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package io.virtdata.basicsmappers.from_long.to_long;

import de.greenrobot.common.hash.Murmur3F;

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

/**
 * 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 UnsafeSignedHash implements LongUnaryOperator {

//    // TODO: Bench this against the non-state based TL implementations
//    private ThreadLocal state_TL = ThreadLocal.withInitial(State::new);

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

    @Override
    public long applyAsLong(long value) {
        murmur3F.reset();
        bb.putLong(0,value);
        murmur3F.update(bb.array(),0,Long.BYTES);
        long result= murmur3F.getValue();
        return result;
    }
//
//    private static class State {
//        public ByteBuffer bb = ByteBuffer.allocate(Long.BYTES);
//        public Murmur3F murmur3F = new Murmur3F();
//    }
}