Update #0 - First Release

sources/main/java/com/google/common/hash/AbstractCompositeHashFunction.java

@@ -0,0 +1,170 @@
+/*
+ * Copyright (C) 2011 The Guava Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.common.hash;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import java.nio.charset.Charset;
+
+/**
+ * An abstract composition of multiple hash functions. {@linkplain #newHasher()}
+ * delegates to the {@code Hasher} objects of the delegate hash functions, and
+ * in the end, they are used by {@linkplain #makeHash(Hasher[])} that constructs
+ * the final {@code HashCode}.
+ *
+ * @author Dimitris Andreou
+ */
+abstract class AbstractCompositeHashFunction extends AbstractStreamingHashFunction {
+	final HashFunction[] functions;
+
+	AbstractCompositeHashFunction(HashFunction... functions) {
+		for (HashFunction function : functions) {
+			checkNotNull(function);
+		}
+		this.functions = functions;
+	}
+
+	/**
+	 * Constructs a {@code HashCode} from the {@code Hasher} objects of the
+	 * functions. Each of them has consumed the entire input and they are ready to
+	 * output a {@code HashCode}. The order of the hashers are the same order as the
+	 * functions given to the constructor.
+	 */
+	// this could be cleaner if it passed HashCode[], but that would create yet
+	// another array...
+	/* protected */ abstract HashCode makeHash(Hasher[] hashers);
+
+	@Override
+	public Hasher newHasher() {
+		final Hasher[] hashers = new Hasher[functions.length];
+		for (int i = 0; i < hashers.length; i++) {
+			hashers[i] = functions[i].newHasher();
+		}
+		return new Hasher() {
+			@Override
+			public Hasher putByte(byte b) {
+				for (Hasher hasher : hashers) {
+					hasher.putByte(b);
+				}
+				return this;
+			}
+
+			@Override
+			public Hasher putBytes(byte[] bytes) {
+				for (Hasher hasher : hashers) {
+					hasher.putBytes(bytes);
+				}
+				return this;
+			}
+
+			@Override
+			public Hasher putBytes(byte[] bytes, int off, int len) {
+				for (Hasher hasher : hashers) {
+					hasher.putBytes(bytes, off, len);
+				}
+				return this;
+			}
+
+			@Override
+			public Hasher putShort(short s) {
+				for (Hasher hasher : hashers) {
+					hasher.putShort(s);
+				}
+				return this;
+			}
+
+			@Override
+			public Hasher putInt(int i) {
+				for (Hasher hasher : hashers) {
+					hasher.putInt(i);
+				}
+				return this;
+			}
+
+			@Override
+			public Hasher putLong(long l) {
+				for (Hasher hasher : hashers) {
+					hasher.putLong(l);
+				}
+				return this;
+			}
+
+			@Override
+			public Hasher putFloat(float f) {
+				for (Hasher hasher : hashers) {
+					hasher.putFloat(f);
+				}
+				return this;
+			}
+
+			@Override
+			public Hasher putDouble(double d) {
+				for (Hasher hasher : hashers) {
+					hasher.putDouble(d);
+				}
+				return this;
+			}
+
+			@Override
+			public Hasher putBoolean(boolean b) {
+				for (Hasher hasher : hashers) {
+					hasher.putBoolean(b);
+				}
+				return this;
+			}
+
+			@Override
+			public Hasher putChar(char c) {
+				for (Hasher hasher : hashers) {
+					hasher.putChar(c);
+				}
+				return this;
+			}
+
+			@Override
+			public Hasher putUnencodedChars(CharSequence chars) {
+				for (Hasher hasher : hashers) {
+					hasher.putUnencodedChars(chars);
+				}
+				return this;
+			}
+
+			@Override
+			public Hasher putString(CharSequence chars, Charset charset) {
+				for (Hasher hasher : hashers) {
+					hasher.putString(chars, charset);
+				}
+				return this;
+			}
+
+			@Override
+			public <T> Hasher putObject(T instance, Funnel<? super T> funnel) {
+				for (Hasher hasher : hashers) {
+					hasher.putObject(instance, funnel);
+				}
+				return this;
+			}
+
+			@Override
+			public HashCode hash() {
+				return makeHash(hashers);
+			}
+		};
+	}
+
+	private static final long serialVersionUID = 0L;
+}