For the latest news and information visit
The GNU Crypto project

gnu.crypto.pad
Class BasePad

java.lang.Object
  extended bygnu.crypto.pad.BasePad
All Implemented Interfaces:
IPad
Direct Known Subclasses:
PKCS1_V1_5, PKCS7, TBC

public abstract class BasePad
extends java.lang.Object
implements IPad

An abstract class to facilitate implementing padding algorithms.

Version:
$Revision: 1.2 $

Field Summary
protected  int blockSize
          The block size, in bytes, for this instance.
protected  java.lang.String name
          The canonical name prefix of the padding algorithm.
 
Constructor Summary
protected BasePad(java.lang.String name)
          Trivial constructor for use by concrete subclasses.
 
Method Summary
 void init(int bs)
          Initialises the padding scheme with a designated block size.
 java.lang.String name()
           
abstract  byte[] pad(byte[] in, int off, int len)
          Returns the byte sequence that should be appended to the designated input.
 void reset()
          Resets the scheme instance for re-initialisation and use with other characteristics.
 boolean selfTest()
          A basic symmetric pad/unpad test.
abstract  void setup()
          If any additional checks or resource setup must be done by the subclass, then this is the hook for it.
abstract  int unpad(byte[] in, int off, int len)
          Returns the number of bytes to discard from a designated input buffer.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

name

protected java.lang.String name
The canonical name prefix of the padding algorithm.


blockSize

protected int blockSize
The block size, in bytes, for this instance.

Constructor Detail

BasePad

protected BasePad(java.lang.String name)
Trivial constructor for use by concrete subclasses.

Method Detail

name

public java.lang.String name()
Specified by:
name in interface IPad
Returns:
the canonical name of this instance.

init

public void init(int bs)
          throws java.lang.IllegalStateException
Description copied from interface: IPad
Initialises the padding scheme with a designated block size.

Specified by:
init in interface IPad
Parameters:
bs - the designated block size.
Throws:
java.lang.IllegalStateException - if the instance is already initialised.

reset

public void reset()
Description copied from interface: IPad
Resets the scheme instance for re-initialisation and use with other characteristics. This method always succeeds.

Specified by:
reset in interface IPad

selfTest

public boolean selfTest()
Description copied from interface: IPad
A basic symmetric pad/unpad test.

Specified by:
selfTest in interface IPad
Returns:
true if the implementation passes a basic symmetric self-test. Returns false otherwise.

setup

public abstract void setup()

If any additional checks or resource setup must be done by the subclass, then this is the hook for it. This method will be called before the init(int) method returns.


pad

public abstract byte[] pad(byte[] in,
                           int off,
                           int len)
Description copied from interface: IPad
Returns the byte sequence that should be appended to the designated input.

Specified by:
pad in interface IPad
Parameters:
in - the input buffer containing the bytes to pad.
off - the starting index of meaningful data in in.
len - the number of meaningful bytes in in.
Returns:
the possibly 0-byte long sequence to be appended to the designated input.

unpad

public abstract int unpad(byte[] in,
                          int off,
                          int len)
                   throws WrongPaddingException
Description copied from interface: IPad
Returns the number of bytes to discard from a designated input buffer.

Specified by:
unpad in interface IPad
Parameters:
in - the input buffer containing the bytes to unpad.
off - the starting index of meaningful data in in.
len - the number of meaningful bytes in in.
Returns:
the number of bytes to discard, to the left of index position offset + length in in. In other words, if the return value of a successful invocation of this method is result, then the unpadded byte sequence will be offset + length - result bytes in in, starting from index position offset.
Throws:
WrongPaddingException - if the data is not terminated with the expected padding bytes.

For the latest news and information visit
The GNU Crypto project

Copyright © 2001, 2002, 2003 Free Software Foundation, Inc. All Rights Reserved.