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: }
| 