package gnu.crypto.hash;

// ----------------------------------------------------------------------------
// $Id: HashFactory.java,v 1.14 2005/10/06 04:24:14 rsdio Exp $
//
// Copyright (C) 2001, 2002, 2003 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 java.util.Collections;
import java.util.HashSet;
import java.util.Set;

/**
 * <p>A <i>Factory</i> to instantiate message digest algorithm instances.</p>
 *
 * @version $Revision: 1.14 $
 */
public class HashFactory {

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

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

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

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

   /**
    * <p>Return an instance of a hash algorithm given its name.</p>
    *
    * @param name the name of the hash algorithm.
    * @return an instance of the hash algorithm, or null if none found.
    * @exception InternalError if the implementation does not pass its self-
    * test.
    */
   public static IMessageDigest getInstance(String name) {
      if (name == null) {
         return null;
      }

      name = name.trim();
      IMessageDigest result = null;
      if (name.equalsIgnoreCase(Registry.WHIRLPOOL_HASH)) {
         result = new Whirlpool();
      } else if (name.equalsIgnoreCase(Registry.RIPEMD128_HASH)
            || name.equalsIgnoreCase(Registry.RIPEMD_128_HASH)) {
         result = new RipeMD128();
      } else if (name.equalsIgnoreCase(Registry.RIPEMD160_HASH)
            || name.equalsIgnoreCase(Registry.RIPEMD_160_HASH)) {
         result = new RipeMD160();
      } else if (name.equalsIgnoreCase(Registry.SHA160_HASH)
            || name.equalsIgnoreCase(Registry.SHA_1_HASH)
            || name.equalsIgnoreCase(Registry.SHA1_HASH)
            || name.equalsIgnoreCase(Registry.SHA_HASH)) {
         result = new Sha160();
      } else if (name.equalsIgnoreCase(Registry.SHA256_HASH)) {
         result = new Sha256();
      } else if (name.equalsIgnoreCase(Registry.SHA384_HASH)) {
         result = new Sha384();
      } else if (name.equalsIgnoreCase(Registry.SHA512_HASH)) {
         result = new Sha512();
      } else if (name.equalsIgnoreCase(Registry.TIGER_HASH)) {
         result = new Tiger();
      } else if (name.equalsIgnoreCase(Registry.HAVAL_HASH)) {
         result = new Haval();
      } else if (name.equalsIgnoreCase(Registry.MD5_HASH)) {
         result = new MD5();
      } else if (name.equalsIgnoreCase(Registry.MD4_HASH)) {
         result = new MD4();
      } else if (name.equalsIgnoreCase(Registry.MD2_HASH)) {
         result = new MD2();
      } else if (name.equalsIgnoreCase(Registry.HAVAL_HASH)) {
         result = new Haval();
      }

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

      return result;
   }

   /**
    * <p>Returns a {@link Set} of names of hash algorithms supported by this
    * <i>Factory</i>.</p>
    *
    * @return a {@link Set} of hash names (Strings).
    */
   public static final Set getNames() {
      HashSet hs = new HashSet();
      hs.add(Registry.WHIRLPOOL_HASH);
      hs.add(Registry.RIPEMD128_HASH);
      hs.add(Registry.RIPEMD160_HASH);
      hs.add(Registry.SHA160_HASH);
      hs.add(Registry.SHA256_HASH);
      hs.add(Registry.SHA384_HASH);
      hs.add(Registry.SHA512_HASH);
      hs.add(Registry.TIGER_HASH);
      hs.add(Registry.HAVAL_HASH);
      hs.add(Registry.MD5_HASH);
      hs.add(Registry.MD4_HASH);
      hs.add(Registry.MD2_HASH);

      return Collections.unmodifiableSet(hs);
   }

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