单向HASH——MurmurHash

//seed 是大质数
unsigned long long MurmurHash64B ( const void * key, int len, unsigned int seed )

{

    const unsigned int m = 0x5bd1e995;

    const int r = ;

    unsigned int h1 = seed ^ len;

    unsigned int h2 = ;

    const unsigned int * data = (const unsigned int *)key;

    while(len >= )

    {

        unsigned int k1 = *data++;

        k1 *= m; k1 ^= k1 >> r; k1 *= m;

        h1 *= m; h1 ^= k1;

        len -= ;

        unsigned int k2 = *data++;

        k2 *= m; k2 ^= k2 >> r; k2 *= m;

        h2 *= m; h2 ^= k2;

        len -= ;

    }

    if(len >= )

    {

        unsigned int k1 = *data++;

        k1 *= m; k1 ^= k1 >> r; k1 *= m;

        h1 *= m; h1 ^= k1;

        len -= ;

    }

    switch(len)

    {

    case : h2 ^= ((unsigned char*)data)[] << ;

    case : h2 ^= ((unsigned char*)data)[] << ;

    case : h2 ^= ((unsigned char*)data)[];

            h2 *= m;

    };

    h1 ^= h2 >> ; h1 *= m;

    h2 ^= h1 >> ; h2 *= m;

    h1 ^= h2 >> ; h1 *= m;

    h2 ^= h1 >> ; h2 *= m;

    unsigned long long h = h1;

    h = (h << ) | h2;

    return h;

}