pw_random

Oveview

Main docs: https://pigweed.dev/pw_random.

Classes
class	pw::random::RandomGenerator
class	pw::random::XorShiftStarRng64

Functions
template<class T >
void	pw::random::RandomGenerator::GetInt (T &dest)
template<class T >
void	pw::random::RandomGenerator::GetInt (T &dest, const T &exclusive_upper_bound)
virtual void	pw::random::RandomGenerator::Get (ByteSpan dest)=0
virtual void	pw::random::RandomGenerator::InjectEntropyBits (uint32_t data, uint_fast8_t num_bits)=0
void	pw::random::RandomGenerator::InjectEntropy (ConstByteSpan data)
	Injects entropy into the pool byte-by-byte.
	pw::random::XorShiftStarRng64::XorShiftStarRng64 (uint64_t initial_seed)
void	pw::random::XorShiftStarRng64::Get (ByteSpan dest) final
void	pw::random::XorShiftStarRng64::InjectEntropyBits (uint32_t data, uint_fast8_t num_bits) final

Function Documentation

Get() [1/2]

void pw::random::XorShiftStarRng64::Get ( ByteSpan  dest )

inlinefinalvirtual

Populates the destination buffer with a randomly generated value.

This generator uses entropy-seeded PRNG to never exhaust its random number pool.

Implements pw::random::RandomGenerator.

Get() [2/2]

virtual void pw::random::RandomGenerator::Get ( ByteSpan  dest )

pure virtual

Populates the destination buffer with a randomly generated value.

Parameters

[out]

dest

The destination buffer.

Implemented in pw::random::XorShiftStarRng64.

GetInt()

template<class T >

void pw::random::RandomGenerator::GetInt ( T &  dest, const T &  exclusive_upper_bound  )

inline

Calculates a uniformly distributed random number in the range [0, exclusive_upper_bound).

This avoids modulo biasing. Uniformity is only guaranteed if the underlying generator generates uniform data. Uniformity is achieved by generating new random numbers until one is generated in the desired range (with optimizations).

Parameters

[out]	dest	The destination to populate the random number into.
[in]	exclusive_upper_bound	The largest number that can be populated into dest, exclusive.

InjectEntropyBits() [1/2]

void pw::random::XorShiftStarRng64::InjectEntropyBits ( uint32_t  data, uint_fast8_t  num_bits  )

inlinefinalvirtual

Injects entropy by rotating the state by the number of entropy bits before XORing the entropy with the current state.

This technique ensures that seeding the random value with single bits will progressively fill the state with more entropy.

Implements pw::random::RandomGenerator.

InjectEntropyBits() [2/2]

virtual void pw::random::RandomGenerator::InjectEntropyBits ( uint32_t  data, uint_fast8_t  num_bits  )

pure virtual

Injects entropy into the pool.

Parameters

[in]	data	Up to 32 bits of random entropy data.
[in]	num_bits	The number of bits of entropy. If less than 32, entropy is assumed to be stored in the least significant bits of data.

Implemented in pw::random::XorShiftStarRng64.