Package org.apache.commons.rng.core

Class BaseProvider

java.lang.Object

org.apache.commons.rng.core.BaseProvider

All Implemented Interfaces:

RestorableUniformRandomProvider, UniformRandomProvider

Direct Known Subclasses:

IntProvider, LongProvider

public abstract class BaseProvider
extends java.lang.Object
implements RestorableUniformRandomProvider

Base class with default implementation for common methods.

Constructor Summary

Constructors

Constructor	Description
BaseProvider()

Method Summary

Modifier and Type	Method	Description
protected void	checkIndex(int min, int max, int index)	Checks whether index is in the range [min, max].
protected void	checkStateSize(byte[] state, int expected)	Deprecated. Method is used internally and should be made private in some future release.
protected byte[]	composeStateInternal(byte[] state, byte[] parentState)	Combine parent and subclass states.
protected void	fillState(int[] state, int[] seed)	Simple filling procedure.
protected void	fillState(long[] state, long[] seed)	Simple filling procedure.
protected byte[]	getStateInternal()	Creates a snapshot of the RNG state.
int	nextInt(int n)	Generates an int value between 0 (inclusive) and the specified value (exclusive).
long	nextLong(long n)	Generates a long value between 0 (inclusive) and the specified value (exclusive).
void	restoreState(RandomProviderState state)	Restores the state of a generator.
RandomProviderState	saveState()	Saves the state of a generator.
protected void	setStateInternal(byte[] state)	Resets the RNG to the given state.
protected byte[][]	splitStateInternal(byte[] state, int localStateLength)	Splits the given state into a part to be consumed by the caller in order to restore its local state, while the reminder is passed to the parent class.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.commons.rng.UniformRandomProvider

nextBoolean, nextBytes, nextBytes, nextDouble, nextFloat, nextInt, nextLong

Constructor Detail

BaseProvider

public BaseProvider()

Method Detail

nextInt

public int nextInt(int n)

Generates an int value between 0 (inclusive) and the specified value (exclusive).

Specified by:

nextInt in interface UniformRandomProvider

Parameters:

n - Bound on the random number to be returned. Must be positive.

Returns:

a random int value between 0 (inclusive) and n (exclusive).

nextLong

public long nextLong(long n)

Generates a long value between 0 (inclusive) and the specified value (exclusive).

Specified by:

nextLong in interface UniformRandomProvider

Parameters:

n - Bound on the random number to be returned. Must be positive.

Returns:

a random long value between 0 (inclusive) and n (exclusive).

saveState

public RandomProviderState saveState()

Saves the state of a generator.

Specified by:

saveState in interface RestorableUniformRandomProvider

Returns:

the current state of this instance. It is a value that can subsequently be passed to the restore method.

restoreState

public void restoreState(RandomProviderState state)

Restores the state of a generator.

Specified by:

restoreState in interface RestorableUniformRandomProvider

Parameters:

state - State which this instance will be set to. This parameter would usually have been obtained by a call to saveState performed either on the same object as this one, or an object of the exact same class.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

composeStateInternal

protected byte[] composeStateInternal(byte[] state,
                                      byte[] parentState)

Combine parent and subclass states. This method must be called by all subclasses in order to ensure that state can be restored in case some of it is stored higher up in the class hierarchy. I.e. the body of the overridden getStateInternal(), will end with a statement like the following:

  
    return composeStateInternal(state,
                                super.getStateInternal());
  
 

where state is the state needed and defined by the class where the method is overridden.

Parameters:

state - State of the calling class.

parentState - State of the calling class' parent.

Returns:

the combined state. Bytes that belong to the local state will be stored at the beginning of the resulting array.

splitStateInternal

protected byte[][] splitStateInternal(byte[] state,
                                      int localStateLength)

Splits the given state into a part to be consumed by the caller in order to restore its local state, while the reminder is passed to the parent class. I.e. the body of the overridden setStateInternal(byte[]), will contain statements like the following:

  
    final byte[][] s = splitState(state, localStateLength);
    // Use "s[0]" to recover the local state.
    super.setStateInternal(s[1]);
  
 

where state is the combined state of the calling class and of all its parents.

Parameters:

state - State. The local state must be stored at the beginning of the array.

localStateLength - Number of elements that will be consumed by the locally defined state.

Returns:

the local state (in slot 0) and the parent state (in slot 1).

Throws:

java.lang.IllegalStateException - if state.length < localStateLength.

getStateInternal

protected byte[] getStateInternal()

Creates a snapshot of the RNG state.

Returns:

the internal state.

setStateInternal

protected void setStateInternal(byte[] state)

Resets the RNG to the given state.

Parameters:

state - State (previously obtained by a call to getStateInternal()).

Throws:

java.lang.IllegalStateException - if the size of the given array is not consistent with the state defined by this class.

See Also:

checkStateSize(byte[],int)

fillState

protected void fillState(int[] state,
                         int[] seed)

Simple filling procedure. It will

1. fill the beginning of state by copying min(seed.length, state.length) elements from seed,
2. set all remaining elements of state with non-zero values (even if seed.length < state.length).

Parameters:

state - State. Must be allocated.

seed - Seed. Cannot be null.

fillState

protected void fillState(long[] state,
                         long[] seed)

Simple filling procedure. It will

1. fill the beginning of state by copying min(seed.length, state.length) elements from seed,
2. set all remaining elements of state with non-zero values (even if seed.length < state.length).

Parameters:

state - State. Must be allocated.

seed - Seed. Cannot be null.

checkStateSize

@Deprecated
protected void checkStateSize(byte[] state,
                              int expected)

Deprecated.

Method is used internally and should be made private in some future release.

Checks that the state has the expected size.

Parameters:

state - State.

expected - Expected length of state array.

Throws:

java.lang.IllegalStateException - if state.length < expected.

checkIndex

protected void checkIndex(int min,
                          int max,
                          int index)

Checks whether index is in the range [min, max].

Parameters:

min - Lower bound.

max - Upper bound.

index - Value that must lie within the [min, max] interval.

Throws:

java.lang.IndexOutOfBoundsException - if index is not within the [min, max] interval.