Source for java.security.DigestInputStream

   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., 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: 
  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: }