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ModeFactory.java

package gnu.crypto.mode;

// ----------------------------------------------------------------------------
// $Id: ModeFactory.java,v 1.10 2005/10/06 04:24:17 rsdio Exp $
//
// Copyright (C) 2001, 2002, 2004 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.Registry;
import gnu.crypto.cipher.CipherFactory;
import gnu.crypto.cipher.IBlockCipher;

import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

/**
 * <p>A <i>Factory</i> to instantiate block cipher modes of operations.</p>
 *
 * @version $Revision: 1.10 $
 */
00060 public class ModeFactory implements Registry {

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

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

   /** Trivial constructor to enforce Singleton pattern. */
00069    private ModeFactory() {
      super();
   }

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

   /**
    * <p>Returns an instance of a block cipher mode of operations given its name
    * and characteristics of the underlying block cipher.</p>
    *
    * @param mode the case-insensitive name of the mode of operations.
    * @param cipher the case-insensitive name of the block cipher.
    * @param cipherBlockSize the block size, in bytes, of the underlying cipher.
    * @return an instance of the block cipher algorithm, operating in a given
    * mode of operations, or <code>null</code> if none found.
    * @exception InternalError if either the mode or the underlying block cipher
    * implementation does not pass its self-test.
    */
   public static IMode
00089    getInstance(String mode, String cipher, int cipherBlockSize) {
      if (mode == null || cipher == null) {
         return null;
      }

      mode = mode.trim();
      cipher = cipher.trim();

      IBlockCipher cipherImpl = CipherFactory.getInstance(cipher);
      if (cipherImpl == null) {
         return null;
      }

      return getInstance(mode, cipherImpl, cipherBlockSize);
   }

   public static IMode
   getInstance(String mode, IBlockCipher cipher, int cipherBlockSize) {
      // ensure that cipherBlockSize is valid for the chosen underlying cipher
      boolean ok = false;
      for (Iterator it = cipher.blockSizes(); it.hasNext(); ) {
         ok = (cipherBlockSize == ((Integer) it.next()).intValue());
         if (ok) {
            break;
         }
      }

      if (!ok) {
         throw new IllegalArgumentException("cipherBlockSize");
      }

      IMode result = null;
      if (mode.equalsIgnoreCase(ECB_MODE)) {
         result = new ECB(cipher, cipherBlockSize);
      } else if (mode.equalsIgnoreCase(CTR_MODE)) {
         result = new CTR(cipher, cipherBlockSize);
      } else if (mode.equalsIgnoreCase(ICM_MODE)) {
         result = new ICM(cipher, cipherBlockSize);
      } else if (mode.equalsIgnoreCase(OFB_MODE)) {
         result = new OFB(cipher, cipherBlockSize);
      } else if (mode.equalsIgnoreCase(CBC_MODE)) {
         result = new CBC(cipher, cipherBlockSize);
      } else if (mode.equalsIgnoreCase(CFB_MODE)) {
         result = new CFB(cipher, cipherBlockSize);
      } else if (mode.equalsIgnoreCase(EAX_MODE)) {
         result = new EAX(cipher, cipherBlockSize);
      }

      if (result != null && !result.selfTest()) {
         throw new InternalError(result.name());
      }

      return result;
   }

   /**
    * <p>Returns a {@link java.util.Set} of names of mode supported by this
    * <i>Factory</i>.</p>
    *
    * @return a {@link java.util.Set} of mode names (Strings).
    */
00150    public static final Set getNames() {
      synchronized (ModeFactory.class) {
         if (names == null) {
            HashSet hs = new HashSet();
            hs.add(ECB_MODE);
            hs.add(CTR_MODE);
            hs.add(ICM_MODE);
            hs.add(OFB_MODE);
            hs.add(CBC_MODE);
            hs.add(CFB_MODE);
            hs.add(EAX_MODE);

            names = Collections.unmodifiableSet(hs);
         }
      }
      return names;
   }

   private static Set names;

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

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