nimcoro

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This is a little proof-of-concept prject to see if I can get Lua-style coroutines semantics in Nim, and use this to build an alternative async implementation. It's built on very low level primitives only: the posix lib for sockets and poll(), and a small wrapper around the posix ucontext functions.

There's a few moving parts in this project:

• coro.nim: This implements simple coroutines based on ucontext. This are basically Lua-style coroutines, but because of Nims static typing it is hard to implement the Lua way of passing data through yield() and resume(). For now I've chosen not to pass data at all, as there are enough other ways to do that outside of the core coroutine

• evq.nim: This is a very basic and naive event loop implementation: register file descriptors with read or write events and a proc, and your proc will be called back when the file descriptor is ready.

• io.nim: Here the above two modules come together to create very friendly async I/O. Look at the waitForFd() proc to see what is happening.

• main.nim: This example creates a listening TCP socket which can handle multiple clients, which are all run inside coroutines.

Note that the curent coro implementation confuses Nim's GC, run with --gc:arc!