scattered notes toward a real API

[srrrse]

I think the Submission future might not be suitable as the building block for a type that implements AsyncBufRead.. it's too focused on ownership, representing a single concrete event. Probably want to pull out the polling and cancelling mechanism so that they can be used on a type that can be polled again and again.

I'm imagining a type called Ring that could work similar to smol's Async. It would have APIs like this:

pub struct Ring<IO, ..> {
    ...
}

impl<IO: Read + AsRawFd> AsyncBufRead for Ring<IO, ...> {
   ...
}

impl<IO: Read + AsRawFd> AsyncRead for Ring<IO, ...> {
   ... // defined in terms of AsyncBufRead
}

Additional parameters for buffer management and reactor management (hopefully with good default types).

So you'd have Ring<File> and Ring<TcpStream> etc.

[srrrse]

Closed by #11