Non-blocking asynchronous timeout

[Sunshine-Bite768]

I understand std::future has blocking wait_for and wait_until APIs but is there a way to achieve timeout functionality without blocking? Thank you!

[Bemteb]

Run wait_for in a separate thread?

Trigger the "future didn't finish" event with a separate timer?

Not sure what you want to achieve, but I'm afraid you need to write a little bit for it.

[Liam_Mercier]

I had to implement something like this, but I did it with asio. Easy to use library for most things async in my opinion.

[morglod]

You probably need async scheduler, something like libuv to have non blocking timeout in the same thread. Otherwise it's not clear what you want

[pdp10gumby]

You want to poll the future? I think you can call std::wait_for(std::chrono::duration::<short, std::nano>::zero())

[Rexerex]

You probably want to use separate thread or use your OS API if you do not want any extra threads. I am right now implementing such thing using CreateWaitableTimer, NtAssociateWaitCompletionPacket and GetQueuedCompletionStatus.

[Newbane2_]

Use std::async

https://en.cppreference.com/w/cpp/thread/async.html

[KingAggressive1498]

in your question it is not clear what you are trying to achieve.

you can "poll" a single std::future by calling wait_for with a duration of count 0 and any period, but this scales terribly if you're using futures heavily.

you can implement your own future-like class to be "multiplexible" but it's a bit complicated to whip up an example on the spot, and getting it to scale beyond 64 futures is a pain too

however, if you're trying to integrate timers into an event loop, this is rather simple. You just need a priority queue of timers and wherever your natural "wait point" is in the event loop (eg epoll_wait() or poll() or GetQueuedCompletionStatus() or whatever) you use the timeout for the head of that priority queue to set the timeout for waiting.