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#![allow(clippy::redundant_clone)]
use crate::future::poll_fn;
use crate::park::{Park, Unpark};
use crate::runtime::driver::Driver;
use crate::sync::Notify;
use crate::util::{waker_ref, Wake};
use std::sync::{Arc, Mutex};
use std::task::Context;
use std::task::Poll::{Pending, Ready};
use std::{future::Future, sync::PoisonError};
#[derive(Debug)]
pub(super) struct Shell {
driver: Mutex<Option<Driver>>,
notify: Notify,
/// TODO: don't store this
unpark: Arc<Handle>,
}
#[derive(Debug)]
struct Handle(<Driver as Park>::Unpark);
impl Shell {
pub(super) fn new(driver: Driver) -> Shell {
let unpark = Arc::new(Handle(driver.unpark()));
Shell {
driver: Mutex::new(Some(driver)),
notify: Notify::new(),
unpark,
}
}
pub(super) fn block_on<F>(&self, f: F) -> F::Output
where
F: Future,
{
let mut enter = crate::runtime::enter(true);
pin!(f);
loop {
if let Some(driver) = &mut self.take_driver() {
return driver.block_on(f);
} else {
let notified = self.notify.notified();
pin!(notified);
if let Some(out) = enter
.block_on(poll_fn(|cx| {
if notified.as_mut().poll(cx).is_ready() {
return Ready(None);
}
if let Ready(out) = f.as_mut().poll(cx) {
return Ready(Some(out));
}
Pending
}))
.expect("Failed to `Enter::block_on`")
{
return out;
}
}
}
}
fn take_driver(&self) -> Option<DriverGuard<'_>> {
let mut lock = self.driver.lock().unwrap();
let driver = lock.take()?;
Some(DriverGuard {
inner: Some(driver),
shell: &self,
})
}
}
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();
}
}
struct DriverGuard<'a> {
inner: Option<Driver>,
shell: &'a Shell,
}
impl DriverGuard<'_> {
fn block_on<F: Future>(&mut self, f: F) -> F::Output {
let driver = self.inner.as_mut().unwrap();
pin!(f);
let waker = waker_ref(&self.shell.unpark);
let mut cx = Context::from_waker(&waker);
loop {
if let Ready(v) = crate::coop::budget(|| f.as_mut().poll(&mut cx)) {
return v;
}
driver.park().unwrap();
}
}
}
impl Drop for DriverGuard<'_> {
fn drop(&mut self) {
if let Some(inner) = self.inner.take() {
self.shell
.driver
.lock()
.unwrap_or_else(PoisonError::into_inner)
.replace(inner);
self.shell.notify.notify_one();
}
}
}
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