Exposing `AsRawHandle` on `Registry` about mio HOT 5 CLOSED

Do you need this for something specifically? Because as far as I'm aware we currently expose types for all support kinds of fds and operations supported by AFD/IOCP (as Mio uses it).

from mio.

Primarily, I'd want to be able to wait for readiness of the IOCP outside mio.

There's an idea I'm experimenting with at the moment. I have a completion IO lib that should be able to be plugged into different kinds of executors.

You have a future that issues I/O requests, and a "backend" that processes them. You have 3 options for how the backend is implemented:

1. Backend itself polls the future to completion - you get a full async executor here.
2. Backend works on the side as a secondary thread or a blocking task - now you possibly run into thread communication bottlenecks.
3. Backend exposes a handle that can be then polled for readiness by the parent executor.

I don't have hard numbers, but 3 seems like the most effective solution. On Linux, if you have a io_uring queue, you can plug its fd in a epoll system, or even another io_uring queue, and wait for multiple queues simultaneously.

I'm not so knowledgeable in windows side of things, and from what I saw, while you technically can WaitForSingleObject on a IOCP handle, it's undocumented, unsupported, and doesn't have stable behavior, but I think you can wait for it with GetQueuedCompletionStatus, without removing events from the queue by passing null lpOverlapped (unless I'm misreding the docs). So I thought exposing raw handle to iocp would make sense.

from mio.

Okay, no, I'm reading more into this and this is not what I need, and exposing the handle to iocp is potentially dangerous, because the code assumes a valid pointer is an instance of Overlapped. What I think I'd need is ability to set hEvent of OVERLAPPED, and basically having such structure set for everything sent to IOCP.

from mio.

It might be worth it to just add an option to wait on a waitable handle to mio.

from mio.

It might be worth it to just add an option to wait on a waitable handle to mio.

I don't remember the details, but if I remember correctly using the handle directly combined with the way Mio uses is quite difficult to use correctly as @h33p also found out, so I rather not add it with a good use case for it.

from mio.