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use core::future::Future;
use core::pin::Pin;
use core::task::{Context, Poll};
use futures_util::future::{select, Either};
use futures_util::{pin_mut, Stream};
use crate::executor::raw;
use crate::time::{Duration, Instant};
/// Error returned by [`with_timeout`] on timeout.
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "defmt", derive(defmt::Format))]
pub struct TimeoutError;
/// Runs a given future with a timeout.
///
/// If the future completes before the timeout, its output is returned. Otherwise, on timeout,
/// work on the future is stopped (`poll` is no longer called), the future is dropped and `Err(TimeoutError)` is returned.
pub async fn with_timeout<F: Future>(timeout: Duration, fut: F) -> Result<F::Output, TimeoutError> {
let timeout_fut = Timer::after(timeout);
pin_mut!(fut);
match select(fut, timeout_fut).await {
Either::Left((r, _)) => Ok(r),
Either::Right(_) => Err(TimeoutError),
}
}
/// A future that completes at a specified [Instant](struct.Instant.html).
pub struct Timer {
expires_at: Instant,
yielded_once: bool,
}
impl Timer {
/// Expire at specified [Instant](struct.Instant.html)
pub fn at(expires_at: Instant) -> Self {
Self {
expires_at,
yielded_once: false,
}
}
/// Expire after specified [Duration](struct.Duration.html).
/// This can be used as a `sleep` abstraction.
///
/// Example:
/// ``` no_run
/// # #![feature(type_alias_impl_trait)]
/// #
/// # fn foo() {}
/// use embassy_executor::time::{Duration, Timer};
///
/// #[embassy_executor::task]
/// async fn demo_sleep_seconds() {
/// // suspend this task for one second.
/// Timer::after(Duration::from_secs(1)).await;
/// }
/// ```
pub fn after(duration: Duration) -> Self {
Self {
expires_at: Instant::now() + duration,
yielded_once: false,
}
}
}
impl Unpin for Timer {}
impl Future for Timer {
type Output = ();
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
if self.yielded_once && self.expires_at <= Instant::now() {
Poll::Ready(())
} else {
unsafe { raw::register_timer(self.expires_at, cx.waker()) };
self.yielded_once = true;
Poll::Pending
}
}
}
/// Asynchronous stream that yields every Duration, indefinitely.
///
/// This stream will tick at uniform intervals, even if blocking work is performed between ticks.
///
/// For instance, consider the following code fragment.
/// ``` no_run
/// # #![feature(type_alias_impl_trait)]
/// #
/// use embassy_executor::time::{Duration, Timer};
/// # fn foo() {}
///
/// #[embassy_executor::task]
/// async fn ticker_example_0() {
/// loop {
/// foo();
/// Timer::after(Duration::from_secs(1)).await;
/// }
/// }
/// ```
///
/// This fragment will not call `foo` every second.
/// Instead, it will call it every second + the time it took to previously call `foo`.
///
/// Example using ticker, which will consistently call `foo` once a second.
///
/// ``` no_run
/// # #![feature(type_alias_impl_trait)]
/// #
/// use embassy_executor::time::{Duration, Ticker};
/// use futures::StreamExt;
/// # fn foo(){}
///
/// #[embassy_executor::task]
/// async fn ticker_example_1() {
/// let mut ticker = Ticker::every(Duration::from_secs(1));
/// loop {
/// foo();
/// ticker.next().await;
/// }
/// }
/// ```
pub struct Ticker {
expires_at: Instant,
duration: Duration,
}
impl Ticker {
/// Creates a new ticker that ticks at the specified duration interval.
pub fn every(duration: Duration) -> Self {
let expires_at = Instant::now() + duration;
Self { expires_at, duration }
}
}
impl Unpin for Ticker {}
impl Stream for Ticker {
type Item = ();
fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
if self.expires_at <= Instant::now() {
let dur = self.duration;
self.expires_at += dur;
Poll::Ready(Some(()))
} else {
unsafe { raw::register_timer(self.expires_at, cx.waker()) };
Poll::Pending
}
}
}
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