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|
use core::cell::UnsafeCell;
use core::future::Future;
use core::mem;
use core::mem::MaybeUninit;
use crate::util::{OnDrop, Signal};
/// Utility to call a closure across tasks.
pub struct Portal<T> {
state: UnsafeCell<State<T>>,
}
enum State<T> {
None,
Running,
Waiting(*mut dyn FnMut(T)),
Done,
}
unsafe impl<T> Send for Portal<T> {}
unsafe impl<T> Sync for Portal<T> {}
fn assert_thread_mode() {
assert!(
cortex_m::peripheral::SCB::vect_active() == cortex_m::peripheral::scb::VectActive::ThreadMode,
"portals are not usable from interrupts"
);
}
impl<T> Portal<T> {
pub const fn new() -> Self {
Self {
state: UnsafeCell::new(State::None),
}
}
pub fn call(&self, val: T) -> bool {
assert_thread_mode();
// safety: this runs from thread mode
unsafe {
match *self.state.get() {
State::None => false,
State::Done => false,
State::Running => panic!("Portall::call() called reentrantly"),
State::Waiting(func) => {
(*func)(val);
true
}
}
}
}
pub fn wait_once<'a, R, F>(&'a self, mut func: F) -> impl Future<Output = R> + 'a
where
F: FnMut(T) -> R + 'a,
{
assert_thread_mode();
async move {
let signal = Signal::new();
let mut result: MaybeUninit<R> = MaybeUninit::uninit();
let mut call_func = |val: T| unsafe {
let state = &mut *self.state.get();
// Set state to Running while running the function to avoid reentrancy.
*state = State::Running;
result.as_mut_ptr().write(func(val));
*state = State::Done;
signal.signal(());
};
let func_ptr: *mut dyn FnMut(T) = &mut call_func as _;
let func_ptr: *mut dyn FnMut(T) = unsafe { mem::transmute(func_ptr) };
let _bomb = OnDrop::new(|| unsafe {
let state = &mut *self.state.get();
*state = State::None;
});
// safety: this runs from thread mode
unsafe {
let state = &mut *self.state.get();
match state {
State::None => {}
_ => panic!("Multiple tasks waiting on same portal"),
}
*state = State::Waiting(func_ptr);
}
signal.wait().await;
unsafe { result.assume_init() }
// dropbomb sets self.state = None
}
}
#[allow(unused)]
pub fn wait_many<'a, R, F>(&'a self, mut func: F) -> impl Future<Output = R> + 'a
where
F: FnMut(T) -> Option<R> + 'a,
{
assert_thread_mode();
async move {
let signal = Signal::new();
let mut result: MaybeUninit<R> = MaybeUninit::uninit();
let mut call_func = |val: T| {
unsafe {
let state = &mut *self.state.get();
let func_ptr = match *state {
State::Waiting(p) => p,
_ => unreachable!(),
};
// Set state to Running while running the function to avoid reentrancy.
*state = State::Running;
*state = match func(val) {
None => State::Waiting(func_ptr),
Some(res) => {
result.as_mut_ptr().write(res);
signal.signal(());
State::Done
}
};
};
};
let func_ptr: *mut dyn FnMut(T) = &mut call_func as _;
let func_ptr: *mut dyn FnMut(T) = unsafe { mem::transmute(func_ptr) };
let _bomb = OnDrop::new(|| unsafe {
let state = &mut *self.state.get();
*state = State::None;
});
// safety: this runs from thread mode
unsafe {
let state = &mut *self.state.get();
match *state {
State::None => {}
_ => panic!("Multiple tasks waiting on same portal"),
}
*state = State::Waiting(func_ptr);
}
signal.wait().await;
unsafe { result.assume_init() }
// dropbomb sets self.state = None
}
}
}
|
