private static int mixK1(int k1) {
        k1 *= C1;
        k1 = Integer.rotateLeft(k1, 15);
        k1 *= C2;
        return k1;
    }
32-bit Murmur3 hasher.  This is based on Guava's Murmur3_32HashFunction.
indexr-common/src/main/java/io/indexr/util/Hasher32.java