Split it up into a number of targeted modules for each purpose, for example loop
data, I/O sources, timeouts, and channels. No actual change is intended to be
part of this commit.
This commit contains a few refactorings, but the major goal is to remove the
`Arc` that's stored inside of each `ReadinessStream` and `Scheduled` slot in the
event loop. The original purpose of this `Arc` was to share the I/O object among
the concrete handle itself and the event loop. The event loop would then change
how the socket is registered over time and then deregister it when it gets a
"shutdown request".
Nowadays, however, once an I/O object is registered with the event loop it's
never updated. Additionally, we don't actually need to call `deregister` but can
rather just instead close the I/O object itself and let the kernel/event loop
take care of the cleanup. All we need to do on deregistering is free up the slab
entry.
The major result of this commit is that I/O objects no longer need to be `Sync`
(as they're not stored in an `Arc`). Instead they just need to be `Send +
'static` as one might otherwise expect.
Along the way this also refactors a few pieces here and there to make more sense
in this new scheme. The `ReadinessStream` type now has a type parameter
indicating an owned reference to the I/O object it wraps. This can be accessed
via the `get_ref` and `get_mut` methods. Additionally I/O tokens on the event
loop are now a full-fledged `IoToken` type which we can change in the future if
we need to.
This type acts for a handle to storage of non-`Send` data. The handle itself is
sendable across threads and is therefore suitable for storage in a `Future`.
This data uses communication internally and a new method on `Task` to ensure
that when the data needs to be accessed the future will find its way to the
right thread.
More on this type coming soon!
Alex Crichton