53 lines
1.7 KiB
Rust
53 lines
1.7 KiB
Rust
use core::mem;
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use core::task::{RawWaker, RawWakerVTable, Waker};
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use super::{wake_task, TaskHeader, TaskRef};
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const 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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// safety: OK because WakerHack has the same layout as Waker.
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// This is not really guaranteed because the structs are `repr(Rust)`, it is
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// indeed the case in the current implementation.
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// TODO use waker_getters when stable. https://github.com/rust-lang/rust/issues/96992
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let hack: &WakerHack = unsafe { mem::transmute(waker) };
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if hack.vtable != &VTABLE {
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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(hack.data as *const TaskHeader) }
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}
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struct WakerHack {
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data: *const (),
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vtable: &'static RawWakerVTable,
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}
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