| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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 org.apache.commons.io.input; |
| |
| import java.io.IOException; |
| import java.io.InputStream; |
| import java.security.MessageDigest; |
| import java.security.NoSuchAlgorithmException; |
| |
| |
| /** |
| * This class is an example for using an {@link ObservableInputStream}. It |
| * creates its own {@link org.apache.commons.io.input.ObservableInputStream.Observer}, |
| * which calculates a checksum using a MessageDigest, for example an MD5 sum. |
| * <em>Note</em>: Neither {@link ObservableInputStream}, nor {@link MessageDigest}, |
| * are thread safe. So is {@link MessageDigestCalculatingInputStream}. |
| */ |
| public class MessageDigestCalculatingInputStream extends ObservableInputStream { |
| |
| /** |
| * Maintains the message digest. |
| */ |
| public static class MessageDigestMaintainingObserver extends Observer { |
| private final MessageDigest messageDigest; |
| |
| /** |
| * Creates an MessageDigestMaintainingObserver for the given MessageDigest. |
| * @param messageDigest the message digest to use |
| */ |
| public MessageDigestMaintainingObserver(final MessageDigest messageDigest) { |
| this.messageDigest = messageDigest; |
| } |
| |
| @Override |
| public void data(final int input) throws IOException { |
| messageDigest.update((byte) input); |
| } |
| |
| @Override |
| public void data(final byte[] input, final int offset, final int length) throws IOException { |
| messageDigest.update(input, offset, length); |
| } |
| } |
| |
| private final MessageDigest messageDigest; |
| |
| /** Creates a new instance, which calculates a signature on the given stream, |
| * using the given {@link MessageDigest}. |
| * @param inputStream the stream to calculate the message digest for |
| * @param messageDigest the message digest to use |
| */ |
| public MessageDigestCalculatingInputStream(final InputStream inputStream, final MessageDigest messageDigest) { |
| super(inputStream, new MessageDigestMaintainingObserver(messageDigest)); |
| this.messageDigest = messageDigest; |
| } |
| |
| /** |
| * Creates a new instance, which calculates a signature on the given stream, using a {@link MessageDigest} with the |
| * given algorithm. |
| * |
| * @param inputStream the stream to calculate the message digest for |
| * @param algorithm the name of the algorithm to use |
| * @throws NoSuchAlgorithmException if no Provider supports a MessageDigestSpi implementation for the specified |
| * algorithm. |
| */ |
| public MessageDigestCalculatingInputStream(final InputStream inputStream, final String algorithm) |
| throws NoSuchAlgorithmException { |
| this(inputStream, MessageDigest.getInstance(algorithm)); |
| } |
| |
| /** |
| * Creates a new instance, which calculates a signature on the given stream, using a {@link MessageDigest} with the |
| * "MD5" algorithm. |
| * |
| * @param inputStream the stream to calculate the message digest for |
| * @throws NoSuchAlgorithmException if no Provider supports a MessageDigestSpi implementation for the specified |
| * algorithm. |
| */ |
| public MessageDigestCalculatingInputStream(final InputStream inputStream) throws NoSuchAlgorithmException { |
| this(inputStream, MessageDigest.getInstance("MD5")); |
| } |
| |
| /** Returns the {@link MessageDigest}, which is being used for generating the |
| * checksum. |
| * <em>Note</em>: The checksum will only reflect the data, which has been read so far. |
| * This is probably not, what you expect. Make sure, that the complete data has been |
| * read, if that is what you want. The easiest way to do so is by invoking |
| * {@link #consume()}. |
| * @return the message digest used |
| */ |
| public MessageDigest getMessageDigest() { |
| return messageDigest; |
| } |
| } |