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compat: use a CurrentRef waker in 01 compat #1262

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merged 1 commit into from
Oct 1, 2018
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compat: use a CurrentRef waker in 01 compat #1262

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32 changes: 25 additions & 7 deletions futures-util/src/compat/compat03to01.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@ use futures_core::{
task as task03, TryFuture as TryFuture03, TryStream as TryStream03,
};
use futures_sink::Sink as Sink03;
use std::{marker::Unpin, pin::PinMut, sync::Arc};
use std::{marker::Unpin, pin::PinMut, ptr::NonNull, sync::Arc};

impl<Fut, Sp> Future01 for Compat<Fut, Sp>
where
Expand Down Expand Up @@ -85,14 +85,32 @@ where
}
}

fn current_as_waker() -> task03::LocalWaker {
let arc_waker = Arc::new(Current(task01::current()));
task03::local_waker_from_nonlocal(arc_waker)
fn current_ref_as_waker() -> task03::LocalWaker {
unsafe {
task03::LocalWaker::new(NonNull::<CurrentRef>::dangling())
}
}

struct Current(task01::Task);
struct CurrentRef;

struct CurrentOwned(task01::Task);

unsafe impl task03::UnsafeWake for CurrentRef {
#[inline]
unsafe fn clone_raw(&self) -> task03::Waker {
task03::Waker::from(Arc::new(CurrentOwned(task01::current())))
}

#[inline]
unsafe fn drop_raw(&self) {} // Does nothing

#[inline]
unsafe fn wake(&self) {
task01::current().notify();
}
}

impl task03::Wake for Current {
impl task03::Wake for CurrentOwned {
fn wake(arc_self: &Arc<Self>) {
arc_self.0.notify();
}
Expand All @@ -104,7 +122,7 @@ where
E: task03::Spawn,
F: FnOnce(PinMut<T>, &mut task03::Context) -> R,
{
let waker = current_as_waker();
let waker = current_ref_as_waker();
let spawn = compat.spawn.as_mut().unwrap();
let mut cx = task03::Context::new(&waker, spawn);
f(PinMut::new(&mut compat.inner), &mut cx)
Expand Down