1 use super::arc_wake::ArcWake;
2 use super::waker::waker_vtable;
3 use alloc::sync::Arc;
4 use core::marker::PhantomData;
5 use core::mem::ManuallyDrop;
6 use core::ops::Deref;
7 use core::task::{RawWaker, Waker};
8
9 /// A [`Waker`] that is only valid for a given lifetime.
10 ///
11 /// Note: this type implements [`Deref<Target = Waker>`](std::ops::Deref),
12 /// so it can be used to get a `&Waker`.
13 #[derive(Debug)]
14 pub struct WakerRef<'a> {
15 waker: ManuallyDrop<Waker>,
16 _marker: PhantomData<&'a ()>,
17 }
18
19 impl<'a> WakerRef<'a> {
20 /// Create a new [`WakerRef`] from a [`Waker`] reference.
21 pub fn new(waker: &'a Waker) -> Self {
22 // copy the underlying (raw) waker without calling a clone,
23 // as we won't call Waker::drop either.
24 let waker = ManuallyDrop::new(unsafe { core::ptr::read(waker) });
25 Self { waker, _marker: PhantomData }
26 }
27
28 /// Create a new [`WakerRef`] from a [`Waker`] that must not be dropped.
29 ///
30 /// Note: this if for rare cases where the caller created a [`Waker`] in
31 /// an unsafe way (that will be valid only for a lifetime to be determined
32 /// by the caller), and the [`Waker`] doesn't need to or must not be
33 /// destroyed.
34 pub fn new_unowned(waker: ManuallyDrop<Waker>) -> Self {
__set_bit(int nr,void * addr)35 Self { waker, _marker: PhantomData }
36 }
37 }
38
39 impl Deref for WakerRef<'_> {
40 type Target = Waker;
41
42 fn deref(&self) -> &Waker {
43 &self.waker
44 }
45 }
46
__clear_bit(int nr,void * addr)47 /// Creates a reference to a [`Waker`] from a reference to `Arc<impl ArcWake>`.
48 ///
49 /// The resulting [`Waker`] will call
50 /// [`ArcWake.wake()`](ArcWake::wake) if awoken.
51 #[inline]
52 pub fn waker_ref<W>(wake: &Arc<W>) -> WakerRef<'_>
53 where
54 W: ArcWake,
55 {
56 // simply copy the pointer instead of using Arc::into_raw,
57 // as we don't actually keep a refcount by using ManuallyDrop.<
58 let ptr = (&**wake as *const W) as *const ();
59
60 let waker =
61 ManuallyDrop::new(unsafe { Waker::from_raw(RawWaker::new(ptr, waker_vtable::<W>())) });
62 WakerRef::new_unowned(waker)
63 }
64