package gnu.crypto.assembly;

// ----------------------------------------------------------------------------
// $Id: $
//
// 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.,
//    59 Temple Place - Suite 330,
//    Boston, MA 02111-1307
//    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;

/**
 * An Adapter to use any address@hidden IPad} as a Transformer in an Assembly.
 *
 * @version $Revision: $
 */
public class PaddingTransformer extends Transformer {

   // Constants and variables
   // -------------------------------------------------------------------------

   private IPad delegate;
   private int outputBlockSize = 1;
   private byte[] buffer;

   // 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;
      buffer = null;
   }

   byte[] updateDelegate(byte[] in, int offset, int length) {
      updateInternal(in, offset, length);
      byte[] result = outBuffer.toByteArray();
      outBuffer.reset();
      return result;
   }

   byte[] lastUpdateDelegate(byte[] in, int offset, int length)
   throws TransformerException {
      updateInternal(in, offset, length);
      byte[] result;
      if (wired == Direction.FORWARD) {
         // 1. get the remaining bytes, if any; there should be < blocksize
         buffer = inBuffer.toByteArray();
         inBuffer.reset();
         // 2. pad'em
         byte[] padding = delegate.pad(buffer, 0, buffer.length);
         // 3. catenate the lot in preparation for flushing them to the tail
         inBuffer.write(buffer, 0, buffer.length);
         inBuffer.write(padding, 0, padding.length);
         buffer = inBuffer.toByteArray();
         inBuffer.reset();
         // 4. flush to the tail
         buffer = tail.lastUpdate(buffer);
         outBuffer.write(buffer, 0, buffer.length);
         // 5. return everything in outBuffer
         result = outBuffer.toByteArray();
         outBuffer.reset();
      } else {
         if (inBuffer.size() > 0) {
            throw new TransformerException("lastUpdateDelegate(): "
                  +"Padding transformer input buffer, before last unpadding, "
                  +"must be empty but isn't");
         }
         buffer = tail.lastUpdate();
         outBuffer.write(buffer, 0, buffer.length);
         buffer = outBuffer.toByteArray();
         outBuffer.reset();
         int realLength;
         try {
            realLength = buffer.length;
            realLength -= delegate.unpad(buffer, 0, buffer.length);
         } catch (WrongPaddingException x) {
            throw new TransformerException("lastUpdateDelegate()", x);
         }
         result = new byte[realLength];
         System.arraycopy(buffer, 0, result, 0, realLength);
      }
      return result;
   }

   private void updateInternal(byte[] in, int offset, int length) {
      for (int i = 0; i < length; i++) {
         inBuffer.write(in[offset++] & 0xFF);
         if (inBuffer.size() >= outputBlockSize) {
            buffer = inBuffer.toByteArray();
            inBuffer.reset();
            buffer = tail.update(buffer, 0, buffer.length);
            outBuffer.write(buffer, 0, buffer.length);
         }
      }
   }
}