TranspositionTable.java

import java.util.Arrays;

public class TranspositionTable {
    private final int size;
    private final int[] keys;
    private final byte[] values;
    private final byte[] depths;
    private final byte[] boundTypes;

    public static final byte BOUND_EXACT = 0;
    public static final byte BOUND_LOWER = 1;
    public static final byte BOUND_UPPER = 2;

    public TranspositionTable(int size) {
        this.size = size;
        keys = new int[size];
        values = new byte[size];
        depths = new byte[size];
        boundTypes = new byte[size];
    }

    public void reset() {
        Arrays.fill(keys, 0);
        Arrays.fill(values, (byte) 0);
        Arrays.fill(depths, (byte) 0);
        Arrays.fill(boundTypes, (byte) 0);
    }

    public void put(long key, byte val) {
        put(key, val, (byte) 0, BOUND_EXACT);
    }

    public void put(long key, byte val, byte depth, byte type) {
        int pos = index(key);
        keys[pos] = (int) key;
        values[pos] = val;
        depths[pos] = depth;
        boundTypes[pos] = type;
    }

    public byte get(long key) {
        TTEntry e = getEntry(key);
        return (e != null ? e.value : 0);
    }

    public TTEntry getEntry(long key) {
        int pos = index(key);
        if (keys[pos] == (int) key) {
            return new TTEntry(values[pos], depths[pos], boundTypes[pos]);
        }
        return null;
    }

    public static class TTEntry {
        public final byte value;
        public final byte depth;
        public final byte boundType;

        public TTEntry(byte value, byte depth, byte boundType) {
            this.value = value;
            this.depth = depth;
            this.boundType = boundType;
        }
    }

    private int index(long key) {
        return (int) (key % size);
    }
}