1// MurmurHash3 was written by Austin Appleby, and is placed in the public
  2// domain. The author hereby disclaims copyright to this source code.
  3
  4#include <mgba-util/hash.h>
  5
  6#if defined(_MSC_VER)
  7
  8#define FORCE_INLINE	__forceinline
  9
 10#include <stdlib.h>
 11
 12#define ROTL32(x,y)	_rotl(x,y)
 13
 14#else
 15
 16#define	FORCE_INLINE inline __attribute__((always_inline))
 17
 18static inline uint32_t rotl32 ( uint32_t x, int8_t r ) {
 19  return (x << r) | (x >> (32 - r));
 20}
 21
 22#define	ROTL32(x,y)	rotl32(x,y)
 23
 24#endif
 25
 26//-----------------------------------------------------------------------------
 27// Block read - if your platform needs to do endian-swapping or can only
 28// handle aligned reads, do the conversion here
 29
 30static FORCE_INLINE uint32_t getblock32 ( const uint32_t * p, int i ) {
 31  return p[i];
 32}
 33
 34//-----------------------------------------------------------------------------
 35// Finalization mix - force all bits of a hash block to avalanche
 36
 37static FORCE_INLINE uint32_t fmix32 (uint32_t h) {
 38  h ^= h >> 16;
 39  h *= 0x85ebca6b;
 40  h ^= h >> 13;
 41  h *= 0xc2b2ae35;
 42  h ^= h >> 16;
 43
 44  return h;
 45}
 46
 47//-----------------------------------------------------------------------------
 48
 49uint32_t hash32(const void* key, int len, uint32_t seed) {
 50  const uint8_t * data = (const uint8_t*)key;
 51  const int nblocks = len / 4;
 52
 53  uint32_t h1 = seed;
 54
 55  const uint32_t c1 = 0xcc9e2d51;
 56  const uint32_t c2 = 0x1b873593;
 57
 58  //----------
 59  // body
 60
 61  const uint32_t * blocks = (const uint32_t *)(data + nblocks*4);
 62
 63  int i;
 64  for(i = -nblocks; i; i++)
 65  {
 66    uint32_t k1 = getblock32(blocks,i);
 67
 68    k1 *= c1;
 69    k1 = ROTL32(k1,15);
 70    k1 *= c2;
 71    
 72    h1 ^= k1;
 73    h1 = ROTL32(h1,13); 
 74    h1 = h1*5+0xe6546b64;
 75  }
 76
 77  //----------
 78  // tail
 79
 80  const uint8_t * tail = (const uint8_t*)(data + nblocks*4);
 81
 82  uint32_t k1 = 0;
 83
 84  switch(len & 3)
 85  {
 86  case 3:
 87    k1 ^= tail[2] << 16;
 88    // Fall through
 89  case 2:
 90    k1 ^= tail[1] << 8;
 91    // Fall through
 92  case 1:
 93    k1 ^= tail[0];
 94    k1 *= c1; k1 = ROTL32(k1,15); k1 *= c2; h1 ^= k1;
 95  };
 96
 97  //----------
 98  // finalization
 99
100  h1 ^= len;
101
102  h1 = fmix32(h1);
103
104  return h1;
105}