redis murmurhash2

uint64_t MurmurHash64A (const void * key, int len, unsigned int seed) {
    const uint64_t m = 0xc6a4a7935bd1e995;
    const int r = 47;
    uint64_t h = seed ^ (len * m);
    const uint8_t *data = (const uint8_t *)key;
    const uint8_t *end = data + (len-(len&7));
    while(data != end) {
        uint64_t k;
        k = *((uint64_t*)data);
#else
        k = (uint64_t) data[0];
        k |= (uint64_t) data[1] << 8;
        k |= (uint64_t) data[2] << 16;
        k |= (uint64_t) data[3] << 24;
        k |= (uint64_t) data[4] << 32;
        k |= (uint64_t) data[5] << 40;
        k |= (uint64_t) data[6] << 48;
        k |= (uint64_t) data[7] << 56;
#endif
        k *= m;
        k ^= k >> r;
        k *= m;
        h ^= k;
        h *= m;
        data += 8;
    }
    switch(len & 7) {
    case 7: h ^= (uint64_t)data[6] << 48;
    case 6: h ^= (uint64_t)data[5] << 40;
    case 5: h ^= (uint64_t)data[4] << 32;
    case 4: h ^= (uint64_t)data[3] << 24;
    case 3: h ^= (uint64_t)data[2] << 16;
    case 2: h ^= (uint64_t)data[1] << 8;
    case 1: h ^= (uint64_t)data[0];
            h *= m;
    };
    h ^= h >> r;
    h *= m;
    h ^= h >> r;
    return h;
}