libjava/classpath/gnu/javax/crypto/pad/BasePad.java

   1 /* BasePad.java --
   2    Copyright (C) 2001, 2002, 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.pad;
  40
  41 /**
  42  * <p>An abstract class to facilitate implementing padding algorithms.</p>
  43  */
  44 public abstract class BasePad implements IPad
  45 {
  46
  47   // Constants and variables
  48   // -------------------------------------------------------------------------
  49
  50   /** The canonical name prefix of the padding algorithm. */
  51   protected String name;
  52
  53   /** The block size, in bytes, for this instance. */
  54   protected int blockSize;
  55
  56   // Constructor(s)
  57   // -------------------------------------------------------------------------
  58
  59   /** Trivial constructor for use by concrete subclasses. */
  60   protected BasePad(final String name)
  61   {
  62     super();
  63
  64     this.name = name;
  65     blockSize = -1;
  66   }
  67
  68   // Class methods
  69   // -------------------------------------------------------------------------
  70
  71   // Instance methods
  72   // -------------------------------------------------------------------------
  73
  74   // IPad interface implementation -------------------------------------------
  75
  76   public String name()
  77   {
  78     final StringBuffer sb = new StringBuffer(name);
  79     if (blockSize != -1)
  80       {
  81         sb.append('-').append(String.valueOf(8 * blockSize));
  82       }
  83     return sb.toString();
  84   }
  85
  86   public void init(final int bs) throws IllegalStateException
  87   {
  88     if (blockSize != -1)
  89       {
  90         throw new IllegalStateException();
  91       }
  92     blockSize = bs;
  93     setup();
  94   }
  95
  96   public void reset()
  97   {
  98     blockSize = -1;
  99   }
 100
 101   public boolean selfTest()
 102   {
 103     byte[] padBytes;
 104     final int offset = 5;
 105     final int limit = 1024;
 106     final byte[] in = new byte[limit];
 107     for (int bs = 2; bs < 256; bs++)
 108       {
 109         this.init(bs);
 110         for (int i = 0; i < limit - offset - blockSize; i++)
 111           {
 112             padBytes = pad(in, offset, i);
 113             if (((i + padBytes.length) % blockSize) != 0)
 114               {
 115                 new RuntimeException(name()).printStackTrace(System.err);
 116                 return false;
 117               }
 118
 119             System.arraycopy(padBytes, 0, in, offset + i, padBytes.length);
 120             try
 121               {
 122                 if (padBytes.length != unpad(in, offset, i + padBytes.length))
 123                   {
 124                     new RuntimeException(name()).printStackTrace(System.err);
 125                     return false;
 126                   }
 127               }
 128             catch (WrongPaddingException x)
 129               {
 130                 x.printStackTrace(System.err);
 131                 return false;
 132               }
 133           }
 134         this.reset();
 135       }
 136
 137     return true;
 138   }
 139
 140   // abstract methods to implement by subclasses -----------------------------
 141
 142   /**
 143    * <p>If any additional checks or resource setup must be done by the
 144    * subclass, then this is the hook for it. This method will be called before
 145    * the {@link #init(int)} method returns.</p>
 146    */
 147   public abstract void setup();
 148
 149   public abstract byte[] pad(byte[] in, int off, int len);
 150
 151   public abstract int unpad(byte[] in, int off, int len)
 152       throws WrongPaddingException;
 153 }