libjava/java/security/DigestInputStream.java

   1 /* DigestInputStream.java --- An Input stream tied to a message digest
   2    Copyright (C) 1999 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., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 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 //import java.security.MessageDigest;
  40 import java.io.InputStream;
  41 import java.io.FilterInputStream;
  42 import java.io.IOException;
  43
  44 /**
  45    DigestInputStream is a class that ties an InputStream with a
  46    MessageDigest. The Message Digest is used by the class to
  47    update it self as bytes are read from the InputStream.
  48
  49    The updating to the digest depends on the on flag which is set
  50    to true by default to tell the class to update the data
  51    in the message digest.
  52
  53    @version 0.0
  54    @author Mark Benvenuto <ivymccough@worldnet.att.net>
  55  */
  56 public class DigestInputStream extends FilterInputStream
  57 {
  58   /**
  59      The message digest for the DigestInputStream
  60    */
  61   protected MessageDigest digest;
  62
  63   //Manages the on flag
  64   private boolean state = true;
  65
  66   /**
  67      Constructs a new DigestInputStream.
  68      It associates a MessageDigest with the stream to
  69      compute the stream as data is written.
  70
  71      @param stream An InputStream to associate this stream with
  72      @param digest A MessageDigest to hash the stream with
  73    */
  74   public DigestInputStream(InputStream stream, MessageDigest digest)
  75   {
  76     super(stream);
  77     //this.in = stream;
  78     this.digest = digest;
  79   }
  80
  81   /**
  82      Returns the MessageDigest associated with this DigestInputStream
  83
  84      @return The MessageDigest used to hash this stream
  85    */
  86   public MessageDigest getMessageDigest()
  87   {
  88     return digest;
  89   }
  90
  91   /**
  92      Sets the current MessageDigest to current parameter
  93
  94      @param digest A MessageDigest to associate with this stream
  95    */
  96   public void setMessageDigest(MessageDigest digest)
  97   {
  98     this.digest = digest;
  99   }
 100
 101   /**
 102      Reads a byte from the input stream and updates the digest.
 103      This method reads the underlying input stream and if the
 104      on flag is true then updates the message digest.
 105
 106      @return Returns a byte from the input stream, -1 is returned to indicate that
 107      the end of stream was reached before this read call
 108
 109      @throws IOException if an IO error occurs in the underlying input stream,
 110      this error is thrown
 111    */
 112   public int read() throws IOException
 113   {
 114     int temp = in.read();
 115
 116     if (state == true && temp != -1)
 117       digest.update((byte) temp);
 118
 119     return temp;
 120   }
 121
 122   /**
 123      Reads bytes from the input stream and updates the digest.
 124      This method reads the underlying input stream and if the
 125      on flag is true then updates the message digest.
 126
 127      @param b a byte array to store the data from the input stream
 128      @param off an offset to start at in the array
 129      @param len length of data to read
 130      @return Returns count of bytes read, -1 is returned to indicate that
 131      the end of stream was reached before this read call
 132
 133      @throws IOException if an IO error occurs in the underlying input stream,
 134      this error is thrown
 135    */
 136   public int read(byte[]b, int off, int len) throws IOException
 137   {
 138     int temp = in.read(b, off, len);
 139
 140     if (state == true && temp != -1)
 141       digest.update(b, off, len);
 142
 143     return temp;
 144   }
 145
 146   /**
 147      Sets the flag specifing if this DigestInputStream updates the
 148      digest in the write() methods. The default is on;
 149
 150      @param on True means it digests stream, false means it does not
 151    */
 152   public void on(boolean on)
 153   {
 154     state = on;
 155   }
 156
 157   /**
 158      Converts the input stream and underlying message digest to a string.
 159
 160      @return A string representing the input stream and message digest.
 161    */
 162   public String toString()
 163   {
 164     return "[Digest Input Stream] " + digest.toString();
 165   }
 166 }