Function MurmurHash64

phxqueue/comm/utils/hash_util.cpp:28–68

using namespace std;

uint64_t MurmurHash64(const void *key, size_t len, uint64_t seed) {
    const uint64_t m = 0xc6a4a7935bd1e995LLU;
    const int r = 47;

    uint64_t h = seed ^ (len * m);

    const uint64_t * data = (const uint64_t *)key;
    const uint64_t * end = data + (len/8);

    while(data != end)
    {
        uint64_t k = *data++;

        k *= m;
        k ^= k >> r;
        k *= m;

        h ^= k;
        h *= m;
    }

    const unsigned char * data2 = (const unsigned char*)data;

    switch(len & 7)
    {
    case 7: h ^= uint64_t(data2[6]) << 48;
    case 6: h ^= uint64_t(data2[5]) << 40;
    case 5: h ^= uint64_t(data2[4]) << 32;
    case 4: h ^= uint64_t(data2[3]) << 24;
    case 3: h ^= uint64_t(data2[2]) << 16;
    case 2: h ^= uint64_t(data2[1]) << 8;
    case 1: h ^= uint64_t(data2[0]);
        h *= m;
    };

    h ^= h >> r;
    h *= m;
    h ^= h >> r;

    return h;
}


}  // namespace utils