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// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
//! This module helps deno implement timers.
//!
//! As an optimization, we want to avoid an expensive calls into rust for every
//! setTimeout in JavaScript. Thus in //js/timers.ts a data structure is
//! implemented that calls into Rust for only the smallest timeout. Thus we
//! only need to be able to start and cancel a single timer (or Delay, as Tokio
//! calls it) for an entire Isolate. This is what is implemented here.
use crate::tokio_util::panic_on_error;
use futures::Future;
use std::time::Instant;
use tokio::sync::oneshot;
use tokio::timer::Delay;
pub struct GlobalTimer {
tx: Option<oneshot::Sender<()>>,
}
impl GlobalTimer {
pub fn new() -> Self {
Self { tx: None }
}
pub fn cancel(&mut self) {
if let Some(tx) = self.tx.take() {
tx.send(()).ok();
}
}
pub fn new_timeout(
&mut self,
deadline: Instant,
) -> impl Future<Item = (), Error = ()> {
if self.tx.is_some() {
self.cancel();
}
assert!(self.tx.is_none());
let (tx, rx) = oneshot::channel();
self.tx = Some(tx);
let delay = panic_on_error(Delay::new(deadline));
let rx = panic_on_error(rx);
delay.select(rx).then(|_| Ok(()))
}
}
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