001 /* DigestInputStream.java --- An Input stream tied to a message digest 002 Copyright (C) 1999, 2003, 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.FilterInputStream; 042 import java.io.IOException; 043 import java.io.InputStream; 044 045 /** 046 * DigestInputStream is a class that ties an InputStream with a 047 * MessageDigest. The Message Digest is used by the class to 048 * update it self as bytes are read from the InputStream. 049 * 050 * The updating to the digest depends on the on flag which is set 051 * to true by default to tell the class to update the data 052 * in the message digest. 053 * 054 * @version 0.0 055 * @author Mark Benvenuto (ivymccough@worldnet.att.net) 056 */ 057 public class DigestInputStream extends FilterInputStream 058 { 059 /** 060 * The message digest for the DigestInputStream 061 */ 062 protected MessageDigest digest; 063 064 //Manages the on flag 065 private boolean state = true; 066 067 /** 068 * Constructs a new DigestInputStream. 069 * It associates a MessageDigest with the stream to 070 * compute the stream as data is written. 071 * 072 * @param stream An InputStream to associate this stream with 073 * @param digest A MessageDigest to hash the stream with 074 */ 075 public DigestInputStream(InputStream stream, MessageDigest digest) 076 { 077 super(stream); 078 //this.in = stream; 079 this.digest = digest; 080 } 081 082 /** 083 * Returns the MessageDigest associated with this DigestInputStream 084 * 085 * @return The MessageDigest used to hash this stream 086 */ 087 public MessageDigest getMessageDigest() 088 { 089 return digest; 090 } 091 092 /** 093 * Sets the current MessageDigest to current parameter 094 * 095 * @param digest A MessageDigest to associate with this stream 096 */ 097 public void setMessageDigest(MessageDigest digest) 098 { 099 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 */ 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 */ 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 */ 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 */ 163 public String toString() 164 { 165 return "[Digest Input Stream] " + digest.toString(); 166 } 167 }