It's really awesome that this was a complete reimplementation with no Linux code, and it's additionally awesome that this is available for both XP/2k3 and ReactOS. I will have to try it out on one of my older machines :-)
It'd be so fracking sweet to see filesystems follow this pattern. If we could re-use the file system logic, but apply it to windows or fuse or Linux or wasm linearly-addressed-storage, that would allow such intensely cool forms of portability/reuse & bending/hacking.
Wonder how well it scales to larger applications. Ie is there a codesize where io-less becomes too difficult? Perhaps performance concerns? Hmm
Also, quite the opposite, it's *easier* to design a library this way because it's strictly less code the library needs to contain. Specifically in Rust it also has the advantage that the library becomes agnostic to sync vs async I/O since that's handled by the library user. Correspondingly, it is slightly harder for the library user to use such a library, but it's usually just a matter of writing a tiny generic wrapper around the network socket type to connect it to the library functions.
That said, a lot of what’s actually hard about IO is the error/fault handling, imposing timeouts and backoffs and all that jazz. At a certain point I’d wonder if extracting this out to a separate interface might obscure the execution flow in some of these scenarios.
Application-level timeout/backoff handling is always scary to me, because I don't know how to make robust tests for it. I wonder if you couldn't use the same I/O-less approach, and split the logic out into pure functions that take the time passed/error state/... as value arguments, instead of measuring the physical time using OS APIs. It's probably not something for reusable libraries, but it could still be a nice benefit to be able to unit test in detail.
Then you can test the decision function trivially, the re-try function by mocking the action and decision, and the action function itself without back off interfering.
That’s what you suggested, just saying that I did that in a Python API client with the backoff library and the result is pretty neat.
https://sans-io.readthedocs.io/
I did it for one of my Rust projects back in 2018 https://github.com/Arnavion/k8s-openapi/commit/9a4fbb718b119... , and it's older than that in Python land.
Cory Benfield - Building Protocol Libraries The Right Way https://youtu.be/7cC3_jGwl_U
But isn't this just good old inversion of control, modularity with maybe some inspiration from Functional Programming. Or even more generally, good Software architecture and engineering?
Anyway, I'm very happy to see this, the more code is architected this way, the better for all our industry.
Not to join in too much on the "but we already had this!" bandwagon ... but actually to join in the bandwagon - we had these sorts of patterns in C 20 years ago. I worked with a TLS implementation like this sometime around 2005.
Either you work with buffer-in/buffer-out types of scenario, or you register callbacks to do the real IO.
It's a great pattern and means that you can do stuff like change transport mechanism, or put in proxying, or whatever you want really, without having to change the library.
With embedded C stuff it was also relatively common to handle memory allocation this way - buy in a library that does whatever proprietrary thing you need from a vendor, then register your custom allocator with it so when it needed heap memory, you could provide that in line with whatever platform restrictions you had going.
ReactOS is supposed to be API-compatible with Windows, so that's not too surprising.