59 lines
1.9 KiB
Rust
59 lines
1.9 KiB
Rust
use super::arc_wake::ArcWake;
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use alloc::sync::Arc;
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use core::mem;
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use core::task::{RawWaker, RawWakerVTable, Waker};
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pub(super) fn waker_vtable<W: ArcWake>() -> &'static RawWakerVTable {
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&RawWakerVTable::new(
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clone_arc_raw::<W>,
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wake_arc_raw::<W>,
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wake_by_ref_arc_raw::<W>,
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drop_arc_raw::<W>,
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)
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}
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/// Creates a [`Waker`] from an `Arc<impl ArcWake>`.
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///
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/// The returned [`Waker`] will call
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/// [`ArcWake.wake()`](ArcWake::wake) if awoken.
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pub fn waker<W>(wake: Arc<W>) -> Waker
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where
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W: ArcWake + 'static,
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{
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let ptr = Arc::into_raw(wake).cast::<()>();
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unsafe { Waker::from_raw(RawWaker::new(ptr, waker_vtable::<W>())) }
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}
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// FIXME: panics on Arc::clone / refcount changes could wreak havoc on the
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// code here. We should guard against this by aborting.
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#[allow(clippy::redundant_clone)] // The clone here isn't actually redundant.
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unsafe fn increase_refcount<T: ArcWake>(data: *const ()) {
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// Retain Arc, but don't touch refcount by wrapping in ManuallyDrop
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let arc = mem::ManuallyDrop::new(Arc::<T>::from_raw(data.cast::<T>()));
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// Now increase refcount, but don't drop new refcount either
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let _arc_clone: mem::ManuallyDrop<_> = arc.clone();
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}
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// used by `waker_ref`
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unsafe fn clone_arc_raw<T: ArcWake>(data: *const ()) -> RawWaker {
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increase_refcount::<T>(data);
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RawWaker::new(data, waker_vtable::<T>())
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}
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unsafe fn wake_arc_raw<T: ArcWake>(data: *const ()) {
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let arc: Arc<T> = Arc::from_raw(data.cast::<T>());
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ArcWake::wake(arc);
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}
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// used by `waker_ref`
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unsafe fn wake_by_ref_arc_raw<T: ArcWake>(data: *const ()) {
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// Retain Arc, but don't touch refcount by wrapping in ManuallyDrop
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let arc = mem::ManuallyDrop::new(Arc::<T>::from_raw(data.cast::<T>()));
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ArcWake::wake_by_ref(&arc);
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}
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unsafe fn drop_arc_raw<T: ArcWake>(data: *const ()) {
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drop(Arc::<T>::from_raw(data.cast::<T>()))
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}
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