Package org.apache.commons.rng.simple.internal

Class SeedUtils

java.lang.Object

org.apache.commons.rng.simple.internal.SeedUtils

final class SeedUtils
extends Object

Utility for creating seeds.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static class	SeedUtils.UnsignedByteProvider	Provider of unsigned 8-bit integers.

Field Summary

Fields

Modifier and Type	Field	Description
private static final byte[]	HEX_DIGIT_ARRAY	The 16 hex digits in an array.
private static final int	MOD_09	The modulus 256 % 9.
private static final int	MOD_10	The modulus 256 % 10.
private static final int	MOD_11	The modulus 256 % 11.
private static final int	MOD_12	The modulus 256 % 12.
private static final int	MOD_13	The modulus 256 % 13.
private static final int	MOD_14	The modulus 256 % 14.
private static final int	MOD_15	The modulus 256 % 15.

Constructor Summary

Constructors

Modifier	Constructor	Description
private	SeedUtils()	Class contains only static methods.

Method Summary

Modifier and Type	Method	Description
private static int	copyToOutput(byte[] digits, int bits, int upper, int lower)	Copy the lower hex digit to the output bits.
(package private) static int	createIntHexPermutation(UniformRandomProvider rng)	Creates an int containing a permutation of 8 hex digits chosen from 16.
(package private) static long	createLongHexPermutation(UniformRandomProvider rng)	Creates a long containing a permutation of 8 hex digits chosen from 16 in the upper and lower 32-bits.
private static int	createUpperBitsHexPermutation(SeedUtils.UnsignedByteProvider provider)	Creates a int containing a permutation of 8 hex digits chosen from 16.
private static int	nextUnsignedByteInRange(SeedUtils.UnsignedByteProvider provider, int threshold, int n)	Get the next unsigned byte in the range [0,n) rejecting any over-represented sample value using the pre-computed modulus.

Methods inherited from class java.lang.Object

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

Field Details

MOD_09

private static final int MOD_09

The modulus 256 % 9.

See Also:

• Constant Field Values

MOD_10

private static final int MOD_10

The modulus 256 % 10.

See Also:

• Constant Field Values

MOD_11

private static final int MOD_11

The modulus 256 % 11.

See Also:

• Constant Field Values

MOD_12

private static final int MOD_12

The modulus 256 % 12.

See Also:

• Constant Field Values

MOD_13

private static final int MOD_13

The modulus 256 % 13.

See Also:

• Constant Field Values

MOD_14

private static final int MOD_14

The modulus 256 % 14.

See Also:

• Constant Field Values

MOD_15

private static final int MOD_15

The modulus 256 % 15.

See Also:

• Constant Field Values

HEX_DIGIT_ARRAY

private static final byte[] HEX_DIGIT_ARRAY

The 16 hex digits in an array.

Constructor Details

SeedUtils

private SeedUtils()

Class contains only static methods.

Method Details

createIntHexPermutation

static int createIntHexPermutation(UniformRandomProvider rng)

Creates an int containing a permutation of 8 hex digits chosen from 16.

Parameters:

rng - Source of randomness.

Returns:

hex digit permutation.

createLongHexPermutation

static long createLongHexPermutation(UniformRandomProvider rng)

Creates a long containing a permutation of 8 hex digits chosen from 16 in the upper and lower 32-bits.

Parameters:

rng - Source of randomness.

Returns:

hex digit permutation.

createUpperBitsHexPermutation

private static int createUpperBitsHexPermutation(SeedUtils.UnsignedByteProvider provider)

Creates a int containing a permutation of 8 hex digits chosen from 16.

Parameters:

provider - Source of randomness.

Returns:

hex digit permutation.

nextUnsignedByteInRange

private static int nextUnsignedByteInRange(SeedUtils.UnsignedByteProvider provider,
 int threshold,
 int n)

Get the next unsigned byte in the range [0,n) rejecting any over-represented sample value using the pre-computed modulus.

This algorithm is as per Lemire (2019) adapted for 8-bit arithmetic.

Parameters:

provider - Provider of bytes.

threshold - Modulus threshold 256 % n.

n - Upper range (exclusive)

Returns:

Value.

See Also:

• Lemire (2019): Fast Random Integer Generation in an Interval

copyToOutput

private static int copyToOutput(byte[] digits,
 int bits,
 int upper,
 int lower)

Copy the lower hex digit to the output bits. Swap the upper hex digit into the lower position. This is equivalent to a swap step of a Fisher-Yates shuffle on an array but the output of the shuffle are written to the bits.

Parameters:

digits - Digits.

bits - Bits.

upper - Upper index.

lower - Lower index.

Returns:

Updated bits.