/*
* Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
package java.security;
import java.io.IOException;
import java.io.EOFException;
import java.io.OutputStream;
import java.io.FilterOutputStream;
import java.io.PrintStream;
import java.io.ByteArrayOutputStream;
/**
* A transparent stream that updates the associated message digest using
* the bits going through the stream.
*
* <p>To complete the message digest computation, call one of the
* {@code digest} methods on the associated message
* digest after your calls to one of this digest ouput stream's
* {@link #write(int) write} methods.
*
* <p>It is possible to turn this stream on or off (see
* {@link #on(boolean) on}). When it is on, a call to one of the
* {@code write} methods results in
* an update on the message digest. But when it is off, the message
* digest is not updated. The default is for the stream to be on.
*
* @see MessageDigest
* @see DigestInputStream
*
* @author Benjamin Renaud
*/
public class DigestOutputStream extends FilterOutputStream {
private boolean on = true;
/**
* The message digest associated with this stream.
*/
protected MessageDigest digest;
/**
* Creates a digest output stream, using the specified output stream
* and message digest.
*
* @param stream the output stream.
*
* @param digest the message digest to associate with this stream.
*/
public DigestOutputStream(OutputStream stream, MessageDigest digest) {
super(stream);
setMessageDigest(digest);
}
/**
* Returns the message digest associated with this stream.
*
* @return the message digest associated with this stream.
* @see #setMessageDigest(java.security.MessageDigest)
*/
public MessageDigest getMessageDigest() {
return digest;
}
/**
* Associates the specified message digest with this stream.
*
* @param digest the message digest to be associated with this stream.
* @see #getMessageDigest()
*/
public void setMessageDigest(MessageDigest digest) {
this.digest = digest;
}
/**
* Updates the message digest (if the digest function is on) using
* the specified byte, and in any case writes the byte
* to the output stream. That is, if the digest function is on
* (see {@link #on(boolean) on}), this method calls
* {@code update} on the message digest associated with this
* stream, passing it the byte {@code b}. This method then
* writes the byte to the output stream, blocking until the byte
* is actually written.
*
* @param b the byte to be used for updating and writing to the
* output stream.
*
* @exception IOException if an I/O error occurs.
*
* @see MessageDigest#update(byte)
*/
public void write(int b) throws IOException {
out.write(b);
if (on) {
digest.update((byte)b);
}
}
/**
* Updates the message digest (if the digest function is on) using
* the specified subarray, and in any case writes the subarray to
* the output stream. That is, if the digest function is on (see
* {@link #on(boolean) on}), this method calls {@code update}
* on the message digest associated with this stream, passing it
* the subarray specifications. This method then writes the subarray
* bytes to the output stream, blocking until the bytes are actually
* written.
*
* @param b the array containing the subarray to be used for updating
* and writing to the output stream.
*
* @param off the offset into {@code b} of the first byte to
* be updated and written.
*
* @param len the number of bytes of data to be updated and written
* from {@code b}, starting at offset {@code off}.
*
* @exception IOException if an I/O error occurs.
*
* @see MessageDigest#update(byte[], int, int)
*/
public void write(byte[] b, int off, int len) throws IOException {
out.write(b, off, len);
if (on) {
digest.update(b, off, len);
}
}
/**
* Turns the digest function on or off. The default is on. When
* it is on, a call to one of the {@code write} methods results in an
* update on the message digest. But when it is off, the message
* digest is not updated.
*
* @param on true to turn the digest function on, false to turn it
* off.
*/
public void on(boolean on) {
this.on = on;
}
/**
* Prints a string representation of this digest output stream and
* its associated message digest object.
*/
public String toString() {
return "[Digest Output Stream] " + digest.toString();
}
}