libjava/classpath/gnu/javax/crypto/mac/MacOutputStream.java

   1 /* MacOutputStream.java --
   2    Copyright (C) 2003, 2006 Free Software Foundation, Inc.
   3
   4 This file is a 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 of the License, or (at
   9 your option) 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; if not, write to the Free Software
  18 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
  19 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 gnu.javax.crypto.mac;
  40
  41 import java.io.FilterOutputStream;
  42 import java.io.IOException;
  43 import java.io.OutputStream;
  44
  45 /**
  46  * <p>A filtering output stream that computes a MAC (message authentication
  47  * code) over all data written to the stream.</p>
  48  */
  49 public class MacOutputStream extends FilterOutputStream
  50 {
  51
  52   // Constants and variables
  53   // -------------------------------------------------------------------------
  54
  55   /** The digesting state. The MAC is updated only if this flag is true. */
  56   private boolean digesting;
  57
  58   /** The MAC being updated. */
  59   private IMac mac;
  60
  61   // Constructor(s)
  62   // -------------------------------------------------------------------------
  63
  64   /**
  65    * <p>Creates a new <code>MacOutputStream</code>. The stream is initially set
  66    * to digest data written, the <code>mac</code> argument must have already
  67    * been initialized, and the <code>mac</code> argument is <b>not</b> cloned.</p>
  68    *
  69    * @param out The underlying output stream.
  70    * @param mac The mac instance to use.
  71    */
  72   public MacOutputStream(OutputStream out, IMac mac)
  73   {
  74     super(out);
  75     if (mac == null)
  76       {
  77         throw new NullPointerException();
  78       }
  79     this.mac = mac;
  80     digesting = true;
  81   }
  82
  83   // Instance methods
  84   // -------------------------------------------------------------------------
  85
  86   /**
  87    * <p>Returns the MAC this stream is updating.</p>
  88    *
  89    * @return The MAC.
  90    */
  91   public IMac getMac()
  92   {
  93     return mac;
  94   }
  95
  96   /**
  97    * <p>Sets the MAC this stream is updating, which must have already been
  98    * initialized. The argument is not cloned by this method.</p>
  99    *
 100    * @param mac The non-null new MAC.
 101    * @throws NullPointerException If the argument is null.
 102    */
 103   public void setMac(IMac mac)
 104   {
 105     if (mac == null)
 106       {
 107         throw new NullPointerException();
 108       }
 109     this.mac = mac;
 110   }
 111
 112   /**
 113    * <p>Turns the digesting state on or off. When off, the MAC will not be
 114    * updated when data is written to the stream.</p>
 115    *
 116    * @param flag The new digesting state.
 117    */
 118   public void on(boolean flag)
 119   {
 120     digesting = flag;
 121   }
 122
 123   public void write(int b) throws IOException
 124   {
 125     if (digesting)
 126       {
 127         mac.update((byte) b);
 128       }
 129     out.write(b);
 130   }
 131
 132   public void write(byte[] buf, int off, int len) throws IOException
 133   {
 134     if (digesting)
 135       {
 136         mac.update(buf, off, len);
 137       }
 138     out.write(buf, off, len);
 139   }
 140 }