001 /*
002 * Copyright 1996-1999 Sun Microsystems, Inc. All Rights Reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation. Sun designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Sun in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022 * CA 95054 USA or visit www.sun.com if you need additional information or
023 * have any questions.
024 */
025
026 package java.security;
027
028 import java.io.IOException;
029 import java.io.EOFException;
030 import java.io.OutputStream;
031 import java.io.FilterOutputStream;
032 import java.io.PrintStream;
033 import java.io.ByteArrayOutputStream;
034
035 /**
036 * A transparent stream that updates the associated message digest using
037 * the bits going through the stream.
038 *
039 * <p>To complete the message digest computation, call one of the
040 * <code>digest</code> methods on the associated message
041 * digest after your calls to one of this digest ouput stream's
042 * {@link #write(int) write} methods.
043 *
044 * <p>It is possible to turn this stream on or off (see
045 * {@link #on(boolean) on}). When it is on, a call to one of the
046 * <code>write</code> methods results in
047 * an update on the message digest. But when it is off, the message
048 * digest is not updated. The default is for the stream to be on.
049 *
050 * @see MessageDigest
051 * @see DigestInputStream
052 *
053 * @version 1.38 07/05/05
054 * @author Benjamin Renaud
055 */
056 public class DigestOutputStream extends FilterOutputStream {
057
058 private boolean on = true;
059
060 /**
061 * The message digest associated with this stream.
062 */
063 protected MessageDigest digest;
064
065 /**
066 * Creates a digest output stream, using the specified output stream
067 * and message digest.
068 *
069 * @param stream the output stream.
070 *
071 * @param digest the message digest to associate with this stream.
072 */
073 public DigestOutputStream(OutputStream stream, MessageDigest digest) {
074 super (stream);
075 setMessageDigest(digest);
076 }
077
078 /**
079 * Returns the message digest associated with this stream.
080 *
081 * @return the message digest associated with this stream.
082 * @see #setMessageDigest(java.security.MessageDigest)
083 */
084 public MessageDigest getMessageDigest() {
085 return digest;
086 }
087
088 /**
089 * Associates the specified message digest with this stream.
090 *
091 * @param digest the message digest to be associated with this stream.
092 * @see #getMessageDigest()
093 */
094 public void setMessageDigest(MessageDigest digest) {
095 this .digest = digest;
096 }
097
098 /**
099 * 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</code> on the message digest associated with this
104 * stream, passing it the byte <code>b</code>. 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 if (on) {
117 digest.update((byte) b);
118 }
119 out.write(b);
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</code>
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</code> 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</code>, starting at offset <code>off</code>.
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 if (on) {
147 digest.update(b, off, len);
148 }
149 out.write(b, off, len);
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</code> 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 }
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