76 lines
1.4 KiB
C
76 lines
1.4 KiB
C
/* This is MurmurHash3. The original C++ code was placed in the public domain
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* by its author, Austin Appleby.
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*
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* SPDX-License-Identifier: CC0-1.0
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* Source: https://github.com/aappleby/smhasher/blob/master/src/MurmurHash3.cpp */
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#include "murmurhash3.h"
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#include "string.h"
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static inline uint32_t fmix(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 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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uint32_t hash(const char* data, size_t len_)
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{
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const int len = (int) len_;
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const int nblocks = len / 4;
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uint32_t h1 = 0xc062fb4a;
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uint32_t c1 = 0xcc9e2d51;
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uint32_t c2 = 0x1b873593;
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//----------
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// body
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for(int i = 0; i < nblocks; ++i)
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{
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uint32_t k1;
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memcpy(&k1, data + i * sizeof(k1), sizeof(k1));
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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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//----------
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// tail
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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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{
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case 3: k1 ^= tail[2] << 16;
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case 2: k1 ^= tail[1] << 8;
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case 1: k1 ^= tail[0];
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k1 *= c1; k1 = rotl32(k1,15); k1 *= c2; h1 ^= k1;
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}
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//----------
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// finalization
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h1 ^= len;
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h1 = fmix(h1);
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return h1;
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}
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