1 #include "murmur3.h"
2
rotl32(uint32_t x,int8_t r)3 static inline uint32_t rotl32(uint32_t x, int8_t r)
4 {
5 return (x << r) | (x >> (32 - r));
6 }
7
8 //-----------------------------------------------------------------------------
9 // Finalization mix - force all bits of a hash block to avalanche
10
fmix32(uint32_t h)11 static inline uint32_t fmix32(uint32_t h)
12 {
13 h ^= h >> 16;
14 h *= 0x85ebca6b;
15 h ^= h >> 13;
16 h *= 0xc2b2ae35;
17 h ^= h >> 16;
18
19 return h;
20 }
21
murmur3_tail(const uint8_t * data,const int nblocks,uint32_t len,const uint32_t c1,const uint32_t c2,uint32_t h1)22 static uint32_t murmur3_tail(const uint8_t *data, const int nblocks,
23 uint32_t len, const uint32_t c1,
24 const uint32_t c2, uint32_t h1)
25 {
26 const uint8_t *tail = (const uint8_t *)(data + nblocks * 4);
27
28 uint32_t k1 = 0;
29 switch (len & 3) {
30 case 3:
31 k1 ^= tail[2] << 16;
32 case 2:
33 k1 ^= tail[1] << 8;
34 case 1:
35 k1 ^= tail[0];
36 k1 *= c1;
37 k1 = rotl32(k1, 15);
38 k1 *= c2;
39 h1 ^= k1;
40 };
41
42 return fmix32(h1 ^ len);
43 }
44
murmurhash3(const void * key,uint32_t len,uint32_t seed)45 uint32_t murmurhash3(const void *key, uint32_t len, uint32_t seed)
46 {
47 const uint8_t *data = (const uint8_t *)key;
48 const int nblocks = len / 4;
49 uint32_t h1 = seed;
50 const uint32_t c1 = 0xcc9e2d51;
51 const uint32_t c2 = 0x1b873593;
52 const uint32_t *blocks = (const uint32_t *)(data + nblocks * 4);
53 int i;
54
55 for (i = -nblocks; i; i++) {
56 uint32_t k1 = blocks[i];
57
58 k1 *= c1;
59 k1 = rotl32(k1, 15);
60 k1 *= c2;
61
62 h1 ^= k1;
63 h1 = rotl32(h1, 13);
64 h1 = h1 * 5 + 0xe6546b64;
65 }
66
67 return murmur3_tail(data, nblocks, len, c1, c2, h1);
68 }
69