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//! Timer queue operations.
use core::cell::Cell;
use super::TaskRef;
#[cfg(feature = "_timer-item-payload")]
macro_rules! define_opaque {
($size:tt) => {
/// An opaque data type.
#[repr(align($size))]
pub struct OpaqueData {
data: [u8; $size],
}
impl OpaqueData {
const fn new() -> Self {
Self { data: [0; $size] }
}
/// Access the data as a reference to a type `T`.
///
/// Safety:
///
/// The caller must ensure that the size of the type `T` is less than, or equal to
/// the size of the payload, and must ensure that the alignment of the type `T` is
/// less than, or equal to the alignment of the payload.
///
/// The type must be valid when zero-initialized.
pub unsafe fn as_ref<T>(&self) -> &T {
&*(self.data.as_ptr() as *const T)
}
}
};
}
#[cfg(feature = "timer-item-payload-size-1")]
define_opaque!(1);
#[cfg(feature = "timer-item-payload-size-2")]
define_opaque!(2);
#[cfg(feature = "timer-item-payload-size-4")]
define_opaque!(4);
#[cfg(feature = "timer-item-payload-size-8")]
define_opaque!(8);
/// An item in the timer queue.
pub struct TimerQueueItem {
/// The next item in the queue.
///
/// If this field contains `Some`, the item is in the queue. The last item in the queue has a
/// value of `Some(dangling_pointer)`
pub next: Cell<Option<TaskRef>>,
/// The time at which this item expires.
pub expires_at: Cell<u64>,
/// Some implementation-defined, zero-initialized piece of data.
#[cfg(feature = "_timer-item-payload")]
pub payload: OpaqueData,
}
unsafe impl Sync for TimerQueueItem {}
impl TimerQueueItem {
pub(crate) const fn new() -> Self {
Self {
next: Cell::new(None),
expires_at: Cell::new(0),
#[cfg(feature = "_timer-item-payload")]
payload: OpaqueData::new(),
}
}
}
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