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use core::mem::{self, ManuallyDrop};
use core::task::{RawWaker, RawWakerVTable, Waker};
use std::rc::Rc;
pub fn waker_fn<F: Fn() + Send + Sync + 'static>(f: F) -> Waker {
let raw = Rc::into_raw(Rc::new(f)) as *const ();
let vtable = &Helper::<F>::VTABLE;
unsafe { Waker::from_raw(RawWaker::new(raw, vtable)) }
}
struct Helper<F>(F);
impl<F: Fn() + Send + Sync + 'static> Helper<F> {
const VTABLE: RawWakerVTable = RawWakerVTable::new(
Self::clone_waker,
Self::wake,
Self::wake_by_ref,
Self::drop_waker,
);
#[allow(clippy::redundant_clone)]
unsafe fn clone_waker(ptr: *const ()) -> RawWaker {
let rc = ManuallyDrop::new(Rc::from_raw(ptr as *const F));
mem::forget(rc.clone());
RawWaker::new(ptr, &Self::VTABLE)
}
unsafe fn wake(ptr: *const ()) {
let rc = Rc::from_raw(ptr as *const F);
(rc)();
}
unsafe fn wake_by_ref(ptr: *const ()) {
let rc = ManuallyDrop::new(Rc::from_raw(ptr as *const F));
(rc)();
}
unsafe fn drop_waker(ptr: *const ()) {
drop(Rc::from_raw(ptr as *const F));
}
}