1 /* DigestInputStream.java --- An Input stream tied to a message digest
2    Copyright (C) 1999, 2003 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    */
DigestInputStream(InputStream stream, MessageDigest digest)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    */
getMessageDigest()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    */
setMessageDigest(MessageDigest digest)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    */
read()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    */
read(byte[]b, int off, int len)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, temp);
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    */
on(boolean on)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    */
toString()162   public String toString()
163   {
164     return "[Digest Input Stream] " + digest.toString();
165   }
166 }
167