mio/poll.rs
1#[cfg(all(
2 unix,
3 not(mio_unsupported_force_poll_poll),
4 not(any(
5 target_os = "aix",
6 target_os = "espidf",
7 target_os = "nuttx",
8 target_os = "fuchsia",
9 target_os = "haiku",
10 target_os = "hermit",
11 target_os = "hurd",
12 target_os = "nto",
13 target_os = "vita",
14 target_os = "cygwin",
15 target_os = "horizon"
16 )),
17))]
18use std::os::fd::{AsFd, AsRawFd, BorrowedFd, RawFd};
19#[cfg(all(debug_assertions, not(any(target_os = "wasi", target_os = "horizon"))))]
20use std::sync::atomic::{AtomicBool, Ordering};
21#[cfg(all(debug_assertions, not(any(target_os = "wasi", target_os = "horizon"))))]
22use std::sync::Arc;
23use std::time::Duration;
24use std::{fmt, io};
25
26use crate::{event, sys, Events, Interest, Token};
27
28/// Polls for readiness events on all registered values.
29///
30/// `Poll` allows a program to monitor a large number of [`event::Source`]s,
31/// waiting until one or more become "ready" for some class of operations; e.g.
32/// reading and writing. An event source is considered ready if it is possible
33/// to immediately perform a corresponding operation; e.g. [`read`] or
34/// [`write`].
35///
36/// To use `Poll`, an `event::Source` must first be registered with the `Poll`
37/// instance using the [`register`] method on its associated `Register`,
38/// supplying readiness interest. The readiness interest tells `Poll` which
39/// specific operations on the handle to monitor for readiness. A `Token` is
40/// also passed to the [`register`] function. When `Poll` returns a readiness
41/// event, it will include this token. This associates the event with the
42/// event source that generated the event.
43///
44/// [`event::Source`]: ./event/trait.Source.html
45/// [`read`]: ./net/struct.TcpStream.html#method.read
46/// [`write`]: ./net/struct.TcpStream.html#method.write
47/// [`register`]: struct.Registry.html#method.register
48///
49/// # Examples
50///
51/// A basic example -- establishing a `TcpStream` connection.
52///
53#[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
54#[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
55/// # use std::error::Error;
56/// # fn main() -> Result<(), Box<dyn Error>> {
57/// use mio::{Events, Poll, Interest, Token};
58/// use mio::net::TcpStream;
59///
60/// use std::net::{self, SocketAddr};
61///
62/// // Bind a server socket to connect to.
63/// let addr: SocketAddr = "127.0.0.1:0".parse()?;
64/// let server = net::TcpListener::bind(addr)?;
65///
66/// // Construct a new `Poll` handle as well as the `Events` we'll store into
67/// let mut poll = Poll::new()?;
68/// let mut events = Events::with_capacity(1024);
69///
70/// // Connect the stream
71/// let mut stream = TcpStream::connect(server.local_addr()?)?;
72///
73/// // Register the stream with `Poll`
74/// poll.registry().register(&mut stream, Token(0), Interest::READABLE | Interest::WRITABLE)?;
75///
76/// // Wait for the socket to become ready. This has to happen in a loop to
77/// // handle spurious wakeups.
78/// loop {
79/// poll.poll(&mut events, None)?;
80///
81/// for event in &events {
82/// if event.token() == Token(0) && event.is_writable() {
83/// // The socket connected (probably, it could still be a spurious
84/// // wakeup)
85/// return Ok(());
86/// }
87/// }
88/// }
89/// # }
90/// ```
91///
92/// # Portability
93///
94/// Using `Poll` provides a portable interface across supported platforms as
95/// long as the caller takes the following into consideration:
96///
97/// ### Spurious events
98///
99/// [`Poll::poll`] may return readiness events even if the associated
100/// event source is not actually ready. Given the same code, this may
101/// happen more on some platforms than others. It is important to never assume
102/// that, just because a readiness event was received, that the associated
103/// operation will succeed as well.
104///
105/// If operation fails with [`WouldBlock`], then the caller should not treat
106/// this as an error, but instead should wait until another readiness event is
107/// received.
108///
109/// ### Draining readiness
110///
111/// Once a readiness event is received, the corresponding operation must be
112/// performed repeatedly until it returns [`WouldBlock`]. Unless this is done,
113/// there is no guarantee that another readiness event will be delivered, even
114/// if further data is received for the event source.
115///
116/// [`WouldBlock`]: std::io::ErrorKind::WouldBlock
117///
118/// ### Readiness operations
119///
120/// The only readiness operations that are guaranteed to be present on all
121/// supported platforms are [`readable`] and [`writable`]. All other readiness
122/// operations may have false negatives and as such should be considered
123/// **hints**. This means that if a socket is registered with [`readable`]
124/// interest and either an error or close is received, a readiness event will
125/// be generated for the socket, but it **may** only include `readable`
126/// readiness. Also note that, given the potential for spurious events,
127/// receiving a readiness event with `read_closed`, `write_closed`, or `error`
128/// doesn't actually mean that a `read` on the socket will return a result
129/// matching the readiness event.
130///
131/// In other words, portable programs that explicitly check for [`read_closed`],
132/// [`write_closed`], or [`error`] readiness should be doing so as an
133/// **optimization** and always be able to handle an error or close situation
134/// when performing the actual read operation.
135///
136/// [`readable`]: ./event/struct.Event.html#method.is_readable
137/// [`writable`]: ./event/struct.Event.html#method.is_writable
138/// [`error`]: ./event/struct.Event.html#method.is_error
139/// [`read_closed`]: ./event/struct.Event.html#method.is_read_closed
140/// [`write_closed`]: ./event/struct.Event.html#method.is_write_closed
141///
142/// ### Registering handles
143///
144/// Unless otherwise noted, it should be assumed that types implementing
145/// [`event::Source`] will never become ready unless they are registered with
146/// `Poll`.
147///
148/// For example:
149///
150#[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
151#[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
152/// # use std::error::Error;
153/// # use std::net;
154/// # fn main() -> Result<(), Box<dyn Error>> {
155/// use mio::{Poll, Interest, Token};
156/// use mio::net::TcpStream;
157/// use std::net::SocketAddr;
158/// use std::time::Duration;
159/// use std::thread;
160///
161/// let address: SocketAddr = "127.0.0.1:0".parse()?;
162/// let listener = net::TcpListener::bind(address)?;
163/// let mut sock = TcpStream::connect(listener.local_addr()?)?;
164///
165/// thread::sleep(Duration::from_secs(1));
166///
167/// let poll = Poll::new()?;
168///
169/// // The connect is not guaranteed to have started until it is registered at
170/// // this point
171/// poll.registry().register(&mut sock, Token(0), Interest::READABLE | Interest::WRITABLE)?;
172/// # Ok(())
173/// # }
174/// ```
175///
176/// ### Dropping `Poll`
177///
178/// When the `Poll` instance is dropped it may cancel in-flight operations for
179/// the registered [event sources], meaning that no further events for them may
180/// be received. It also means operations on the registered event sources may no
181/// longer work. It is up to the user to keep the `Poll` instance alive while
182/// registered event sources are being used.
183///
184/// [event sources]: ./event/trait.Source.html
185///
186/// ### Accessing raw fd/socket/handle
187///
188/// Mio makes it possible for many types to be converted into a raw file
189/// descriptor (fd, Unix), socket (Windows) or handle (Windows). This makes it
190/// possible to support more operations on the type than Mio supports, for
191/// example it makes [mio-aio] possible. However accessing the raw fd is not
192/// without it's pitfalls.
193///
194/// Specifically performing I/O operations outside of Mio on these types (via
195/// the raw fd) has unspecified behaviour. It could cause no more events to be
196/// generated for the type even though it returned `WouldBlock` (in an operation
197/// directly accessing the fd). The behaviour is OS specific and Mio can only
198/// guarantee cross-platform behaviour if it can control the I/O.
199///
200/// [mio-aio]: https://github.com/asomers/mio-aio
201///
202/// *The following is **not** guaranteed, just a description of the current
203/// situation!* Mio is allowed to change the following without it being considered
204/// a breaking change, don't depend on this, it's just here to inform the user.
205/// Currently the kqueue and epoll implementation support direct I/O operations
206/// on the fd without Mio's knowledge. Windows however needs **all** I/O
207/// operations to go through Mio otherwise it is not able to update it's
208/// internal state properly and won't generate events.
209///
210/// ### Polling without registering event sources
211///
212///
213/// *The following is **not** guaranteed, just a description of the current
214/// situation!* Mio is allowed to change the following without it being
215/// considered a breaking change, don't depend on this, it's just here to inform
216/// the user. On platforms that use epoll, kqueue or IOCP (see implementation
217/// notes below) polling without previously registering [event sources] will
218/// result in sleeping forever, only a process signal will be able to wake up
219/// the thread.
220///
221/// On WASM/WASI this is different as it doesn't support process signals,
222/// furthermore the WASI specification doesn't specify a behaviour in this
223/// situation, thus it's up to the implementation what to do here. As an
224/// example, the wasmtime runtime will return `EINVAL` in this situation, but
225/// different runtimes may return different results. If you have further
226/// insights or thoughts about this situation (and/or how Mio should handle it)
227/// please add you comment to [pull request#1580].
228///
229/// [event sources]: crate::event::Source
230/// [pull request#1580]: https://github.com/tokio-rs/mio/pull/1580
231///
232/// # Implementation notes
233///
234/// `Poll` is backed by the selector provided by the operating system.
235///
236/// | OS | Selector |
237/// |---------------|-----------|
238/// | Android | [epoll] |
239/// | DragonFly BSD | [kqueue] |
240/// | FreeBSD | [kqueue] |
241/// | iOS | [kqueue] |
242/// | illumos | [epoll] |
243/// | Linux | [epoll] |
244/// | NetBSD | [kqueue] |
245/// | OpenBSD | [kqueue] |
246/// | Solaris | [event ports] |
247/// | Windows | [IOCP] |
248/// | macOS | [kqueue] |
249///
250/// On all supported platforms, socket operations are handled by using the
251/// system selector. Platform specific extensions (e.g. [`SourceFd`]) allow
252/// accessing other features provided by individual system selectors. For
253/// example, Linux's [`signalfd`] feature can be used by registering the FD with
254/// `Poll` via [`SourceFd`].
255///
256/// On all platforms except windows, a call to [`Poll::poll`] is mostly just a
257/// direct call to the system selector. However, [IOCP] uses a completion model
258/// instead of a readiness model. In this case, `Poll` must adapt the completion
259/// model Mio's API. While non-trivial, the bridge layer is still quite
260/// efficient. The most expensive part being calls to `read` and `write` require
261/// data to be copied into an intermediate buffer before it is passed to the
262/// kernel.
263///
264/// [epoll]: https://man7.org/linux/man-pages/man7/epoll.7.html
265/// [event ports]: https://docs.oracle.com/cd/E88353_01/html/E37843/port-create-3c.html
266/// [kqueue]: https://www.freebsd.org/cgi/man.cgi?query=kqueue&sektion=2
267/// [IOCP]: https://docs.microsoft.com/en-us/windows/win32/fileio/i-o-completion-ports
268/// [`signalfd`]: https://man7.org/linux/man-pages/man2/signalfd.2.html
269/// [`SourceFd`]: unix/struct.SourceFd.html
270/// [`Poll::poll`]: struct.Poll.html#method.poll
271pub struct Poll {
272 registry: Registry,
273}
274
275/// Registers I/O resources.
276pub struct Registry {
277 selector: sys::Selector,
278 /// Whether this selector currently has an associated waker.
279 #[cfg(all(debug_assertions, not(any(target_os = "wasi", target_os = "horizon"))))]
280 has_waker: Arc<AtomicBool>,
281}
282
283impl Poll {
284 cfg_os_poll! {
285 /// Return a new `Poll` handle.
286 ///
287 /// This function will make a syscall to the operating system to create
288 /// the system selector. If this syscall fails, `Poll::new` will return
289 /// with the error.
290 ///
291 /// close-on-exec flag is set on the file descriptors used by the selector to prevent
292 /// leaking it to executed processes.
293 ///
294 /// See [struct] level docs for more details.
295 ///
296 /// [struct]: struct.Poll.html
297 ///
298 /// # Examples
299 ///
300 /// ```
301 /// # use std::error::Error;
302 /// # fn main() -> Result<(), Box<dyn Error>> {
303 /// use mio::{Poll, Events};
304 /// use std::time::Duration;
305 ///
306 /// let mut poll = match Poll::new() {
307 /// Ok(poll) => poll,
308 /// Err(e) => panic!("failed to create Poll instance; err={:?}", e),
309 /// };
310 ///
311 /// // Create a structure to receive polled events
312 /// let mut events = Events::with_capacity(1024);
313 ///
314 /// // Wait for events, but none will be received because no
315 /// // `event::Source`s have been registered with this `Poll` instance.
316 /// poll.poll(&mut events, Some(Duration::from_millis(500)))?;
317 /// assert!(events.is_empty());
318 /// # Ok(())
319 /// # }
320 /// ```
321 pub fn new() -> io::Result<Poll> {
322 sys::Selector::new().map(|selector| Poll {
323 registry: Registry {
324 selector,
325 #[cfg(all(debug_assertions, not(any(target_os = "wasi", target_os = "horizon"))))]
326 has_waker: Arc::new(AtomicBool::new(false)),
327 },
328 })
329 }
330 }
331
332 /// Returns a `Registry` which can be used to register
333 /// `event::Source`s.
334 pub fn registry(&self) -> &Registry {
335 &self.registry
336 }
337
338 /// Wait for readiness events
339 ///
340 /// Blocks the current thread and waits for readiness events for any of the
341 /// [`event::Source`]s that have been registered with this `Poll` instance.
342 /// The function will block until either at least one readiness event has
343 /// been received or `timeout` has elapsed. A `timeout` of `None` means that
344 /// `poll` will block until a readiness event has been received.
345 ///
346 /// The supplied `events` will be cleared and newly received readiness events
347 /// will be pushed onto the end. At most `events.capacity()` events will be
348 /// returned. If there are further pending readiness events, they will be
349 /// returned on the next call to `poll`.
350 ///
351 /// A single call to `poll` may result in multiple readiness events being
352 /// returned for a single event source. For example, if a TCP socket becomes
353 /// both readable and writable, it may be possible for a single readiness
354 /// event to be returned with both [`readable`] and [`writable`] readiness
355 /// **OR** two separate events may be returned, one with [`readable`] set
356 /// and one with [`writable`] set.
357 ///
358 /// Note that the `timeout` will be rounded up to the system clock
359 /// granularity (usually 1ms), and kernel scheduling delays mean that
360 /// the blocking interval may be overrun by a small amount. A timeout
361 /// of [`Duration::ZERO`] is not affected by this rounding.
362 ///
363 /// See the [struct] level documentation for a higher level discussion of
364 /// polling.
365 ///
366 /// [`event::Source`]: ./event/trait.Source.html
367 /// [`readable`]: struct.Interest.html#associatedconstant.READABLE
368 /// [`writable`]: struct.Interest.html#associatedconstant.WRITABLE
369 /// [struct]: struct.Poll.html
370 /// [`iter`]: ./event/struct.Events.html#method.iter
371 ///
372 /// # Notes
373 ///
374 /// This returns any errors without attempting to retry, previous versions
375 /// of Mio would automatically retry the poll call if it was interrupted
376 /// (if `EINTR` was returned).
377 ///
378 /// Currently if the `timeout` elapses without any readiness events
379 /// triggering this will return `Ok(())`. However we're not guaranteeing
380 /// this behaviour as this depends on the OS.
381 ///
382 /// # Examples
383 ///
384 /// A basic example -- establishing a `TcpStream` connection.
385 ///
386 #[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
387 #[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
388 /// # use std::error::Error;
389 /// # fn main() -> Result<(), Box<dyn Error>> {
390 /// # // WASI does not yet support multithreading:
391 /// # if cfg!(target_os = "wasi") { return Ok(()) }
392 /// use mio::{Events, Poll, Interest, Token};
393 /// use mio::net::TcpStream;
394 ///
395 /// use std::net::{TcpListener, SocketAddr};
396 /// use std::thread;
397 ///
398 /// // Bind a server socket to connect to.
399 /// let addr: SocketAddr = "127.0.0.1:0".parse()?;
400 /// let server = TcpListener::bind(addr)?;
401 /// let addr = server.local_addr()?.clone();
402 ///
403 /// // Spawn a thread to accept the socket
404 /// thread::spawn(move || {
405 /// let _ = server.accept();
406 /// });
407 ///
408 /// // Construct a new `Poll` handle as well as the `Events` we'll store into
409 /// let mut poll = Poll::new()?;
410 /// let mut events = Events::with_capacity(1024);
411 ///
412 /// // Connect the stream
413 /// let mut stream = TcpStream::connect(addr)?;
414 ///
415 /// // Register the stream with `Poll`
416 /// poll.registry().register(
417 /// &mut stream,
418 /// Token(0),
419 /// Interest::READABLE | Interest::WRITABLE)?;
420 ///
421 /// // Wait for the socket to become ready. This has to happen in a loop to
422 /// // handle spurious wakeups.
423 /// loop {
424 /// poll.poll(&mut events, None)?;
425 ///
426 /// for event in &events {
427 /// if event.token() == Token(0) && event.is_writable() {
428 /// // The socket connected (probably, it could still be a spurious
429 /// // wakeup)
430 /// return Ok(());
431 /// }
432 /// }
433 /// }
434 /// # }
435 /// ```
436 ///
437 /// [struct]: #
438 pub fn poll(&mut self, events: &mut Events, timeout: Option<Duration>) -> io::Result<()> {
439 self.registry.selector.select(events.sys(), timeout)
440 }
441}
442
443#[cfg(all(
444 unix,
445 not(mio_unsupported_force_poll_poll),
446 not(any(
447 target_os = "aix",
448 target_os = "espidf",
449 target_os = "nuttx",
450 target_os = "fuchsia",
451 target_os = "haiku",
452 target_os = "hermit",
453 target_os = "hurd",
454 target_os = "nto",
455 target_os = "vita",
456 target_os = "cygwin",
457 target_os = "horizon"
458 )),
459))]
460impl AsRawFd for Poll {
461 fn as_raw_fd(&self) -> RawFd {
462 self.registry.as_raw_fd()
463 }
464}
465
466impl fmt::Debug for Poll {
467 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
468 fmt.debug_struct("Poll").finish()
469 }
470}
471
472impl Registry {
473 /// Register an [`event::Source`] with the `Poll` instance.
474 ///
475 /// Once registered, the `Poll` instance will monitor the event source for
476 /// readiness state changes. When it notices a state change, it will return
477 /// a readiness event for the handle the next time [`poll`] is called.
478 ///
479 /// See [`Poll`] docs for a high level overview.
480 ///
481 /// # Arguments
482 ///
483 /// `source: &mut S: event::Source`: This is the source of events that the
484 /// `Poll` instance should monitor for readiness state changes.
485 ///
486 /// `token: Token`: The caller picks a token to associate with the socket.
487 /// When [`poll`] returns an event for the handle, this token is included.
488 /// This allows the caller to map the event to its source. The token
489 /// associated with the `event::Source` can be changed at any time by
490 /// calling [`reregister`].
491 ///
492 /// See documentation on [`Token`] for an example showing how to pick
493 /// [`Token`] values.
494 ///
495 /// `interest: Interest`: Specifies which operations `Poll` should monitor
496 /// for readiness. `Poll` will only return readiness events for operations
497 /// specified by this argument.
498 ///
499 /// If a socket is registered with readable interest and the socket becomes
500 /// writable, no event will be returned from [`poll`].
501 ///
502 /// The readiness interest for an `event::Source` can be changed at any time
503 /// by calling [`reregister`].
504 ///
505 /// # Notes
506 ///
507 /// Callers must ensure that if a source being registered with a `Poll`
508 /// instance was previously registered with that `Poll` instance, then a
509 /// call to [`deregister`] has already occurred. Consecutive calls to
510 /// `register` is unspecified behavior.
511 ///
512 /// Unless otherwise specified, the caller should assume that once an event
513 /// source is registered with a `Poll` instance, it is bound to that `Poll`
514 /// instance for the lifetime of the event source. This remains true even
515 /// if the event source is deregistered from the poll instance using
516 /// [`deregister`].
517 ///
518 /// [`event::Source`]: ./event/trait.Source.html
519 /// [`poll`]: struct.Poll.html#method.poll
520 /// [`reregister`]: struct.Registry.html#method.reregister
521 /// [`deregister`]: struct.Registry.html#method.deregister
522 /// [`Token`]: struct.Token.html
523 ///
524 /// # Examples
525 ///
526 #[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
527 #[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
528 /// # use std::error::Error;
529 /// # use std::net;
530 /// # fn main() -> Result<(), Box<dyn Error>> {
531 /// use mio::{Events, Poll, Interest, Token};
532 /// use mio::net::TcpStream;
533 /// use std::net::SocketAddr;
534 /// use std::time::{Duration, Instant};
535 ///
536 /// let mut poll = Poll::new()?;
537 ///
538 /// let address: SocketAddr = "127.0.0.1:0".parse()?;
539 /// let listener = net::TcpListener::bind(address)?;
540 /// let mut socket = TcpStream::connect(listener.local_addr()?)?;
541 ///
542 /// // Register the socket with `poll`
543 /// poll.registry().register(
544 /// &mut socket,
545 /// Token(0),
546 /// Interest::READABLE | Interest::WRITABLE)?;
547 ///
548 /// let mut events = Events::with_capacity(1024);
549 /// let start = Instant::now();
550 /// let timeout = Duration::from_millis(500);
551 ///
552 /// loop {
553 /// let elapsed = start.elapsed();
554 ///
555 /// if elapsed >= timeout {
556 /// // Connection timed out
557 /// return Ok(());
558 /// }
559 ///
560 /// let remaining = timeout - elapsed;
561 /// poll.poll(&mut events, Some(remaining))?;
562 ///
563 /// for event in &events {
564 /// if event.token() == Token(0) {
565 /// // Something (probably) happened on the socket.
566 /// return Ok(());
567 /// }
568 /// }
569 /// }
570 /// # }
571 /// ```
572 pub fn register<S>(&self, source: &mut S, token: Token, interests: Interest) -> io::Result<()>
573 where
574 S: event::Source + ?Sized,
575 {
576 trace!(
577 "registering event source with poller: token={:?}, interests={:?}",
578 token,
579 interests
580 );
581 source.register(self, token, interests)
582 }
583
584 /// Re-register an [`event::Source`] with the `Poll` instance.
585 ///
586 /// Re-registering an event source allows changing the details of the
587 /// registration. Specifically, it allows updating the associated `token`
588 /// and `interests` specified in previous `register` and `reregister` calls.
589 ///
590 /// The `reregister` arguments fully override the previous values. In other
591 /// words, if a socket is registered with [`readable`] interest and the call
592 /// to `reregister` specifies [`writable`], then read interest is no longer
593 /// requested for the handle.
594 ///
595 /// The event source must have previously been registered with this instance
596 /// of `Poll`, otherwise the behavior is unspecified.
597 ///
598 /// See the [`register`] documentation for details about the function
599 /// arguments and see the [`struct`] docs for a high level overview of
600 /// polling.
601 ///
602 /// # Examples
603 ///
604 #[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
605 #[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
606 /// # use std::error::Error;
607 /// # use std::net;
608 /// # fn main() -> Result<(), Box<dyn Error>> {
609 /// use mio::{Poll, Interest, Token};
610 /// use mio::net::TcpStream;
611 /// use std::net::SocketAddr;
612 ///
613 /// let poll = Poll::new()?;
614 ///
615 /// let address: SocketAddr = "127.0.0.1:0".parse()?;
616 /// let listener = net::TcpListener::bind(address)?;
617 /// let mut socket = TcpStream::connect(listener.local_addr()?)?;
618 ///
619 /// // Register the socket with `poll`, requesting readable
620 /// poll.registry().register(
621 /// &mut socket,
622 /// Token(0),
623 /// Interest::READABLE)?;
624 ///
625 /// // Reregister the socket specifying write interest instead. Even though
626 /// // the token is the same it must be specified.
627 /// poll.registry().reregister(
628 /// &mut socket,
629 /// Token(0),
630 /// Interest::WRITABLE)?;
631 /// # Ok(())
632 /// # }
633 /// ```
634 ///
635 /// [`event::Source`]: ./event/trait.Source.html
636 /// [`struct`]: struct.Poll.html
637 /// [`register`]: struct.Registry.html#method.register
638 /// [`readable`]: ./event/struct.Event.html#is_readable
639 /// [`writable`]: ./event/struct.Event.html#is_writable
640 pub fn reregister<S>(&self, source: &mut S, token: Token, interests: Interest) -> io::Result<()>
641 where
642 S: event::Source + ?Sized,
643 {
644 trace!(
645 "reregistering event source with poller: token={:?}, interests={:?}",
646 token,
647 interests
648 );
649 source.reregister(self, token, interests)
650 }
651
652 /// Deregister an [`event::Source`] with the `Poll` instance.
653 ///
654 /// When an event source is deregistered, the `Poll` instance will no longer
655 /// monitor it for readiness state changes. Deregistering clears up any
656 /// internal resources needed to track the handle. After an explicit call
657 /// to this method completes, it is guaranteed that the token previously
658 /// registered to this handle will not be returned by a future poll, so long
659 /// as a happens-before relationship is established between this call and
660 /// the poll.
661 ///
662 /// The event source must have previously been registered with this instance
663 /// of `Poll`, otherwise the behavior is unspecified.
664 ///
665 /// A handle can be passed back to `register` after it has been
666 /// deregistered; however, it must be passed back to the **same** `Poll`
667 /// instance, otherwise the behavior is unspecified.
668 ///
669 /// # Examples
670 ///
671 #[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
672 #[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
673 /// # use std::error::Error;
674 /// # use std::net;
675 /// # fn main() -> Result<(), Box<dyn Error>> {
676 /// use mio::{Events, Poll, Interest, Token};
677 /// use mio::net::TcpStream;
678 /// use std::net::SocketAddr;
679 /// use std::time::Duration;
680 ///
681 /// let mut poll = Poll::new()?;
682 ///
683 /// let address: SocketAddr = "127.0.0.1:0".parse()?;
684 /// let listener = net::TcpListener::bind(address)?;
685 /// let mut socket = TcpStream::connect(listener.local_addr()?)?;
686 ///
687 /// // Register the socket with `poll`
688 /// poll.registry().register(
689 /// &mut socket,
690 /// Token(0),
691 /// Interest::READABLE)?;
692 ///
693 /// poll.registry().deregister(&mut socket)?;
694 ///
695 /// let mut events = Events::with_capacity(1024);
696 ///
697 /// // Set a timeout because this poll should never receive any events.
698 /// poll.poll(&mut events, Some(Duration::from_secs(1)))?;
699 /// assert!(events.is_empty());
700 /// # Ok(())
701 /// # }
702 /// ```
703 pub fn deregister<S>(&self, source: &mut S) -> io::Result<()>
704 where
705 S: event::Source + ?Sized,
706 {
707 trace!("deregistering event source from poller");
708 source.deregister(self)
709 }
710
711 /// Creates a new independently owned `Registry`.
712 ///
713 /// Event sources registered with this `Registry` will be registered with
714 /// the original `Registry` and `Poll` instance.
715 pub fn try_clone(&self) -> io::Result<Registry> {
716 self.selector.try_clone().map(|selector| Registry {
717 selector,
718 #[cfg(all(debug_assertions, not(any(target_os = "wasi", target_os = "horizon"))))]
719 has_waker: Arc::clone(&self.has_waker),
720 })
721 }
722
723 /// Internal check to ensure only a single `Waker` is active per [`Poll`]
724 /// instance.
725 #[cfg(all(debug_assertions, not(any(target_os = "wasi", target_os = "horizon"))))]
726 pub(crate) fn register_waker(&self) {
727 assert!(
728 !self.has_waker.swap(true, Ordering::AcqRel),
729 "Only a single `Waker` can be active per `Poll` instance"
730 );
731 }
732
733 /// Get access to the `sys::Selector`.
734 #[cfg(any(not(target_os = "wasi"), feature = "net"))]
735 #[cfg_attr(target_os = "horizon", allow(dead_code))]
736 pub(crate) fn selector(&self) -> &sys::Selector {
737 &self.selector
738 }
739}
740
741impl fmt::Debug for Registry {
742 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
743 fmt.debug_struct("Registry").finish()
744 }
745}
746
747#[cfg(all(
748 unix,
749 not(mio_unsupported_force_poll_poll),
750 not(any(
751 target_os = "aix",
752 target_os = "espidf",
753 target_os = "nuttx",
754 target_os = "haiku",
755 target_os = "fuchsia",
756 target_os = "hermit",
757 target_os = "hurd",
758 target_os = "nto",
759 target_os = "vita",
760 target_os = "cygwin",
761 target_os = "horizon"
762 )),
763))]
764impl AsFd for Registry {
765 fn as_fd(&self) -> BorrowedFd<'_> {
766 self.selector.as_fd()
767 }
768}
769
770#[cfg(all(
771 unix,
772 not(mio_unsupported_force_poll_poll),
773 not(any(
774 target_os = "aix",
775 target_os = "espidf",
776 target_os = "nuttx",
777 target_os = "haiku",
778 target_os = "fuchsia",
779 target_os = "hermit",
780 target_os = "hurd",
781 target_os = "nto",
782 target_os = "vita",
783 target_os = "cygwin",
784 target_os = "horizon"
785 )),
786))]
787impl AsRawFd for Registry {
788 fn as_raw_fd(&self) -> RawFd {
789 self.selector.as_raw_fd()
790 }
791}
792
793cfg_os_poll! {
794 #[cfg(all(
795 unix,
796 not(mio_unsupported_force_poll_poll),
797 not(any(
798 target_os = "aix",
799 target_os = "espidf",
800 target_os = "nuttx",
801 target_os = "hermit",
802 target_os = "hurd",
803 target_os = "nto",
804 target_os = "vita",
805 target_os = "cygwin",
806 target_os = "horizon"
807 )),
808 ))]
809 #[test]
810 pub fn as_raw_fd() {
811 let poll = Poll::new().unwrap();
812 assert!(poll.as_raw_fd() > 0);
813 }
814}