1 /* DigestInputStream.java --- An Input stream tied to a message digest 2 Copyright (C) 1999, 2003, 2004, 2005 Free Software Foundation, Inc. 3 4 This file is part of GNU Classpath. 5 6 GNU Classpath is free software; you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 2, or (at your option) 9 any later version. 10 11 GNU Classpath is distributed in the hope that it will be useful, but 12 WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with GNU Classpath; see the file COPYING. If not, write to the 18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19 02110-1301 USA. 20 21 Linking this library statically or dynamically with other modules is 22 making a combined work based on this library. Thus, the terms and 23 conditions of the GNU General Public License cover the whole 24 combination. 25 26 As a special exception, the copyright holders of this library give you 27 permission to link this library with independent modules to produce an 28 executable, regardless of the license terms of these independent 29 modules, and to copy and distribute the resulting executable under 30 terms of your choice, provided that you also meet, for each linked 31 independent module, the terms and conditions of the license of that 32 module. An independent module is a module which is not derived from 33 or based on this library. If you modify this library, you may extend 34 this exception to your version of the library, but you are not 35 obligated to do so. If you do not wish to do so, delete this 36 exception statement from your version. */ 37 38 39 package java.security; 40 41 import java.io.FilterInputStream; 42 import java.io.IOException; 43 import java.io.InputStream; 44 45 /** 46 * DigestInputStream is a class that ties an InputStream with a 47 * MessageDigest. The Message Digest is used by the class to 48 * update it self as bytes are read from the InputStream. 49 * 50 * The updating to the digest depends on the on flag which is set 51 * to true by default to tell the class to update the data 52 * in the message digest. 53 * 54 * @version 0.0 55 * @author Mark Benvenuto (ivymccough@worldnet.att.net) 56 */ 57 public class DigestInputStream extends FilterInputStream 58 { 59 /** 60 * The message digest for the DigestInputStream 61 */ 62 protected MessageDigest digest; 63 64 //Manages the on flag 65 private boolean state = true; 66 67 /** 68 * Constructs a new DigestInputStream. 69 * It associates a MessageDigest with the stream to 70 * compute the stream as data is written. 71 * 72 * @param stream An InputStream to associate this stream with 73 * @param digest A MessageDigest to hash the stream with 74 */ DigestInputStream(InputStream stream, MessageDigest digest)75 public DigestInputStream(InputStream stream, MessageDigest digest) 76 { 77 super(stream); 78 //this.in = stream; 79 this.digest = digest; 80 } 81 82 /** 83 * Returns the MessageDigest associated with this DigestInputStream 84 * 85 * @return The MessageDigest used to hash this stream 86 */ getMessageDigest()87 public MessageDigest getMessageDigest() 88 { 89 return digest; 90 } 91 92 /** 93 * Sets the current MessageDigest to current parameter 94 * 95 * @param digest A MessageDigest to associate with this stream 96 */ setMessageDigest(MessageDigest digest)97 public void setMessageDigest(MessageDigest digest) 98 { 99 this.digest = digest; 100 } 101 102 /** 103 * Reads a byte from the input stream and updates the digest. 104 * This method reads the underlying input stream and if the 105 * on flag is true then updates the message digest. 106 * 107 * @return Returns a byte from the input stream, -1 is returned to indicate that 108 * the end of stream was reached before this read call 109 * 110 * @throws IOException if an IO error occurs in the underlying input stream, 111 * this error is thrown 112 */ read()113 public int read() throws IOException 114 { 115 int temp = in.read(); 116 117 if (state == true && temp != -1) 118 digest.update((byte) temp); 119 120 return temp; 121 } 122 123 /** 124 * Reads bytes from the input stream and updates the digest. 125 * This method reads the underlying input stream and if the 126 * on flag is true then updates the message digest. 127 * 128 * @param b a byte array to store the data from the input stream 129 * @param off an offset to start at in the array 130 * @param len length of data to read 131 * @return Returns count of bytes read, -1 is returned to indicate that 132 * the end of stream was reached before this read call 133 * 134 * @throws IOException if an IO error occurs in the underlying input stream, 135 * this error is thrown 136 */ read(byte[]b, int off, int len)137 public int read(byte[]b, int off, int len) throws IOException 138 { 139 int temp = in.read(b, off, len); 140 141 if (state == true && temp != -1) 142 digest.update(b, off, temp); 143 144 return temp; 145 } 146 147 /** 148 * Sets the flag specifing if this DigestInputStream updates the 149 * digest in the write() methods. The default is on; 150 * 151 * @param on True means it digests stream, false means it does not 152 */ on(boolean on)153 public void on(boolean on) 154 { 155 state = on; 156 } 157 158 /** 159 * Converts the input stream and underlying message digest to a string. 160 * 161 * @return A string representing the input stream and message digest. 162 */ toString()163 public String toString() 164 { 165 return "[Digest Input Stream] " + digest.toString(); 166 } 167 } 168