Re: Reimplementing ASIOs

From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2024-07-16 19:35:23

On 16/07/2024 20:12, Christian Mazakas via Boost wrote:

> Sounds sick. You should paste a link if you can.

Employer's code, not mine. They'll be open sourcing everything next 
year, and unlike most promises of that kind in this situation they 
really will have to.

> Check this out: https://github.com/cmazakas/fiona
> 
> It's a take two on Asio that aims to fix all of the things I found
> annoying about it. Namely, my implementation here actually supports
> foreign awaitables because I just copied Rust's Waker approach.

I'm all for foreign awaitables support. Everything I do in C++ 
coroutines allows arbitrary awaitable types. A library has no business 
imposing what users can use there in my opinion, and Klemens of course 
took that boat right out to sea with Boost.Cobalt.

But ... I don't agree with hard coding in C++ coroutines personally. I 
think Sender-Receiver (before WG21 corrupted it) is a better design 
choice here especially as if within a C++ coroutine you can co_await and 
it'll "just work" without any extra effort. Here's what I did:

- Free function `co_initialize()` connects a Sender to an appropriate 
C++ coroutine resuming Receiver and launches it.

- Free function `initialize()` is a customisation point for how to 
launch connected S&R states.

- Free function `connect()` is a customisation point for how to generate 
connected S&R states.

So, as an example, you might `connect()` a Sender to a 
`boost::fiber::future` and that would connect to a Receiver which sets 
the future's promise on completion. As you can see, this is very 
flexible, and you can completely avoid all malloc-free cycles entirely 
which C++ coroutines make it hard to do.

(My new 100% C executor has runtime switchable context switchers, so you 
can configure a C++ coroutine context switcher if you want. It being C 
it just isn't compile time enforced nor checkable, that's all)

I see in your github repo you are benching against ASIO. What kinds of 
results did you get?

Niall