gnu.crypto.prng

Class BasePRNG

Implemented Interfaces:
Cloneable, IRandom
Known Direct 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

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.

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

void
addRandomBytes(byte[] buffer)
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.

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.

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

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)

Field Details

buffer

protected byte[] buffer
A temporary buffer to serve random bytes.

initialised

protected boolean initialised
Indicate if this instance has already been initialised or not.

name

protected String name
The canonical name prefix of the PRNG algorithm.

ndx

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

Constructor Details

BasePRNG

protected BasePRNG(String name)
Trivial constructor for use by concrete subclasses.
Parameters:
name - the canonical name of this instance.

Method Details

addRandomByte

public void addRandomByte(byte b)
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)
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:

addRandomBytes

public 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.

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:
offset - The offset from whence to begin reading random bytes.
length - The number of random bytes to add.

clone

public Object clone()
            throws CloneNotSupportedException
Returns a clone copy of this instance.
Specified by:
clone in interface IRandom
Returns:
a clone copy of this instance.

fillBlock

public abstract void fillBlock()
            throws LimitReachedException

init

public void init(Map attributes)
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.

isInitialised

public boolean isInitialised()

name

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

nextByte

public byte nextByte()
            throws IllegalStateException,
                   LimitReachedException
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:
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

nextBytes

public void nextBytes(byte[] out,
                      int offset,
                      int length)
            throws IllegalStateException,
                   LimitReachedException
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:
LimitReachedException - if this instance has reached its theoretical limit for generating non-repetitive pseudo-random data.

setup

public abstract void setup(Map attributes)

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