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use futures::task::AtomicWaker;
use futures::Future;
use crate::std::Instant;
use crate::timer::arc_list::Node;
use crate::timer::{ScheduledTimer, TimerHandle};
use std::fmt;
use std::pin::Pin;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::{Arc, Mutex};
use std::task::{Context, Poll};
use std::time::Duration;
pub struct Sleep {
state: Option<Arc<Node<ScheduledTimer>>>,
deadline: Instant,
}
impl Sleep {
/// Creates a new future which will fire at `dur` time into the future.
///
/// The returned object will be bound to the default timer for this thread.
/// The default timer will be spun up in a helper thread on first use.
#[inline]
pub(crate) fn new(dur: Duration) -> Sleep {
Sleep::new_at(Instant::now() + dur)
}
/// Creates a new future which will fire at the time specified by `at`.
///
/// The returned object will be bound to the default timer for this thread.
/// The default timer will be spun up in a helper thread on first use.
#[inline]
pub(crate) fn new_at(at: Instant) -> Sleep {
Sleep::new_handle(at, Default::default())
}
/// Creates a new future which will fire at the time specified by `at`.
///
/// The returned instance of `Delay` will be bound to the timer specified by
/// the `handle` argument.
pub(crate) fn new_handle(at: Instant, handle: TimerHandle) -> Sleep {
let inner = match handle.inner.upgrade() {
Some(i) => i,
None => {
return Sleep {
state: None,
deadline: at,
}
}
};
let state = Arc::new(Node::new(ScheduledTimer {
at: Mutex::new(Some(at)),
state: AtomicUsize::new(0),
waker: AtomicWaker::new(),
inner: handle.inner,
slot: Mutex::new(None),
}));
// If we fail to actually push our node then we've become an inert
// timer, meaning that we'll want to immediately return an error from
// `poll`.
if inner.list.push(&state).is_err() {
return Sleep {
state: None,
deadline: at,
};
}
inner.waker.wake();
Sleep {
state: Some(state),
deadline: at,
}
}
/// Returns the instant at which the future will complete.
pub fn deadline(&self) -> Instant {
self.deadline
}
/// Returns `true` if `Sleep` has elapsed
///
/// A `Sleep` instance is elapsed when the requested duration has elapsed
pub fn is_elapsed(&self) -> bool {
match self.state {
Some(ref state) => state.state.load(Ordering::SeqCst) & 1 != 0,
None => false,
}
}
/// Resets this timeout to an new timeout which will fire at the time
/// specified by `dur`.
///
/// This method is usable even of this instance of `Delay` has "already
/// fired". That is, if this future has resovled, calling this method means
/// that the future will still re-resolve at the specified instant.
///
/// If `at` is in the past then this future will immediately be resolved
/// (when `poll` is called).
///
/// Note that if any task is currently blocked on this future then that task
/// will be dropped. It is required to call `poll` again after this method
/// has been called to ensure tha ta task is blocked on this future.
// Actually we do not want to self to be a `Pin` but we gauranteed the
// API should be similiar to tokio API. So we have to accept a `Pin` to
// this method
#[inline]
pub fn reset(self: Pin<&mut Self>, deadline: Instant) {
let inner = self.get_mut();
inner.deadline = deadline;
if inner._reset(deadline).is_err() {
inner.state = None
}
}
fn _reset(&mut self, at: Instant) -> Result<(), ()> {
let state = match self.state {
Some(ref state) => state,
None => return Err(()),
};
if let Some(timeouts) = state.inner.upgrade() {
let mut bits = state.state.load(Ordering::SeqCst);
loop {
// If we've been invalidated, cancel this reset
if bits & 0b10 != 0 {
return Err(());
}
let new = bits.wrapping_add(0b100) & !0b11;
match state
.state
.compare_exchange(bits, new, Ordering::SeqCst, Ordering::SeqCst)
{
Ok(_) => break,
Err(s) => bits = s,
}
}
*state.at.lock().unwrap() = Some(at);
// If we fail to push our node then we've become an inert timer, so
// we'll want to clear our `state` field accordingly
timeouts.list.push(state)?;
timeouts.waker.wake();
}
Ok(())
}
}
pub fn sleep(duration: Duration) -> Sleep {
Sleep::new(duration)
}
pub fn sleep_until(instant: Instant) -> Sleep {
Sleep::new_at(instant)
}
impl Future for Sleep {
type Output = ();
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let state = match self.state {
Some(ref state) => state,
None => panic!("timer has gone away"),
};
if state.state.load(Ordering::SeqCst) & 1 != 0 {
return Poll::Ready(());
}
state.waker.register(cx.waker());
// Now that we've registered, do the full check of our own internal
// state. If we've fired the first bit is set, and if we've been
// invalidated the second bit is set.
match state.state.load(Ordering::SeqCst) {
n if n & 0b01 != 0 => Poll::Ready(()),
n if n & 0b10 != 0 => panic!("Timer has gone away"),
_ => Poll::Pending,
}
}
}
impl Drop for Sleep {
fn drop(&mut self) {
let state = match self.state {
Some(ref s) => s,
None => return,
};
if let Some(timeouts) = state.inner.upgrade() {
*state.at.lock().unwrap() = None;
if timeouts.list.push(state).is_ok() {
timeouts.waker.wake();
}
}
}
}
impl fmt::Debug for Sleep {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
f.debug_struct("Delay")
.field("deadline", &self.deadline)
.finish()
}
}