Finding Stakker-compatible crates

Here are some considerations to help decide whether a crate is usable with Stakker:

• Non-blocking: If it is going to be called directly from an actor, the crate must never block or sleep, because that would hold up all the work of the whole thread.

• Data processing only: If it just does data processing when called, and doesn't require any I/O or timers or anything, then that would be straightforward to use. (For example regex crate.)

• Event-loop independent: If it requires I/O but says it can run on top of any event loop, then that is a very good sign. Even crates that may appear dependent on a particular I/O system (mio, Tokio, etc) might still be usable if the protocol handling can be called independently. (For example tungstenite)

• Event-loop providers: If a crate provides an event loop (or the basis for an event loop), for example SDL or mio, then Stakker can almost certainly be run on top of it, so long as the underlying crate can guarantee that Stakker is always called from the same thread.

Where a required crate can't be run on top of Stakker, for example a crate that depends on Tokio, then you can still run it in the same process by running Tokio in another thread and communicating with the Stakker thread via channels.

A possible future extension to Stakker would be to add a simple async/await executor, one that allows a subset of async/await crates to run, for example ones that can process futures or streams passed from the actor runtime, and that don't require direct I/O themselves.