/* ModeFactory.java -- 
   Copyright (C) 2001, 2002, 2004, 2006 Free Software Foundation, Inc.

This file is a part of GNU Classpath.

GNU Classpath 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 of the License, or (at
your option) any later version.

GNU Classpath 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.

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along with GNU Classpath; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, 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
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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
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package gnu.javax.crypto.mode;

import gnu.java.security.Registry;

import gnu.javax.crypto.cipher.CipherFactory;
import gnu.javax.crypto.cipher.IBlockCipher;

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

/**
 * A <i>Factory</i> to instantiate block cipher modes of operations.
 */
public class ModeFactory
    implements Registry
{
  private static Set names;

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

  /**
   * Returns an instance of a block cipher mode of operations given its name and
   * characteristics of the underlying block cipher.
   * 
   * @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 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;
  }

  /**
   * Returns a {@link Set} of names of mode supported by this <i>Factory</i>.
   * 
   * @return a {@link Set} of mode names (Strings).
   */
  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;
  }
}