package gnu.crypto.assembly;
// ----------------------------------------------------------------------------
// $Id: PaddingTransformer.java,v 1.2 2005/10/06 04:24:13 rsdio Exp $
//
// Copyright (C) 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.
// ----------------------------------------------------------------------------
import gnu.crypto.pad.IPad;
import gnu.crypto.pad.WrongPaddingException;
import java.util.Map;
/**
* <p>An Adapter to use any {@link IPad} as a {@link Transformer} in an
* {@link Assembly}.</p>
*
* <p>When using such a {@link Transformer}, in an {@link Assembly}, there must
* be at least one element behind this instance in the constructed chain;
* otherwise, a {@link TransformerException} is thrown at initialisation time.</p>
*
* @version $Revision: 1.2 $
*/
class PaddingTransformer extends Transformer {
// Constants and variables
// -------------------------------------------------------------------------
private IPad delegate;
private int outputBlockSize = 1;
// Constructor(s)
// -------------------------------------------------------------------------
PaddingTransformer(IPad padding) {
super();
this.delegate = padding;
}
// Class methods
// -------------------------------------------------------------------------
// Instance methods
// -------------------------------------------------------------------------
void initDelegate(Map attributes) throws TransformerException {
if (tail == null) {
throw new TransformerException("initDelegate()",
new IllegalStateException("Padding transformer missing its tail!"));
}
outputBlockSize = tail.currentBlockSize();
delegate.init(outputBlockSize);
}
int delegateBlockSize() {
return outputBlockSize;
}
void resetDelegate() {
delegate.reset();
outputBlockSize = 1;
}
byte[] updateDelegate(byte[] in, int offset, int length) throws TransformerException {
inBuffer.write(in, offset, length);
byte[] tmp = inBuffer.toByteArray();
inBuffer.reset();
byte[] result;
if (wired == Direction.FORWARD) { // padding
// buffers remaining bytes from (inBuffer + in) that are less than 1 block
if (tmp.length < outputBlockSize) {
inBuffer.write(tmp, 0, tmp.length);
result = new byte[0];
} else {
int newlen = outputBlockSize * (tmp.length / outputBlockSize);
inBuffer.write(tmp, newlen, tmp.length - newlen);
result = new byte[newlen];
System.arraycopy(tmp, 0, result, 0, newlen);
}
} else { // unpadding
// always keep in own buffer a max of 1 block to cater for lastUpdate
if (tmp.length < outputBlockSize) {
inBuffer.write(tmp, 0, tmp.length);
result = new byte[0];
} else {
result = new byte[tmp.length - outputBlockSize];
System.arraycopy(tmp, 0, result, 0, result.length);
inBuffer.write(tmp, result.length, outputBlockSize);
}
}
return result;
}
byte[] lastUpdateDelegate() throws TransformerException {
byte[] result;
// process multiples of blocksize as much as possible
// catenate result from processing inBuffer with last-update( tail )
if (wired == Direction.FORWARD) { // padding
result = inBuffer.toByteArray();
byte[] padding = delegate.pad(result, 0, result.length);
inBuffer.write(padding, 0, padding.length);
} else { // unpadding
byte[] tmp = inBuffer.toByteArray();
inBuffer.reset();
int realLength;
try {
realLength = tmp.length; // should be outputBlockSize
realLength -= delegate.unpad(tmp, 0, tmp.length);
} catch (WrongPaddingException x) {
throw new TransformerException("lastUpdateDelegate()", x);
}
inBuffer.write(tmp, 0, realLength);
}
result = inBuffer.toByteArray();
inBuffer.reset();
return result;
}
}