Added cached hasher generator

Author: GreenWizard2015

YASL-Core/src/YASL/Hashing/ChgCached.java

@@ -0,0 +1,51 @@
+package YASL.Hashing;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class ChgCached<T> implements IHashingGenerator<T> {
+	private final IHashingGenerator<T>						_gen;
+	private final Map<CHasherParams, IHasher<T>>	_cache	= new HashMap<>();
+
+	public ChgCached(IHashingGenerator<T> gen) {
+		this._gen = gen;
+	}
+
+	@Override
+	public IHasher<T> generate(int range, int levels) {
+		final CHasherParams params = new CHasherParams(range, levels);
+		IHasher<T> res = _cache.get(params);
+		if (null == res) {
+			res = _gen.generate(range, levels);
+			_cache.put(params, res);
+		}
+		return res;
+	}
+
+	private static class CHasherParams {
+		private final int	_range;
+		private final int	_levels;
+
+		public CHasherParams(int range, int levels) {
+			this._range = range;
+			this._levels = levels;
+		}
+
+		@Override
+		public int hashCode() {
+			final int prime = 31;
+			return prime * _levels + _range;
+		}
+
+		@Override
+		public boolean equals(Object obj) {
+			if (this == obj)
+				return true;
+			if ((obj == null) || (getClass() != obj.getClass()))
+				return false;
+
+			final CHasherParams other = (CHasherParams) obj;
+			return ((_levels == other._levels) && (_range == other._range));
+		}
+	}
+}

YASL-Tests/src/Tests/Hashing/Test_hgCached.java

@@ -0,0 +1,32 @@
+package Tests.Hashing;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import YASL.Hashing.ChgBasic;
+import YASL.Hashing.ChgCached;
+import YASL.Hashing.IHasher;
+import YASL.Hashing.IHashingGenerator;
+
+public class Test_hgCached {
+
+	@Test
+	public void sameHasherWhenSameParams() {
+		final IHashingGenerator<Integer> gen = new ChgCached<>( //
+		    new ChgBasic<>() //
+		);
+
+		final IHasher<Integer> first = gen.generate(1, 1);
+		Assert.assertEquals(first, gen.generate(1, 1));
+	}
+
+	@Test
+	public void diffHasherWhenDiffParams() {
+		final IHashingGenerator<Integer> gen = new ChgCached<>( //
+		    new ChgBasic<>() //
+		);
+
+		final IHasher<Integer> first = gen.generate(1, 1);
+		Assert.assertNotEquals(first, gen.generate(2, 2));
+	}
+}