com.groupbyinc.common.apache.commons.io.input.MessageDigestCalculatingInputStream Maven / Gradle / Ivy
/*
* 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.
* Note: 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 md;
/**
* Creates an MessageDigestMaintainingObserver for the given MessageDigest.
* @param pMd the message digest to use
*/
public MessageDigestMaintainingObserver(final MessageDigest pMd) {
md = pMd;
}
@Override
void data(final int pByte) throws IOException {
md.update((byte) pByte);
}
@Override
void data(final byte[] pBuffer, final int pOffset, final int pLength) throws IOException {
md.update(pBuffer, pOffset, pLength);
}
}
private final MessageDigest messageDigest;
/** Creates a new instance, which calculates a signature on the given stream,
* using the given {@link MessageDigest}.
* @param pStream the stream to calculate the message digest for
* @param pDigest the message digest to use
*/
public MessageDigestCalculatingInputStream(final InputStream pStream, final MessageDigest pDigest) {
super(pStream);
messageDigest = pDigest;
add(new MessageDigestMaintainingObserver(pDigest));
}
/** Creates a new instance, which calculates a signature on the given stream,
* using a {@link MessageDigest} with the given algorithm.
* @param pStream the stream to calculate the message digest for
* @param pAlgorithm the name of the algorithm to use
* @throws NoSuchAlgorithmException if no Provider supports a MessageDigestSpi implementation for the specified algorithm.
*/
public MessageDigestCalculatingInputStream(final InputStream pStream, final String pAlgorithm) throws NoSuchAlgorithmException {
this(pStream, MessageDigest.getInstance(pAlgorithm));
}
/** Creates a new instance, which calculates a signature on the given stream,
* using a {@link MessageDigest} with the "MD5" algorithm.
* @param pStream 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 pStream) throws NoSuchAlgorithmException {
this(pStream, MessageDigest.getInstance("MD5"));
}
/** Returns the {@link MessageDigest}, which is being used for generating the
* checksum.
* Note: 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;
}
}