murmur3.h

#ifndef _MURMURHASH3_H_
#define _MURMURHASH3_H_

#include <stdint.h>


#define MAX_PRIME32 1229



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

static 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 getblock(p, i) (p[i])



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

  return h;
}


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

uint32_t inline MurmurHash3_x86_32 (const void *key, int len, uint32_t seed){
    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);
    
    return h1;
}


#endif // _MURMURHASH3_H_