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.InputStream;
031 import java.io.FilterInputStream;
032 import java.io.PrintStream;
033 import java.io.ByteArrayInputStream;
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 input stream's
042 * {@link #read() read} 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>read</code> methods
047 * results in an update on the message digest. But when it is off,
048 * the message digest is not updated. The default is for the stream
049 * to be on.
050 *
051 * <p>Note that digest objects can compute only one digest (see
052 * {@link MessageDigest}),
053 * so that in order to compute intermediate digests, a caller should
054 * retain a handle onto the digest object, and clone it for each
055 * digest to be computed, leaving the orginal digest untouched.
056 *
057 * @see MessageDigest
058 *
059 * @see DigestOutputStream
060 *
061 * @version 1.44 07/05/05
062 * @author Benjamin Renaud
063 */
064
065 public class DigestInputStream extends FilterInputStream {
066
067 /* NOTE: This should be made a generic UpdaterInputStream */
068
069 /* Are we on or off? */
070 private boolean on = true;
071
072 /**
073 * The message digest associated with this stream.
074 */
075 protected MessageDigest digest;
076
077 /**
078 * Creates a digest input stream, using the specified input stream
079 * and message digest.
080 *
081 * @param stream the input stream.
082 *
083 * @param digest the message digest to associate with this stream.
084 */
085 public DigestInputStream(InputStream stream, MessageDigest digest) {
086 super (stream);
087 setMessageDigest(digest);
088 }
089
090 /**
091 * Returns the message digest associated with this stream.
092 *
093 * @return the message digest associated with this stream.
094 * @see #setMessageDigest(java.security.MessageDigest)
095 */
096 public MessageDigest getMessageDigest() {
097 return digest;
098 }
099
100 /**
101 * Associates the specified message digest with this stream.
102 *
103 * @param digest the message digest to be associated with this stream.
104 * @see #getMessageDigest()
105 */
106 public void setMessageDigest(MessageDigest digest) {
107 this .digest = digest;
108 }
109
110 /**
111 * Reads a byte, and updates the message digest (if the digest
112 * function is on). That is, this method reads a byte from the
113 * input stream, blocking until the byte is actually read. If the
114 * digest function is on (see {@link #on(boolean) on}), this method
115 * will then call <code>update</code> on the message digest associated
116 * with this stream, passing it the byte read.
117 *
118 * @return the byte read.
119 *
120 * @exception IOException if an I/O error occurs.
121 *
122 * @see MessageDigest#update(byte)
123 */
124 public int read() throws IOException {
125 int ch = in.read();
126 if (on && ch != -1) {
127 digest.update((byte) ch);
128 }
129 return ch;
130 }
131
132 /**
133 * Reads into a byte array, and updates the message digest (if the
134 * digest function is on). That is, this method reads up to
135 * <code>len</code> bytes from the input stream into the array
136 * <code>b</code>, starting at offset <code>off</code>. This method
137 * blocks until the data is actually
138 * read. If the digest function is on (see
139 * {@link #on(boolean) on}), this method will then call <code>update</code>
140 * on the message digest associated with this stream, passing it
141 * the data.
142 *
143 * @param b the array into which the data is read.
144 *
145 * @param off the starting offset into <code>b</code> of where the
146 * data should be placed.
147 *
148 * @param len the maximum number of bytes to be read from the input
149 * stream into b, starting at offset <code>off</code>.
150 *
151 * @return the actual number of bytes read. This is less than
152 * <code>len</code> if the end of the stream is reached prior to
153 * reading <code>len</code> bytes. -1 is returned if no bytes were
154 * read because the end of the stream had already been reached when
155 * the call was made.
156 *
157 * @exception IOException if an I/O error occurs.
158 *
159 * @see MessageDigest#update(byte[], int, int)
160 */
161 public int read(byte[] b, int off, int len) throws IOException {
162 int result = in.read(b, off, len);
163 if (on && result != -1) {
164 digest.update(b, off, result);
165 }
166 return result;
167 }
168
169 /**
170 * Turns the digest function on or off. The default is on. When
171 * it is on, a call to one of the <code>read</code> methods results in an
172 * update on the message digest. But when it is off, the message
173 * digest is not updated.
174 *
175 * @param on true to turn the digest function on, false to turn
176 * it off.
177 */
178 public void on(boolean on) {
179 this .on = on;
180 }
181
182 /**
183 * Prints a string representation of this digest input stream and
184 * its associated message digest object.
185 */
186 public String toString() {
187 return "[Digest Input Stream] " + digest.toString();
188 }
189 }
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