ion::Latch Class Reference

Single use thread-coordination mechanism modelled after std::latch. More...

#include <ion/latch.hpp>

Public Member Functions
constexpr	Latch (std::ptrdiff_t expected) noexcept
	Construct latch with expected number of arrivals.
void	CountDown (std::ptrdiff_t n=1) noexcept
	Decrements expected count by n without waiting.
bool	TryWait () const noexcept
	Equivalent to Wait().
void	Wait () const noexcept
	Block until expected count reaches zero.
void	ArriveAndWait (std::ptrdiff_t n=1) noexcept
	Decrements expected count by n and waits.
Latch requires stable address and is neither copyable or movable.
	Latch (Latch const &)=delete
Latch &	operator= (Latch const &)=delete

Static Public Member Functions
static constexpr std::ptrdiff_t	Max () noexcept

Detailed Description

Single use thread-coordination mechanism modelled after std::latch.

Modelled after C++20 std::latch but does not perform system calls or yields and as such is more suitable in a real-time environment. Notable differences:

• Methods are noexcept

Latch has two states:

1. arrival, when threads fetch and decrement the expected count
2. departure, when all threads have arrived and will depart.

After departure the only allowed operation is to delete the latch.

Memory Order

All calls to ArriveAndWait() or CountDown() synchronizes-with any calls to ArriveAndWait() or Wait().

Thread Safety

thread-safe

Constructor & Destructor Documentation

Latch()

ion::Latch::Latch ( std::ptrdiff_t expected )

inlineexplicitconstexprnoexcept

Construct latch with expected number of arrivals.

Parameters

expected

Expected number of arrivals.

Member Function Documentation

ArriveAndWait()

void ion::Latch::ArriveAndWait ( std::ptrdiff_t n = 1 )

inlinenoexcept

Decrements expected count by n and waits.

Precondition

n must be > 0 and <= the expected count.

Parameters

n	the value by which the internal counter is decreased.

CountDown()

void ion::Latch::CountDown ( std::ptrdiff_t n = 1 )

inlinenoexcept

Decrements expected count by n without waiting.

Parameters

n	the value by which the internal counter is decreased.

Max()

std::ptrdiff_t ion::Latch::Max ( )

inlinestaticconstexprnoexcept

Returns

Maximum possible value for expected count.

TryWait()

bool ion::Latch::TryWait ( ) const

inlinenoexcept

Equivalent to Wait().

Note

Method is only provided for conceptual compatibility of std::latch.

Returns

true