io.virtdata.long_int.SignedHash Maven / Gradle / Ivy

package io.virtdata.long_int;

import de.greenrobot.common.hash.Murmur3F;

import java.nio.ByteBuffer;
import java.util.function.LongToIntFunction;

/**
 * This uses the Murmur3F (64-bit optimized) version of Murmur3,
 * not as a checksum, but as a simple hash. It doesn't bother
 * pushing the high-64 bits of input, since it only uses the lower
 * 64 bits of output. This version returns the full signed result.
 */
public class SignedHash implements LongToIntFunction {

    private ByteBuffer bb = ByteBuffer.allocate(Long.BYTES);
    private Murmur3F murmur3F= new Murmur3F();

    @Override
    public int applyAsInt(long value) {
        murmur3F.reset();
        bb.putLong(0,value);
        murmur3F.update(bb.array(),0,Long.BYTES);
        long result= murmur3F.getValue();
        return (int) (result & Integer.MAX_VALUE);
    }
}