001/* DigestOutputStream.java --- An output stream tied to a message digest 002 Copyright (C) 1999, 2004, 2005 Free Software Foundation, Inc. 003 004This file is part of GNU Classpath. 005 006GNU Classpath is free software; you can redistribute it and/or modify 007it under the terms of the GNU General Public License as published by 008the Free Software Foundation; either version 2, or (at your option) 009any later version. 010 011GNU Classpath is distributed in the hope that it will be useful, but 012WITHOUT ANY WARRANTY; without even the implied warranty of 013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014General Public License for more details. 015 016You should have received a copy of the GNU General Public License 017along with GNU Classpath; see the file COPYING. If not, write to the 018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 01902110-1301 USA. 020 021Linking this library statically or dynamically with other modules is 022making a combined work based on this library. Thus, the terms and 023conditions of the GNU General Public License cover the whole 024combination. 025 026As a special exception, the copyright holders of this library give you 027permission to link this library with independent modules to produce an 028executable, regardless of the license terms of these independent 029modules, and to copy and distribute the resulting executable under 030terms of your choice, provided that you also meet, for each linked 031independent module, the terms and conditions of the license of that 032module. An independent module is a module which is not derived from 033or based on this library. If you modify this library, you may extend 034this exception to your version of the library, but you are not 035obligated to do so. If you do not wish to do so, delete this 036exception statement from your version. */ 037 038 039package java.security; 040 041import java.io.FilterOutputStream; 042import java.io.IOException; 043import java.io.OutputStream; 044 045/** 046 * DigestOutputStream is a class that ties an OutputStream with a 047 * MessageDigest. The Message Digest is used by the class to update it 048 * self as bytes are written to the OutputStream. 049 * 050 * The updating to the digest depends on the on flag which is set to 051 * true by default that tells the class to update the data in the 052 * message digest. 053 * 054 * @version 0.0 055 * @author Mark Benvenuto (ivymccough@worldnet.att.net) 056 */ 057public class DigestOutputStream extends FilterOutputStream 058{ 059 /** 060 * The message digest for the DigestOutputStream 061 */ 062 protected MessageDigest digest; 063 064 //Manages the on flag 065 private boolean state = true; 066 067 /** 068 * Constructs a new DigestOutputStream. It associates a 069 * MessageDigest with the stream to compute the stream as data is 070 * written. 071 * 072 * @param stream An OutputStream to associate this stream with 073 * @param digest A MessageDigest to hash the stream with 074 */ 075 public DigestOutputStream(OutputStream stream, MessageDigest digest) 076 { 077 super(stream); 078 this.digest = digest; 079 } 080 081 /** 082 * Returns the MessageDigest associated with this DigestOutputStream 083 * 084 * @return The MessageDigest used to hash this stream 085 */ 086 public MessageDigest getMessageDigest() 087 { 088 return digest; 089 } 090 091 /** 092 * Sets the current MessageDigest to current parameter 093 * 094 * @param digest A MessageDigest to associate with this stream 095 */ 096 public void setMessageDigest(MessageDigest digest) 097 { 098 this.digest = digest; 099 } 100 101 102 /** 103 * Updates the hash if the on flag is true and then writes a byte to 104 * the underlying output stream. 105 * 106 * @param b A byte to write to the output stream 107 * 108 * @exception IOException if the underlying output stream 109 * cannot write the byte, this is thrown. 110 */ 111 public void write(int b) throws IOException 112 { 113 if (state) 114 digest.update((byte) b); 115 116 out.write(b); 117 } 118 119 /** 120 * Updates the hash if the on flag is true and then writes the bytes 121 * to the underlying output stream. 122 * 123 * @param b Bytes to write to the output stream 124 * @param off Offset to start to start at in array 125 * @param len Length of data to write 126 * 127 * @exception IOException if the underlying output stream 128 * cannot write the bytes, this is thrown. 129 */ 130 public void write(byte[]b, int off, int len) throws IOException 131 { 132 if (state) 133 digest.update(b, off, len); 134 135 out.write(b, off, len); 136 } 137 138 /** 139 * Sets the flag specifying if this DigestOutputStream updates the 140 * digest in the write() methods. The default is on; 141 * 142 * @param on True means it digests stream, false means it does not 143 */ 144 public void on(boolean on) 145 { 146 state = on; 147 } 148 149 /** 150 * Converts the output stream and underlying message digest to a string. 151 * 152 * @return A string representing the output stream and message digest. 153 */ 154 public String toString() 155 { 156 return "[Digest Output Stream] " + digest.toString(); 157 } 158}