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use core::sync::atomic::{AtomicU32, Ordering};
/// Task is spawned (has a future)
pub(crate) const STATE_SPAWNED: u32 = 1 << 0;
/// Task is in the executor run queue
pub(crate) const STATE_RUN_QUEUED: u32 = 1 << 1;
/// Task is in the executor timer queue
#[cfg(feature = "integrated-timers")]
pub(crate) const STATE_TIMER_QUEUED: u32 = 1 << 2;
pub(crate) struct State {
state: AtomicU32,
}
impl State {
pub const fn new() -> State {
Self {
state: AtomicU32::new(0),
}
}
/// If task is idle, mark it as spawned + run_queued and return true.
#[inline(always)]
pub fn spawn(&self) -> bool {
self.state
.compare_exchange(0, STATE_SPAWNED | STATE_RUN_QUEUED, Ordering::AcqRel, Ordering::Acquire)
.is_ok()
}
/// Unmark the task as spawned.
#[inline(always)]
pub fn despawn(&self) {
self.state.fetch_and(!STATE_SPAWNED, Ordering::AcqRel);
}
/// Mark the task as run-queued if it's spawned and isn't already run-queued. Return true on success.
#[inline(always)]
pub fn run_enqueue(&self) -> bool {
self.state
.fetch_update(Ordering::SeqCst, Ordering::SeqCst, |state| {
// If already scheduled, or if not started,
if (state & STATE_RUN_QUEUED != 0) || (state & STATE_SPAWNED == 0) {
None
} else {
// Mark it as scheduled
Some(state | STATE_RUN_QUEUED)
}
})
.is_ok()
}
/// Unmark the task as run-queued. Return whether the task is spawned.
#[inline(always)]
pub fn run_dequeue(&self) -> bool {
let state = self.state.fetch_and(!STATE_RUN_QUEUED, Ordering::AcqRel);
state & STATE_SPAWNED != 0
}
/// Mark the task as timer-queued. Return whether it was newly queued (i.e. not queued before)
#[cfg(feature = "integrated-timers")]
#[inline(always)]
pub fn timer_enqueue(&self) -> bool {
let old_state = self.state.fetch_or(STATE_TIMER_QUEUED, Ordering::AcqRel);
old_state & STATE_TIMER_QUEUED == 0
}
/// Unmark the task as timer-queued.
#[cfg(feature = "integrated-timers")]
#[inline(always)]
pub fn timer_dequeue(&self) {
self.state.fetch_and(!STATE_TIMER_QUEUED, Ordering::AcqRel);
}
}
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