gnu.java.security.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.

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.
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<K,V> 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<K,V> attributes)

Methods inherited from class java.lang.Object

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

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.
Throws:
IndexOutOfBoundsException - If offset, length, or offset+length is out of bounds.

clone

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

fillBlock

public abstract void fillBlock()
            throws LimitReachedException

init

public void init(Map<K,V> 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.
Throws:
IllegalArgumentException - if at least one of the defined name/ value pairs contains invalid data.

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:
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

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:
IllegalStateException - if the instance is not yet initialised.
LimitReachedException - if this instance has reached its theoretical limit for generating non-repetitive pseudo-random data.

setup

public abstract void setup(Map<K,V> attributes)

BasePRNG.java -- Copyright (C) 2001, 2002, 2006 Free Software Foundation, Inc. This file is a 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 of the License, 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; if not, write to the Free Software Foundation, Inc., 51 Franklin St, 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.