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use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll};
cfg_rt! {
/// Yields execution back to the Tokio runtime.
///
/// A task yields by awaiting on `yield_now()`, and may resume when that
/// future completes (with no output.) The current task will be re-added as
/// a pending task at the _back_ of the pending queue. Any other pending
/// tasks will be scheduled. No other waking is required for the task to
/// continue.
///
/// See also the usage example in the [task module](index.html#yield_now).
#[must_use = "yield_now does nothing unless polled/`await`-ed"]
pub async fn yield_now() {
/// Yield implementation
struct YieldNow {
yielded: bool,
}
impl Future for YieldNow {
type Output = ();
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()> {
if self.yielded {
return Poll::Ready(());
}
self.yielded = true;
cx.waker().wake_by_ref();
Poll::Pending
}
}
YieldNow { yielded: false }.await
}
}
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