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//! Thread-mode executor.
use core::marker::PhantomData;
use crate::raw::{OpaqueThreadContext, Pender};
use crate::{raw, Spawner};
/// TODO
// Name pending
pub trait ThreadContext: Sized {
/// TODO
fn context(&self) -> OpaqueThreadContext;
/// TODO
fn wait(&mut self);
}
/// Thread mode executor, using WFE/SEV.
///
/// This is the simplest and most common kind of executor. It runs on
/// thread mode (at the lowest priority level), and uses the `WFE` ARM instruction
/// to sleep when it has no more work to do. When a task is woken, a `SEV` instruction
/// is executed, to make the `WFE` exit from sleep and poll the task.
///
/// This executor allows for ultra low power consumption for chips where `WFE`
/// triggers low-power sleep without extra steps. If your chip requires extra steps,
/// you may use [`raw::Executor`] directly to program custom behavior.
pub struct ThreadModeExecutor<C: ThreadContext> {
inner: raw::Executor,
context: C,
not_send: PhantomData<*mut ()>,
}
impl<C: ThreadContext> ThreadModeExecutor<C> {
/// Create a new Executor.
pub fn new() -> Self
where
C: Default,
{
Self::with_context(C::default())
}
/// Create a new Executor.
pub fn with_context(context: C) -> Self {
Self {
inner: raw::Executor::new(Pender::Thread(context.context())),
context,
not_send: PhantomData,
}
}
/// Run the executor.
///
/// The `init` closure is called with a [`Spawner`] that spawns tasks on
/// this executor. Use it to spawn the initial task(s). After `init` returns,
/// the executor starts running the tasks.
///
/// To spawn more tasks later, you may keep copies of the [`Spawner`] (it is `Copy`),
/// for example by passing it as an argument to the initial tasks.
///
/// This function requires `&'static mut self`. This means you have to store the
/// Executor instance in a place where it'll live forever and grants you mutable
/// access. There's a few ways to do this:
///
/// - a [StaticCell](https://docs.rs/static_cell/latest/static_cell/) (safe)
/// - a `static mut` (unsafe)
/// - a local variable in a function you know never returns (like `fn main() -> !`), upgrading its lifetime with `transmute`. (unsafe)
///
/// This function never returns.
pub fn run(&'static mut self, init: impl FnOnce(Spawner)) -> ! {
init(self.inner.spawner());
loop {
unsafe {
self.inner.poll();
self.context.wait();
};
}
}
}
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