Make timers act like normal ops

This is in preperation for core integration.

1 files changed, 49 insertions, 0 deletions

diff --git a/src/global_timer.rs b/src/global_timer.rs
new file mode 100644
index 000000000..eef70ddc2
--- /dev/null
+++ b/src/global_timer.rs
@@ -0,0 +1,49 @@
+// 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(()))
+  }
+}