Nils O. Selåsdal
56 lines
1021 B
C
56 lines
1021 B
C
#include <ucore/ucore_hash.h>
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// 'm' and 'r' are mixing constants generated offline.
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// They're not really 'magic', they just happen to work well.
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#define m 0x5bd1e995
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#define r 24
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uint32_t
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uc_murmurmash2(const void *key, int len, uint32_t seed )
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{
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// Initialize the hash to a 'random' value
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uint32_t h = seed ^ len;
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// Mix 4 bytes at a time into the hash
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const unsigned char * data = (const unsigned char *)key;
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while (len >= 4)
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{
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uint32_t k = *(const uint32_t *)data;
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k *= m;
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k ^= k >> r;
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k *= m;
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h *= m;
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h ^= k;
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data += 4;
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len -= 4;
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}
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// Handle the last few bytes of the input array
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switch (len)
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{
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case 3: h ^= data[2] << 16;
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case 2: h ^= data[1] << 8;
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case 1: h ^= data[0];
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h *= m;
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};
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// Do a few final mixes of the hash to ensure the last few
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// bytes are well-incorporated.
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h ^= h >> 13;
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h *= m;
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h ^= h >> 15;
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return h;
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}
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