Package io.github.pr0methean.betterrandom.seed

Enum DefaultSeedGenerator

java.lang.Object

java.lang.Enum<DefaultSeedGenerator>

io.github.pr0methean.betterrandom.seed.DefaultSeedGenerator

All Implemented Interfaces:

SeedGenerator, Serializable, Comparable<DefaultSeedGenerator>

public enum DefaultSeedGenerator
extends Enum<DefaultSeedGenerator>
implements SeedGenerator

Seed generator that is the default for the program where it is running. PRNGs that are serialized using one program's default and deserialized in another program will use the latter's default seed generator, which is part of the static state. This means a PRNG's serial form won't specify a particular seed generator if it was constructed without specifying one.

The default implementation maintains multiple strategies for seed generation and will delegate to the best one available at any moment. It uses, in order of preference:

1. DevRandomSeedGenerator with 128-byte buffer
2. RandomDotOrgSeedGenerator.DELAYED_RETRY with 625-byte buffer
3. SecureRandomSeedGenerator with no buffer

Author:

Daniel Dyer

Enum Constant Summary

Enum Constants

Enum Constant	Description
DEFAULT_SEED_GENERATOR	Singleton instance.

Field Summary

Fields inherited from interface io.github.pr0methean.betterrandom.seed.SeedGenerator

EMPTY_SEED

Method Summary

Modifier and Type	Method	Description
void	generateSeed(byte[] output)	Generates a seed value for a random number generator in an existing array.
byte[]	generateSeed(int length)	Generates and returns a seed value for a random number generator as a new array.
static SeedGenerator	get()	Returns the current delegate used by this class's singleton instance.
boolean	isWorthTrying()	Returns true if we cannot determine quickly (i.e.
static void	set(SeedGenerator delegate)	Sets the default seed generator (a delegate used by this class's singleton instance).
static DefaultSeedGenerator	valueOf(String name)	Returns the enum constant of this type with the specified name.
static DefaultSeedGenerator[]	values()	Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

DEFAULT_SEED_GENERATOR

public static final DefaultSeedGenerator DEFAULT_SEED_GENERATOR

Singleton instance.

Method Detail

values

public static DefaultSeedGenerator[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (DefaultSeedGenerator c : DefaultSeedGenerator.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static DefaultSeedGenerator valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null

get

public static SeedGenerator get()

Returns the current delegate used by this class's singleton instance.

Returns:

the current delegate

set

public static void set(SeedGenerator delegate)

Sets the default seed generator (a delegate used by this class's singleton instance).

Parameters:

delegate - the new delegate

generateSeed

public void generateSeed(byte[] output)
                  throws SeedException

Generates a seed value for a random number generator in an existing array.

Generates a seed by trying each of the available strategies in turn until one succeeds. Tries the most suitable strategy first and eventually degrades to the least suitable (but guaranteed to work) strategy.

Specified by:

generateSeed in interface SeedGenerator

Parameters:

output - The array that is to be populated with the seed.

Throws:

SeedException - If a seed cannot be generated for any reason.

generateSeed

public byte[] generateSeed(int length)
                    throws SeedException

Description copied from interface: SeedGenerator

Generates and returns a seed value for a random number generator as a new array.

Specified by:

generateSeed in interface SeedGenerator

Parameters:

length - The length of the seed to generate (in bytes).

Returns:

A byte array containing the seed data.

Throws:

SeedException - If a seed cannot be generated for any reason.

isWorthTrying

public boolean isWorthTrying()

Returns true if we cannot determine quickly (i.e. without I/O calls) that this SeedGenerator would throw a SeedException if generateSeed(int) or generateSeed(byte[]) were being called right now.

Specified by:

isWorthTrying in interface SeedGenerator

Returns:

true if this SeedGenerator will get as far as an I/O call or other slow operation in attempting to generate a seed immediately.