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use core::cell::Cell;
use core::task::Waker;
use crate::blocking_mutex::raw::{CriticalSectionRawMutex, RawMutex};
use crate::blocking_mutex::Mutex;
/// Utility struct to register and wake a waker.
/// If a waker is registered, registering another waker will replace the previous one without waking it.
/// Intended to wake a task from an interrupt. Therefore, it is generally not expected,
/// that multiple tasks register try to register a waker simultaneously.
pub struct GenericAtomicWaker<M: RawMutex> {
waker: Mutex<M, Cell<Option<Waker>>>,
}
impl<M: RawMutex> GenericAtomicWaker<M> {
/// Create a new `AtomicWaker`.
pub const fn new(mutex: M) -> Self {
Self {
waker: Mutex::const_new(mutex, Cell::new(None)),
}
}
/// Register a waker. Overwrites the previous waker, if any.
pub fn register(&self, w: &Waker) {
self.waker.lock(|cell| {
cell.set(match cell.replace(None) {
Some(w2) if (w2.will_wake(w)) => Some(w2),
_ => Some(w.clone()),
})
})
}
/// Wake the registered waker, if any.
pub fn wake(&self) {
self.waker.lock(|cell| {
if let Some(w) = cell.replace(None) {
w.wake_by_ref();
cell.set(Some(w));
}
})
}
}
/// Utility struct to register and wake a waker.
pub struct AtomicWaker {
waker: GenericAtomicWaker<CriticalSectionRawMutex>,
}
impl AtomicWaker {
/// Create a new `AtomicWaker`.
pub const fn new() -> Self {
Self {
waker: GenericAtomicWaker::new(CriticalSectionRawMutex::new()),
}
}
/// Register a waker. Overwrites the previous waker, if any.
pub fn register(&self, w: &Waker) {
self.waker.register(w);
}
/// Wake the registered waker, if any.
pub fn wake(&self) {
self.waker.wake();
}
}
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