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 As a special exception, if you link this library with other files to
  22 produce an executable, this library does not by itself cause the
  23 resulting executable to be covered by the GNU General Public License.
  24 This exception does not however invalidate any other reasons why the
  25 executable file might be covered by the GNU General Public License. */
  26
  27 package java.security;
  28 //import java.security.MessageDigest;
  29 import java.io.InputStream;
  30 import java.io.FilterInputStream;
  31 import java.io.IOException;
  32
  33 /**
  34    DigestInputStream is a class that ties an InputStream with a
  35    MessageDigest. The Message Digest is used by the class to
  36    update it self as bytes are read from the InputStream.
  37
  38    The updating to the digest depends on the on flag which is set
  39    to true by default to tell the class to update the data
  40    in the message digest.
  41
  42    @version 0.0
  43    @author Mark Benvenuto <ivymccough@worldnet.att.net>
  44  */
  45 public class DigestInputStream extends FilterInputStream
  46 {
  47   /**
  48      The message digest for the DigestInputStream
  49    */
  50   protected MessageDigest digest;
  51
  52   //Manages the on flag
  53   private boolean state = true;
  54
  55   /**
  56      Constructs a new DigestInputStream.
  57      It associates a MessageDigest with the stream to
  58      compute the stream as data is written.
  59
  60      @param stream An InputStream to associate this stream with
  61      @param digest A MessageDigest to hash the stream with
  62    */
  63   public DigestInputStream(InputStream stream, MessageDigest digest)
  64   {
  65     super(stream);
  66     //this.in = stream;
  67     this.digest = digest;
  68   }
  69
  70   /**
  71      Returns the MessageDigest associated with this DigestInputStream
  72
  73      @return The MessageDigest used to hash this stream
  74    */
  75   public MessageDigest getMessageDigest()
  76   {
  77     return digest;
  78   }
  79
  80   /**
  81      Sets the current MessageDigest to current parameter
  82
  83      @param digest A MessageDigest to associate with this stream
  84    */
  85   public void setMessageDigest(MessageDigest digest)
  86   {
  87     this.digest = digest;
  88   }
  89
  90   /**
  91      Reads a byte from the input stream and updates the digest.
  92      This method reads the underlying input stream and if the
  93      on flag is true then updates the message digest.
  94
  95      @return Returns a byte from the input stream, -1 is returned to indicate that
  96      the end of stream was reached before this read call
  97
  98      @throws IOException if an IO error occurs in the underlying input stream,
  99      this error is thrown
 100    */
 101   public int read() throws IOException
 102   {
 103     int temp = in.read();
 104
 105     if (state == true && temp != -1)
 106       digest.update((byte) temp);
 107
 108     return temp;
 109   }
 110
 111   /**
 112      Reads bytes from the input stream and updates the digest.
 113      This method reads the underlying input stream and if the
 114      on flag is true then updates the message digest.
 115
 116      @param b a byte array to store the data from the input stream
 117      @param off an offset to start at in the array
 118      @param len length of data to read
 119      @return Returns count of bytes read, -1 is returned to indicate that
 120      the end of stream was reached before this read call
 121
 122      @throws IOException if an IO error occurs in the underlying input stream,
 123      this error is thrown
 124    */
 125   public int read(byte[]b, int off, int len) throws IOException
 126   {
 127     int temp = in.read(b, off, len);
 128
 129     if (state == true && temp != -1)
 130       digest.update(b, off, len);
 131
 132     return temp;
 133   }
 134
 135   /**
 136      Sets the flag specifing if this DigestInputStream updates the
 137      digest in the write() methods. The default is on;
 138
 139      @param on True means it digests stream, false means it does not
 140    */
 141   public void on(boolean on)
 142   {
 143     state = on;
 144   }
 145
 146   /**
 147      Converts the input stream and underlying message digest to a string.
 148
 149      @return A string representing the input stream and message digest.
 150    */
 151   public String toString()
 152   {
 153     return "[Digest Input Stream] " + digest.toString();
 154   }
 155 }