1/*
2 * Copyright (c) 1996, 1999, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package java.security;
27
28import java.io.IOException;
29import java.io.EOFException;
30import java.io.OutputStream;
31import java.io.FilterOutputStream;
32import java.io.PrintStream;
33import java.io.ByteArrayOutputStream;
34
35/**
36 * A transparent stream that updates the associated message digest using
37 * the bits going through the stream.
38 *
39 * <p>To complete the message digest computation, call one of the
40 * <code>digest</code> methods on the associated message
41 * digest after your calls to one of this digest ouput stream's
42 * {@link #write(int) write} methods.
43 *
44 * <p>It is possible to turn this stream on or off (see
45 * {@link #on(boolean) on}). When it is on, a call to one of the
46 * <code>write</code> methods results in
47 * an update on the message digest.  But when it is off, the message
48 * digest is not updated. The default is for the stream to be on.
49 *
50 * @see MessageDigest
51 * @see DigestInputStream
52 *
53 * @author Benjamin Renaud
54 */
55public class DigestOutputStream extends FilterOutputStream {
56
57    private boolean on = true;
58
59    /**
60     * The message digest associated with this stream.
61     */
62    protected MessageDigest digest;
63
64    /**
65     * Creates a digest output stream, using the specified output stream
66     * and message digest.
67     *
68     * @param stream the output stream.
69     *
70     * @param digest the message digest to associate with this stream.
71     */
72    public DigestOutputStream(OutputStream stream, MessageDigest digest) {
73        super(stream);
74        setMessageDigest(digest);
75    }
76
77    /**
78     * Returns the message digest associated with this stream.
79     *
80     * @return the message digest associated with this stream.
81     * @see #setMessageDigest(java.security.MessageDigest)
82     */
83    public MessageDigest getMessageDigest() {
84        return digest;
85    }
86
87    /**
88     * Associates the specified message digest with this stream.
89     *
90     * @param digest the message digest to be associated with this stream.
91     * @see #getMessageDigest()
92     */
93    public void setMessageDigest(MessageDigest digest) {
94        this.digest = digest;
95    }
96
97    /**
98     * Updates the message digest (if the digest function is on) using
99     * the specified byte, and in any case writes the byte
100     * to the output stream. That is, if the digest function is on
101     * (see {@link #on(boolean) on}), this method calls
102     * <code>update</code> on the message digest associated with this
103     * stream, passing it the byte <code>b</code>. This method then
104     * writes the byte to the output stream, blocking until the byte
105     * is actually written.
106     *
107     * @param b the byte to be used for updating and writing to the
108     * output stream.
109     *
110     * @exception IOException if an I/O error occurs.
111     *
112     * @see MessageDigest#update(byte)
113     */
114    public void write(int b) throws IOException {
115        if (on) {
116            digest.update((byte)b);
117        }
118        out.write(b);
119    }
120
121    /**
122     * Updates the message digest (if the digest function is on) using
123     * the specified subarray, and in any case writes the subarray to
124     * the output stream. That is, if the digest function is on (see
125     * {@link #on(boolean) on}), this method calls <code>update</code>
126     * on the message digest associated with this stream, passing it
127     * the subarray specifications. This method then writes the subarray
128     * bytes to the output stream, blocking until the bytes are actually
129     * written.
130     *
131     * @param b the array containing the subarray to be used for updating
132     * and writing to the output stream.
133     *
134     * @param off the offset into <code>b</code> of the first byte to
135     * be updated and written.
136     *
137     * @param len the number of bytes of data to be updated and written
138     * from <code>b</code>, starting at offset <code>off</code>.
139     *
140     * @exception IOException if an I/O error occurs.
141     *
142     * @see MessageDigest#update(byte[], int, int)
143     */
144    public void write(byte[] b, int off, int len) throws IOException {
145        if (on) {
146            digest.update(b, off, len);
147        }
148        out.write(b, off, len);
149    }
150
151    /**
152     * Turns the digest function on or off. The default is on.  When
153     * it is on, a call to one of the <code>write</code> methods results in an
154     * update on the message digest.  But when it is off, the message
155     * digest is not updated.
156     *
157     * @param on true to turn the digest function on, false to turn it
158     * off.
159     */
160    public void on(boolean on) {
161        this.on = on;
162    }
163
164    /**
165     * Prints a string representation of this digest output stream and
166     * its associated message digest object.
167     */
168     public String toString() {
169         return "[Digest Output Stream] " + digest.toString();
170     }
171}
172