Source for gnu.javax.crypto.mac.HMacFactory

   1: /* HMacFactory.java --
   2:    Copyright (C) 2001, 2002, 2006 Free Software Foundation, Inc.
   3: 
   4: This file is a part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2 of the License, or (at
   9: your option) any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; if not, write to the Free Software
  18: Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
  19: USA
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version.  */
  37: 
  38: 
  39: package gnu.javax.crypto.mac;
  40: 
  41: import gnu.java.security.Registry;
  42: import gnu.java.security.hash.HashFactory;
  43: 
  44: import java.util.Collections;
  45: import java.util.HashSet;
  46: import java.util.Iterator;
  47: import java.util.Set;
  48: 
  49: /**
  50:  * A <i>Factory</i> to instantiate Keyed-Hash Message Authentication Code
  51:  * (HMAC) algorithm instances.
  52:  */
  53: public class HMacFactory
  54:     implements Registry
  55: {
  56:   /** Trivial constructor to enforce <i>Singleton</i> pattern. */
  57:   private HMacFactory()
  58:   {
  59:     super();
  60:   }
  61: 
  62:   /**
  63:    * Return an instance of a <i>HMAC</i> algorithm given the name of its
  64:    * underlying hash function, prefixed with the literal defined in
  65:    * {@link Registry#HMAC_NAME_PREFIX}.
  66:    *
  67:    * @param name the fully qualified name of the underlying algorithm: composed
  68:    *          as the concatenation of a literal prefix (see
  69:    *          {@link Registry#HMAC_NAME_PREFIX}) and the name of the underlying
  70:    *          hash algorithm.
  71:    * @return an instance of the <i>HMAC</i> algorithm, or <code>null</code>
  72:    *         if none can be constructed.
  73:    * @exception InternalError if the implementation does not pass its self-test.
  74:    */
  75:   public static IMac getInstance(String name)
  76:   {
  77:     if (name == null)
  78:       return null;
  79: 
  80:     name = name.trim();
  81:     name = name.toLowerCase();
  82:     if (! name.startsWith(HMAC_NAME_PREFIX))
  83:       return null;
  84: 
  85:     // strip the prefix
  86:     name = name.substring(HMAC_NAME_PREFIX.length()).trim();
  87:     IMac result = new HMac(HashFactory.getInstance(name));
  88:     if (result != null && ! result.selfTest())
  89:       throw new InternalError(result.name());
  90: 
  91:     return result;
  92:   }
  93: 
  94:   /**
  95:    * <p>
  96:    * Returns a {@link java.util.Set} of names of <i>HMAC</i> algorithms
  97:    * supported by this <i>Factory</i>.
  98:    * </p>
  99:    *
 100:    * @return a {@link java.util.Set} of HMAC algorithm names (Strings).
 101:    */
 102:   public static final Set getNames()
 103:   {
 104:     Set hashNames = HashFactory.getNames();
 105:     HashSet hs = new HashSet();
 106:     for (Iterator it = hashNames.iterator(); it.hasNext();)
 107:       hs.add(HMAC_NAME_PREFIX + ((String) it.next()));
 108: 
 109:     return Collections.unmodifiableSet(hs);
 110:   }
 111: }