Source for gnu.javax.crypto.mac.MacInputStream

   1: /* MacInputStream.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.FilterInputStream;
  42: import java.io.InputStream;
  43: import java.io.IOException;
  44: 
  45: /**
  46:  * A filtering input stream that computes a MAC (message authentication code)
  47:  * over all data read from the stream.
  48:  */
  49: public class MacInputStream
  50:     extends FilterInputStream
  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 MacInputStream. The stream is initially set to digest data
  59:    * written, the <i>mac</i> argument must have already been initialized, and
  60:    * the <i>mac</i> argument is <b>not</b> cloned.
  61:    *
  62:    * @param in The underlying input stream.
  63:    * @param mac The mac instance to use.
  64:    */
  65:   public MacInputStream(InputStream in, IMac mac)
  66:   {
  67:     super(in);
  68:     if (mac == null)
  69:       throw new NullPointerException();
  70:     this.mac = mac;
  71:     digesting = true;
  72:   }
  73: 
  74:   /**
  75:    * Returns the MAC this stream is updating.
  76:    *
  77:    * @return The MAC.
  78:    */
  79:   public IMac getMac()
  80:   {
  81:     return mac;
  82:   }
  83: 
  84:   /**
  85:    * Sets the MAC this stream is updating, which must have already been
  86:    * initialized. The argument is not cloned by this method.
  87:    *
  88:    * @param mac The new MAC.
  89:    * @throws NullPointerException If the argument is null.
  90:    */
  91:   public void setMac(IMac mac)
  92:   {
  93:     if (mac == null)
  94:       throw new NullPointerException();
  95:     this.mac = mac;
  96:   }
  97: 
  98:   /**
  99:    * Turns the digesting state on or off. When off, the MAC will not be updated
 100:    * when data is written to the stream.
 101:    *
 102:    * @param flag The new digesting state.
 103:    */
 104:   public void on(boolean flag)
 105:   {
 106:     digesting = flag;
 107:   }
 108: 
 109:   public int read() throws IOException
 110:   {
 111:     int i = in.read();
 112:     if (digesting && i != -1)
 113:       mac.update((byte) i);
 114:     return i;
 115:   }
 116: 
 117:   public int read(byte[] buf, int off, int len) throws IOException
 118:   {
 119:     int i = in.read(buf, off, len);
 120:     if (digesting && i != -1)
 121:       mac.update(buf, off, i);
 122:     return i;
 123:   }
 124: }