Update #0 - First Release

sources/main/java/com/google/common/hash/AbstractNonStreamingHashFunction.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 java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.charset.Charset;
+
+import com.google.common.base.Preconditions;
+
+/**
+ * Skeleton implementation of {@link HashFunction}, appropriate for
+ * non-streaming algorithms. All the hash computation done using
+ * {@linkplain #newHasher()} are delegated to the
+ * {@linkplain #hashBytes(byte[], int, int)} method.
+ *
+ * @author Dimitris Andreou
+ */
+abstract class AbstractNonStreamingHashFunction implements HashFunction {
+	@Override
+	public Hasher newHasher() {
+		return new BufferingHasher(32);
+	}
+
+	@Override
+	public Hasher newHasher(int expectedInputSize) {
+		Preconditions.checkArgument(expectedInputSize >= 0);
+		return new BufferingHasher(expectedInputSize);
+	}
+
+	@Override
+	public <T> HashCode hashObject(T instance, Funnel<? super T> funnel) {
+		return newHasher().putObject(instance, funnel).hash();
+	}
+
+	@Override
+	public HashCode hashUnencodedChars(CharSequence input) {
+		int len = input.length();
+		Hasher hasher = newHasher(len * 2);
+		for (int i = 0; i < len; i++) {
+			hasher.putChar(input.charAt(i));
+		}
+		return hasher.hash();
+	}
+
+	@Override
+	public HashCode hashString(CharSequence input, Charset charset) {
+		return hashBytes(input.toString().getBytes(charset));
+	}
+
+	@Override
+	public HashCode hashInt(int input) {
+		return newHasher(4).putInt(input).hash();
+	}
+
+	@Override
+	public HashCode hashLong(long input) {
+		return newHasher(8).putLong(input).hash();
+	}
+
+	@Override
+	public HashCode hashBytes(byte[] input) {
+		return hashBytes(input, 0, input.length);
+	}
+
+	/**
+	 * In-memory stream-based implementation of Hasher.
+	 */
+	private final class BufferingHasher extends AbstractHasher {
+		final ExposedByteArrayOutputStream stream;
+		static final int BOTTOM_BYTE = 0xFF;
+
+		BufferingHasher(int expectedInputSize) {
+			this.stream = new ExposedByteArrayOutputStream(expectedInputSize);
+		}
+
+		@Override
+		public Hasher putByte(byte b) {
+			stream.write(b);
+			return this;
+		}
+
+		@Override
+		public Hasher putBytes(byte[] bytes) {
+			try {
+				stream.write(bytes);
+			} catch (IOException e) {
+				throw new RuntimeException(e);
+			}
+			return this;
+		}
+
+		@Override
+		public Hasher putBytes(byte[] bytes, int off, int len) {
+			stream.write(bytes, off, len);
+			return this;
+		}
+
+		@Override
+		public Hasher putShort(short s) {
+			stream.write(s & BOTTOM_BYTE);
+			stream.write((s >>> 8) & BOTTOM_BYTE);
+			return this;
+		}
+
+		@Override
+		public Hasher putInt(int i) {
+			stream.write(i & BOTTOM_BYTE);
+			stream.write((i >>> 8) & BOTTOM_BYTE);
+			stream.write((i >>> 16) & BOTTOM_BYTE);
+			stream.write((i >>> 24) & BOTTOM_BYTE);
+			return this;
+		}
+
+		@Override
+		public Hasher putLong(long l) {
+			for (int i = 0; i < 64; i += 8) {
+				stream.write((byte) ((l >>> i) & BOTTOM_BYTE));
+			}
+			return this;
+		}
+
+		@Override
+		public Hasher putChar(char c) {
+			stream.write(c & BOTTOM_BYTE);
+			stream.write((c >>> 8) & BOTTOM_BYTE);
+			return this;
+		}
+
+		@Override
+		public <T> Hasher putObject(T instance, Funnel<? super T> funnel) {
+			funnel.funnel(instance, this);
+			return this;
+		}
+
+		@Override
+		public HashCode hash() {
+			return hashBytes(stream.byteArray(), 0, stream.length());
+		}
+	}
+
+	// Just to access the byte[] without introducing an unnecessary copy
+	private static final class ExposedByteArrayOutputStream extends ByteArrayOutputStream {
+		ExposedByteArrayOutputStream(int expectedInputSize) {
+			super(expectedInputSize);
+		}
+
+		byte[] byteArray() {
+			return buf;
+		}
+
+		int length() {
+			return count;
+		}
+	}
+}