libjava/java/security/DigestOutputStream.java

   1 /* DigestOutputStream.java --- An output stream tied to a message digest
   2    Copyright (C) 1999, 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., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 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.FilterOutputStream;
  42 import java.io.IOException;
  43 import java.io.OutputStream;
  44
  45 /**
  46  * DigestOutputStream is a class that ties an OutputStream with a
  47  * MessageDigest. The Message Digest is used by the class to update it
  48  * self as bytes are written to the OutputStream.
  49  *
  50  * The updating to the digest depends on the on flag which is set to
  51  * true by default that tells the class to update the data in the
  52  * message digest.
  53  *
  54  * @version 0.0
  55  * @author Mark Benvenuto (ivymccough@worldnet.att.net)
  56  */
  57 public class DigestOutputStream extends FilterOutputStream
  58 {
  59   /**
  60    * The message digest for the DigestOutputStream
  61    */
  62   protected MessageDigest digest;
  63
  64   //Manages the on flag
  65   private boolean state = true;
  66
  67   /**
  68    * Constructs a new DigestOutputStream.  It associates a
  69    * MessageDigest with the stream to compute the stream as data is
  70    * written.
  71    *
  72    * @param stream An OutputStream to associate this stream with
  73    * @param digest A MessageDigest to hash the stream with
  74    */
  75   public DigestOutputStream(OutputStream stream, MessageDigest digest)
  76   {
  77     super(stream);
  78     this.digest = digest;
  79   }
  80
  81   /**
  82    * Returns the MessageDigest associated with this DigestOutputStream
  83    *
  84    * @return The MessageDigest used to hash this stream
  85    */
  86   public MessageDigest getMessageDigest()
  87   {
  88     return digest;
  89   }
  90
  91   /**
  92    * Sets the current MessageDigest to current parameter
  93    *
  94    * @param digest A MessageDigest to associate with this stream
  95    */
  96   public void setMessageDigest(MessageDigest digest)
  97   {
  98     this.digest = digest;
  99   }
 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 }