mio/poll.rs
1#[cfg(all(
2 unix,
3 not(mio_unsupported_force_poll_poll),
4 not(any(
5 target_os = "espidf",
6 target_os = "fuchsia",
7 target_os = "haiku",
8 target_os = "hermit",
9 target_os = "hurd",
10 target_os = "nto",
11 target_os = "solaris",
12 target_os = "vita"
13 )),
14))]
15use std::os::fd::{AsRawFd, RawFd};
16#[cfg(all(debug_assertions, not(target_os = "wasi")))]
17use std::sync::atomic::{AtomicBool, Ordering};
18#[cfg(all(debug_assertions, not(target_os = "wasi")))]
19use std::sync::Arc;
20use std::time::Duration;
21use std::{fmt, io};
22
23use crate::{event, sys, Events, Interest, Token};
24
25/// Polls for readiness events on all registered values.
26///
27/// `Poll` allows a program to monitor a large number of [`event::Source`]s,
28/// waiting until one or more become "ready" for some class of operations; e.g.
29/// reading and writing. An event source is considered ready if it is possible
30/// to immediately perform a corresponding operation; e.g. [`read`] or
31/// [`write`].
32///
33/// To use `Poll`, an `event::Source` must first be registered with the `Poll`
34/// instance using the [`register`] method on its associated `Register`,
35/// supplying readiness interest. The readiness interest tells `Poll` which
36/// specific operations on the handle to monitor for readiness. A `Token` is
37/// also passed to the [`register`] function. When `Poll` returns a readiness
38/// event, it will include this token. This associates the event with the
39/// event source that generated the event.
40///
41/// [`event::Source`]: ./event/trait.Source.html
42/// [`read`]: ./net/struct.TcpStream.html#method.read
43/// [`write`]: ./net/struct.TcpStream.html#method.write
44/// [`register`]: struct.Registry.html#method.register
45///
46/// # Examples
47///
48/// A basic example -- establishing a `TcpStream` connection.
49///
50#[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
51#[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
52/// # use std::error::Error;
53/// # fn main() -> Result<(), Box<dyn Error>> {
54/// use mio::{Events, Poll, Interest, Token};
55/// use mio::net::TcpStream;
56///
57/// use std::net::{self, SocketAddr};
58///
59/// // Bind a server socket to connect to.
60/// let addr: SocketAddr = "127.0.0.1:0".parse()?;
61/// let server = net::TcpListener::bind(addr)?;
62///
63/// // Construct a new `Poll` handle as well as the `Events` we'll store into
64/// let mut poll = Poll::new()?;
65/// let mut events = Events::with_capacity(1024);
66///
67/// // Connect the stream
68/// let mut stream = TcpStream::connect(server.local_addr()?)?;
69///
70/// // Register the stream with `Poll`
71/// poll.registry().register(&mut stream, Token(0), Interest::READABLE | Interest::WRITABLE)?;
72///
73/// // Wait for the socket to become ready. This has to happens in a loop to
74/// // handle spurious wakeups.
75/// loop {
76/// poll.poll(&mut events, None)?;
77///
78/// for event in &events {
79/// if event.token() == Token(0) && event.is_writable() {
80/// // The socket connected (probably, it could still be a spurious
81/// // wakeup)
82/// return Ok(());
83/// }
84/// }
85/// }
86/// # }
87/// ```
88///
89/// # Portability
90///
91/// Using `Poll` provides a portable interface across supported platforms as
92/// long as the caller takes the following into consideration:
93///
94/// ### Spurious events
95///
96/// [`Poll::poll`] may return readiness events even if the associated
97/// event source is not actually ready. Given the same code, this may
98/// happen more on some platforms than others. It is important to never assume
99/// that, just because a readiness event was received, that the associated
100/// operation will succeed as well.
101///
102/// If operation fails with [`WouldBlock`], then the caller should not treat
103/// this as an error, but instead should wait until another readiness event is
104/// received.
105///
106/// ### Draining readiness
107///
108/// Once a readiness event is received, the corresponding operation must be
109/// performed repeatedly until it returns [`WouldBlock`]. Unless this is done,
110/// there is no guarantee that another readiness event will be delivered, even
111/// if further data is received for the event source.
112///
113/// [`WouldBlock`]: std::io::ErrorKind::WouldBlock
114///
115/// ### Readiness operations
116///
117/// The only readiness operations that are guaranteed to be present on all
118/// supported platforms are [`readable`] and [`writable`]. All other readiness
119/// operations may have false negatives and as such should be considered
120/// **hints**. This means that if a socket is registered with [`readable`]
121/// interest and either an error or close is received, a readiness event will
122/// be generated for the socket, but it **may** only include `readable`
123/// readiness. Also note that, given the potential for spurious events,
124/// receiving a readiness event with `read_closed`, `write_closed`, or `error`
125/// doesn't actually mean that a `read` on the socket will return a result
126/// matching the readiness event.
127///
128/// In other words, portable programs that explicitly check for [`read_closed`],
129/// [`write_closed`], or [`error`] readiness should be doing so as an
130/// **optimization** and always be able to handle an error or close situation
131/// when performing the actual read operation.
132///
133/// [`readable`]: ./event/struct.Event.html#method.is_readable
134/// [`writable`]: ./event/struct.Event.html#method.is_writable
135/// [`error`]: ./event/struct.Event.html#method.is_error
136/// [`read_closed`]: ./event/struct.Event.html#method.is_read_closed
137/// [`write_closed`]: ./event/struct.Event.html#method.is_write_closed
138///
139/// ### Registering handles
140///
141/// Unless otherwise noted, it should be assumed that types implementing
142/// [`event::Source`] will never become ready unless they are registered with
143/// `Poll`.
144///
145/// For example:
146///
147#[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
148#[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
149/// # use std::error::Error;
150/// # use std::net;
151/// # fn main() -> Result<(), Box<dyn Error>> {
152/// use mio::{Poll, Interest, Token};
153/// use mio::net::TcpStream;
154/// use std::net::SocketAddr;
155/// use std::time::Duration;
156/// use std::thread;
157///
158/// let address: SocketAddr = "127.0.0.1:0".parse()?;
159/// let listener = net::TcpListener::bind(address)?;
160/// let mut sock = TcpStream::connect(listener.local_addr()?)?;
161///
162/// thread::sleep(Duration::from_secs(1));
163///
164/// let poll = Poll::new()?;
165///
166/// // The connect is not guaranteed to have started until it is registered at
167/// // this point
168/// poll.registry().register(&mut sock, Token(0), Interest::READABLE | Interest::WRITABLE)?;
169/// # Ok(())
170/// # }
171/// ```
172///
173/// ### Dropping `Poll`
174///
175/// When the `Poll` instance is dropped it may cancel in-flight operations for
176/// the registered [event sources], meaning that no further events for them may
177/// be received. It also means operations on the registered event sources may no
178/// longer work. It is up to the user to keep the `Poll` instance alive while
179/// registered event sources are being used.
180///
181/// [event sources]: ./event/trait.Source.html
182///
183/// ### Accessing raw fd/socket/handle
184///
185/// Mio makes it possible for many types to be converted into a raw file
186/// descriptor (fd, Unix), socket (Windows) or handle (Windows). This makes it
187/// possible to support more operations on the type than Mio supports, for
188/// example it makes [mio-aio] possible. However accessing the raw fd is not
189/// without it's pitfalls.
190///
191/// Specifically performing I/O operations outside of Mio on these types (via
192/// the raw fd) has unspecified behaviour. It could cause no more events to be
193/// generated for the type even though it returned `WouldBlock` (in an operation
194/// directly accessing the fd). The behaviour is OS specific and Mio can only
195/// guarantee cross-platform behaviour if it can control the I/O.
196///
197/// [mio-aio]: https://github.com/asomers/mio-aio
198///
199/// *The following is **not** guaranteed, just a description of the current
200/// situation!* Mio is allowed to change the following without it being considered
201/// a breaking change, don't depend on this, it's just here to inform the user.
202/// Currently the kqueue and epoll implementation support direct I/O operations
203/// on the fd without Mio's knowledge. Windows however needs **all** I/O
204/// operations to go through Mio otherwise it is not able to update it's
205/// internal state properly and won't generate events.
206///
207/// ### Polling without registering event sources
208///
209///
210/// *The following is **not** guaranteed, just a description of the current
211/// situation!* Mio is allowed to change the following without it being
212/// considered a breaking change, don't depend on this, it's just here to inform
213/// the user. On platforms that use epoll, kqueue or IOCP (see implementation
214/// notes below) polling without previously registering [event sources] will
215/// result in sleeping forever, only a process signal will be able to wake up
216/// the thread.
217///
218/// On WASM/WASI this is different as it doesn't support process signals,
219/// furthermore the WASI specification doesn't specify a behaviour in this
220/// situation, thus it's up to the implementation what to do here. As an
221/// example, the wasmtime runtime will return `EINVAL` in this situation, but
222/// different runtimes may return different results. If you have further
223/// insights or thoughts about this situation (and/or how Mio should handle it)
224/// please add you comment to [pull request#1580].
225///
226/// [event sources]: crate::event::Source
227/// [pull request#1580]: https://github.com/tokio-rs/mio/pull/1580
228///
229/// # Implementation notes
230///
231/// `Poll` is backed by the selector provided by the operating system.
232///
233/// | OS | Selector |
234/// |---------------|-----------|
235/// | Android | [epoll] |
236/// | DragonFly BSD | [kqueue] |
237/// | FreeBSD | [kqueue] |
238/// | iOS | [kqueue] |
239/// | illumos | [epoll] |
240/// | Linux | [epoll] |
241/// | NetBSD | [kqueue] |
242/// | OpenBSD | [kqueue] |
243/// | Windows | [IOCP] |
244/// | macOS | [kqueue] |
245///
246/// On all supported platforms, socket operations are handled by using the
247/// system selector. Platform specific extensions (e.g. [`SourceFd`]) allow
248/// accessing other features provided by individual system selectors. For
249/// example, Linux's [`signalfd`] feature can be used by registering the FD with
250/// `Poll` via [`SourceFd`].
251///
252/// On all platforms except windows, a call to [`Poll::poll`] is mostly just a
253/// direct call to the system selector. However, [IOCP] uses a completion model
254/// instead of a readiness model. In this case, `Poll` must adapt the completion
255/// model Mio's API. While non-trivial, the bridge layer is still quite
256/// efficient. The most expensive part being calls to `read` and `write` require
257/// data to be copied into an intermediate buffer before it is passed to the
258/// kernel.
259///
260/// [epoll]: https://man7.org/linux/man-pages/man7/epoll.7.html
261/// [kqueue]: https://www.freebsd.org/cgi/man.cgi?query=kqueue&sektion=2
262/// [IOCP]: https://docs.microsoft.com/en-us/windows/win32/fileio/i-o-completion-ports
263/// [`signalfd`]: https://man7.org/linux/man-pages/man2/signalfd.2.html
264/// [`SourceFd`]: unix/struct.SourceFd.html
265/// [`Poll::poll`]: struct.Poll.html#method.poll
266pub struct Poll {
267 registry: Registry,
268}
269
270/// Registers I/O resources.
271pub struct Registry {
272 selector: sys::Selector,
273 /// Whether this selector currently has an associated waker.
274 #[cfg(all(debug_assertions, not(target_os = "wasi")))]
275 has_waker: Arc<AtomicBool>,
276}
277
278impl Poll {
279 cfg_os_poll! {
280 /// Return a new `Poll` handle.
281 ///
282 /// This function will make a syscall to the operating system to create
283 /// the system selector. If this syscall fails, `Poll::new` will return
284 /// with the error.
285 ///
286 /// close-on-exec flag is set on the file descriptors used by the selector to prevent
287 /// leaking it to executed processes. However, on some systems such as
288 /// old Linux systems that don't support `epoll_create1` syscall it is done
289 /// non-atomically, so a separate thread executing in parallel to this
290 /// function may accidentally leak the file descriptor if it executes a
291 /// new process before this function returns.
292 ///
293 /// See [struct] level docs for more details.
294 ///
295 /// [struct]: struct.Poll.html
296 ///
297 /// # Examples
298 ///
299 /// ```
300 /// # use std::error::Error;
301 /// # fn main() -> Result<(), Box<dyn Error>> {
302 /// use mio::{Poll, Events};
303 /// use std::time::Duration;
304 ///
305 /// let mut poll = match Poll::new() {
306 /// Ok(poll) => poll,
307 /// Err(e) => panic!("failed to create Poll instance; err={:?}", e),
308 /// };
309 ///
310 /// // Create a structure to receive polled events
311 /// let mut events = Events::with_capacity(1024);
312 ///
313 /// // Wait for events, but none will be received because no
314 /// // `event::Source`s have been registered with this `Poll` instance.
315 /// poll.poll(&mut events, Some(Duration::from_millis(500)))?;
316 /// assert!(events.is_empty());
317 /// # Ok(())
318 /// # }
319 /// ```
320 pub fn new() -> io::Result<Poll> {
321 sys::Selector::new().map(|selector| Poll {
322 registry: Registry {
323 selector,
324 #[cfg(all(debug_assertions, not(target_os = "wasi")))]
325 has_waker: Arc::new(AtomicBool::new(false)),
326 },
327 })
328 }
329 }
330
331 /// Create a separate `Registry` which can be used to register
332 /// `event::Source`s.
333 pub fn registry(&self) -> &Registry {
334 &self.registry
335 }
336
337 /// Wait for readiness events
338 ///
339 /// Blocks the current thread and waits for readiness events for any of the
340 /// [`event::Source`]s that have been registered with this `Poll` instance.
341 /// The function will block until either at least one readiness event has
342 /// been received or `timeout` has elapsed. A `timeout` of `None` means that
343 /// `poll` will block until a readiness event has been received.
344 ///
345 /// The supplied `events` will be cleared and newly received readiness events
346 /// will be pushed onto the end. At most `events.capacity()` events will be
347 /// returned. If there are further pending readiness events, they will be
348 /// returned on the next call to `poll`.
349 ///
350 /// A single call to `poll` may result in multiple readiness events being
351 /// returned for a single event source. For example, if a TCP socket becomes
352 /// both readable and writable, it may be possible for a single readiness
353 /// event to be returned with both [`readable`] and [`writable`] readiness
354 /// **OR** two separate events may be returned, one with [`readable`] set
355 /// and one with [`writable`] set.
356 ///
357 /// Note that the `timeout` will be rounded up to the system clock
358 /// granularity (usually 1ms), and kernel scheduling delays mean that
359 /// the blocking interval may be overrun by a small amount.
360 ///
361 /// See the [struct] level documentation for a higher level discussion of
362 /// polling.
363 ///
364 /// [`event::Source`]: ./event/trait.Source.html
365 /// [`readable`]: struct.Interest.html#associatedconstant.READABLE
366 /// [`writable`]: struct.Interest.html#associatedconstant.WRITABLE
367 /// [struct]: struct.Poll.html
368 /// [`iter`]: ./event/struct.Events.html#method.iter
369 ///
370 /// # Notes
371 ///
372 /// This returns any errors without attempting to retry, previous versions
373 /// of Mio would automatically retry the poll call if it was interrupted
374 /// (if `EINTR` was returned).
375 ///
376 /// Currently if the `timeout` elapses without any readiness events
377 /// triggering this will return `Ok(())`. However we're not guaranteeing
378 /// this behaviour as this depends on the OS.
379 ///
380 /// # Examples
381 ///
382 /// A basic example -- establishing a `TcpStream` connection.
383 ///
384 #[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
385 #[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
386 /// # use std::error::Error;
387 /// # fn main() -> Result<(), Box<dyn Error>> {
388 /// use mio::{Events, Poll, Interest, Token};
389 /// use mio::net::TcpStream;
390 ///
391 /// use std::net::{TcpListener, SocketAddr};
392 /// use std::thread;
393 ///
394 /// // Bind a server socket to connect to.
395 /// let addr: SocketAddr = "127.0.0.1:0".parse()?;
396 /// let server = TcpListener::bind(addr)?;
397 /// let addr = server.local_addr()?.clone();
398 ///
399 /// // Spawn a thread to accept the socket
400 /// thread::spawn(move || {
401 /// let _ = server.accept();
402 /// });
403 ///
404 /// // Construct a new `Poll` handle as well as the `Events` we'll store into
405 /// let mut poll = Poll::new()?;
406 /// let mut events = Events::with_capacity(1024);
407 ///
408 /// // Connect the stream
409 /// let mut stream = TcpStream::connect(addr)?;
410 ///
411 /// // Register the stream with `Poll`
412 /// poll.registry().register(
413 /// &mut stream,
414 /// Token(0),
415 /// Interest::READABLE | Interest::WRITABLE)?;
416 ///
417 /// // Wait for the socket to become ready. This has to happens in a loop to
418 /// // handle spurious wakeups.
419 /// loop {
420 /// poll.poll(&mut events, None)?;
421 ///
422 /// for event in &events {
423 /// if event.token() == Token(0) && event.is_writable() {
424 /// // The socket connected (probably, it could still be a spurious
425 /// // wakeup)
426 /// return Ok(());
427 /// }
428 /// }
429 /// }
430 /// # }
431 /// ```
432 ///
433 /// [struct]: #
434 pub fn poll(&mut self, events: &mut Events, timeout: Option<Duration>) -> io::Result<()> {
435 self.registry.selector.select(events.sys(), timeout)
436 }
437}
438
439#[cfg(all(
440 unix,
441 not(mio_unsupported_force_poll_poll),
442 not(any(
443 target_os = "espidf",
444 target_os = "fuchsia",
445 target_os = "haiku",
446 target_os = "hermit",
447 target_os = "hurd",
448 target_os = "nto",
449 target_os = "solaris",
450 target_os = "vita"
451 )),
452))]
453impl AsRawFd for Poll {
454 fn as_raw_fd(&self) -> RawFd {
455 self.registry.as_raw_fd()
456 }
457}
458
459impl fmt::Debug for Poll {
460 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
461 fmt.debug_struct("Poll").finish()
462 }
463}
464
465impl Registry {
466 /// Register an [`event::Source`] with the `Poll` instance.
467 ///
468 /// Once registered, the `Poll` instance will monitor the event source for
469 /// readiness state changes. When it notices a state change, it will return
470 /// a readiness event for the handle the next time [`poll`] is called.
471 ///
472 /// See [`Poll`] docs for a high level overview.
473 ///
474 /// # Arguments
475 ///
476 /// `source: &mut S: event::Source`: This is the source of events that the
477 /// `Poll` instance should monitor for readiness state changes.
478 ///
479 /// `token: Token`: The caller picks a token to associate with the socket.
480 /// When [`poll`] returns an event for the handle, this token is included.
481 /// This allows the caller to map the event to its source. The token
482 /// associated with the `event::Source` can be changed at any time by
483 /// calling [`reregister`].
484 ///
485 /// See documentation on [`Token`] for an example showing how to pick
486 /// [`Token`] values.
487 ///
488 /// `interest: Interest`: Specifies which operations `Poll` should monitor
489 /// for readiness. `Poll` will only return readiness events for operations
490 /// specified by this argument.
491 ///
492 /// If a socket is registered with readable interest and the socket becomes
493 /// writable, no event will be returned from [`poll`].
494 ///
495 /// The readiness interest for an `event::Source` can be changed at any time
496 /// by calling [`reregister`].
497 ///
498 /// # Notes
499 ///
500 /// Callers must ensure that if a source being registered with a `Poll`
501 /// instance was previously registered with that `Poll` instance, then a
502 /// call to [`deregister`] has already occurred. Consecutive calls to
503 /// `register` is unspecified behavior.
504 ///
505 /// Unless otherwise specified, the caller should assume that once an event
506 /// source is registered with a `Poll` instance, it is bound to that `Poll`
507 /// instance for the lifetime of the event source. This remains true even
508 /// if the event source is deregistered from the poll instance using
509 /// [`deregister`].
510 ///
511 /// [`event::Source`]: ./event/trait.Source.html
512 /// [`poll`]: struct.Poll.html#method.poll
513 /// [`reregister`]: struct.Registry.html#method.reregister
514 /// [`deregister`]: struct.Registry.html#method.deregister
515 /// [`Token`]: struct.Token.html
516 ///
517 /// # Examples
518 ///
519 #[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
520 #[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
521 /// # use std::error::Error;
522 /// # use std::net;
523 /// # fn main() -> Result<(), Box<dyn Error>> {
524 /// use mio::{Events, Poll, Interest, Token};
525 /// use mio::net::TcpStream;
526 /// use std::net::SocketAddr;
527 /// use std::time::{Duration, Instant};
528 ///
529 /// let mut poll = Poll::new()?;
530 ///
531 /// let address: SocketAddr = "127.0.0.1:0".parse()?;
532 /// let listener = net::TcpListener::bind(address)?;
533 /// let mut socket = TcpStream::connect(listener.local_addr()?)?;
534 ///
535 /// // Register the socket with `poll`
536 /// poll.registry().register(
537 /// &mut socket,
538 /// Token(0),
539 /// Interest::READABLE | Interest::WRITABLE)?;
540 ///
541 /// let mut events = Events::with_capacity(1024);
542 /// let start = Instant::now();
543 /// let timeout = Duration::from_millis(500);
544 ///
545 /// loop {
546 /// let elapsed = start.elapsed();
547 ///
548 /// if elapsed >= timeout {
549 /// // Connection timed out
550 /// return Ok(());
551 /// }
552 ///
553 /// let remaining = timeout - elapsed;
554 /// poll.poll(&mut events, Some(remaining))?;
555 ///
556 /// for event in &events {
557 /// if event.token() == Token(0) {
558 /// // Something (probably) happened on the socket.
559 /// return Ok(());
560 /// }
561 /// }
562 /// }
563 /// # }
564 /// ```
565 pub fn register<S>(&self, source: &mut S, token: Token, interests: Interest) -> io::Result<()>
566 where
567 S: event::Source + ?Sized,
568 {
569 trace!(
570 "registering event source with poller: token={:?}, interests={:?}",
571 token,
572 interests
573 );
574 source.register(self, token, interests)
575 }
576
577 /// Re-register an [`event::Source`] with the `Poll` instance.
578 ///
579 /// Re-registering an event source allows changing the details of the
580 /// registration. Specifically, it allows updating the associated `token`
581 /// and `interests` specified in previous `register` and `reregister` calls.
582 ///
583 /// The `reregister` arguments fully override the previous values. In other
584 /// words, if a socket is registered with [`readable`] interest and the call
585 /// to `reregister` specifies [`writable`], then read interest is no longer
586 /// requested for the handle.
587 ///
588 /// The event source must have previously been registered with this instance
589 /// of `Poll`, otherwise the behavior is unspecified.
590 ///
591 /// See the [`register`] documentation for details about the function
592 /// arguments and see the [`struct`] docs for a high level overview of
593 /// polling.
594 ///
595 /// # Examples
596 ///
597 #[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
598 #[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
599 /// # use std::error::Error;
600 /// # use std::net;
601 /// # fn main() -> Result<(), Box<dyn Error>> {
602 /// use mio::{Poll, Interest, Token};
603 /// use mio::net::TcpStream;
604 /// use std::net::SocketAddr;
605 ///
606 /// let poll = Poll::new()?;
607 ///
608 /// let address: SocketAddr = "127.0.0.1:0".parse()?;
609 /// let listener = net::TcpListener::bind(address)?;
610 /// let mut socket = TcpStream::connect(listener.local_addr()?)?;
611 ///
612 /// // Register the socket with `poll`, requesting readable
613 /// poll.registry().register(
614 /// &mut socket,
615 /// Token(0),
616 /// Interest::READABLE)?;
617 ///
618 /// // Reregister the socket specifying write interest instead. Even though
619 /// // the token is the same it must be specified.
620 /// poll.registry().reregister(
621 /// &mut socket,
622 /// Token(0),
623 /// Interest::WRITABLE)?;
624 /// # Ok(())
625 /// # }
626 /// ```
627 ///
628 /// [`event::Source`]: ./event/trait.Source.html
629 /// [`struct`]: struct.Poll.html
630 /// [`register`]: struct.Registry.html#method.register
631 /// [`readable`]: ./event/struct.Event.html#is_readable
632 /// [`writable`]: ./event/struct.Event.html#is_writable
633 pub fn reregister<S>(&self, source: &mut S, token: Token, interests: Interest) -> io::Result<()>
634 where
635 S: event::Source + ?Sized,
636 {
637 trace!(
638 "reregistering event source with poller: token={:?}, interests={:?}",
639 token,
640 interests
641 );
642 source.reregister(self, token, interests)
643 }
644
645 /// Deregister an [`event::Source`] with the `Poll` instance.
646 ///
647 /// When an event source is deregistered, the `Poll` instance will no longer
648 /// monitor it for readiness state changes. Deregistering clears up any
649 /// internal resources needed to track the handle. After an explicit call
650 /// to this method completes, it is guaranteed that the token previously
651 /// registered to this handle will not be returned by a future poll, so long
652 /// as a happens-before relationship is established between this call and
653 /// the poll.
654 ///
655 /// The event source must have previously been registered with this instance
656 /// of `Poll`, otherwise the behavior is unspecified.
657 ///
658 /// A handle can be passed back to `register` after it has been
659 /// deregistered; however, it must be passed back to the **same** `Poll`
660 /// instance, otherwise the behavior is unspecified.
661 ///
662 /// # Examples
663 ///
664 #[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
665 #[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
666 /// # use std::error::Error;
667 /// # use std::net;
668 /// # fn main() -> Result<(), Box<dyn Error>> {
669 /// use mio::{Events, Poll, Interest, Token};
670 /// use mio::net::TcpStream;
671 /// use std::net::SocketAddr;
672 /// use std::time::Duration;
673 ///
674 /// let mut poll = Poll::new()?;
675 ///
676 /// let address: SocketAddr = "127.0.0.1:0".parse()?;
677 /// let listener = net::TcpListener::bind(address)?;
678 /// let mut socket = TcpStream::connect(listener.local_addr()?)?;
679 ///
680 /// // Register the socket with `poll`
681 /// poll.registry().register(
682 /// &mut socket,
683 /// Token(0),
684 /// Interest::READABLE)?;
685 ///
686 /// poll.registry().deregister(&mut socket)?;
687 ///
688 /// let mut events = Events::with_capacity(1024);
689 ///
690 /// // Set a timeout because this poll should never receive any events.
691 /// poll.poll(&mut events, Some(Duration::from_secs(1)))?;
692 /// assert!(events.is_empty());
693 /// # Ok(())
694 /// # }
695 /// ```
696 pub fn deregister<S>(&self, source: &mut S) -> io::Result<()>
697 where
698 S: event::Source + ?Sized,
699 {
700 trace!("deregistering event source from poller");
701 source.deregister(self)
702 }
703
704 /// Creates a new independently owned `Registry`.
705 ///
706 /// Event sources registered with this `Registry` will be registered with
707 /// the original `Registry` and `Poll` instance.
708 pub fn try_clone(&self) -> io::Result<Registry> {
709 self.selector.try_clone().map(|selector| Registry {
710 selector,
711 #[cfg(all(debug_assertions, not(target_os = "wasi")))]
712 has_waker: Arc::clone(&self.has_waker),
713 })
714 }
715
716 /// Internal check to ensure only a single `Waker` is active per [`Poll`]
717 /// instance.
718 #[cfg(all(debug_assertions, not(target_os = "wasi")))]
719 pub(crate) fn register_waker(&self) {
720 assert!(
721 !self.has_waker.swap(true, Ordering::AcqRel),
722 "Only a single `Waker` can be active per `Poll` instance"
723 );
724 }
725
726 /// Get access to the `sys::Selector`.
727 #[cfg(any(not(target_os = "wasi"), feature = "net"))]
728 pub(crate) fn selector(&self) -> &sys::Selector {
729 &self.selector
730 }
731}
732
733impl fmt::Debug for Registry {
734 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
735 fmt.debug_struct("Registry").finish()
736 }
737}
738
739#[cfg(all(
740 unix,
741 not(mio_unsupported_force_poll_poll),
742 not(any(
743 target_os = "espidf",
744 target_os = "haiku",
745 target_os = "fuchsia",
746 target_os = "hermit",
747 target_os = "hurd",
748 target_os = "nto",
749 target_os = "solaris",
750 target_os = "vita"
751 )),
752))]
753impl AsRawFd for Registry {
754 fn as_raw_fd(&self) -> RawFd {
755 self.selector.as_raw_fd()
756 }
757}
758
759cfg_os_poll! {
760 #[cfg(all(
761 unix,
762 not(mio_unsupported_force_poll_poll),
763 not(any(
764 target_os = "espidf",
765 target_os = "hermit",
766 target_os = "hurd",
767 target_os = "nto",
768 target_os = "solaris",
769 target_os = "vita"
770 )),
771 ))]
772 #[test]
773 pub fn as_raw_fd() {
774 let poll = Poll::new().unwrap();
775 assert!(poll.as_raw_fd() > 0);
776 }
777}