Update #0 - First Release

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

@@ -0,0 +1,108 @@
+/*
+ * Copyright (C) 2013 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.io.FilterInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+import com.google.common.annotations.Beta;
+
+/**
+ * An {@link InputStream} that maintains a hash of the data read from it.
+ *
+ * @author Qian Huang
+ * @since 16.0
+ */
+@Beta
+public final class HashingInputStream extends FilterInputStream {
+	private final Hasher hasher;
+
+	/**
+	 * Creates an input stream that hashes using the given {@link HashFunction} and
+	 * delegates all data read from it to the underlying {@link InputStream}.
+	 *
+	 * <p>
+	 * The {@link InputStream} should not be read from before or after the hand-off.
+	 */
+	public HashingInputStream(HashFunction hashFunction, InputStream in) {
+		super(checkNotNull(in));
+		this.hasher = checkNotNull(hashFunction.newHasher());
+	}
+
+	/**
+	 * Reads the next byte of data from the underlying input stream and updates the
+	 * hasher with the byte read.
+	 */
+	@Override
+	public int read() throws IOException {
+		int b = in.read();
+		if (b != -1) {
+			hasher.putByte((byte) b);
+		}
+		return b;
+	}
+
+	/**
+	 * Reads the specified bytes of data from the underlying input stream and
+	 * updates the hasher with the bytes read.
+	 */
+	@Override
+	public int read(byte[] bytes, int off, int len) throws IOException {
+		int numOfBytesRead = in.read(bytes, off, len);
+		if (numOfBytesRead != -1) {
+			hasher.putBytes(bytes, off, numOfBytesRead);
+		}
+		return numOfBytesRead;
+	}
+
+	/**
+	 * mark() is not supported for HashingInputStream
+	 * 
+	 * @return {@code false} always
+	 */
+	@Override
+	public boolean markSupported() {
+		return false;
+	}
+
+	/**
+	 * mark() is not supported for HashingInputStream
+	 */
+	@Override
+	public void mark(int readlimit) {
+	}
+
+	/**
+	 * reset() is not supported for HashingInputStream.
+	 * 
+	 * @throws IOException this operation is not supported
+	 */
+	@Override
+	public void reset() throws IOException {
+		throw new IOException("reset not supported");
+	}
+
+	/**
+	 * Returns the {@link HashCode} based on the data read from this stream. The
+	 * result is unspecified if this method is called more than once on the same
+	 * instance.
+	 */
+	public HashCode hash() {
+		return hasher.hash();
+	}
+}