1/*
2 * Copyright (c) 1996, 2013, 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} methods on the associated message
41 * digest after your calls to one of this digest output 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} 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 * @since 1.2
55 */
56public class DigestOutputStream extends FilterOutputStream {
57
58    private boolean on = true;
59
60    /**
61     * The message digest associated with this stream.
62     */
63    protected MessageDigest digest;
64
65    /**
66     * Creates a digest output stream, using the specified output stream
67     * and message digest.
68     *
69     * @param stream the output stream.
70     *
71     * @param digest the message digest to associate with this stream.
72     */
73    public DigestOutputStream(OutputStream stream, MessageDigest digest) {
74        super(stream);
75        setMessageDigest(digest);
76    }
77
78    /**
79     * Returns the message digest associated with this stream.
80     *
81     * @return the message digest associated with this stream.
82     * @see #setMessageDigest(java.security.MessageDigest)
83     */
84    public MessageDigest getMessageDigest() {
85        return digest;
86    }
87
88    /**
89     * Associates the specified message digest with this stream.
90     *
91     * @param digest the message digest to be associated with this stream.
92     * @see #getMessageDigest()
93     */
94    public void setMessageDigest(MessageDigest digest) {
95        this.digest = digest;
96    }
97
98    /**
99     * Updates the message digest (if the digest function is on) using
100     * the specified byte, and in any case writes the byte
101     * to the output stream. That is, if the digest function is on
102     * (see {@link #on(boolean) on}), this method calls
103     * {@code update} on the message digest associated with this
104     * stream, passing it the byte {@code b}. This method then
105     * writes the byte to the output stream, blocking until the byte
106     * is actually written.
107     *
108     * @param b the byte to be used for updating and writing to the
109     * output stream.
110     *
111     * @exception IOException if an I/O error occurs.
112     *
113     * @see MessageDigest#update(byte)
114     */
115    public void write(int b) throws IOException {
116        out.write(b);
117        if (on) {
118            digest.update((byte)b);
119        }
120    }
121
122    /**
123     * Updates the message digest (if the digest function is on) using
124     * the specified subarray, and in any case writes the subarray to
125     * the output stream. That is, if the digest function is on (see
126     * {@link #on(boolean) on}), this method calls {@code update}
127     * on the message digest associated with this stream, passing it
128     * the subarray specifications. This method then writes the subarray
129     * bytes to the output stream, blocking until the bytes are actually
130     * written.
131     *
132     * @param b the array containing the subarray to be used for updating
133     * and writing to the output stream.
134     *
135     * @param off the offset into {@code b} of the first byte to
136     * be updated and written.
137     *
138     * @param len the number of bytes of data to be updated and written
139     * from {@code b}, starting at offset {@code off}.
140     *
141     * @exception IOException if an I/O error occurs.
142     *
143     * @see MessageDigest#update(byte[], int, int)
144     */
145    public void write(byte[] b, int off, int len) throws IOException {
146        out.write(b, off, len);
147        if (on) {
148            digest.update(b, off, len);
149        }
150    }
151
152    /**
153     * Turns the digest function on or off. The default is on.  When
154     * it is on, a call to one of the {@code write} methods results in an
155     * update on the message digest.  But when it is off, the message
156     * digest is not updated.
157     *
158     * @param on true to turn the digest function on, false to turn it
159     * off.
160     */
161    public void on(boolean on) {
162        this.on = on;
163    }
164
165    /**
166     * Prints a string representation of this digest output stream and
167     * its associated message digest object.
168     */
169     public String toString() {
170         return "[Digest Output Stream] " + digest.toString();
171     }
172}
173