TEventCount | Unreal Engine 5.7 Documentation

A type of event that avoids missed notifications by maintaining a notification count.

This type of event is suited to waiting on another thread conditionally. Typical usage looks similar to this example: FEventCount Event; std::atomic CurrentValue = 0;

On the waiting thread: FEventCountToken Token = Event.PrepareWait(); if (CurrentValue < TargetValue) { Event.Wait(Token); }

On the notifying thread: if (++CurrentValue == TargetValue) { Event.Notify(); }

Acquiring a token before checking the condition avoids a race because Wait returns immediately when the token no longer matches the notification count.


Name	TEventCount
Type	class
Header File	/Engine/Source/Runtime/Core/Public/Async/EventCount.h
Include Path	#include "Async/EventCount.h"

Syntax

template<typename CounterType>  
class TEventCount

Constructors

Name	Remarks	Include Path	Unreal Specifiers
constexpr TEventCount ()		Async/EventCount.h
TEventCount ( const TEventCount& )		Async/EventCount.h

Variables

Protected

Name	Type	Remarks	Include Path	Unreal Specifiers
Count	std::atomic< CounterType >		Async/EventCount.h

Functions

Public

Name	Remarks	Include Path
void Notify ()	Notifies all waiting threads.	Async/EventCount.h
void NotifyWeak ()	Notifies all waiting threads.	Async/EventCount.h
TEventCountToken< CounterType > PrepareWait ()	Prepare to wait.	Async/EventCount.h
void Wait ( TEventCountToken< CounterType > Compare )	Wait until the event is notified. Returns immediately if notified since the token was acquired.	Async/EventCount.h
bool WaitFor ( TEventCountToken< CounterType > Compare, FMonotonicTimeSpan WaitTime )	Wait until the event is notified. Returns immediately if notified since the token was acquired.	Async/EventCount.h
bool WaitUntil ( TEventCountToken< CounterType > Compare, FMonotonicTimePoint WaitTime )	Wait until the event is notified. Returns immediately if notified since the token was acquired.	Async/EventCount.h

Operators

Name	Remarks	Include Path	Unreal Specifiers
TEventCount & operator= ( const TEventCount& )		Async/EventCount.h

Navigation