001/* DigestInputStream.java --- An Input stream tied to a message digest
002   Copyright (C) 1999, 2003, 2004, 2005  Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package java.security;
040
041import java.io.FilterInputStream;
042import java.io.IOException;
043import java.io.InputStream;
044
045/**
046 * DigestInputStream is a class that ties an InputStream with a 
047 * MessageDigest. The Message Digest is used by the class to 
048 * update it self as bytes are read from the InputStream.
049 *
050 * The updating to the digest depends on the on flag which is set
051 * to true by default to tell the class to update the data
052 * in the message digest.
053 *
054 * @version 0.0
055 * @author Mark Benvenuto (ivymccough@worldnet.att.net)
056 */
057public class DigestInputStream extends FilterInputStream
058{
059  /**
060   * The message digest for the DigestInputStream 
061   */
062  protected MessageDigest digest;
063
064  //Manages the on flag
065  private boolean state = true;
066
067  /**
068   * Constructs a new DigestInputStream.
069   * It associates a MessageDigest with the stream to 
070   * compute the stream as data is written.
071   *
072   * @param stream An InputStream to associate this stream with
073   * @param digest A MessageDigest to hash the stream with
074   */
075  public DigestInputStream(InputStream stream, MessageDigest digest)
076  {
077    super(stream);
078    //this.in = stream;
079    this.digest = digest;
080  }
081
082  /**
083   * Returns the MessageDigest associated with this DigestInputStream 
084   *
085   * @return The MessageDigest used to hash this stream
086   */
087  public MessageDigest getMessageDigest()
088  {
089    return digest;
090  }
091
092  /**
093   * Sets the current MessageDigest to current parameter
094   *
095   * @param digest A MessageDigest to associate with this stream
096   */
097  public void setMessageDigest(MessageDigest digest)
098  {
099    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}