1 /*
2 * Copyright 1996-1999 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any 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</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 */
55 public 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 }
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