libjava/java/security/DigestInputStream.java

   1 /* DigestInputStream.java --- An Input stream tied to a message digest
   2    Copyright (C) 1999, 2003, 2004, 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., 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
  39 package java.security;
  40
  41 import java.io.FilterInputStream;
  42 import java.io.IOException;
  43 import java.io.InputStream;
  44
  45 /**
  46  * DigestInputStream is a class that ties an InputStream with a
  47  * MessageDigest. The Message Digest is used by the class to
  48  * update it self as bytes are read from the InputStream.
  49  *
  50  * The updating to the digest depends on the on flag which is set
  51  * to true by default to tell the class to update the data
  52  * in the message digest.
  53  *
  54  * @version 0.0
  55  * @author Mark Benvenuto (ivymccough@worldnet.att.net)
  56  */
  57 public class DigestInputStream extends FilterInputStream
  58 {
  59   /**
  60    * The message digest for the DigestInputStream
  61    */
  62   protected MessageDigest digest;
  63
  64   //Manages the on flag
  65   private boolean state = true;
  66
  67   /**
  68    * Constructs a new DigestInputStream.
  69    * It associates a MessageDigest with the stream to
  70    * compute the stream as data is written.
  71    *
  72    * @param stream An InputStream to associate this stream with
  73    * @param digest A MessageDigest to hash the stream with
  74    */
  75   public DigestInputStream(InputStream stream, MessageDigest digest)
  76   {
  77     super(stream);
  78     //this.in = stream;
  79     this.digest = digest;
  80   }
  81
  82   /**
  83    * Returns the MessageDigest associated with this DigestInputStream
  84    *
  85    * @return The MessageDigest used to hash this stream
  86    */
  87   public MessageDigest getMessageDigest()
  88   {
  89     return digest;
  90   }
  91
  92   /**
  93    * Sets the current MessageDigest to current parameter
  94    *
  95    * @param digest A MessageDigest to associate with this stream
  96    */
  97   public void setMessageDigest(MessageDigest digest)
  98   {
  99     this.digest = digest;
 100   }
 101
 102   /**
 103    * Reads a byte from the input stream and updates the digest.
 104    * This method reads the underlying input stream and if the
 105    * on flag is true then updates the message digest.
 106    *
 107    * @return Returns a byte from the input stream, -1 is returned to indicate that
 108    * the end of stream was reached before this read call
 109    *
 110    * @throws IOException if an IO error occurs in the underlying input stream,
 111    * this error is thrown
 112    */
 113   public int read() throws IOException
 114   {
 115     int temp = in.read();
 116
 117     if (state == true && temp != -1)
 118       digest.update((byte) temp);
 119
 120     return temp;
 121   }
 122
 123   /**
 124    * Reads bytes from the input stream and updates the digest.
 125    * This method reads the underlying input stream and if the
 126    * on flag is true then updates the message digest.
 127    *
 128    * @param b a byte array to store the data from the input stream
 129    * @param off an offset to start at in the array
 130    * @param len length of data to read
 131    * @return Returns count of bytes read, -1 is returned to indicate that
 132    * the end of stream was reached before this read call
 133    *
 134    * @throws IOException if an IO error occurs in the underlying input stream,
 135    * this error is thrown
 136    */
 137   public int read(byte[]b, int off, int len) throws IOException
 138   {
 139     int temp = in.read(b, off, len);
 140
 141     if (state == true && temp != -1)
 142       digest.update(b, off, temp);
 143
 144     return temp;
 145   }
 146
 147   /**
 148    * Sets the flag specifing if this DigestInputStream updates the
 149    * digest in the write() methods. The default is on;
 150    *
 151    * @param on True means it digests stream, false means it does not
 152    */
 153   public void on(boolean on)
 154   {
 155     state = on;
 156   }
 157
 158   /**
 159    * Converts the input stream and underlying message digest to a string.
 160    *
 161    * @return A string representing the input stream and message digest.
 162    */
 163   public String toString()
 164   {
 165     return "[Digest Input Stream] " + digest.toString();
 166   }
 167 }