68 lines
1.3 KiB
C
68 lines
1.3 KiB
C
#include "murmur3.h"
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static inline uint32_t rotl32(uint32_t x, int8_t r)
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{
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return (x << r) | (x >> (32 - r));
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}
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//-----------------------------------------------------------------------------
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// Finalization mix - force all bits of a hash block to avalanche
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static inline uint32_t fmix32(uint32_t h)
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{
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h ^= h >> 16;
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h *= 0x85ebca6b;
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h ^= h >> 13;
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h *= 0xc2b2ae35;
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h ^= h >> 16;
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return h;
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}
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static uint32_t murmur3_tail(const uint8_t *data, const int nblocks,
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uint32_t len, const uint32_t c1,
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const uint32_t c2, uint32_t h1)
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{
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const uint8_t *tail = (const uint8_t *)(data + nblocks * 4);
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uint32_t k1 = 0;
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switch (len & 3) {
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case 3:
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k1 ^= tail[2] << 16;
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case 2:
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k1 ^= tail[1] << 8;
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case 1:
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k1 ^= tail[0];
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k1 *= c1;
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k1 = rotl32(k1, 15);
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k1 *= c2;
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h1 ^= k1;
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};
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return fmix32(h1 ^ len);
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}
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uint32_t murmurhash3(const void *key, uint32_t len, uint32_t seed)
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{
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const uint8_t *data = (const uint8_t *)key;
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const int nblocks = len / 4;
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uint32_t h1 = seed;
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const uint32_t c1 = 0xcc9e2d51;
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const uint32_t c2 = 0x1b873593;
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const uint32_t *blocks = (const uint32_t *)(data + nblocks * 4);
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int i;
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for (i = -nblocks; i; i++) {
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uint32_t k1 = blocks[i];
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k1 *= c1;
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k1 = rotl32(k1, 15);
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k1 *= c2;
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h1 ^= k1;
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h1 = rotl32(h1, 13);
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h1 = h1 * 5 + 0xe6546b64;
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}
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return murmur3_tail(data, nblocks, len, c1, c2, h1);
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}
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