1 /* 2 * Copyright (c) 1996, 2013, Oracle and/or its affiliates. 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. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.security; 27 28 import java.io.IOException; 29 import java.io.EOFException; 30 import java.io.InputStream; 31 import java.io.FilterInputStream; 32 import java.io.PrintStream; 33 import java.io.ByteArrayInputStream; 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} methods on the associated message 41 * digest after your calls to one of this digest input stream's 42 * {@link #read() read} 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 read} methods 47 * results in an update on the message digest. But when it is off, 48 * the message digest is not updated. The default is for the stream 49 * to be on. 50 * 51 * <p>Note that digest objects can compute only one digest (see 52 * {@link MessageDigest}), 53 * so that in order to compute intermediate digests, a caller should 54 * retain a handle onto the digest object, and clone it for each 55 * digest to be computed, leaving the orginal digest untouched. 56 * 57 * @see MessageDigest 58 * 59 * @see DigestOutputStream 60 * 61 * @author Benjamin Renaud 62 */ 63 64 public class DigestInputStream extends FilterInputStream { 65 66 /* NOTE: This should be made a generic UpdaterInputStream */ 67 68 /* Are we on or off? */ 69 private boolean on = true; 70 71 /** 72 * The message digest associated with this stream. 73 */ 74 protected MessageDigest digest; 75 76 /** 77 * Creates a digest input stream, using the specified input stream 78 * and message digest. 79 * 80 * @param stream the input stream. 81 * 82 * @param digest the message digest to associate with this stream. 83 */ DigestInputStream(InputStream stream, MessageDigest digest)84 public DigestInputStream(InputStream stream, MessageDigest digest) { 85 super(stream); 86 setMessageDigest(digest); 87 } 88 89 /** 90 * Returns the message digest associated with this stream. 91 * 92 * @return the message digest associated with this stream. 93 * @see #setMessageDigest(java.security.MessageDigest) 94 */ getMessageDigest()95 public MessageDigest getMessageDigest() { 96 return digest; 97 } 98 99 /** 100 * Associates the specified message digest with this stream. 101 * 102 * @param digest the message digest to be associated with this stream. 103 * @see #getMessageDigest() 104 */ setMessageDigest(MessageDigest digest)105 public void setMessageDigest(MessageDigest digest) { 106 this.digest = digest; 107 } 108 109 /** 110 * Reads a byte, and updates the message digest (if the digest 111 * function is on). That is, this method reads a byte from the 112 * input stream, blocking until the byte is actually read. If the 113 * digest function is on (see {@link #on(boolean) on}), this method 114 * will then call {@code update} on the message digest associated 115 * with this stream, passing it the byte read. 116 * 117 * @return the byte read. 118 * 119 * @exception IOException if an I/O error occurs. 120 * 121 * @see MessageDigest#update(byte) 122 */ read()123 public int read() throws IOException { 124 int ch = in.read(); 125 if (on && ch != -1) { 126 digest.update((byte)ch); 127 } 128 return ch; 129 } 130 131 /** 132 * Reads into a byte array, and updates the message digest (if the 133 * digest function is on). That is, this method reads up to 134 * {@code len} bytes from the input stream into the array 135 * {@code b}, starting at offset {@code off}. This method 136 * blocks until the data is actually 137 * read. If the digest function is on (see 138 * {@link #on(boolean) on}), this method will then call {@code update} 139 * on the message digest associated with this stream, passing it 140 * the data. 141 * 142 * @param b the array into which the data is read. 143 * 144 * @param off the starting offset into {@code b} of where the 145 * data should be placed. 146 * 147 * @param len the maximum number of bytes to be read from the input 148 * stream into b, starting at offset {@code off}. 149 * 150 * @return the actual number of bytes read. This is less than 151 * {@code len} if the end of the stream is reached prior to 152 * reading {@code len} bytes. -1 is returned if no bytes were 153 * read because the end of the stream had already been reached when 154 * the call was made. 155 * 156 * @exception IOException if an I/O error occurs. 157 * 158 * @see MessageDigest#update(byte[], int, int) 159 */ read(byte[] b, int off, int len)160 public int read(byte[] b, int off, int len) throws IOException { 161 int result = in.read(b, off, len); 162 if (on && result != -1) { 163 digest.update(b, off, result); 164 } 165 return result; 166 } 167 168 /** 169 * Turns the digest function on or off. The default is on. When 170 * it is on, a call to one of the {@code read} methods results in an 171 * update on the message digest. But when it is off, the message 172 * digest is not updated. 173 * 174 * @param on true to turn the digest function on, false to turn 175 * it off. 176 */ on(boolean on)177 public void on(boolean on) { 178 this.on = on; 179 } 180 181 /** 182 * Prints a string representation of this digest input stream and 183 * its associated message digest object. 184 */ toString()185 public String toString() { 186 return "[Digest Input Stream] " + digest.toString(); 187 } 188 } 189