Source for gnu.javax.crypto.mac.MacOutputStream

   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:  * A filtering output stream that computes a MAC (message authentication code)
  47:  * over all data written to the stream.
  48:  */
  49: public class MacOutputStream
  50:     extends FilterOutputStream
  51: {
  52:   /** The digesting state. The MAC is updated only if this flag is true. */
  53:   private boolean digesting;
  54:   /** The MAC being updated. */
  55:   private IMac mac;
  56: 
  57:   /**
  58:    * Creates a new <code>MacOutputStream</code>. The stream is initially set
  59:    * to digest data written, the <code>mac</code> argument must have already
  60:    * been initialized, and the <code>mac</code> argument is <b>not</b>
  61:    * cloned.
  62:    *
  63:    * @param out The underlying output stream.
  64:    * @param mac The mac instance to use.
  65:    */
  66:   public MacOutputStream(OutputStream out, IMac mac)
  67:   {
  68:     super(out);
  69:     if (mac == null)
  70:       throw new NullPointerException();
  71:     this.mac = mac;
  72:     digesting = true;
  73:   }
  74: 
  75:   /**
  76:    * Returns the MAC this stream is updating.
  77:    *
  78:    * @return The MAC.
  79:    */
  80:   public IMac getMac()
  81:   {
  82:     return mac;
  83:   }
  84: 
  85:   /**
  86:    * Sets the MAC this stream is updating, which must have already been
  87:    * initialized. The argument is not cloned by this method.
  88:    *
  89:    * @param mac The non-null new MAC.
  90:    * @throws NullPointerException If the argument is null.
  91:    */
  92:   public void setMac(IMac mac)
  93:   {
  94:     if (mac == null)
  95:       throw new NullPointerException();
  96:     this.mac = mac;
  97:   }
  98: 
  99:   /**
 100:    * Turns the digesting state on or off. When off, the MAC will not be updated
 101:    * when data is written to the stream.
 102:    *
 103:    * @param flag The new digesting state.
 104:    */
 105:   public void on(boolean flag)
 106:   {
 107:     digesting = flag;
 108:   }
 109: 
 110:   public void write(int b) throws IOException
 111:   {
 112:     if (digesting)
 113:       mac.update((byte) b);
 114:     out.write(b);
 115:   }
 116: 
 117:   public void write(byte[] buf, int off, int len) throws IOException
 118:   {
 119:     if (digesting)
 120:       mac.update(buf, off, len);
 121:     out.write(buf, off, len);
 122:   }
 123: }