MAmax_k·Nov 13, 2022
I love C++ coroutines! (The spec has a few warts and gives me enough reasons to hate them, like not being able by definition to properly inline nested coroutine calls, but I love them anyway.)
I've written several libraries for integrating C++ coroutines with stuff like io_uring, libcurl, c_ares, libpq and more. For example, this is how using my io_uring/coroutine library can be used:
https://github.com/CM4all/libcommon/blob/master/test/co/RunC...
auto result = co_await CoReadTextFile(queue, AT_FDCWD, path);
co_await CoWrite(queue, STDOUT_FILENO, result.data(), result.size(), 0);
This opens a file, stats it, reads its contents, and writes it to stdout - all 4 I/O operations are asynchronous with io_uring.
Source code for CoReadTextFile() which is also a coroutine: https://github.com/CM4all/libcommon/blob/master/src/io/uring...
Sample
Read the rest
code for libpq: https://github.com/CM4all/libcommon/blob/master/test/co/RunC... and c_ares https://github.com/CM4all/libcommon/blob/master/test/co/RunC... and libcurl https://github.com/CM4all/libcommon/blob/master/test/curl/Ru...
I wrote all of this for proprietary applications at dayjob, but the core library is open source, as is much of my dayjob code. The I/O event loop this integrates with is also used by several open source projects I maintain, e.g. the Music Player Daemon (https://github.com/MusicPlayerDaemon/MPD/tree/master/src/eve...) which can also take advantage of io_uring, though not (yet) with coroutines, only "classic" non-blocking I/O.
My code is optimized for low-overhead; the very core doesn't even use std::function because I fear its implicit heap allocations. Long ago, I used boost::asio (which also integrates well with coroutines) but didn't like it because it was too bloated for me.
I've rarely seen other nerds talk about C++ coroutines, and never about integrating them with io_uring, made me thinking I'm the only one. But maybe all the others just don't write/blog about it - I never did either...
That's why this blog was a refreshing read for me, thanks.