/* * Copyright (c) 1996, 1999, 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 * or visit www.oracle.com if you need additional information or have any * questions. */ 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</code> 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</code> 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</code> on the message digest associated with this     * stream, passing it the byte <code>b</code>. 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 {        if (on) {            digest.update((byte)b);        }        out.write(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</code>     * 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</code> 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</code>, starting at offset <code>off</code>.     *     * @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 {        if (on) {            digest.update(b, off, len);        }        out.write(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</code> 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();     }}