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  uint32_t ret;
 32  LOAD_32LE(ret, i << 2, p);
 33  return ret;
 34}
 35
 36//-----------------------------------------------------------------------------
 37// Finalization mix - force all bits of a hash block to avalanche
 38
 39static FORCE_INLINE uint32_t fmix32 (uint32_t h) {
 40  h ^= h >> 16;
 41  h *= 0x85ebca6b;
 42  h ^= h >> 13;
 43  h *= 0xc2b2ae35;
 44  h ^= h >> 16;
 45
 46  return h;
 47}
 48
 49//-----------------------------------------------------------------------------
 50
 51uint32_t hash32(const void* key, int len, uint32_t seed) {
 52  const uint8_t * data = (const uint8_t*)key;
 53  const int nblocks = len / 4;
 54
 55  uint32_t h1 = seed;
 56
 57  const uint32_t c1 = 0xcc9e2d51;
 58  const uint32_t c2 = 0x1b873593;
 59
 60  //----------
 61  // body
 62
 63  const uint32_t * blocks = (const uint32_t *)(data + nblocks*4);
 64
 65  int i;
 66  for(i = -nblocks; i; i++)
 67  {
 68    uint32_t k1 = getblock32(blocks,i);
 69
 70    k1 *= c1;
 71    k1 = ROTL32(k1,15);
 72    k1 *= c2;
 73    
 74    h1 ^= k1;
 75    h1 = ROTL32(h1,13); 
 76    h1 = h1*5+0xe6546b64;
 77  }
 78
 79  //----------
 80  // tail
 81
 82  const uint8_t * tail = (const uint8_t*)(data + nblocks*4);
 83
 84  uint32_t k1 = 0;
 85
 86  switch(len & 3)
 87  {
 88  case 3:
 89    k1 ^= tail[2] << 16;
 90    // Fall through
 91  case 2:
 92    k1 ^= tail[1] << 8;
 93    // Fall through
 94  case 1:
 95    k1 ^= tail[0];
 96    k1 *= c1; k1 = ROTL32(k1,15); k1 *= c2; h1 ^= k1;
 97  };
 98
 99  //----------
100  // finalization
101
102  h1 ^= len;
103
104  h1 = fmix32(h1);
105
106  return h1;
107}