java.security

Class MessageDigestSpi

Known Direct Subclasses:
MessageDigest

public abstract class MessageDigestSpi
extends Object

This is the Service Provider Interface (SPI) for MessageDigest class in java.security. It provides the back end functionality for the MessageDigest class so that it can compute message hashes. The default hashes are SHA-1 and MD5. A message hash takes data of arbitrary length and produces a unique number representing it. Cryptography service providers who want to implement their own message digest hashes need only to subclass this class. The implementation of a Cloneable interface is left to up to the programmer of a subclass.

Constructor Summary

MessageDigestSpi()
Default constructor of the MessageDigestSpi class

Method Summary

Object
clone()
Returns a clone of this class.
protected abstract byte[]
engineDigest()
Computes the final digest of the stored bytes and returns them.
protected int
engineDigest(byte[] buf, int offset, int len)
Computes the final digest of the stored bytes and returns them.
protected int
engineGetDigestLength()
Returns the length of the digest.
protected abstract void
engineReset()
Resets the digest engine.
protected abstract void
engineUpdate(byte input)
Updates the digest with the specified byte.
protected abstract void
engineUpdate(byte[] input, int offset, int len)
Updates the digest with the specified bytes starting with the offset and proceeding for the specified length.
protected void
engineUpdate(ByteBuffer input)
Updates this digest with the remaining bytes of a byte buffer.

Methods inherited from class java.lang.Object

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

Constructor Details

MessageDigestSpi

public MessageDigestSpi()
Default constructor of the MessageDigestSpi class

Method Details

clone

public Object clone()
            throws CloneNotSupportedException
Returns a clone of this class. If cloning is not supported, then by default the class throws a CloneNotSupportedException. The MessageDigestSpi provider implementation has to overload this class in order to be cloneable.
Overrides:
clone in interface Object

engineDigest

protected abstract byte[] engineDigest()
Computes the final digest of the stored bytes and returns them. It performs any necessary padding. The message digest should reset sensitive data after performing the digest.
Returns:
An array of bytes containing the digest

engineDigest

protected int engineDigest(byte[] buf,
                           int offset,
                           int len)
            throws DigestException
Computes the final digest of the stored bytes and returns them. It performs any necessary padding. The message digest should reset sensitive data after performing the digest. This method is left concrete for backwards compatibility with JDK1.1 message digest classes.
Parameters:
buf - An array of bytes to store the digest
offset - An offset to start storing the digest at
len - The length of the buffer
Returns:
Returns the length of the buffer
Since:
1.2

engineGetDigestLength

protected int engineGetDigestLength()
Returns the length of the digest. It may be overridden by the provider to return the length of the digest. Default is to return 0. It is concrete for backwards compatibility with JDK1.1 message digest classes.
Returns:
Length of Digest in Bytes
Since:
1.2

engineReset

protected abstract void engineReset()
Resets the digest engine. Reinitializes internal variables and clears sensitive data.

engineUpdate

protected abstract void engineUpdate(byte input)
Updates the digest with the specified byte.
Parameters:
input - the byte to update digest with

engineUpdate

protected abstract void engineUpdate(byte[] input,
                                     int offset,
                                     int len)
Updates the digest with the specified bytes starting with the offset and proceeding for the specified length.
Parameters:
input - the byte array to update digest with
offset - the offset of the byte to start with
len - the number of the bytes to update with

engineUpdate

protected void engineUpdate(ByteBuffer input)
Updates this digest with the remaining bytes of a byte buffer.
Parameters:
input - The input buffer.
Since:
1.5

MessageDigestSpi.java --- The message digest service provider interface. Copyright (C) 1999, 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.