Source for gnu.javax.crypto.mac.MacFactory

   1: /* MacFactory.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.javax.crypto.cipher.CipherFactory;
  43: import gnu.javax.crypto.cipher.IBlockCipher;
  44: 
  45: import java.util.Collections;
  46: import java.util.HashSet;
  47: import java.util.Iterator;
  48: import java.util.Set;
  49: 
  50: /**
  51:  * A <i>Factory</i> that instantiates instances of every supported Message
  52:  * Authentication Code algorithms, including all <i>HMAC</i> algorithms.
  53:  */
  54: public class MacFactory
  55:     implements Registry
  56: {
  57:   private static Set names;
  58: 
  59:   /** Trivial constructor to enforce <i>Singleton</i> pattern. */
  60:   private MacFactory()
  61:   {
  62:     super();
  63:   }
  64: 
  65:   /**
  66:    * Returns an instance of a <i>MAC</i> algorithm given its name.
  67:    *
  68:    * @param name the name of the MAC algorithm.
  69:    * @return an instance of the <i>MAC</i> algorithm, or <code>null</code> if
  70:    *         none can be constructed.
  71:    * @exception InternalError if the implementation does not pass its self-test.
  72:    */
  73:   public static IMac getInstance(String name)
  74:   {
  75:     if (name == null)
  76:       return null;
  77: 
  78:     name = name.trim();
  79:     name = name.toLowerCase();
  80:     if (name.startsWith(HMAC_NAME_PREFIX))
  81:       return HMacFactory.getInstance(name);
  82: 
  83:     if (name.startsWith(OMAC_PREFIX))
  84:       {
  85:         name = name.substring(OMAC_PREFIX.length());
  86:         IBlockCipher cipher = CipherFactory.getInstance(name);
  87:         if (cipher == null)
  88:           return null;
  89:         return new OMAC(cipher);
  90:       }
  91:     IMac result = null;
  92:     if (name.equalsIgnoreCase(UHASH32))
  93:       result = new UHash32();
  94:     else if (name.equalsIgnoreCase(UMAC32))
  95:       result = new UMac32();
  96:     else if (name.equalsIgnoreCase(TMMH16))
  97:       result = new TMMH16();
  98: 
  99:     if (result != null && ! result.selfTest())
 100:       throw new InternalError(result.name());
 101: 
 102:     return result;
 103:   }
 104: 
 105:   /**
 106:    * Returns a {@link Set} of names of <i>MAC</i> algorithms supported by this
 107:    * <i>Factory</i>.
 108:    *
 109:    * @return a {@link Set} of MAC names (Strings).
 110:    */
 111:   public static final Set getNames()
 112:   {
 113:     synchronized (MacFactory.class)
 114:       {
 115:         if (names == null)
 116:           {
 117:             HashSet hs = new HashSet();
 118:             hs.addAll(HMacFactory.getNames());
 119:             hs.add(UHASH32);
 120:             hs.add(UMAC32);
 121:             hs.add(TMMH16);
 122:             for (Iterator it = CipherFactory.getNames().iterator(); it.hasNext();)
 123:               hs.add(OMAC_PREFIX + it.next());
 124: 
 125:             names = Collections.unmodifiableSet(hs);
 126:           }
 127:       }
 128:     return names;
 129:   }
 130: }