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use std::{cell::RefCell, collections::HashMap, rc::Rc, sync::Arc, time::Duration};
#[cfg(unix)]
use std::os::unix::io::{AsFd, AsRawFd, BorrowedFd as Borrowed, RawFd as Raw};
#[cfg(windows)]
use std::os::windows::io::{AsRawSocket, AsSocket, BorrowedSocket as Borrowed, RawSocket as Raw};
use polling::{Event, Events, PollMode, Poller};
use crate::sources::timer::TimerWheel;
use crate::token::TokenInner;
use crate::RegistrationToken;
/// Possible modes for registering a file descriptor
#[derive(Copy, Clone, Debug)]
pub enum Mode {
/// Single event generation
///
/// This FD will be disabled as soon as it has generated one event.
///
/// The user will need to use `LoopHandle::update()` to re-enable it if
/// desired.
OneShot,
/// Level-triggering
///
/// This FD will report events on every poll as long as the requested interests
/// are available.
Level,
/// Edge-triggering
///
/// This FD will report events only when it *gains* one of the requested interests.
/// it must thus be fully processed before it'll generate events again.
///
/// This mode is not supported on certain platforms, and an error will be returned
/// if it is used.
///
/// ## Supported Platforms
///
/// As of the time of writing, the platforms that support edge triggered polling are
/// as follows:
///
/// - Linux/Android
/// - macOS/iOS/tvOS/watchOS
/// - FreeBSD/OpenBSD/NetBSD/DragonflyBSD
Edge,
}
/// Interest to register regarding the file descriptor
#[derive(Copy, Clone, Debug)]
pub struct Interest {
/// Wait for the FD to be readable
pub readable: bool,
/// Wait for the FD to be writable
pub writable: bool,
}
impl Interest {
/// Shorthand for empty interest
pub const EMPTY: Interest = Interest {
readable: false,
writable: false,
};
/// Shorthand for read interest
pub const READ: Interest = Interest {
readable: true,
writable: false,
};
/// Shorthand for write interest
pub const WRITE: Interest = Interest {
readable: false,
writable: true,
};
/// Shorthand for read and write interest
pub const BOTH: Interest = Interest {
readable: true,
writable: true,
};
}
/// Readiness for a file descriptor notification
#[derive(Copy, Clone, Debug)]
pub struct Readiness {
/// Is the FD readable
pub readable: bool,
/// Is the FD writable
pub writable: bool,
/// Is the FD in an error state
pub error: bool,
}
impl Readiness {
/// Shorthand for empty readiness
pub const EMPTY: Readiness = Readiness {
readable: false,
writable: false,
error: false,
};
}
#[derive(Debug)]
pub(crate) struct PollEvent {
pub(crate) readiness: Readiness,
pub(crate) token: Token,
}
/// Factory for creating tokens in your registrations
///
/// When composing event sources, each sub-source needs to
/// have its own token to identify itself. This factory is
/// provided to produce such unique tokens.
#[derive(Debug)]
pub struct TokenFactory {
next_token: TokenInner,
}
impl TokenFactory {
pub(crate) fn new(token: TokenInner) -> TokenFactory {
TokenFactory {
next_token: token.forget_sub_id(),
}
}
/// Get the "raw" registration token of this TokenFactory
pub(crate) fn registration_token(&self) -> RegistrationToken {
RegistrationToken::new(self.next_token.forget_sub_id())
}
/// Produce a new unique token
pub fn token(&mut self) -> Token {
let token = self.next_token;
self.next_token = token.increment_sub_id();
Token { inner: token }
}
}
/// A token (for implementation of the [`EventSource`](crate::EventSource) trait)
///
/// This token is produced by the [`TokenFactory`] and is used when calling the
/// [`EventSource`](crate::EventSource) implementations to process event, in order
/// to identify which sub-source produced them.
///
/// You should forward it to the [`Poll`] when registering your file descriptors.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct Token {
pub(crate) inner: TokenInner,
}
/// The polling system
///
/// This type represents the polling system of calloop, on which you
/// can register your file descriptors. This interface is only accessible in
/// implementations of the [`EventSource`](crate::EventSource) trait.
///
/// You only need to interact with this type if you are implementing your
/// own event sources, while implementing the [`EventSource`](crate::EventSource) trait.
/// And even in this case, you can often just use the [`Generic`](crate::generic::Generic) event
/// source and delegate the implementations to it.
pub struct Poll {
/// The handle to wepoll/epoll/kqueue/... used to poll for events.
pub(crate) poller: Arc<Poller>,
/// The buffer of events returned by the poller.
events: RefCell<Events>,
/// The sources registered as level triggered.
///
/// Some platforms that `polling` supports do not support level-triggered events. As of the time
/// of writing, this only includes Solaris and illumos. To work around this, we emulate level
/// triggered events by keeping this map of file descriptors.
///
/// One can emulate level triggered events on top of oneshot events by just re-registering the
/// file descriptor every time it is polled. However, this is not ideal, as it requires a
/// system call every time. It's better to use the intergrated system, if available.
level_triggered: Option<RefCell<HashMap<usize, (Raw, polling::Event)>>>,
pub(crate) timers: Rc<RefCell<TimerWheel>>,
}
impl std::fmt::Debug for Poll {
#[cfg_attr(feature = "nightly_coverage", coverage(off))]
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.write_str("Poll { ... }")
}
}
impl Poll {
pub(crate) fn new() -> crate::Result<Poll> {
Self::new_inner(false)
}
fn new_inner(force_fallback_lt: bool) -> crate::Result<Poll> {
let poller = Poller::new()?;
let level_triggered = if poller.supports_level() && !force_fallback_lt {
None
} else {
Some(RefCell::new(HashMap::new()))
};
Ok(Poll {
poller: Arc::new(poller),
events: RefCell::new(Events::new()),
timers: Rc::new(RefCell::new(TimerWheel::new())),
level_triggered,
})
}
pub(crate) fn poll(&self, mut timeout: Option<Duration>) -> crate::Result<Vec<PollEvent>> {
let now = std::time::Instant::now();
// Adjust the timeout for the timers.
if let Some(next_timeout) = self.timers.borrow().next_deadline() {
if next_timeout <= now {
timeout = Some(Duration::ZERO);
} else if let Some(deadline) = timeout {
timeout = Some(std::cmp::min(deadline, next_timeout - now));
} else {
timeout = Some(next_timeout - now);
}
};
let mut events = self.events.borrow_mut();
events.clear();
self.poller.wait(&mut events, timeout)?;
// Convert `polling` events to `calloop` events.
let level_triggered = self.level_triggered.as_ref().map(RefCell::borrow);
let mut poll_events = events
.iter()
.map(|ev| {
// If we need to emulate level-triggered events...
if let Some(level_triggered) = level_triggered.as_ref() {
// ...and this event is from a level-triggered source...
if let Some((source, interest)) = level_triggered.get(&ev.key) {
// ...then we need to re-register the source.
// SAFETY: The source is valid.
self.poller
.modify(unsafe { Borrowed::borrow_raw(*source) }, *interest)?;
}
}
Ok(PollEvent {
readiness: Readiness {
readable: ev.readable,
writable: ev.writable,
error: false,
},
token: Token {
inner: TokenInner::from(ev.key),
},
})
})
.collect::<std::io::Result<Vec<_>>>()?;
drop(events);
// Update 'now' as some time may have elapsed in poll()
let now = std::time::Instant::now();
let mut timers = self.timers.borrow_mut();
while let Some((_, token)) = timers.next_expired(now) {
poll_events.push(PollEvent {
readiness: Readiness {
readable: true,
writable: false,
error: false,
},
token,
});
}
Ok(poll_events)
}
/// Register a new file descriptor for polling
///
/// The file descriptor will be registered with given interest,
/// mode and token. This function will fail if given a
/// bad file descriptor or if the provided file descriptor is already
/// registered.
///
/// # Safety
///
/// The registered source must not be dropped before it is unregistered.
///
/// # Leaking tokens
///
/// If your event source is dropped without being unregistered, the token
/// passed in here will remain on the heap and continue to be used by the
/// polling system even though no event source will match it.
pub unsafe fn register(
&self,
#[cfg(unix)] fd: impl AsFd,
#[cfg(windows)] fd: impl AsSocket,
interest: Interest,
mode: Mode,
token: Token,
) -> crate::Result<()> {
let raw = {
#[cfg(unix)]
{
fd.as_fd().as_raw_fd()
}
#[cfg(windows)]
{
fd.as_socket().as_raw_socket()
}
};
let ev = cvt_interest(interest, token);
// SAFETY: See invariant on function.
unsafe {
self.poller
.add_with_mode(raw, ev, cvt_mode(mode, self.poller.supports_level()))?;
}
// If this is level triggered and we're emulating level triggered mode...
if let (Mode::Level, Some(level_triggered)) = (mode, self.level_triggered.as_ref()) {
// ...then we need to keep track of the source.
let mut level_triggered = level_triggered.borrow_mut();
level_triggered.insert(ev.key, (raw, ev));
}
Ok(())
}
/// Update the registration for a file descriptor
///
/// This allows you to change the interest, mode or token of a file
/// descriptor. Fails if the provided fd is not currently registered.
///
/// See note on [`register()`](Self::register()) regarding leaking.
pub fn reregister(
&self,
#[cfg(unix)] fd: impl AsFd,
#[cfg(windows)] fd: impl AsSocket,
interest: Interest,
mode: Mode,
token: Token,
) -> crate::Result<()> {
let (borrowed, raw) = {
#[cfg(unix)]
{
(fd.as_fd(), fd.as_fd().as_raw_fd())
}
#[cfg(windows)]
{
(fd.as_socket(), fd.as_socket().as_raw_socket())
}
};
let ev = cvt_interest(interest, token);
self.poller
.modify_with_mode(borrowed, ev, cvt_mode(mode, self.poller.supports_level()))?;
// If this is level triggered and we're emulating level triggered mode...
if let (Mode::Level, Some(level_triggered)) = (mode, self.level_triggered.as_ref()) {
// ...then we need to keep track of the source.
let mut level_triggered = level_triggered.borrow_mut();
level_triggered.insert(ev.key, (raw, ev));
}
Ok(())
}
/// Unregister a file descriptor
///
/// This file descriptor will no longer generate events. Fails if the
/// provided file descriptor is not currently registered.
pub fn unregister(
&self,
#[cfg(unix)] fd: impl AsFd,
#[cfg(windows)] fd: impl AsSocket,
) -> crate::Result<()> {
let (borrowed, raw) = {
#[cfg(unix)]
{
(fd.as_fd(), fd.as_fd().as_raw_fd())
}
#[cfg(windows)]
{
(fd.as_socket(), fd.as_socket().as_raw_socket())
}
};
self.poller.delete(borrowed)?;
if let Some(level_triggered) = self.level_triggered.as_ref() {
let mut level_triggered = level_triggered.borrow_mut();
level_triggered.retain(|_, (source, _)| *source != raw);
}
Ok(())
}
/// Get a thread-safe handle which can be used to wake up the `Poll`.
pub(crate) fn notifier(&self) -> Notifier {
Notifier(self.poller.clone())
}
/// Get a reference to the poller.
pub(crate) fn poller(&self) -> &Arc<Poller> {
&self.poller
}
}
/// Thread-safe handle which can be used to wake up the `Poll`.
#[derive(Clone)]
pub(crate) struct Notifier(Arc<Poller>);
impl Notifier {
pub(crate) fn notify(&self) -> crate::Result<()> {
self.0.notify()?;
Ok(())
}
}
fn cvt_interest(interest: Interest, tok: Token) -> Event {
let mut event = Event::none(tok.inner.into());
event.readable = interest.readable;
event.writable = interest.writable;
event
}
fn cvt_mode(mode: Mode, supports_other_modes: bool) -> PollMode {
if !supports_other_modes {
return PollMode::Oneshot;
}
match mode {
Mode::Edge => PollMode::Edge,
Mode::Level => PollMode::Level,
Mode::OneShot => PollMode::Oneshot,
}
}