1#include "murmur3.h"
2
3static 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
11static 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
22static 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
45uint32_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