Some contexts, like EC2, have `Instant::now` as a relatively expensive function
to call. To help amortize the cost of this function this commit exposes a new
function on `Interval` and `Timeout` to pass in the assumed current time.
The `consume_queue` function can be relatively slow for an empty queue (the fast
path) so optimize this a bit with a preflight check that should just touch a few
atomics.
My slab bump in #246 added a potential new panic in Core's Inner's
`cancel_timeout`.
Thankfully, the only way `cancel_timeout` can be called is from
TimeoutToken's `cancel_timeout`, which is crate-internal only and is
only called from Timeout's and Interval's drop fn's.
This change simply adds new clarifying documentation around
TokenTimeout's cancel_timeout to "future proof" anybody looking to use
cancel_timeout directly (not just on drop).
This patch disables various Unix-specific platform features that are
not enabled on Fuchsia. It also updates the mio version to 0.6.10,
which is the first release that supports Fuchsia.
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.
Using Linux's `epoll(7)` interface, a `EPOLLHUP` condition is
signalled for the reading end of a pipe or socket when the other end
is closed for writing. This may happen in combination with `EPOLLIN`
being signalled (if further data is available for reading), or with
`EPOLLIN`.
If `EPOLLHUP` is signalled without `EPOLLIN` it indicates an immediate
EOF condition, which will result in the next `read()` suceeding with 0
bytes read. It is thus not required to handle `EPOLLHUP` specially in
the reader, but we need to indicate readiness upon encountering it.
Looking at the `kqueue` and `windows` mio backends, they seem to be
turn a detected EOF and connection reset into `mio::Ready::hup()`
events, so it may be reasonable to speculate that this change is an
improvement for these platforms as well.
Fixes#117.
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.
Alex Gaynor