private static int mixH1(int h1, int k1) {
        h1 ^= k1;
        h1 = Integer.rotateLeft(h1, 13);
        h1 = h1 * 5 + 0xe6546b64;
        return h1;
    }
32-bit Murmur3 hasher.  This is based on Guava's Murmur3_32HashFunction.
indexr-common/src/main/java/io/indexr/util/Hasher32.java