use std::cell::RefCell;
use std::collections::VecDeque;
use std::rc::Rc;
use std::sync::atomic::{AtomicBool, Ordering};
pub(crate) type Shared<T> = Rc<RefCell<T>>;
thread_local! {
static SCHEDULER: Rc<Scheduler> =
Rc::new(Scheduler::new());
}
pub(crate) fn scheduler() -> Rc<Scheduler> {
SCHEDULER.with(Rc::clone)
}
pub(crate) trait Runnable {
fn run(self: Box<Self>);
}
pub(crate) struct Scheduler {
lock: Rc<AtomicBool>,
sequence: Shared<VecDeque<Box<dyn Runnable>>>,
}
impl Clone for Scheduler {
fn clone(&self) -> Self {
Scheduler {
lock: self.lock.clone(),
sequence: self.sequence.clone(),
}
}
}
impl Scheduler {
fn new() -> Self {
let sequence = VecDeque::new();
Scheduler {
lock: Rc::new(AtomicBool::new(false)),
sequence: Rc::new(RefCell::new(sequence)),
}
}
pub(crate) fn put_and_try_run(&self, runnable: Box<dyn Runnable>) {
self.sequence.borrow_mut().push_back(runnable);
if self.lock.compare_and_swap(false, true, Ordering::Relaxed) {
return;
}
loop {
let do_next = self.sequence.borrow_mut().pop_front();
if let Some(runnable) = do_next {
runnable.run();
} else {
break;
}
}
self.lock.store(false, Ordering::Relaxed);
}
}