/* PRNGFactory.java -- 
   Copyright (C) 2001, 2002, 2003, 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
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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independent module, the terms and conditions of the license of that
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this exception to your version of the library, but you are not
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package gnu.javax.crypto.prng;

import gnu.java.security.Registry;
import gnu.java.security.prng.IRandom;
import gnu.javax.crypto.mac.HMacFactory;
import gnu.javax.crypto.mac.IMac;
import gnu.javax.crypto.mac.MacFactory;

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

/**
 * A Factory to instantiate pseudo random number generators.
 */
public class PRNGFactory
    implements Registry
{
  /** Trivial constructor to enforce <i>Singleton</i> pattern. */
  private PRNGFactory()
  {
  }

  /**
   * Returns an instance of a padding algorithm given its name.
   * 
   * @param prng the case-insensitive name of the PRNG.
   * @return an instance of the pseudo-random number generator.
   * @exception InternalError if the implementation does not pass its self-
   *              test.
   */
  public static IRandom getInstance(String prng)
  {
    if (prng == null)
      return null;
    prng = prng.trim();
    IRandom result = null;
    if (prng.equalsIgnoreCase(ARCFOUR_PRNG) || prng.equalsIgnoreCase(RC4_PRNG))
      result = new ARCFour();
    else if (prng.equalsIgnoreCase(ICM_PRNG))
      result = new ICMGenerator();
    else if (prng.equalsIgnoreCase(UMAC_PRNG))
      result = new UMacGenerator();
    else if (prng.toLowerCase().startsWith(PBKDF2_PRNG_PREFIX))
      {
        String macName = prng.substring(PBKDF2_PRNG_PREFIX.length());
        IMac mac = MacFactory.getInstance(macName);
        if (mac == null)
          return null;
        result = new PBKDF2(mac);
      }

    if (result != null)
      return result;

    return gnu.java.security.prng.PRNGFactory.getInstance(prng);
  }

  /**
   * Returns a {@link Set} of names of padding algorithms supported by this
   * <i>Factory</i>.
   * 
   * @return a {@link Set} of pseudo-random number generator algorithm names
   *         (Strings).
   */
  public static Set getNames()
  {
    HashSet hs = new HashSet(gnu.java.security.prng.PRNGFactory.getNames());
    hs.add(ICM_PRNG);
    hs.add(UMAC_PRNG);
    // add all hmac implementations as candidate PBKDF2 ones too
    for (Iterator it = HMacFactory.getNames().iterator(); it.hasNext();)
      hs.add(PBKDF2_PRNG_PREFIX + ((String) it.next()));
    return Collections.unmodifiableSet(hs);
  }
}
