1use core::task::{RawWaker, RawWakerVTable, Waker};
2
3use super::{wake_task, TaskHeader, TaskRef};
4
5static VTABLE: RawWakerVTable = RawWakerVTable::new(clone, wake, wake, drop);
6
7unsafe fn clone(p: *const ()) -> RawWaker {
8 RawWaker::new(data:p, &VTABLE)
9}
10
11unsafe fn wake(p: *const ()) {
12 wake_task(TaskRef::from_ptr(p as *const TaskHeader))
13}
14
15unsafe fn drop(_: *const ()) {
16 // nop
17}
18
19pub(crate) unsafe fn from_task(p: TaskRef) -> Waker {
20 Waker::from_raw(waker:RawWaker::new(data:p.as_ptr() as _, &VTABLE))
21}
22
23/// Get a task pointer from a waker.
24///
25/// This can be used as an optimization in wait queues to store task pointers
26/// (1 word) instead of full Wakers (2 words). This saves a bit of RAM and helps
27/// avoid dynamic dispatch.
28///
29/// You can use the returned task pointer to wake the task with [`wake_task`](super::wake_task).
30///
31/// # Panics
32///
33/// Panics if the waker is not created by the Embassy executor.
34pub fn task_from_waker(waker: &Waker) -> TaskRef {
35 // make sure to compare vtable addresses. Doing `==` on the references
36 // will compare the contents, which is slower.
37 if waker.vtable() as *const _ != &VTABLE as *const _ {
38 panic!("Found waker not created by the Embassy executor. `embassy_time::Timer` only works with the Embassy executor.")
39 }
40 // safety: our wakers are always created with `TaskRef::as_ptr`
41 unsafe { TaskRef::from_ptr(waker.data() as *const TaskHeader) }
42}
43