/* HashFactory.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
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WITHOUT ANY WARRANTY; without even the implied warranty of
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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
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permission to link this library with independent modules to produce an
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package gnu.java.security.hash;

import gnu.java.security.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>
 */
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
  // -------------------------------------------------------------------------
}
