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shell.rs
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shell.rs
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#![allow(clippy::redundant_clone)]
use crate::coop::Budget;
use crate::park::{Park, Unpark};
use crate::runtime::enter;
use crate::runtime::time;
use crate::util::{waker_ref, Wake};
use std::future::Future;
use std::sync::Arc;
use std::task::Context;
use std::task::Poll::Ready;
#[derive(Debug)]
pub(super) struct Shell {
driver: time::Driver,
/// TODO: don't store this
unpark: Arc<Handle>,
/// The coop_budget used by this shell when blocking on tasks.
coop_budget: Budget,
}
#[derive(Debug)]
struct Handle(<time::Driver as Park>::Unpark);
impl Shell {
pub(super) fn new(driver: time::Driver, coop_budget: Budget) -> Shell {
let unpark = Arc::new(Handle(driver.unpark()));
Shell {
driver,
unpark,
coop_budget,
}
}
pub(super) fn block_on<F>(&mut self, f: F) -> F::Output
where
F: Future,
{
let _e = enter(true, self.coop_budget);
pin!(f);
let waker = waker_ref(&self.unpark);
let mut cx = Context::from_waker(&waker);
loop {
if let Ready(v) =
crate::coop::with_budget(self.coop_budget, || f.as_mut().poll(&mut cx))
{
return v;
}
self.driver.park().unwrap();
}
}
}
impl Wake for Handle {
/// Wake by value
fn wake(self: Arc<Self>) {
Wake::wake_by_ref(&self);
}
/// Wake by reference
fn wake_by_ref(arc_self: &Arc<Self>) {
arc_self.0.unpark();
}
}