Source for java.security.DigestOutputStream

   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., 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.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: }