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use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll};
use slab::Slab;
use crate::cell::Cell;
use crate::task::LocalWaker;
pub struct Condition(Cell<Inner>);
struct Inner {
data: Slab<Option<LocalWaker>>,
}
impl Default for Condition {
fn default() -> Self {
Self::new()
}
}
impl Condition {
pub fn new() -> Condition {
Condition(Cell::new(Inner { data: Slab::new() }))
}
pub fn wait(&mut self) -> Waiter {
let token = self.0.get_mut().data.insert(None);
Waiter {
token,
inner: self.0.clone(),
}
}
pub fn notify(&self) {
let inner = self.0.get_ref();
for item in inner.data.iter() {
if let Some(waker) = item.1 {
waker.wake();
}
}
}
}
impl Drop for Condition {
fn drop(&mut self) {
self.notify()
}
}
#[must_use = "Waiter do nothing unless polled"]
pub struct Waiter {
token: usize,
inner: Cell<Inner>,
}
impl Clone for Waiter {
fn clone(&self) -> Self {
let token = unsafe { self.inner.get_mut_unsafe() }.data.insert(None);
Waiter {
token,
inner: self.inner.clone(),
}
}
}
impl Future for Waiter {
type Output = ();
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let this = self.get_mut();
let inner = unsafe { this.inner.get_mut().data.get_unchecked_mut(this.token) };
if inner.is_none() {
let waker = LocalWaker::default();
waker.register(cx.waker());
*inner = Some(waker);
Poll::Pending
} else if inner.as_mut().unwrap().register(cx.waker()) {
Poll::Pending
} else {
Poll::Ready(())
}
}
}
impl Drop for Waiter {
fn drop(&mut self) {
self.inner.get_mut().data.remove(self.token);
}
}
#[cfg(test)]
mod tests {
use super::*;
use futures::future::lazy;
#[actori_rt::test]
async fn test_condition() {
let mut cond = Condition::new();
let mut waiter = cond.wait();
assert_eq!(
lazy(|cx| Pin::new(&mut waiter).poll(cx)).await,
Poll::Pending
);
cond.notify();
assert_eq!(waiter.await, ());
let mut waiter = cond.wait();
assert_eq!(
lazy(|cx| Pin::new(&mut waiter).poll(cx)).await,
Poll::Pending
);
let mut waiter2 = waiter.clone();
assert_eq!(
lazy(|cx| Pin::new(&mut waiter2).poll(cx)).await,
Poll::Pending
);
drop(cond);
assert_eq!(waiter.await, ());
assert_eq!(waiter2.await, ());
}
}