embedded_runtime/
spin.rs

1//! A future to spin once to give up a timeslice
2
3use core::{
4    future::Future,
5    pin::Pin,
6    task::{Context, Poll},
7};
8
9/// A future that can be polled once before it becomes ready; useful to cooperatively give up a timeslice to the
10/// runtime/other pending futures
11///
12/// # Behaviour
13/// Polling this future will immediately wake the waker again and yield, making room for other futures to execute. This
14/// is useful for e.g. running intensive loops or similar inside a future.
15#[derive(Debug, Default)]
16pub struct SpinFuture {
17    /// Whether the future has been polled already or not
18    polled: bool,
19}
20impl SpinFuture {
21    /// Creates a new spin future
22    ///
23    /// # Note
24    /// This future should usually not be constructed directly, use [`spin_once`] instead.
25    pub const fn new() -> Self {
26        Self { polled: false }
27    }
28}
29impl Future for SpinFuture {
30    type Output = ();
31
32    fn poll(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
33        if !self.polled {
34            // Mark the future as polled so that it returns ready the next time
35            self.polled = true;
36            cx.waker().wake_by_ref();
37            Poll::Pending
38        } else {
39            // The future has been polled, so it's ready now
40            Poll::Ready(())
41        }
42    }
43}
44
45/// A function that can be awaited once before it returns; useful to cooperatively give up a timeslice to the
46/// runtime/other pending futures
47///
48/// # Behaviour
49/// Awaiting this function will immediately wake the waker again and yield, making room for other futures to execute.
50/// This is useful for e.g. running intensive loops or similar inside a future.
51pub async fn spin_once() {
52    SpinFuture::new().await
53}
embedded_runtime/spin.rs

embedded_runtime/
spin.rs
