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Diffstat (limited to 'third_party/rust/mio/src/poll.rs')
| -rw-r--r-- | third_party/rust/mio/src/poll.rs | 682 |
1 files changed, 682 insertions, 0 deletions
diff --git a/third_party/rust/mio/src/poll.rs b/third_party/rust/mio/src/poll.rs new file mode 100644 index 0000000000..fd643fdd00 --- /dev/null +++ b/third_party/rust/mio/src/poll.rs @@ -0,0 +1,682 @@ +use crate::{event, sys, Events, Interest, Token}; +use log::trace; +#[cfg(unix)] +use std::os::unix::io::{AsRawFd, RawFd}; +use std::time::Duration; +use std::{fmt, io}; + +/// Polls for readiness events on all registered values. +/// +/// `Poll` allows a program to monitor a large number of [`event::Source`]s, +/// waiting until one or more become "ready" for some class of operations; e.g. +/// reading and writing. An event source is considered ready if it is possible +/// to immediately perform a corresponding operation; e.g. [`read`] or +/// [`write`]. +/// +/// To use `Poll`, an `event::Source` must first be registered with the `Poll` +/// instance using the [`register`] method on its associated `Register`, +/// supplying readiness interest. The readiness interest tells `Poll` which +/// specific operations on the handle to monitor for readiness. A `Token` is +/// also passed to the [`register`] function. When `Poll` returns a readiness +/// event, it will include this token. This associates the event with the +/// event source that generated the event. +/// +/// [`event::Source`]: ./event/trait.Source.html +/// [`read`]: ./net/struct.TcpStream.html#method.read +/// [`write`]: ./net/struct.TcpStream.html#method.write +/// [`register`]: struct.Registry.html#method.register +/// +/// # Examples +/// +/// A basic example -- establishing a `TcpStream` connection. +/// +#[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")] +#[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")] +/// # use std::error::Error; +/// # fn main() -> Result<(), Box<dyn Error>> { +/// use mio::{Events, Poll, Interest, Token}; +/// use mio::net::TcpStream; +/// +/// use std::net::{self, SocketAddr}; +/// +/// // Bind a server socket to connect to. +/// let addr: SocketAddr = "127.0.0.1:0".parse()?; +/// let server = net::TcpListener::bind(addr)?; +/// +/// // Construct a new `Poll` handle as well as the `Events` we'll store into +/// let mut poll = Poll::new()?; +/// let mut events = Events::with_capacity(1024); +/// +/// // Connect the stream +/// let mut stream = TcpStream::connect(server.local_addr()?)?; +/// +/// // Register the stream with `Poll` +/// poll.registry().register(&mut stream, Token(0), Interest::READABLE | Interest::WRITABLE)?; +/// +/// // Wait for the socket to become ready. This has to happens in a loop to +/// // handle spurious wakeups. +/// loop { +/// poll.poll(&mut events, None)?; +/// +/// for event in &events { +/// if event.token() == Token(0) && event.is_writable() { +/// // The socket connected (probably, it could still be a spurious +/// // wakeup) +/// return Ok(()); +/// } +/// } +/// } +/// # } +/// ``` +/// +/// # Portability +/// +/// Using `Poll` provides a portable interface across supported platforms as +/// long as the caller takes the following into consideration: +/// +/// ### Spurious events +/// +/// [`Poll::poll`] may return readiness events even if the associated +/// event source is not actually ready. Given the same code, this may +/// happen more on some platforms than others. It is important to never assume +/// that, just because a readiness event was received, that the associated +/// operation will succeed as well. +/// +/// If operation fails with [`WouldBlock`], then the caller should not treat +/// this as an error, but instead should wait until another readiness event is +/// received. +/// +/// ### Draining readiness +/// +/// Once a readiness event is received, the corresponding operation must be +/// performed repeatedly until it returns [`WouldBlock`]. Unless this is done, +/// there is no guarantee that another readiness event will be delivered, even +/// if further data is received for the event source. +/// +/// [`WouldBlock`]: std::io::ErrorKind::WouldBlock +/// +/// ### Readiness operations +/// +/// The only readiness operations that are guaranteed to be present on all +/// supported platforms are [`readable`] and [`writable`]. All other readiness +/// operations may have false negatives and as such should be considered +/// **hints**. This means that if a socket is registered with [`readable`] +/// interest and either an error or close is received, a readiness event will +/// be generated for the socket, but it **may** only include `readable` +/// readiness. Also note that, given the potential for spurious events, +/// receiving a readiness event with `read_closed`, `write_closed`, or `error` +/// doesn't actually mean that a `read` on the socket will return a result +/// matching the readiness event. +/// +/// In other words, portable programs that explicitly check for [`read_closed`], +/// [`write_closed`], or [`error`] readiness should be doing so as an +/// **optimization** and always be able to handle an error or close situation +/// when performing the actual read operation. +/// +/// [`readable`]: ./event/struct.Event.html#method.is_readable +/// [`writable`]: ./event/struct.Event.html#method.is_writable +/// [`error`]: ./event/struct.Event.html#method.is_error +/// [`read_closed`]: ./event/struct.Event.html#method.is_read_closed +/// [`write_closed`]: ./event/struct.Event.html#method.is_write_closed +/// +/// ### Registering handles +/// +/// Unless otherwise noted, it should be assumed that types implementing +/// [`event::Source`] will never become ready unless they are registered with +/// `Poll`. +/// +/// For example: +/// +#[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")] +#[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")] +/// # use std::error::Error; +/// # use std::net; +/// # fn main() -> Result<(), Box<dyn Error>> { +/// use mio::{Poll, Interest, Token}; +/// use mio::net::TcpStream; +/// use std::net::SocketAddr; +/// use std::time::Duration; +/// use std::thread; +/// +/// let address: SocketAddr = "127.0.0.1:0".parse()?; +/// let listener = net::TcpListener::bind(address)?; +/// let mut sock = TcpStream::connect(listener.local_addr()?)?; +/// +/// thread::sleep(Duration::from_secs(1)); +/// +/// let poll = Poll::new()?; +/// +/// // The connect is not guaranteed to have started until it is registered at +/// // this point +/// poll.registry().register(&mut sock, Token(0), Interest::READABLE | Interest::WRITABLE)?; +/// # Ok(()) +/// # } +/// ``` +/// +/// ### Dropping `Poll` +/// +/// When the `Poll` instance is dropped it may cancel in-flight operations for +/// the registered [event sources], meaning that no further events for them may +/// be received. It also means operations on the registered event sources may no +/// longer work. It is up to the user to keep the `Poll` instance alive while +/// registered event sources are being used. +/// +/// [event sources]: ./event/trait.Source.html +/// +/// ### Accessing raw fd/socket/handle +/// +/// Mio makes it possible for many types to be converted into a raw file +/// descriptor (fd, Unix), socket (Windows) or handle (Windows). This makes it +/// possible to support more operations on the type than Mio supports, for +/// example it makes [mio-aio] possible. However accessing the raw fd is not +/// without it's pitfalls. +/// +/// Specifically performing I/O operations outside of Mio on these types (via +/// the raw fd) has unspecified behaviour. It could cause no more events to be +/// generated for the type even though it returned `WouldBlock` (in an operation +/// directly accessing the fd). The behaviour is OS specific and Mio can only +/// guarantee cross-platform behaviour if it can control the I/O. +/// +/// [mio-aio]: https://github.com/asomers/mio-aio +/// +/// *The following is **not** guaranteed, just a description of the current +/// situation!* Mio is allowed to change the following without it being considered +/// a breaking change, don't depend on this, it's just here to inform the user. +/// Currently the kqueue and epoll implementation support direct I/O operations +/// on the fd without Mio's knowledge. Windows however needs **all** I/O +/// operations to go through Mio otherwise it is not able to update it's +/// internal state properly and won't generate events. +/// +/// # Implementation notes +/// +/// `Poll` is backed by the selector provided by the operating system. +/// +/// | OS | Selector | +/// |---------------|-----------| +/// | Android | [epoll] | +/// | DragonFly BSD | [kqueue] | +/// | FreeBSD | [kqueue] | +/// | iOS | [kqueue] | +/// | illumos | [epoll] | +/// | Linux | [epoll] | +/// | NetBSD | [kqueue] | +/// | OpenBSD | [kqueue] | +/// | Windows | [IOCP] | +/// | macOS | [kqueue] | +/// +/// On all supported platforms, socket operations are handled by using the +/// system selector. Platform specific extensions (e.g. [`SourceFd`]) allow +/// accessing other features provided by individual system selectors. For +/// example, Linux's [`signalfd`] feature can be used by registering the FD with +/// `Poll` via [`SourceFd`]. +/// +/// On all platforms except windows, a call to [`Poll::poll`] is mostly just a +/// direct call to the system selector. However, [IOCP] uses a completion model +/// instead of a readiness model. In this case, `Poll` must adapt the completion +/// model Mio's API. While non-trivial, the bridge layer is still quite +/// efficient. The most expensive part being calls to `read` and `write` require +/// data to be copied into an intermediate buffer before it is passed to the +/// kernel. +/// +/// [epoll]: http://man7.org/linux/man-pages/man7/epoll.7.html +/// [kqueue]: https://www.freebsd.org/cgi/man.cgi?query=kqueue&sektion=2 +/// [IOCP]: https://msdn.microsoft.com/en-us/library/windows/desktop/aa365198(v=vs.85).aspx +/// [`signalfd`]: http://man7.org/linux/man-pages/man2/signalfd.2.html +/// [`SourceFd`]: unix/struct.SourceFd.html +/// [`Poll::poll`]: struct.Poll.html#method.poll +pub struct Poll { + registry: Registry, +} + +/// Registers I/O resources. +pub struct Registry { + selector: sys::Selector, +} + +impl Poll { + /// Create a separate `Registry` which can be used to register + /// `event::Source`s. + pub fn registry(&self) -> &Registry { + &self.registry + } + + /// Wait for readiness events + /// + /// Blocks the current thread and waits for readiness events for any of the + /// [`event::Source`]s that have been registered with this `Poll` instance. + /// The function will block until either at least one readiness event has + /// been received or `timeout` has elapsed. A `timeout` of `None` means that + /// `poll` will block until a readiness event has been received. + /// + /// The supplied `events` will be cleared and newly received readiness events + /// will be pushed onto the end. At most `events.capacity()` events will be + /// returned. If there are further pending readiness events, they will be + /// returned on the next call to `poll`. + /// + /// A single call to `poll` may result in multiple readiness events being + /// returned for a single event source. For example, if a TCP socket becomes + /// both readable and writable, it may be possible for a single readiness + /// event to be returned with both [`readable`] and [`writable`] readiness + /// **OR** two separate events may be returned, one with [`readable`] set + /// and one with [`writable`] set. + /// + /// Note that the `timeout` will be rounded up to the system clock + /// granularity (usually 1ms), and kernel scheduling delays mean that + /// the blocking interval may be overrun by a small amount. + /// + /// See the [struct] level documentation for a higher level discussion of + /// polling. + /// + /// [`event::Source`]: ./event/trait.Source.html + /// [`readable`]: struct.Interest.html#associatedconstant.READABLE + /// [`writable`]: struct.Interest.html#associatedconstant.WRITABLE + /// [struct]: struct.Poll.html + /// [`iter`]: ./event/struct.Events.html#method.iter + /// + /// # Notes + /// + /// This returns any errors without attempting to retry, previous versions + /// of Mio would automatically retry the poll call if it was interrupted + /// (if `EINTR` was returned). + /// + /// # Examples + /// + /// A basic example -- establishing a `TcpStream` connection. + /// + #[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")] + #[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")] + /// # use std::error::Error; + /// # fn main() -> Result<(), Box<dyn Error>> { + /// use mio::{Events, Poll, Interest, Token}; + /// use mio::net::TcpStream; + /// + /// use std::net::{TcpListener, SocketAddr}; + /// use std::thread; + /// + /// // Bind a server socket to connect to. + /// let addr: SocketAddr = "127.0.0.1:0".parse()?; + /// let server = TcpListener::bind(addr)?; + /// let addr = server.local_addr()?.clone(); + /// + /// // Spawn a thread to accept the socket + /// thread::spawn(move || { + /// let _ = server.accept(); + /// }); + /// + /// // Construct a new `Poll` handle as well as the `Events` we'll store into + /// let mut poll = Poll::new()?; + /// let mut events = Events::with_capacity(1024); + /// + /// // Connect the stream + /// let mut stream = TcpStream::connect(addr)?; + /// + /// // Register the stream with `Poll` + /// poll.registry().register( + /// &mut stream, + /// Token(0), + /// Interest::READABLE | Interest::WRITABLE)?; + /// + /// // Wait for the socket to become ready. This has to happens in a loop to + /// // handle spurious wakeups. + /// loop { + /// poll.poll(&mut events, None)?; + /// + /// for event in &events { + /// if event.token() == Token(0) && event.is_writable() { + /// // The socket connected (probably, it could still be a spurious + /// // wakeup) + /// return Ok(()); + /// } + /// } + /// } + /// # } + /// ``` + /// + /// [struct]: # + pub fn poll(&mut self, events: &mut Events, timeout: Option<Duration>) -> io::Result<()> { + self.registry.selector.select(events.sys(), timeout) + } +} + +cfg_os_poll! { + impl Poll { + /// Return a new `Poll` handle. + /// + /// This function will make a syscall to the operating system to create + /// the system selector. If this syscall fails, `Poll::new` will return + /// with the error. + /// + /// See [struct] level docs for more details. + /// + /// [struct]: struct.Poll.html + /// + /// # Examples + /// + /// ``` + /// # use std::error::Error; + /// # fn main() -> Result<(), Box<dyn Error>> { + /// use mio::{Poll, Events}; + /// use std::time::Duration; + /// + /// let mut poll = match Poll::new() { + /// Ok(poll) => poll, + /// Err(e) => panic!("failed to create Poll instance; err={:?}", e), + /// }; + /// + /// // Create a structure to receive polled events + /// let mut events = Events::with_capacity(1024); + /// + /// // Wait for events, but none will be received because no + /// // `event::Source`s have been registered with this `Poll` instance. + /// poll.poll(&mut events, Some(Duration::from_millis(500)))?; + /// assert!(events.is_empty()); + /// # Ok(()) + /// # } + /// ``` + pub fn new() -> io::Result<Poll> { + sys::Selector::new().map(|selector| Poll { + registry: Registry { selector }, + }) + } + } +} + +#[cfg(unix)] +impl AsRawFd for Poll { + fn as_raw_fd(&self) -> RawFd { + self.registry.as_raw_fd() + } +} + +impl fmt::Debug for Poll { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt.debug_struct("Poll").finish() + } +} + +impl Registry { + /// Register an [`event::Source`] with the `Poll` instance. + /// + /// Once registered, the `Poll` instance will monitor the event source for + /// readiness state changes. When it notices a state change, it will return + /// a readiness event for the handle the next time [`poll`] is called. + /// + /// See [`Poll`] docs for a high level overview. + /// + /// # Arguments + /// + /// `source: &mut S: event::Source`: This is the source of events that the + /// `Poll` instance should monitor for readiness state changes. + /// + /// `token: Token`: The caller picks a token to associate with the socket. + /// When [`poll`] returns an event for the handle, this token is included. + /// This allows the caller to map the event to its source. The token + /// associated with the `event::Source` can be changed at any time by + /// calling [`reregister`]. + /// + /// See documentation on [`Token`] for an example showing how to pick + /// [`Token`] values. + /// + /// `interest: Interest`: Specifies which operations `Poll` should monitor + /// for readiness. `Poll` will only return readiness events for operations + /// specified by this argument. + /// + /// If a socket is registered with readable interest and the socket becomes + /// writable, no event will be returned from [`poll`]. + /// + /// The readiness interest for an `event::Source` can be changed at any time + /// by calling [`reregister`]. + /// + /// # Notes + /// + /// Callers must ensure that if a source being registered with a `Poll` + /// instance was previously registered with that `Poll` instance, then a + /// call to [`deregister`] has already occurred. Consecutive calls to + /// `register` is unspecified behavior. + /// + /// Unless otherwise specified, the caller should assume that once an event + /// source is registered with a `Poll` instance, it is bound to that `Poll` + /// instance for the lifetime of the event source. This remains true even + /// if the event source is deregistered from the poll instance using + /// [`deregister`]. + /// + /// [`event::Source`]: ./event/trait.Source.html + /// [`poll`]: struct.Poll.html#method.poll + /// [`reregister`]: struct.Registry.html#method.reregister + /// [`deregister`]: struct.Registry.html#method.deregister + /// [`Token`]: struct.Token.html + /// + /// # Examples + /// + #[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")] + #[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")] + /// # use std::error::Error; + /// # use std::net; + /// # fn main() -> Result<(), Box<dyn Error>> { + /// use mio::{Events, Poll, Interest, Token}; + /// use mio::net::TcpStream; + /// use std::net::SocketAddr; + /// use std::time::{Duration, Instant}; + /// + /// let mut poll = Poll::new()?; + /// + /// let address: SocketAddr = "127.0.0.1:0".parse()?; + /// let listener = net::TcpListener::bind(address)?; + /// let mut socket = TcpStream::connect(listener.local_addr()?)?; + /// + /// // Register the socket with `poll` + /// poll.registry().register( + /// &mut socket, + /// Token(0), + /// Interest::READABLE | Interest::WRITABLE)?; + /// + /// let mut events = Events::with_capacity(1024); + /// let start = Instant::now(); + /// let timeout = Duration::from_millis(500); + /// + /// loop { + /// let elapsed = start.elapsed(); + /// + /// if elapsed >= timeout { + /// // Connection timed out + /// return Ok(()); + /// } + /// + /// let remaining = timeout - elapsed; + /// poll.poll(&mut events, Some(remaining))?; + /// + /// for event in &events { + /// if event.token() == Token(0) { + /// // Something (probably) happened on the socket. + /// return Ok(()); + /// } + /// } + /// } + /// # } + /// ``` + pub fn register<S>(&self, source: &mut S, token: Token, interests: Interest) -> io::Result<()> + where + S: event::Source + ?Sized, + { + trace!( + "registering event source with poller: token={:?}, interests={:?}", + token, + interests + ); + source.register(self, token, interests) + } + + /// Re-register an [`event::Source`] with the `Poll` instance. + /// + /// Re-registering an event source allows changing the details of the + /// registration. Specifically, it allows updating the associated `token` + /// and `interests` specified in previous `register` and `reregister` calls. + /// + /// The `reregister` arguments fully override the previous values. In other + /// words, if a socket is registered with [`readable`] interest and the call + /// to `reregister` specifies [`writable`], then read interest is no longer + /// requested for the handle. + /// + /// The event source must have previously been registered with this instance + /// of `Poll`, otherwise the behavior is unspecified. + /// + /// See the [`register`] documentation for details about the function + /// arguments and see the [`struct`] docs for a high level overview of + /// polling. + /// + /// # Examples + /// + #[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")] + #[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")] + /// # use std::error::Error; + /// # use std::net; + /// # fn main() -> Result<(), Box<dyn Error>> { + /// use mio::{Poll, Interest, Token}; + /// use mio::net::TcpStream; + /// use std::net::SocketAddr; + /// + /// let poll = Poll::new()?; + /// + /// let address: SocketAddr = "127.0.0.1:0".parse()?; + /// let listener = net::TcpListener::bind(address)?; + /// let mut socket = TcpStream::connect(listener.local_addr()?)?; + /// + /// // Register the socket with `poll`, requesting readable + /// poll.registry().register( + /// &mut socket, + /// Token(0), + /// Interest::READABLE)?; + /// + /// // Reregister the socket specifying write interest instead. Even though + /// // the token is the same it must be specified. + /// poll.registry().reregister( + /// &mut socket, + /// Token(0), + /// Interest::WRITABLE)?; + /// # Ok(()) + /// # } + /// ``` + /// + /// [`event::Source`]: ./event/trait.Source.html + /// [`struct`]: struct.Poll.html + /// [`register`]: struct.Registry.html#method.register + /// [`readable`]: ./event/struct.Event.html#is_readable + /// [`writable`]: ./event/struct.Event.html#is_writable + pub fn reregister<S>(&self, source: &mut S, token: Token, interests: Interest) -> io::Result<()> + where + S: event::Source + ?Sized, + { + trace!( + "reregistering event source with poller: token={:?}, interests={:?}", + token, + interests + ); + source.reregister(self, token, interests) + } + + /// Deregister an [`event::Source`] with the `Poll` instance. + /// + /// When an event source is deregistered, the `Poll` instance will no longer + /// monitor it for readiness state changes. Deregistering clears up any + /// internal resources needed to track the handle. After an explicit call + /// to this method completes, it is guaranteed that the token previously + /// registered to this handle will not be returned by a future poll, so long + /// as a happens-before relationship is established between this call and + /// the poll. + /// + /// The event source must have previously been registered with this instance + /// of `Poll`, otherwise the behavior is unspecified. + /// + /// A handle can be passed back to `register` after it has been + /// deregistered; however, it must be passed back to the **same** `Poll` + /// instance, otherwise the behavior is unspecified. + /// + /// # Examples + /// + #[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")] + #[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")] + /// # use std::error::Error; + /// # use std::net; + /// # fn main() -> Result<(), Box<dyn Error>> { + /// use mio::{Events, Poll, Interest, Token}; + /// use mio::net::TcpStream; + /// use std::net::SocketAddr; + /// use std::time::Duration; + /// + /// let mut poll = Poll::new()?; + /// + /// let address: SocketAddr = "127.0.0.1:0".parse()?; + /// let listener = net::TcpListener::bind(address)?; + /// let mut socket = TcpStream::connect(listener.local_addr()?)?; + /// + /// // Register the socket with `poll` + /// poll.registry().register( + /// &mut socket, + /// Token(0), + /// Interest::READABLE)?; + /// + /// poll.registry().deregister(&mut socket)?; + /// + /// let mut events = Events::with_capacity(1024); + /// + /// // Set a timeout because this poll should never receive any events. + /// poll.poll(&mut events, Some(Duration::from_secs(1)))?; + /// assert!(events.is_empty()); + /// # Ok(()) + /// # } + /// ``` + pub fn deregister<S>(&self, source: &mut S) -> io::Result<()> + where + S: event::Source + ?Sized, + { + trace!("deregistering event source from poller"); + source.deregister(self) + } + + /// Creates a new independently owned `Registry`. + /// + /// Event sources registered with this `Registry` will be registered with + /// the original `Registry` and `Poll` instance. + pub fn try_clone(&self) -> io::Result<Registry> { + self.selector + .try_clone() + .map(|selector| Registry { selector }) + } + + /// Internal check to ensure only a single `Waker` is active per [`Poll`] + /// instance. + #[cfg(debug_assertions)] + pub(crate) fn register_waker(&self) { + assert!( + !self.selector.register_waker(), + "Only a single `Waker` can be active per `Poll` instance" + ); + } + + /// Get access to the `sys::Selector`. + pub(crate) fn selector(&self) -> &sys::Selector { + &self.selector + } +} + +impl fmt::Debug for Registry { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt.debug_struct("Registry").finish() + } +} + +#[cfg(unix)] +impl AsRawFd for Registry { + fn as_raw_fd(&self) -> RawFd { + self.selector.as_raw_fd() + } +} + +cfg_os_poll! { + #[cfg(unix)] + #[test] + pub fn as_raw_fd() { + let poll = Poll::new().unwrap(); + assert!(poll.as_raw_fd() > 0); + } +} |