libjava/classpath/java/security/MessageDigestSpi.java

   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 }