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use
{
std::{ future::Future, pin::Pin, task::{ Context, Poll } } ,
blanket::blanket,
};
/// Trait indicating that tasks can yield to the executor. This put's
/// the current task at the back of the schedulers queue, giving other
/// tasks a chance to run.
///
/// In practice for most executors this just returns a future that will,
/// the first time it is polled, wake up the waker and then return Pending.
///
/// The problem with using the executors native implementation is that they
/// generally return an opaque future we would have to box.
//
#[ blanket( derive(Ref, Mut, Arc, Rc, Box) ) ]
//
pub trait YieldNow
{
/// Await this future in order to yield to the executor.
//
fn yield_now( &self ) -> YieldNowFut
{
YieldNowFut{ done: false }
}
}
/// Future returned by [`YieldNow::yield_now`].
//
#[must_use = "YieldNowFut doesn't do anything unless polled or awaited."]
//
#[ derive( Debug, Copy, Clone ) ]
//
pub struct YieldNowFut
{
pub(crate) done: bool,
}
impl Future for YieldNowFut
{
type Output = ();
fn poll( mut self: Pin<&mut Self>, cx: &mut Context<'_> ) -> Poll<()>
{
if self.done
{
return Poll::Ready(());
}
self.done = true;
cx.waker().wake_by_ref();
Poll::Pending
}
}