diff options
Diffstat (limited to 'tokio/src/io/driver/registration.rs')
| -rw-r--r-- | tokio/src/io/driver/registration.rs | 222 |
1 files changed, 222 insertions, 0 deletions
diff --git a/tokio/src/io/driver/registration.rs b/tokio/src/io/driver/registration.rs new file mode 100644 index 00000000..db9afdd7 --- /dev/null +++ b/tokio/src/io/driver/registration.rs @@ -0,0 +1,222 @@ +use crate::io::driver::{Direction, Handle, Interest, ReadyEvent, ScheduledIo}; +use crate::util::slab; + +use mio::event::Source; +use std::io; +use std::task::{Context, Poll}; + +cfg_io_driver! { + /// Associates an I/O resource with the reactor instance that drives it. + /// + /// A registration represents an I/O resource registered with a Reactor such + /// that it will receive task notifications on readiness. This is the lowest + /// level API for integrating with a reactor. + /// + /// The association between an I/O resource is made by calling [`new`]. Once + /// the association is established, it remains established until the + /// registration instance is dropped. + /// + /// A registration instance represents two separate readiness streams. One + /// for the read readiness and one for write readiness. These streams are + /// independent and can be consumed from separate tasks. + /// + /// **Note**: while `Registration` is `Sync`, the caller must ensure that + /// there are at most two tasks that use a registration instance + /// concurrently. One task for [`poll_read_ready`] and one task for + /// [`poll_write_ready`]. While violating this requirement is "safe" from a + /// Rust memory safety point of view, it will result in unexpected behavior + /// in the form of lost notifications and tasks hanging. + /// + /// ## Platform-specific events + /// + /// `Registration` also allows receiving platform-specific `mio::Ready` + /// events. These events are included as part of the read readiness event + /// stream. The write readiness event stream is only for `Ready::writable()` + /// events. + /// + /// [`new`]: method@Self::new + /// [`poll_read_ready`]: method@Self::poll_read_ready` + /// [`poll_write_ready`]: method@Self::poll_write_ready` + #[derive(Debug)] + pub(crate) struct Registration { + /// Handle to the associated driver. + handle: Handle, + + /// Reference to state stored by the driver. + shared: slab::Ref<ScheduledIo>, + } +} + +unsafe impl Send for Registration {} +unsafe impl Sync for Registration {} + +// ===== impl Registration ===== + +impl Registration { + /// Registers the I/O resource with the default reactor, for a specific + /// `Interest`. `new_with_interest` should be used over `new` when you need + /// control over the readiness state, such as when a file descriptor only + /// allows reads. This does not add `hup` or `error` so if you are + /// interested in those states, you will need to add them to the readiness + /// state passed to this function. + /// + /// # Return + /// + /// - `Ok` if the registration happened successfully + /// - `Err` if an error was encountered during registration + pub(crate) fn new_with_interest_and_handle( + io: &mut impl Source, + interest: Interest, + handle: Handle, + ) -> io::Result<Registration> { + let shared = if let Some(inner) = handle.inner() { + inner.add_source(io, interest)? + } else { + return Err(io::Error::new( + io::ErrorKind::Other, + "failed to find event loop", + )); + }; + + Ok(Registration { handle, shared }) + } + + /// Deregisters the I/O resource from the reactor it is associated with. + /// + /// This function must be called before the I/O resource associated with the + /// registration is dropped. + /// + /// Note that deregistering does not guarantee that the I/O resource can be + /// registered with a different reactor. Some I/O resource types can only be + /// associated with a single reactor instance for their lifetime. + /// + /// # Return + /// + /// If the deregistration was successful, `Ok` is returned. Any calls to + /// `Reactor::turn` that happen after a successful call to `deregister` will + /// no longer result in notifications getting sent for this registration. + /// + /// `Err` is returned if an error is encountered. + pub(crate) fn deregister(&mut self, io: &mut impl Source) -> io::Result<()> { + let inner = match self.handle.inner() { + Some(inner) => inner, + None => return Err(io::Error::new(io::ErrorKind::Other, "reactor gone")), + }; + inner.deregister_source(io) + } + + pub(crate) fn clear_readiness(&self, event: ReadyEvent) { + self.shared.clear_readiness(event); + } + + // Uses the poll path, requiring the caller to ensure mutual exclusion for + // correctness. Only the last task to call this function is notified. + pub(crate) fn poll_read_ready(&self, cx: &mut Context<'_>) -> Poll<io::Result<ReadyEvent>> { + self.poll_ready(cx, Direction::Read) + } + + // Uses the poll path, requiring the caller to ensure mutual exclusion for + // correctness. Only the last task to call this function is notified. + pub(crate) fn poll_write_ready(&self, cx: &mut Context<'_>) -> Poll<io::Result<ReadyEvent>> { + self.poll_ready(cx, Direction::Write) + } + + // Uses the poll path, requiring the caller to ensure mutual exclusion for + // correctness. Only the last task to call this function is notified. + pub(crate) fn poll_read_io<R>( + &self, + cx: &mut Context<'_>, + f: impl FnMut() -> io::Result<R>, + ) -> Poll<io::Result<R>> { + self.poll_io(cx, Direction::Read, f) + } + + // Uses the poll path, requiring the caller to ensure mutual exclusion for + // correctness. Only the last task to call this function is notified. + pub(crate) fn poll_write_io<R>( + &self, + cx: &mut Context<'_>, + f: impl FnMut() -> io::Result<R>, + ) -> Poll<io::Result<R>> { + self.poll_io(cx, Direction::Write, f) + } + + /// Polls for events on the I/O resource's `direction` readiness stream. + /// + /// If called with a task context, notify the task when a new event is + /// received. + fn poll_ready( + &self, + cx: &mut Context<'_>, + direction: Direction, + ) -> Poll<io::Result<ReadyEvent>> { + // Keep track of task budget + let coop = ready!(crate::coop::poll_proceed(cx)); + let ev = ready!(self.shared.poll_readiness(cx, direction)); + + if self.handle.inner().is_none() { + return Poll::Ready(Err(gone())); + } + + coop.made_progress(); + Poll::Ready(Ok(ev)) + } + + fn poll_io<R>( + &self, + cx: &mut Context<'_>, + direction: Direction, + mut f: impl FnMut() -> io::Result<R>, + ) -> Poll<io::Result<R>> { + loop { + let ev = ready!(self.poll_ready(cx, direction))?; + + match f() { + Ok(ret) => { + return Poll::Ready(Ok(ret)); + } + Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => { + self.clear_readiness(ev); + } + Err(e) => return Poll::Ready(Err(e)), + } + } + } +} + +fn gone() -> io::Error { + io::Error::new(io::ErrorKind::Other, "IO driver has terminated") +} + +cfg_io_readiness! { + impl Registration { + pub(crate) async fn readiness(&self, interest: Interest) -> io::Result<ReadyEvent> { + use std::future::Future; + use std::pin::Pin; + + let fut = self.shared.readiness(interest); + pin!(fut); + + crate::future::poll_fn(|cx| { + if self.handle.inner().is_none() { + return Poll::Ready(Err(io::Error::new(io::ErrorKind::Other, "reactor gone"))); + } + + Pin::new(&mut fut).poll(cx).map(Ok) + }).await + } + + pub(crate) async fn async_io<R>(&self, interest: Interest, mut f: impl FnMut() -> io::Result<R>) -> io::Result<R> { + loop { + let event = self.readiness(interest).await?; + + match f() { + Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => { + self.clear_readiness(event); + } + x => return x, + } + } + } + } +} |