This commit adds a general-purpose method for querying the readiness of a
`PollEvented` type. This new method, `poll_ready`, takes a blanket `mio::Ready`
and tests if any part of it is ready. The purpose of this is to expose
platform-specific events through `PollReady` such as `hup` and `error` events
other than just the platform-agnostic readable/writable events.
The semanatics of this method are:
* The `poll_ready` function takes a mask, and the return value is either
`Async::Ready` with a subset of these events that are ready or `None` if none
of them are ready.
* There can be up to two tasks blocked on a `PollEvented`, so we need to pick
which one is suitable for these new events. Currently all events are routed to
the `read` task unless the writable bit is set. This is mostly only relevant
for multi-task usage or if you're manually calling `need_read` and/or
`need_write`, and hopefully the docs will cover this now.
Typically this happens automatically as the `E` in `PollEvented<E>` is an owned
reference (e.g. a `TcpStream`) where dropping that will close the resource,
automatically unregistering it from the event loop. In some situations, however,
this isn't always the case, so the deregistering needs to happen manually.
* Handle -> Remote
* Pinned -> Handle
All APIs now take a `&Handle` by default and in general can return an immediate
`io::Result` instead of an `IoFuture`. This reflects how most usage will likely
be done through handles rather than remotes, and also all previous functionality
can be recovered with a `oneshot` plus `Remote::spawn`.
Closes#15
Alex Crichton