MessageDigestInputStream.java
/*
* 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;
import java.util.Objects;
import org.apache.commons.io.build.AbstractStreamBuilder;
/**
* 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 {@link MessageDigest}, for example, a SHA-512 sum.
* <p>
* To build an instance, use {@link Builder}.
* </p>
* <p>
* See the MessageDigest section in the <a href= "https://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html#MessageDigest"> Java
* Cryptography Architecture Standard Algorithm Name Documentation</a> for information about standard algorithm names.
* </p>
* <p>
* You must specify a message digest algorithm name or instance.
* </p>
* <p>
* <em>Note</em>: Neither {@link ObservableInputStream}, nor {@link MessageDigest}, are thread safe, so is {@link MessageDigestInputStream}.
* </p>
*
* @see Builder
* @since 2.15.0
*/
public final class MessageDigestInputStream extends ObservableInputStream {
// @formatter:off
/**
* Builds new {@link MessageDigestInputStream}.
*
* <p>
* For example:
* </p>
* <pre>{@code
* MessageDigestInputStream s = MessageDigestInputStream.builder()
* .setPath(path)
* .setMessageDigest("SHA-512")
* .get();}
* </pre>
* <p>
* You must specify a message digest algorithm name or instance.
* </p>
*
* @see #get()
*/
// @formatter:on
public static class Builder extends AbstractStreamBuilder<MessageDigestInputStream, Builder> {
private MessageDigest messageDigest;
/**
* Constructs a new {@link Builder}.
*/
public Builder() {
// empty
}
/**
* Builds new {@link MessageDigestInputStream}.
* <p>
* You must set input that supports {@link #getInputStream()}, otherwise, this method throws an exception.
* </p>
* <p>
* This builder use the following aspects:
* </p>
* <ul>
* <li>{@link #getPath()}</li>
* <li>{@link MessageDigest}</li>
* </ul>
*
* @return a new instance.
* @throws NullPointerException if messageDigest is null.
* @throws IllegalStateException if the {@code origin} is {@code null}.
* @throws UnsupportedOperationException if the origin cannot be converted to an {@link InputStream}.
* @throws IOException if an I/O error occurs.
* @see #getInputStream()
*/
@SuppressWarnings("resource")
@Override
public MessageDigestInputStream get() throws IOException {
return new MessageDigestInputStream(getInputStream(), messageDigest);
}
/**
* Sets the message digest.
* <p>
* The MD5 cryptographic algorithm is weak and should not be used.
* </p>
*
* @param messageDigest the message digest.
* @return this
*/
public Builder setMessageDigest(final MessageDigest messageDigest) {
this.messageDigest = messageDigest;
return this;
}
/**
* Sets the name of the name of the message digest algorithm.
* <p>
* The MD5 cryptographic algorithm is weak and should not be used.
* </p>
*
* @param algorithm the name of the algorithm. See the MessageDigest section in the
* <a href= "https://docs.oracle.com/javase/8/docs/technotes/guides/security/StandardNames.html#MessageDigest"> Java Cryptography
* Architecture Standard Algorithm Name Documentation</a> for information about standard algorithm names.
* @return this
* @throws NoSuchAlgorithmException if no Provider supports a MessageDigestSpi implementation for the specified algorithm.
*/
public Builder setMessageDigest(final String algorithm) throws NoSuchAlgorithmException {
this.messageDigest = MessageDigest.getInstance(algorithm);
return this;
}
}
/**
* Maintains the message digest.
*/
public static class MessageDigestMaintainingObserver extends Observer {
private final MessageDigest messageDigest;
/**
* Constructs an MessageDigestMaintainingObserver for the given MessageDigest.
*
* @param messageDigest the message digest to use
* @throws NullPointerException if messageDigest is null.
*/
public MessageDigestMaintainingObserver(final MessageDigest messageDigest) {
this.messageDigest = Objects.requireNonNull(messageDigest, "messageDigest");
}
@Override
public void data(final byte[] input, final int offset, final int length) throws IOException {
messageDigest.update(input, offset, length);
}
@Override
public void data(final int input) throws IOException {
messageDigest.update((byte) input);
}
}
/**
* Constructs a new {@link Builder}.
*
* @return a new {@link Builder}.
*/
public static Builder builder() {
return new Builder();
}
private final MessageDigest messageDigest;
/**
* Constructs a new instance, which calculates a signature on the given stream, using the given {@link MessageDigest}.
* <p>
* The MD5 cryptographic algorithm is weak and should not be used.
* </p>
*
* @param inputStream the stream to calculate the message digest for
* @param messageDigest the message digest to use
* @throws NullPointerException if messageDigest is null.
*/
private MessageDigestInputStream(final InputStream inputStream, final MessageDigest messageDigest) {
super(inputStream, new MessageDigestMaintainingObserver(messageDigest));
this.messageDigest = messageDigest;
}
/**
* Gets the {@link MessageDigest}, which is being used for generating the checksum.
* <p>
* <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()}.
* </p>
*
* @return the message digest used
*/
public MessageDigest getMessageDigest() {
return messageDigest;
}
}