43 lines
1.4 KiB
Rust
43 lines
1.4 KiB
Rust
use core::task::{RawWaker, RawWakerVTable, Waker};
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use super::{wake_task, TaskHeader, TaskRef};
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static VTABLE: RawWakerVTable = RawWakerVTable::new(clone, wake, wake, drop);
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unsafe fn clone(p: *const ()) -> RawWaker {
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RawWaker::new(p, &VTABLE)
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}
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unsafe fn wake(p: *const ()) {
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wake_task(TaskRef::from_ptr(p as *const TaskHeader))
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}
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unsafe fn drop(_: *const ()) {
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// nop
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}
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pub(crate) unsafe fn from_task(p: TaskRef) -> Waker {
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Waker::from_raw(RawWaker::new(p.as_ptr() as _, &VTABLE))
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}
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/// Get a task pointer from a waker.
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///
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/// This can be used as an optimization in wait queues to store task pointers
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/// (1 word) instead of full Wakers (2 words). This saves a bit of RAM and helps
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/// avoid dynamic dispatch.
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///
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/// You can use the returned task pointer to wake the task with [`wake_task`](super::wake_task).
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///
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/// # Panics
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///
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/// Panics if the waker is not created by the Embassy executor.
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pub fn task_from_waker(waker: &Waker) -> TaskRef {
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// make sure to compare vtable addresses. Doing `==` on the references
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// will compare the contents, which is slower.
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if waker.vtable() as *const _ != &VTABLE as *const _ {
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panic!("Found waker not created by the Embassy executor. `embassy_time::Timer` only works with the Embassy executor.")
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}
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// safety: our wakers are always created with `TaskRef::as_ptr`
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unsafe { TaskRef::from_ptr(waker.data() as *const TaskHeader) }
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}
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