package gnu.crypto.pad;
// ----------------------------------------------------------------------------
// $Id: BasePad.java,v 1.6 2005/10/06 04:24:17 rsdio Exp $
//
// Copyright (C) 2001, 2002, 2003 Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2, or (at your option)
// any later version.
//
// GNU Crypto is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; see the file COPYING. If not, write to the
//
// Free Software Foundation Inc.,
// 51 Franklin Street, Fifth Floor,
// Boston, MA 02110-1301
// USA
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library. Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
//
// As a special exception, the copyright holders of this library give
// you permission to link this library with independent modules to
// produce an executable, regardless of the license terms of these
// independent modules, and to copy and distribute the resulting
// executable under terms of your choice, provided that you also meet,
// for each linked independent module, the terms and conditions of the
// license of that module. An independent module is a module which is
// not derived from or based on this library. If you modify this
// library, you may extend this exception to your version of the
// library, but you are not obligated to do so. If you do not wish to
// do so, delete this exception statement from your version.
// ----------------------------------------------------------------------------
/**
* <p>An abstract class to facilitate implementing padding algorithms.</p>
*
* @version $Revision: 1.6 $
*/
public abstract class BasePad implements IPad {
// Constants and variables
// -------------------------------------------------------------------------
/** The canonical name prefix of the padding algorithm. */
protected String name;
/** The block size, in bytes, for this instance. */
protected int blockSize;
// Constructor(s)
// -------------------------------------------------------------------------
/** Trivial constructor for use by concrete subclasses. */
protected BasePad(final String name) {
super();
this.name = name;
blockSize = -1;
}
// Class methods
// -------------------------------------------------------------------------
// Instance methods
// -------------------------------------------------------------------------
// IPad interface implementation -------------------------------------------
public String name() {
final StringBuffer sb = new StringBuffer(name);
if (blockSize != -1) {
sb.append('-').append(String.valueOf(8*blockSize));
}
return sb.toString();
}
public void init(final int bs) throws IllegalStateException {
if (blockSize != -1) {
throw new IllegalStateException();
}
blockSize = bs;
setup();
}
public void reset() {
blockSize = -1;
}
public boolean selfTest() {
byte[] padBytes;
final int offset = 5;
final int limit = 1024;
final byte[] in = new byte[limit];
for (int bs = 2; bs < 256; bs++) {
this.init(bs);
for (int i = 0; i < limit-offset-blockSize; i++) {
padBytes = pad(in, offset, i);
if (((i + padBytes.length) % blockSize) != 0) {
new RuntimeException(name()).printStackTrace(System.err);
return false;
}
System.arraycopy(padBytes, 0, in, offset+i, padBytes.length);
try {
if (padBytes.length != unpad(in, offset, i+padBytes.length)) {
new RuntimeException(name()).printStackTrace(System.err);
return false;
}
} catch (WrongPaddingException x) {
x.printStackTrace(System.err);
return false;
}
}
this.reset();
}
return true;
}
// abstract methods to implement by subclasses -----------------------------
/**
* <p>If any additional checks or resource setup must be done by the
* subclass, then this is the hook for it. This method will be called before
* the {@link #init(int)} method returns.</p>
*/
public abstract void setup();
public abstract byte[] pad(byte[] in, int off, int len);
public abstract int unpad(byte[] in, int off, int len)
throws WrongPaddingException;
}