Update #0 - First Release

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

@@ -0,0 +1,96 @@
+/*
+ * Copyright (C) 2012 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.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import java.io.Serializable;
+import java.util.zip.Checksum;
+
+import com.google.common.base.Supplier;
+
+/**
+ * {@link HashFunction} adapter for {@link Checksum} instances.
+ *
+ * @author Colin Decker
+ */
+final class ChecksumHashFunction extends AbstractStreamingHashFunction implements Serializable {
+
+	private final Supplier<? extends Checksum> checksumSupplier;
+	private final int bits;
+	private final String toString;
+
+	ChecksumHashFunction(Supplier<? extends Checksum> checksumSupplier, int bits, String toString) {
+		this.checksumSupplier = checkNotNull(checksumSupplier);
+		checkArgument(bits == 32 || bits == 64, "bits (%s) must be either 32 or 64", bits);
+		this.bits = bits;
+		this.toString = checkNotNull(toString);
+	}
+
+	@Override
+	public int bits() {
+		return bits;
+	}
+
+	@Override
+	public Hasher newHasher() {
+		return new ChecksumHasher(checksumSupplier.get());
+	}
+
+	@Override
+	public String toString() {
+		return toString;
+	}
+
+	/**
+	 * Hasher that updates a checksum.
+	 */
+	private final class ChecksumHasher extends AbstractByteHasher {
+
+		private final Checksum checksum;
+
+		private ChecksumHasher(Checksum checksum) {
+			this.checksum = checkNotNull(checksum);
+		}
+
+		@Override
+		protected void update(byte b) {
+			checksum.update(b);
+		}
+
+		@Override
+		protected void update(byte[] bytes, int off, int len) {
+			checksum.update(bytes, off, len);
+		}
+
+		@Override
+		public HashCode hash() {
+			long value = checksum.getValue();
+			if (bits == 32) {
+				/*
+				 * The long returned from a 32-bit Checksum will have all 0s for its second
+				 * word, so the cast won't lose any information and is necessary to return a
+				 * HashCode of the correct size.
+				 */
+				return HashCode.fromInt((int) value);
+			} else {
+				return HashCode.fromLong(value);
+			}
+		}
+	}
+
+	private static final long serialVersionUID = 0L;
+}