For the latest news and information visit
The GNU Crypto project

gnu.crypto.prng
Class BasePRNG

java.lang.Object
  extended by gnu.crypto.prng.BasePRNG
All Implemented Interfaces:
IRandom, Cloneable
Direct Known Subclasses:
ARCFour, CSPRNG, Fortuna, Fortuna.Generator, ICMGenerator, MDGenerator, PBKDF2, UMacGenerator

public abstract class BasePRNG
extends Object
implements IRandom

An abstract class to facilitate implementing PRNG algorithms.

Version:
$Revision: 1.12 $

Field Summary
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
protected BasePRNG(String name)
          Trivial constructor for use by concrete subclasses.
 
Method Summary
 void addRandomByte(byte b)
          Supplement, or possibly replace, the random state of this PRNG with a random byte.
 void addRandomBytes(byte[] buffer)
          Supplement, or possibly replace, the random state of this PRNG with a sequence of new random bytes.
 void addRandomBytes(byte[] buffer, int offset, int length)
          Supplement, or possibly replace, the random state of this PRNG with a sequence of new random bytes.
 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)
           
 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)
               throws IllegalStateException,
                      LimitReachedException
Throws:
IllegalStateException
LimitReachedException

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.

addRandomByte

public void addRandomByte(byte b)
Description copied from interface: IRandom

Supplement, or possibly replace, the random state of this PRNG with a random byte.

Implementations are not required to implement this method in any meaningful way; this may be a no-operation, and implementations may throw an UnsupportedOperationException.

Specified by:
addRandomByte in interface IRandom
Parameters:
b - The byte to add.

addRandomBytes

public void addRandomBytes(byte[] buffer)
Description copied from interface: IRandom

Supplement, or possibly replace, the random state of this PRNG with a sequence of new random bytes.

Implementations are not required to implement this method in any meaningful way; this may be a no-operation, and implementations may throw an UnsupportedOperationException.

Specified by:
addRandomBytes in interface IRandom
Parameters:
buffer - The buffer of new random bytes to add.

addRandomBytes

public void addRandomBytes(byte[] buffer,
                           int offset,
                           int length)
Description copied from interface: IRandom

Supplement, or possibly replace, the random state of this PRNG with a sequence of new random bytes.

Implementations are not required to implement this method in any meaningful way; this may be a no-operation, and implementations may throw an UnsupportedOperationException.

Specified by:
addRandomBytes in interface IRandom
Parameters:
buffer - The buffer of new random bytes to add.
offset - The offset from whence to begin reading random bytes.
length - The number of random bytes to add.

isInitialised

public boolean isInitialised()

clone

public Object clone()
             throws CloneNotSupportedException
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.
Throws:
CloneNotSupportedException

setup

public abstract void setup(Map attributes)

fillBlock

public abstract void fillBlock()
                        throws LimitReachedException
Throws:
LimitReachedException

For the latest news and information visit
The GNU Crypto project

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