Source for java.security.MessageDigestSpi

   1: /* MessageDigestSpi.java --- The message digest service provider interface.
   2:    Copyright (C) 1999, 2005  Free Software Foundation, Inc.
   3: 
   4: This file is 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, or (at your option)
   9: 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; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 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: package java.security;
  39: 
  40: import java.nio.ByteBuffer;
  41: 
  42: /**
  43:    This is the Service Provider Interface (SPI) for MessageDigest
  44:    class in java.security. It provides the back end functionality
  45:    for the MessageDigest class so that it can compute message
  46:    hashes. The default hashes are SHA-1 and MD5. A message hash
  47:    takes data of arbitrary length and produces a unique number
  48:    representing it.
  49: 
  50:    Cryptography service providers who want to implement their
  51:    own message digest hashes need only to subclass this class.
  52: 
  53:    The implementation of a Cloneable interface is left to up to
  54:    the programmer of a subclass.
  55: 
  56:    @version 0.0
  57: 
  58:    @author Mark Benvenuto (ivymccough@worldnet.att.net)
  59:  */
  60: public abstract class MessageDigestSpi
  61: {
  62:   /**
  63:      Default constructor of the MessageDigestSpi class
  64:    */
  65:   public MessageDigestSpi()
  66:   {
  67:   }
  68: 
  69:   /**
  70:      Returns the length of the digest.  It may be overridden by the
  71:      provider to return the length of the digest.  Default is to
  72:      return 0.  It is concrete for backwards compatibility with JDK1.1
  73:      message digest classes.
  74: 
  75:      @return Length of Digest in Bytes
  76: 
  77:      @since 1.2
  78:    */
  79:   protected int engineGetDigestLength()
  80:   {
  81:     return 0;
  82:   }
  83: 
  84:   /**
  85:      Updates the digest with the specified byte.
  86: 
  87:      @param input the byte to update digest with
  88:    */
  89:   protected abstract void engineUpdate(byte input);
  90: 
  91: 
  92:   /**
  93:      Updates the digest with the specified bytes starting with the
  94:      offset and proceeding for the specified length.
  95: 
  96:      @param input the byte array to update digest with
  97:      @param offset the offset of the byte to start with
  98:      @param len the number of the bytes to update with
  99:    */
 100:   protected abstract void engineUpdate(byte[]input, int offset, int len);
 101: 
 102:   /**
 103:    * Updates this digest with the remaining bytes of a byte buffer.
 104:    * 
 105:    * @param input The input buffer.
 106:    * @since 1.5
 107:    */
 108:   protected void engineUpdate (ByteBuffer input)
 109:   {
 110:     byte[] buf = new byte[1024];
 111:     while (input.hasRemaining())
 112:       {
 113:         int n = Math.min(input.remaining(), buf.length);
 114:         input.get (buf, 0, n);
 115:         engineUpdate (buf, 0, n);
 116:       }
 117:   }
 118:   
 119:   /**
 120:      Computes the final digest of the stored bytes and returns
 121:      them. It performs any necessary padding. The message digest
 122:      should reset sensitive data after performing the digest.
 123: 
 124:      @return An array of bytes containing the digest
 125:    */
 126:   protected abstract byte[] engineDigest();
 127: 
 128:   /**
 129:      Computes the final digest of the stored bytes and returns
 130:      them. It performs any necessary padding. The message digest
 131:      should reset sensitive data after performing the digest.  This
 132:      method is left concrete for backwards compatibility with JDK1.1
 133:      message digest classes.
 134: 
 135:      @param buf An array of bytes to store the digest
 136:      @param offset An offset to start storing the digest at
 137:      @param len The length of the buffer
 138:      @return Returns the length of the buffer
 139: 
 140:      @since 1.2
 141:    */
 142:   protected int engineDigest(byte[]buf, int offset, int len)
 143:     throws DigestException
 144:   {
 145:     if (engineGetDigestLength() > len)
 146:       throw new DigestException("Buffer is too small.");
 147: 
 148:     byte[] tmp = engineDigest();
 149:     if (tmp.length > len)
 150:       throw new DigestException("Buffer is too small");
 151: 
 152:     System.arraycopy(tmp, 0, buf, offset, tmp.length);
 153:     return tmp.length;
 154:   }
 155: 
 156:   /**
 157:      Resets the digest engine. Reinitializes internal variables
 158:      and clears sensitive data.
 159:    */
 160:   protected abstract void engineReset();
 161: 
 162:   /**
 163:      Returns a clone of this class.
 164: 
 165:      If cloning is not supported, then by default the class throws a
 166:      CloneNotSupportedException.  The MessageDigestSpi provider
 167:      implementation has to overload this class in order to be
 168:      cloneable.
 169:    */
 170:   public Object clone() throws CloneNotSupportedException
 171:   {
 172:     return super.clone();
 173:   }
 174: }