/* PadFactory.java -- 
   Copyright (C) 2001, 2002, 2003, 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
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your option) any later version.

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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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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
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package gnu.javax.crypto.pad;

import gnu.java.security.Registry;

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

/**
 * A Factory to instantiate padding schemes.
 */
public class PadFactory
    implements Registry
{
  /** Collection of padding algorithm names --cached for speed. */
  private static Set names;

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

  /**
   * Returns an instance of a padding algorithm given its name.
   * 
   * @param pad the case-insensitive name of the padding algorithm.
   * @return an instance of the padding algorithm, operating with a given block
   *         size, or <code>null</code> if none found.
   * @throws InternalError if the implementation does not pass its self-test.
   */
  public static final IPad getInstance(String pad)
  {
    if (pad == null)
      return null;

    pad = pad.trim().toLowerCase();
    if (pad.endsWith("padding"))
      pad = pad.substring(0, pad.length() - "padding".length());
    IPad result = null;
    if (pad.equals(PKCS7_PAD) || pad.equals(PKCS5_PAD))
      result = new PKCS7();
    else if (pad.equals(TBC_PAD))
      result = new TBC();
    else if (pad.equals(EME_PKCS1_V1_5_PAD))
      result = new PKCS1_V1_5();
    else if (pad.equals(SSL3_PAD))
      result = new SSL3();
    else if (pad.equals(TLS1_PAD))
      result = new TLS1();
    else if (pad.equals(ISO10126_PAD))
      result = new ISO10126();

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

    return result;
  }

  /**
   * Returns a {@link Set} of names of padding algorithms supported by this
   * <i>Factory</i>.
   * 
   * @return a {@link Set} of padding algorithm names (Strings).
   */
  public static final Set getNames()
  {
    if (names == null)
      {
        HashSet hs = new HashSet();
        hs.add(PKCS5_PAD);
        hs.add(PKCS7_PAD);
        hs.add(TBC_PAD);
        hs.add(EME_PKCS1_V1_5_PAD);
        hs.add(SSL3_PAD);
        hs.add(TLS1_PAD);
        hs.add(ISO10126_PAD);
        names = Collections.unmodifiableSet(hs);
      }
    return names;
  }
}