CLI app: readLine and structured concurrency

[kabiroberai]

I haven’t tested this out but you might have luck with FileHandle.standardInput.bytes.lines, which is an AsyncSequence.

bytes | Apple Developer Documentation

I agree that Swift Concurrency as it stands today leaves a lot to be desired in the IO realm; for example, the above API solves reading asynchronously but there’s no FileHandle API for async backpressure-enabled writing, and if you’re dealing with non-POSIX (or Win32) IO APIs you’re still on your own. Also very relevant to this discussion is another concurrent thread (pun intended) here on the Swift Forums:

Blocking I/O and concurrency

I'm working on using Swift in an embedded device that talks to a peripheral over SPI, which only has a blocking API on Linux (at least, without writing a kernel driver). SPI supports full duplex which is accessible using ioctl(2) instead of read(2) or write(2), although the latter are also supported for half-duplex operation. The rest of my code is asynchronous, using async/await and dispatch queues depending on its vintage. Ideally I'd like to poll SPI at, say, 30Hz in a thread and exchange …