93 lines
2.6 KiB
C++
93 lines
2.6 KiB
C++
#include<hgl/util/hash/Hash.h>
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namespace hgl
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{
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namespace util
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{
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namespace
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{
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//本代码来自Github Copilot
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//MurmurHash 是一种高性能的哈希算法，特别适用于哈希表。它具有良好的分布性和较低的碰撞率。
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uint32_t CountMurmurHash3(const void *key, int 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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// Body
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const uint32_t *blocks = (const uint32_t *)(data + nblocks * 4);
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for (int i = -nblocks; i; i++) {
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uint32_t k1 = blocks[i];
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k1 *= c1;
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k1 = (k1 << 15) | (k1 >> (32 - 15));
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k1 *= c2;
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h1 ^= k1;
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h1 = (h1 << 13) | (h1 >> (32 - 13));
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h1 = h1 * 5 + 0xe6546b64;
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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:
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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 = (k1 << 15) | (k1 >> (32 - 15));
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k1 *= c2;
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h1 ^= k1;
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}
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// Finalization
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h1 ^= len;
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h1 ^= h1 >> 16;
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h1 *= 0x85ebca6b;
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h1 ^= h1 >> 13;
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h1 *= 0xc2b2ae35;
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h1 ^= h1 >> 16;
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return h1;
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}
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}//namespace
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class MurmurHash3:public Hash
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{
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uint32_t result;
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public:
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MurmurHash3():Hash(4,"MurmurHash3")
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{}
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void Init()override
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{
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result=0;
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}
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void Update(const void *input,uint inputLen)override
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{
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result=CountMurmurHash3(input,inputLen,result);
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}
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void Final(void *digest)override
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{
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*(uint32_t *)digest=result;
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}
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};//class MurmurHash3
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template<> Hash *CreateHash<HASH::Murmur3>()
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{
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return(new MurmurHash3);
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}
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}//namespace util
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}//namespace hgl
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