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
26 package java.security;
27
28 import java.io.IOException;
29 import java.io.EOFException;
30 import java.io.OutputStream;
31 import java.io.FilterOutputStream;
32 import java.io.PrintStream;
33 import 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 */
56 public 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 }