/* MacFactory.java -- 
   Copyright (C) 2001, 2002, 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.

You should have received a copy of the GNU General Public License
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
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
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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package gnu.javax.crypto.mac;

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> that instantiates instances of every supported Message
 * Authentication Code algorithms, including all <i>HMAC</i> algorithms.
 */
public class MacFactory
    implements Registry
{
  private static Set names;

  /** Trivial constructor to enforce <i>Singleton</i> pattern. */
  private MacFactory()
  {
    super();
  }

  /**
   * Returns an instance of a <i>MAC</i> algorithm given its name.
   * 
   * @param name the name of the MAC algorithm.
   * @return an instance of the <i>MAC</i> algorithm, or <code>null</code> if
   *         none can be constructed.
   * @exception InternalError if the implementation does not pass its self-test.
   */
  public static IMac getInstance(String name)
  {
    if (name == null)
      return null;

    name = name.trim();
    name = name.toLowerCase();
    if (name.startsWith(HMAC_NAME_PREFIX))
      return HMacFactory.getInstance(name);

    if (name.startsWith(OMAC_PREFIX))
      {
        name = name.substring(OMAC_PREFIX.length());
        IBlockCipher cipher = CipherFactory.getInstance(name);
        if (cipher == null)
          return null;
        return new OMAC(cipher);
      }
    IMac result = null;
    if (name.equalsIgnoreCase(UHASH32))
      result = new UHash32();
    else if (name.equalsIgnoreCase(UMAC32))
      result = new UMac32();
    else if (name.equalsIgnoreCase(TMMH16))
      result = new TMMH16();

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

    return result;
  }

  /**
   * Returns a {@link Set} of names of <i>MAC</i> algorithms supported by this
   * <i>Factory</i>.
   * 
   * @return a {@link Set} of MAC names (Strings).
   */
  public static final Set getNames()
  {
    synchronized (MacFactory.class)
      {
        if (names == null)
          {
            HashSet hs = new HashSet();
            hs.addAll(HMacFactory.getNames());
            hs.add(UHASH32);
            hs.add(UMAC32);
            hs.add(TMMH16);
            for (Iterator it = CipherFactory.getNames().iterator(); it.hasNext();)
              hs.add(OMAC_PREFIX + it.next());

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