package gnu.crypto.assembly;

// ----------------------------------------------------------------------------
// $Id: Stage.java,v 1.7 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.mode.IMode;

import java.security.InvalidKeyException;
import java.util.Map;
import java.util.Set;

/**
 * <p>A <i>Stage</i> in a Cascade Cipher.</p>
 *
 * <p>Each stage may be either an implementation of a Block Cipher Mode of
 * Operation ({@link IMode}) or another Cascade Cipher ({@link Cascade}). Each
 * stage has also a <i>natural</i> operational direction when constructed for
 * inclusion within a {@link Cascade}. This <i>natural</i> direction dictates
 * how data flows from one stage into another when stages are chained together
 * in a cascade. One can think of a stage and its natural direction as the
 * specification of how to wire the stage into the chain. The following diagrams
 * may help understand the paradigme. The first shows two stages chained each
 * with a {@link Direction#FORWARD} direction.</p>
 * <pre>
 *           FORWARD         FORWARD
 *       +------+       +-------+
 *       |      |       |       |
 *       |  +--in --+   |   +--in --+
 *    ---+  | Stage |   |   | Stage |  +---
 *          +--out--+   |   +--out--+  |
 *              |       |       |      |
 *              +-------+       +------+
 * </pre>
 * <p>The second diagram shows two stages, one in a {@link Direction#FORWARD}
 * direction, while the other is wired in a {@link Direction#REVERSED}
 * direction.</p>
 * <pre>
 *           FORWARD         REVERSED
 *       +------+               +------+
 *       |      |               |      |
 *       |  +--in --+       +--in --+  |
 *    ---+  | Stage |       | Stage |  +---
 *          +--out--+       +--out--+
 *              |               |
 *              +---------------+
 * </pre>
 *
 * @see ModeStage
 * @see CascadeStage
 * @version $Revision: 1.7 $
 */
public abstract class Stage {

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

   public static final String DIRECTION = "gnu.crypto.assembly.stage.direction";

   protected Direction forward;
   protected Direction wired;

   // Constructor(s)
   // -------------------------------------------------------------------------

   protected Stage(Direction forwardDirection) {
      super();

      this.forward = forwardDirection;
      this.wired = null;
   }

   // Class methods
   // -------------------------------------------------------------------------

   public static final Stage
   getInstance(IMode mode, Direction forwardDirection) {
      return new ModeStage(mode, forwardDirection);
   }

   public static final Stage
   getInstance(Cascade cascade, Direction forwardDirection) {
      return new CascadeStage(cascade, forwardDirection);
   }

   // Instance methods
   // -------------------------------------------------------------------------

   /**
    * Returns the {@link Set} of supported block sizes for this
    * <code>Stage</code>. Each element in the returned {@link Set} is an
    * instance of {@link Integer}.
    *
    * @return a {@link Set} of supported block sizes.
    */
   public abstract Set blockSizes();

   /**
    * Initialises the stage for operation with specific characteristics.
    *
    * @param attributes a set of name-value pairs that describes the desired
    * future behaviour of this instance.
    * @throws IllegalStateException if the instance is already initialised.
    * @throws InvalidKeyException if the key data is invalid.
    */
   public void init(Map attributes) throws InvalidKeyException {
      if (wired != null) {
         throw new IllegalStateException();
      }
      Direction flow = (Direction) attributes.get(DIRECTION);
      if (flow == null) {
         flow = Direction.FORWARD;
         attributes.put(DIRECTION, flow);
      }
      initDelegate(attributes);
      wired = flow;
   }

   /**
    * Returns the currently set block size for the stage.
    *
    * @return the current block size for this stage.
    * @throws IllegalStateException if the instance is not initialised.
    */
   public abstract int currentBlockSize() throws IllegalStateException;

   /**
    * Resets the stage for re-initialisation and use with other characteristics.
    * This method always succeeds.
    */
   public void reset() {
      resetDelegate();
      wired = null;
   }

   /**
    * Processes exactly one block of <i>plaintext</i> (if initialised in the
    * {@link Direction#FORWARD} state) or <i>ciphertext</i> (if initialised in
    * the {@link Direction#REVERSED} state).
    *
    * @param in the plaintext.
    * @param inOffset index of <code>in</code> from which to start considering
    * data.
    * @param out the ciphertext.
    * @param outOffset index of <code>out</code> from which to store result.
    * @throws IllegalStateException if the instance is not initialised.
    */
   public void update(byte[] in, int inOffset, byte[] out, int outOffset) {
      if (wired == null) {
         throw new IllegalStateException();
      }
      updateDelegate(in, inOffset, out, outOffset);
   }

   /**
    * Conducts a simple <i>correctness</i> test that consists of basic symmetric
    * encryption / decryption test(s) for all supported block and key sizes of
    * underlying block cipher(s) wrapped by Mode leafs. The test also includes
    * one (1) variable key Known Answer Test (KAT) for each block cipher.
    *
    * @return <code>true</code> if the implementation passes simple
    * <i>correctness</i> tests. Returns <code>false</code> otherwise.
    */
   public abstract boolean selfTest();

   // abstract methods to be implemented by concrete subclasses ---------------

   abstract void initDelegate(Map attributes) throws InvalidKeyException;
   abstract void resetDelegate();
   abstract void updateDelegate(byte[] in, int inOffset, byte[] out, int outOffset);
}
