Support stdin/stdout (io-std feature) in WASM

[Timmmm]

Support stdin/stdout (io-std feature) in WASM

[Darksonn]

I suppose they probably work with #6510.

But it sounds like we could have a different implementation of this for wasm.

[FrankReh]

@Timmmm Are you asking about this in terms of getting tokio to support wasip2 down the road where a Pollable could be used by the tokio guest to recognize when data was available on stdin? Or do the semantics of wasip1 already provide a way to create a Future that is tied to the state of the stdin being ready to read?

Tokio's Stdin has to support the AsyncRead trait and I don't see how that would be done given just the original WASI definition which is now called WASI Preview 1. But I'm no expert and almost asked about this on the ByteAlliance Zulip channel but thought I would ask here first.

[Darksonn]

Ah, yes, please be aware that we only support preview 1 right now. So if this is a feature for some newer version of wasm, then this cannot happen until after #6323.

[Timmmm]

Ah yeah I didn't notice this is only in preview 2. Guess it will have to wait!

[FrankReh]

Yes, I'm eagerly watching how pollables are added to tokio for Preview 2 myself. I think a lot of the current-thread runtime can be made to work within a Wasm Component environment.