java.security

Class DigestInputStream

Implemented Interfaces:
AutoCloseable, Closeable

public class DigestInputStream
extends FilterInputStream

DigestInputStream is a class that ties an InputStream with a MessageDigest. The Message Digest is used by the class to update it self as bytes are read from the InputStream. The updating to the digest depends on the on flag which is set to true by default to tell the class to update the data in the message digest.

Field Summary

protected MessageDigest
digest
The message digest for the DigestInputStream

Fields inherited from class java.io.FilterInputStream

in

Constructor Summary

DigestInputStream(InputStream stream, MessageDigest digest)
Constructs a new DigestInputStream.

Method Summary

MessageDigest
getMessageDigest()
Returns the MessageDigest associated with this DigestInputStream
void
on(boolean on)
Sets the flag specifing if this DigestInputStream updates the digest in the write() methods.
int
read()
Reads a byte from the input stream and updates the digest.
int
read(byte[] b, int off, int len)
Reads bytes from the input stream and updates the digest.
void
setMessageDigest(MessageDigest digest)
Sets the current MessageDigest to current parameter
String
toString()
Converts the input stream and underlying message digest to a string.

Methods inherited from class java.io.FilterInputStream

available, close, mark, markSupported, read, read, read, reset, skip

Methods inherited from class java.io.InputStream

available, close, mark, markSupported, read, read, read, reset, skip

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

digest

protected MessageDigest digest
The message digest for the DigestInputStream

Constructor Details

DigestInputStream

public DigestInputStream(InputStream stream,
                         MessageDigest digest)
Constructs a new DigestInputStream. It associates a MessageDigest with the stream to compute the stream as data is written.
Parameters:
stream - An InputStream to associate this stream with
digest - A MessageDigest to hash the stream with

Method Details

getMessageDigest

public MessageDigest getMessageDigest()
Returns the MessageDigest associated with this DigestInputStream
Returns:
The MessageDigest used to hash this stream

on

public void on(boolean on)
Sets the flag specifing if this DigestInputStream updates the digest in the write() methods. The default is on;
Parameters:
on - True means it digests stream, false means it does not

read

public int read()
            throws IOException
Reads a byte from the input stream and updates the digest. This method reads the underlying input stream and if the on flag is true then updates the message digest.
Overrides:
read in interface FilterInputStream
Returns:
Returns a byte from the input stream, -1 is returned to indicate that the end of stream was reached before this read call
Throws:
IOException - if an IO error occurs in the underlying input stream, this error is thrown

read

public int read(byte[] b,
                int off,
                int len)
            throws IOException
Reads bytes from the input stream and updates the digest. This method reads the underlying input stream and if the on flag is true then updates the message digest.
Overrides:
read in interface FilterInputStream
Parameters:
b - a byte array to store the data from the input stream
off - an offset to start at in the array
len - length of data to read
Returns:
Returns count of bytes read, -1 is returned to indicate that the end of stream was reached before this read call
Throws:
IOException - if an IO error occurs in the underlying input stream, this error is thrown

setMessageDigest

public void setMessageDigest(MessageDigest digest)
Sets the current MessageDigest to current parameter
Parameters:
digest - A MessageDigest to associate with this stream

toString

public String toString()
Converts the input stream and underlying message digest to a string.
Overrides:
toString in interface Object
Returns:
A string representing the input stream and message digest.

DigestInputStream.java --- An Input stream tied to a message digest Copyright (C) 1999, 2003, 2004, 2005 Free Software Foundation, Inc. This file is part of GNU Classpath. GNU Classpath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. GNU Classpath is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GNU Classpath; see the file COPYING. If not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. Linking this library statically or dynamically with other modules is making a combined work based on this library. Thus, the terms and conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.