gnu.crypto.prng

Class BasePRNG

java.lang.Object

gnu.crypto.prng.BasePRNG

All Implemented Interfaces:

IRandom, Cloneable

Direct Known Subclasses:

ARCFour

public abstract class BasePRNG
extends Object
implements IRandom

An abstract class to facilitate implementing PRNG algorithms.

Version:

$Revision: 1.7 $

Field Summary

Fields

Modifier and Type	Field and Description
protected byte[]	buffer A temporary buffer to serve random bytes.
protected boolean	initialised Indicate if this instance has already been initialised or not.
protected String	name The canonical name prefix of the PRNG algorithm.
protected int	ndx The index into buffer of where the next byte will come from.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	BasePRNG(String name) Trivial constructor for use by concrete subclasses.

Method Summary

Modifier and Type	Method and Description
abstract Object	clone() Returns a clone copy of this instance.
abstract void	fillBlock()
void	init(Map attributes) Initialises the pseudo-random number generator scheme with the appropriate attributes.
boolean	isInitialised()
String	name() Returns the canonical name of this instance.
byte	nextByte() Returns the next 8 bits of random data generated from this instance.
void	nextBytes(byte[] out, int offset, int length) Fills the designated byte array, starting from byte at index offset, for a maximum of length bytes with the output of this generator instance.
abstract void	setup(Map attributes)

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

name

protected String name

The canonical name prefix of the PRNG algorithm.

initialised

protected boolean initialised

Indicate if this instance has already been initialised or not.

buffer

protected byte[] buffer

A temporary buffer to serve random bytes.

ndx

protected int ndx

The index into buffer of where the next byte will come from.

Constructor Detail

BasePRNG

protected BasePRNG(String name)

Trivial constructor for use by concrete subclasses.

Parameters:

name - the canonical name of this instance.

Method Detail

name

public String name()

Description copied from interface: IRandom

Returns the canonical name of this instance.

Specified by:

name in interface IRandom

Returns:

the canonical name of this instance.

init

public void init(Map attributes)

Description copied from interface: IRandom

Initialises the pseudo-random number generator scheme with the appropriate attributes.

Specified by:

init in interface IRandom

Parameters:

attributes - a set of name-value pairs that describe the desired future instance behaviour.

nextByte

public byte nextByte()
              throws IllegalStateException,
                     LimitReachedException

Description copied from interface: IRandom

Returns the next 8 bits of random data generated from this instance.

Specified by:

nextByte in interface IRandom

Returns:

the next 8 bits of random data generated from this instance.

Throws:

IllegalStateException - if the instance is not yet initialised.

LimitReachedException - if this instance has reached its theoretical limit for generating non-repetitive pseudo-random data.

nextBytes

public void nextBytes(byte[] out,
                      int offset,
                      int length)
               throws IllegalStateException,
                      LimitReachedException

Description copied from interface: IRandom

Fills the designated byte array, starting from byte at index offset, for a maximum of length bytes with the output of this generator instance.

Specified by:

nextBytes in interface IRandom

Parameters:

out - the placeholder to contain the generated random bytes.

offset - the starting index in out to consider. This method does nothing if this parameter is not within 0 and out.length.

length - the maximum number of required random bytes. This method does nothing if this parameter is less than 1.

Throws:

IllegalStateException - if the instance is not yet initialised.

LimitReachedException - if this instance has reached its theoretical limit for generating non-repetitive pseudo-random data.

isInitialised

public boolean isInitialised()

clone

public abstract Object clone()

Description copied from interface: IRandom

Returns a clone copy of this instance.

Specified by:

clone in interface IRandom

Overrides:

clone in class Object

Returns:

a clone copy of this instance.

setup

public abstract void setup(Map attributes)

fillBlock

public abstract void fillBlock()
                        throws LimitReachedException

Throws:

LimitReachedException