001 /* DigestOutputStream.java --- An output stream tied to a message digest
002 Copyright (C) 1999, 2004, 2005 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
016 You should have received a copy of the GNU General Public License
017 along with GNU Classpath; see the file COPYING. If not, write to the
018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038
039 package java.security;
040
041 import java.io.FilterOutputStream;
042 import java.io.IOException;
043 import java.io.OutputStream;
044
045 /**
046 * DigestOutputStream is a class that ties an OutputStream with a
047 * MessageDigest. The Message Digest is used by the class to update it
048 * self as bytes are written to the OutputStream.
049 *
050 * The updating to the digest depends on the on flag which is set to
051 * true by default that tells the class to update the data in the
052 * message digest.
053 *
054 * @version 0.0
055 * @author Mark Benvenuto (ivymccough@worldnet.att.net)
056 */
057 public class DigestOutputStream extends FilterOutputStream
058 {
059 /**
060 * The message digest for the DigestOutputStream
061 */
062 protected MessageDigest digest;
063
064 //Manages the on flag
065 private boolean state = true;
066
067 /**
068 * Constructs a new DigestOutputStream. It associates a
069 * MessageDigest with the stream to compute the stream as data is
070 * written.
071 *
072 * @param stream An OutputStream to associate this stream with
073 * @param digest A MessageDigest to hash the stream with
074 */
075 public DigestOutputStream(OutputStream stream, MessageDigest digest)
076 {
077 super(stream);
078 this.digest = digest;
079 }
080
081 /**
082 * Returns the MessageDigest associated with this DigestOutputStream
083 *
084 * @return The MessageDigest used to hash this stream
085 */
086 public MessageDigest getMessageDigest()
087 {
088 return digest;
089 }
090
091 /**
092 * Sets the current MessageDigest to current parameter
093 *
094 * @param digest A MessageDigest to associate with this stream
095 */
096 public void setMessageDigest(MessageDigest digest)
097 {
098 this.digest = digest;
099 }
100
101
102 /**
103 * Updates the hash if the on flag is true and then writes a byte to
104 * the underlying output stream.
105 *
106 * @param b A byte to write to the output stream
107 *
108 * @exception IOException if the underlying output stream
109 * cannot write the byte, this is thrown.
110 */
111 public void write(int b) throws IOException
112 {
113 if (state)
114 digest.update((byte) b);
115
116 out.write(b);
117 }
118
119 /**
120 * Updates the hash if the on flag is true and then writes the bytes
121 * to the underlying output stream.
122 *
123 * @param b Bytes to write to the output stream
124 * @param off Offset to start to start at in array
125 * @param len Length of data to write
126 *
127 * @exception IOException if the underlying output stream
128 * cannot write the bytes, this is thrown.
129 */
130 public void write(byte[]b, int off, int len) throws IOException
131 {
132 if (state)
133 digest.update(b, off, len);
134
135 out.write(b, off, len);
136 }
137
138 /**
139 * Sets the flag specifying if this DigestOutputStream updates the
140 * digest in the write() methods. The default is on;
141 *
142 * @param on True means it digests stream, false means it does not
143 */
144 public void on(boolean on)
145 {
146 state = on;
147 }
148
149 /**
150 * Converts the output stream and underlying message digest to a string.
151 *
152 * @return A string representing the output stream and message digest.
153 */
154 public String toString()
155 {
156 return "[Digest Output Stream] " + digest.toString();
157 }
158 }