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|
use std::{
cell::RefCell,
collections::VecDeque,
marker::PhantomData,
mem,
rc::Rc,
task::{RawWaker, RawWakerVTable, Waker, Context}, pin::Pin,
};
use futures::{future::LocalBoxFuture, Future, FutureExt};
use crate::reactor::Reactor;
scoped_tls::scoped_thread_local!(pub(crate) static EX: Executor);
pub struct Executor {
local_queue: TaskQueue,
pub(crate) reactor: Rc<RefCell<Reactor>>,
/// Make sure the type is `!Send` and `!Sync`.
_marker: PhantomData<Rc<()>>,
}
impl Default for Executor {
fn default() -> Self {
Self::new()
}
}
impl Executor {
pub fn new() -> Self {
Self {
local_queue: TaskQueue::default(),
reactor: Rc::new(RefCell::new(Reactor::default())),
_marker: PhantomData,
}
}
pub fn spawn(fut: impl Future<Output = ()> + 'static) {
let t = Rc::new(Task {
future: RefCell::new(fut.boxed_local()),
});
EX.with(|ex| ex.local_queue.push(t));
}
pub fn block_on<F, T, O>(&self, f: F) -> O
where
F: Fn() -> T,
T: Future<Output = O> + 'static,
{
let _waker = waker_fn::waker_fn(|| {});
let cx = &mut Context::from_waker(&_waker);
EX.set(self, || {
let fut = f();
pin_utils::pin_mut!(fut);
loop {
// return if the outer future is ready
if let std::task::Poll::Ready(t) = fut.as_mut().poll(cx) {
break t;
}
// consume all tasks
while let Some(t) = self.local_queue.pop() {
let future = t.future.borrow_mut();
let w = waker(t.clone());
let mut context = Context::from_waker(&w);
let _ = Pin::new(future).as_mut().poll(&mut context);
}
// no task to execute now, it may ready
if let std::task::Poll::Ready(t) = fut.as_mut().poll(cx) {
break t;
}
// block for io
self.reactor.borrow_mut().wait();
}
})
}
}
pub struct TaskQueue {
queue: RefCell<VecDeque<Rc<Task>>>,
}
impl Default for TaskQueue {
fn default() -> Self {
Self::new()
}
}
impl TaskQueue {
pub fn new() -> Self {
const DEFAULT_TASK_QUEUE_SIZE: usize = 4096;
Self::new_with_capacity(DEFAULT_TASK_QUEUE_SIZE)
}
pub fn new_with_capacity(capacity: usize) -> Self {
Self {
queue: RefCell::new(VecDeque::with_capacity(capacity)),
}
}
pub(crate) fn push(&self, runnable: Rc<Task>) {
println!("add task");
self.queue.borrow_mut().push_back(runnable);
}
pub(crate) fn pop(&self) -> Option<Rc<Task>> {
println!("remove task");
self.queue.borrow_mut().pop_front()
}
}
pub struct Task {
future: RefCell<LocalBoxFuture<'static, ()>>,
}
fn waker(wake: Rc<Task>) -> Waker {
let ptr = Rc::into_raw(wake) as *const ();
let vtable = &Helper::VTABLE;
unsafe { Waker::from_raw(RawWaker::new(ptr, vtable)) }
}
impl Task {
fn wake_(self: Rc<Self>) {
Self::wake_by_ref_(&self)
}
fn wake_by_ref_(self: &Rc<Self>) {
EX.with(|ex| ex.local_queue.push(self.clone()));
}
}
struct Helper;
impl Helper {
const VTABLE: RawWakerVTable = RawWakerVTable::new(
Self::clone_waker,
Self::wake,
Self::wake_by_ref,
Self::drop_waker,
);
unsafe fn clone_waker(data: *const ()) -> RawWaker {
increase_refcount(data);
let vtable = &Self::VTABLE;
RawWaker::new(data, vtable)
}
unsafe fn wake(ptr: *const ()) {
let rc = Rc::from_raw(ptr as *const Task);
rc.wake_();
}
unsafe fn wake_by_ref(ptr: *const ()) {
let rc = mem::ManuallyDrop::new(Rc::from_raw(ptr as *const Task));
rc.wake_by_ref_();
}
unsafe fn drop_waker(ptr: *const ()) {
drop(Rc::from_raw(ptr as *const Task));
}
}
#[allow(clippy::redundant_clone)] // The clone here isn't actually redundant.
unsafe fn increase_refcount(data: *const ()) {
// Retain Rc, but don't touch refcount by wrapping in ManuallyDrop
let rc = mem::ManuallyDrop::new(Rc::<Task>::from_raw(data as *const Task));
// Now increase refcount, but don't drop new refcount either
let _rc_clone: mem::ManuallyDrop<_> = rc.clone();
}
|
