#include <userver/engine/single_consumer_event.hpp>

Detailed Description

A multiple-producers, single-consumer event.

Definition at line 19 of file single_consumer_event.hpp.

Classes
struct	NoAutoReset

Public Member Functions
	SingleConsumerEvent () noexcept
	Creates an event that resets automatically on retrieval.

	SingleConsumerEvent (NoAutoReset) noexcept
	Creates an event that does not reset automatically.

	SingleConsumerEvent (const SingleConsumerEvent &)=delete

	SingleConsumerEvent (SingleConsumerEvent &&)=delete

SingleConsumerEvent &	operator= (const SingleConsumerEvent &)=delete

SingleConsumerEvent &	operator= (SingleConsumerEvent &&)=delete

bool	IsAutoReset () const noexcept

bool	WaitForEvent ()
	Waits until the event is in a signaled state.

template<typename Clock , typename Duration >
bool	WaitForEventFor (std::chrono::duration< Clock, Duration >)

template<typename Clock , typename Duration >
bool	WaitForEventUntil (std::chrono::time_point< Clock, Duration >)

bool	WaitForEventUntil (Deadline)

void	Reset () noexcept

void	Send ()

bool	IsReady () const noexcept
	Returns `true` iff already signaled. Never resets the signal.

Member Function Documentation

◆ IsAutoReset()

bool engine::SingleConsumerEvent::IsAutoReset ( ) const

noexcept

Returns: whether this event resets automatically on retrieval

◆ Reset()

void engine::SingleConsumerEvent::Reset ( )

noexcept

Resets the signal flag. Guarantees at least 'acquire' and 'release' memory ordering. Must only be called by the waiting task.

◆ Send()

void engine::SingleConsumerEvent::Send ( )

Sets the signal flag and wakes a coroutine that waits on it (if any). If the signal flag is already set, does nothing.

The waiter is allowed to destroy the SingleConsumerEvent immediately after exiting WaitForEvent, ONLY IF the wait succeeded. Otherwise a concurrent task may call Send on a destroyed SingleConsumerEvent. Here is an example of this situation:

  engine::TaskWithResult<void> sender;
  {
    engine::SingleConsumerEvent event;
    sender = engine::AsyncNoSpan([&event] { event.Send(); });
    // will be woken up by 'Send()' above
    const bool success = event.WaitForEvent();
 
    if (!success) {
      // If the waiting failed due to deadline or cancellation, we must somehow
      // wait until the parallel task does Send (or prevent the parallel task
      // from ever doing Send) before destroying the SingleConsumerEvent.
      sender.SyncCancel();
    }
 
    // 'event' is destroyed here. Note that 'Send' might continue executing, but
    // it will still complete safely.
  }

◆ WaitForEvent()

bool engine::SingleConsumerEvent::WaitForEvent ( )

Waits until the event is in a signaled state.

If the event is auto-resetting, clears the signal flag upon waking up. If already in a signaled state, does the same without sleeping.

If we the waiting failed (the event did not signal), because the optional deadline is expired or the current task is cancelled, returns false.

Returns: whether the event signaled

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

◆ WaitForEventFor()

template<typename Clock , typename Duration >

bool engine::SingleConsumerEvent::WaitForEventFor ( std::chrono::duration< Clock, Duration > duration )

Definition at line 88 of file single_consumer_event.hpp.

◆ WaitForEventUntil()

template<typename Clock , typename Duration >

bool engine::SingleConsumerEvent::WaitForEventUntil ( std::chrono::time_point< Clock, Duration > time_point )

Definition at line 94 of file single_consumer_event.hpp.

The documentation for this class was generated from the following file:

userver/engine/single_consumer_event.hpp