SC::AsyncEventLoop Struct Reference

Asynchronous I/O (files, sockets, timers, processes, fs events, threads wake-up) (see Async) AsyncEventLoop pushes all AsyncRequest derived classes to I/O queues in the OS. More...

#include <Async.h>

Classes
struct	Options
	Options given to AsyncEventLoop::create. More...

Public Types
using	InternalOpaque = OpaqueObject< InternalDefinition >

Public Member Functions
Result	create (Options options=Options())
	Creates the event loop kernel object. More...
Result	close ()
	Closes the event loop kernel object. More...
Result	run ()
	Blocks until there are no more active queued requests, dispatching all completions. More...
Result	runOnce ()
	Blocks until at least one request proceeds, ensuring forward progress, dispatching all completions. More...
Result	runNoWait ()
	Process active requests if any, dispatching their completions, or returns immediately without blocking. More...
Result	submitRequests (AsyncKernelEvents &kernelEvents)
	Submits all queued async requests. More...
Result	blockingPoll (AsyncKernelEvents &kernelEvents)
	Blocks until at least one event happens, ensuring forward progress, without executing completions. More...
Result	dispatchCompletions (AsyncKernelEvents &kernelEvents)
	Invokes completions for the AsyncKernelEvents collected by a call to AsyncEventLoop::blockingPoll. More...
Result	wakeUpFromExternalThread (AsyncLoopWakeUp &wakeUp)
	Wake up the event loop from a thread different than the one where run() is called (and potentially blocked). More...
Result	wakeUpFromExternalThread ()
	Wake up the event loop from a thread different than the one where run() is called (and potentially blocked) More...
Result	createAsyncTCPSocket (SocketFlags::AddressFamily family, SocketDescriptor &outDescriptor)
	Helper to creates a TCP socket with AsyncRequest flags of the given family (IPV4 / IPV6). More...
Result	associateExternallyCreatedTCPSocket (SocketDescriptor &outDescriptor)
	Associates a TCP Socket created externally (without using createAsyncTCPSocket) with the eventLoop. More...
Result	associateExternallyCreatedFileDescriptor (FileDescriptor &outDescriptor)
	Associates a File descriptor created externally with the eventLoop. More...
Time::HighResolutionCounter	getLoopTime () const
	Get Loop time. More...

Static Public Member Functions
static bool	tryLoadingLiburing ()
	Check if liburing is loadable (only on Linux) More...

Friends
struct	AsyncRequest
struct	AsyncFileWrite
struct	AsyncFileRead

Detailed Description

Asynchronous I/O (files, sockets, timers, processes, fs events, threads wake-up) (see Async) AsyncEventLoop pushes all AsyncRequest derived classes to I/O queues in the OS.

See also

AsyncEventLoopMonitor can be used to integrate AsyncEventLoop with a GUI event loop

Basic lifetime for an event loop is:

AsyncEventLoop eventLoop;
SC_TRY(eventLoop.create()); // Create OS specific queue handles
// ...
// Add all needed AsyncRequest
// ...
SC_TRY(eventLoop.run());
// ...
// Here all AsyncRequest have either finished or have been stopped
// ...
SC_TRY(eventLoop.close()); // Free OS specific queue handles

Member Function Documentation

associateExternallyCreatedFileDescriptor()

Result SC::AsyncEventLoop::associateExternallyCreatedFileDescriptor

(

FileDescriptor &

outDescriptor

)

Associates a File descriptor created externally with the eventLoop.

associateExternallyCreatedTCPSocket()

Result SC::AsyncEventLoop::associateExternallyCreatedTCPSocket

(

SocketDescriptor &

outDescriptor

)

Associates a TCP Socket created externally (without using createAsyncTCPSocket) with the eventLoop.

blockingPoll()

Result SC::AsyncEventLoop::blockingPoll

(

AsyncKernelEvents &

kernelEvents

)

Blocks until at least one event happens, ensuring forward progress, without executing completions.

It's one of the three building blocks of AsyncEventLoop::runOnce allowing co-operation of AsyncEventLoop within another event loop (for example a GUI event loop or another IO event loop).

One possible example of such integration with a GUI event loop could:

• Call AsyncEventLoop::submitRequests on the GUI thread to queue some requests
• Call AsyncEventLoop::blockingPoll on a secondary thread, storying AsyncKernelEvents
• Wake up the GUI event loop from the secondary thread after AsyncEventLoop::blockingPoll returns
• Call AsyncEventLoop:dispatchCompletions on the GUI event loop to dispatch callbacks on GUI thread
• Repeat all steps

Waiting on requests blocks the current thread with 0% CPU utilization.

Parameters

kernelEvents

Mandatory parameter to store kernel IO events WITHOUT running their completions. In that case user is expected to run completions passing it to AsyncEventLoop::dispatchCompletions.

See also

AsyncEventLoop::submitRequests sends async requests to kernel before calling blockingPoll

AsyncEventLoop::dispatchCompletions invokes callbacks associated with kernel events after blockingPoll

close()

Result SC::AsyncEventLoop::close

(

)

Closes the event loop kernel object.

create()

Result SC::AsyncEventLoop::create

(

Options

options = Options()

)

Creates the event loop kernel object.

createAsyncTCPSocket()

Result SC::AsyncEventLoop::createAsyncTCPSocket	(	SocketFlags::AddressFamily	family,
		SocketDescriptor &	outDescriptor
	)

Helper to creates a TCP socket with AsyncRequest flags of the given family (IPV4 / IPV6).

It also automatically registers the socket with the eventLoop (associateExternallyCreatedTCPSocket)

dispatchCompletions()

Result SC::AsyncEventLoop::dispatchCompletions

(

AsyncKernelEvents &

kernelEvents

)

Invokes completions for the AsyncKernelEvents collected by a call to AsyncEventLoop::blockingPoll.

This is typically done when user wants to pool for events on a thread (calling AsyncEventLoop::blockingPoll) and dispatch the callbacks on another thread (calling AsyncEventLoop::dispatchCompletions). The typical example would be integrating AsyncEventLoop with a GUI event loop.

See also

AsyncEventLoop::blockingPoll for a description on how to integrate AsyncEventLoop with another event loop

getLoopTime()

Time::HighResolutionCounter SC::AsyncEventLoop::getLoopTime

(

)

const

Get Loop time.

run()

Result SC::AsyncEventLoop::run

(

)

Blocks until there are no more active queued requests, dispatching all completions.

It's useful for applications where the eventLoop is the only (or the main) loop. One example could be a console based app doing socket IO or a web server. Waiting on kernel events blocks the current thread with 0% CPU utilization.

See also

AsyncEventLoop::blockingPoll to integrate the loop with a GUI event loop

runNoWait()

Result SC::AsyncEventLoop::runNoWait

(

)

Process active requests if any, dispatching their completions, or returns immediately without blocking.

It's useful for game-like applications where the event loop runs every frame and one would like to check and dispatch its I/O callbacks in-between frames. This call allows poll-checking I/O without blocking.

See also

AsyncEventLoop::blockingPoll to integrate the loop with a GUI event loop

runOnce()

Result SC::AsyncEventLoop::runOnce

(

)

Blocks until at least one request proceeds, ensuring forward progress, dispatching all completions.

It's useful for application where it's needed to run some idle work after every IO event. Waiting on requests blocks the current thread with 0% CPU utilization.

This function is a shortcut invoking async event loop building blocks:

• AsyncEventLoop::submitRequests
• AsyncEventLoop::blockingPoll
• AsyncEventLoop::dispatchCompletions

  See also

  AsyncEventLoop::blockingPoll for a description on how to integrate AsyncEventLoop with another event loop

submitRequests()

Result SC::AsyncEventLoop::submitRequests

(

AsyncKernelEvents &

kernelEvents

)

Submits all queued async requests.

An AsyncRequest becomes queued after user calls its specific AsyncRequest::start method.

See also

AsyncEventLoop::blockingPoll for a description on how to integrate AsyncEventLoop with another event loop

tryLoadingLiburing()

static bool SC::AsyncEventLoop::tryLoadingLiburing ( )

static

Check if liburing is loadable (only on Linux)

Returns

true if liburing has been loaded, false otherwise (and on any non-Linux os)

wakeUpFromExternalThread() [1/2]

Result SC::AsyncEventLoop::wakeUpFromExternalThread

(

)

Wake up the event loop from a thread different than the one where run() is called (and potentially blocked)

wakeUpFromExternalThread() [2/2]

Result SC::AsyncEventLoop::wakeUpFromExternalThread

(

AsyncLoopWakeUp &

wakeUp

)

Wake up the event loop from a thread different than the one where run() is called (and potentially blocked).

The parameter is an AsyncLoopWakeUp that must have been previously started (with AsyncLoopWakeUp::start).

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

• Async.h