
	uint64_t h2 = seed;

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

	//----------
	// body
	int i;
	const uint64_t * blocks = (const uint64_t *)(data);

	const uint8_t * tail;
	uint64_t k1 = 0;
	uint64_t k2 = 0;

	for(i = 0; i < nblocks; i++)
	{
		uint64_t k1 = getblock64(blocks,i*2+0);
		uint64_t k2 = getblock64(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

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

	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;
}

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