1 /*
   2  * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.security;
  27 
  28 import java.io.IOException;
  29 import java.io.EOFException;
  30 import java.io.OutputStream;
  31 import java.io.FilterOutputStream;
  32 import java.io.PrintStream;
  33 import java.io.ByteArrayOutputStream;
  34 
  35 /**
  36  * A transparent stream that updates the associated message digest using
  37  * the bits going through the stream.
  38  *
  39  * <p>To complete the message digest computation, call one of the
  40  * {@code digest} methods on the associated message
  41  * digest after your calls to one of this digest output stream's
  42  * {@link #write(int) write} methods.
  43  *
  44  * <p>It is possible to turn this stream on or off (see
  45  * {@link #on(boolean) on}). When it is on, a call to one of the
  46  * {@code write} methods results in
  47  * an update on the message digest.  But when it is off, the message
  48  * digest is not updated. The default is for the stream to be on.
  49  *
  50  * @see MessageDigest
  51  * @see DigestInputStream
  52  *
  53  * @author Benjamin Renaud
  54  */
  55 public class DigestOutputStream extends FilterOutputStream {
  56 
  57     private boolean on = true;
  58 
  59     /**
  60      * The message digest associated with this stream.
  61      */
  62     protected MessageDigest digest;
  63 
  64     /**
  65      * Creates a digest output stream, using the specified output stream
  66      * and message digest.
  67      *
  68      * @param stream the output stream.
  69      *
  70      * @param digest the message digest to associate with this stream.
  71      */
  72     public DigestOutputStream(OutputStream stream, MessageDigest digest) {
  73         super(stream);
  74         setMessageDigest(digest);
  75     }
  76 
  77     /**
  78      * Returns the message digest associated with this stream.
  79      *
  80      * @return the message digest associated with this stream.
  81      * @see #setMessageDigest(java.security.MessageDigest)
  82      */
  83     public MessageDigest getMessageDigest() {
  84         return digest;
  85     }
  86 
  87     /**
  88      * Associates the specified message digest with this stream.
  89      *
  90      * @param digest the message digest to be associated with this stream.
  91      * @see #getMessageDigest()
  92      */
  93     public void setMessageDigest(MessageDigest digest) {
  94         this.digest = digest;
  95     }
  96 
  97     /**
  98      * Updates the message digest (if the digest function is on) using
  99      * the specified byte, and in any case writes the byte
 100      * to the output stream. That is, if the digest function is on
 101      * (see {@link #on(boolean) on}), this method calls
 102      * {@code update} on the message digest associated with this
 103      * stream, passing it the byte {@code b}. This method then
 104      * writes the byte to the output stream, blocking until the byte
 105      * is actually written.
 106      *
 107      * @param b the byte to be used for updating and writing to the
 108      * output stream.
 109      *
 110      * @exception IOException if an I/O error occurs.
 111      *
 112      * @see MessageDigest#update(byte)
 113      */
 114     public void write(int b) throws IOException {
 115         out.write(b);
 116         if (on) {
 117             digest.update((byte)b);
 118         }
 119     }
 120 
 121     /**
 122      * Updates the message digest (if the digest function is on) using
 123      * the specified subarray, and in any case writes the subarray to
 124      * the output stream. That is, if the digest function is on (see
 125      * {@link #on(boolean) on}), this method calls {@code update}
 126      * on the message digest associated with this stream, passing it
 127      * the subarray specifications. This method then writes the subarray
 128      * bytes to the output stream, blocking until the bytes are actually
 129      * written.
 130      *
 131      * @param b the array containing the subarray to be used for updating
 132      * and writing to the output stream.
 133      *
 134      * @param off the offset into {@code b} of the first byte to
 135      * be updated and written.
 136      *
 137      * @param len the number of bytes of data to be updated and written
 138      * from {@code b}, starting at offset {@code off}.
 139      *
 140      * @exception IOException if an I/O error occurs.
 141      *
 142      * @see MessageDigest#update(byte[], int, int)
 143      */
 144     public void write(byte[] b, int off, int len) throws IOException {
 145         out.write(b, off, len);
 146         if (on) {
 147             digest.update(b, off, len);
 148         }
 149     }
 150 
 151     /**
 152      * Turns the digest function on or off. The default is on.  When
 153      * it is on, a call to one of the {@code write} methods results in an
 154      * update on the message digest.  But when it is off, the message
 155      * digest is not updated.
 156      *
 157      * @param on true to turn the digest function on, false to turn it
 158      * off.
 159      */
 160     public void on(boolean on) {
 161         this.on = on;
 162     }
 163 
 164     /**
 165      * Prints a string representation of this digest output stream and
 166      * its associated message digest object.
 167      */
 168      public String toString() {
 169          return "[Digest Output Stream] " + digest.toString();
 170      }
 171 }