1 files changed, 193 insertions, 0 deletions
diff --git a/ext/timers/lib.rs b/ext/timers/lib.rs
new file mode 100644
index 000000000..2b9948d1f
--- /dev/null
+++ b/ext/timers/lib.rs
@@ -0,0 +1,193 @@
+// Copyright 2018-2021 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, cancel and await a single timer (or Delay, as Tokio
+//! calls it) for an entire Isolate. This is what is implemented here.
+
+use deno_core::error::AnyError;
+use deno_core::futures;
+use deno_core::futures::channel::oneshot;
+use deno_core::futures::FutureExt;
+use deno_core::futures::TryFutureExt;
+use deno_core::include_js_files;
+use deno_core::op_async;
+use deno_core::op_sync;
+use deno_core::Extension;
+use deno_core::OpState;
+use std::cell::RefCell;
+use std::future::Future;
+use std::pin::Pin;
+use std::rc::Rc;
+use std::thread::sleep;
+use std::time::Duration;
+use std::time::Instant;
+
+pub trait TimersPermission {
+  fn allow_hrtime(&mut self) -> bool;
+  fn check_unstable(&self, state: &OpState, api_name: &'static str);
+}
+
+pub struct NoTimersPermission;
+
+impl TimersPermission for NoTimersPermission {
+  fn allow_hrtime(&mut self) -> bool {
+    false
+  }
+  fn check_unstable(&self, _: &OpState, _: &'static str) {}
+}
+
+pub fn init<P: TimersPermission + 'static>() -> Extension {
+  Extension::builder()
+    .js(include_js_files!(
+      prefix "deno:ext/timers",
+      "01_timers.js",
+      "02_performance.js",
+    ))
+    .ops(vec![
+      ("op_global_timer_stop", op_sync(op_global_timer_stop)),
+      ("op_global_timer_start", op_sync(op_global_timer_start)),
+      ("op_global_timer", op_async(op_global_timer)),
+      ("op_now", op_sync(op_now::<P>)),
+      ("op_sleep_sync", op_sync(op_sleep_sync::<P>)),
+    ])
+    .state(|state| {
+      state.put(GlobalTimer::default());
+      state.put(StartTime::now());
+      Ok(())
+    })
+    .build()
+}
+
+pub type StartTime = Instant;
+
+type TimerFuture = Pin<Box<dyn Future<Output = Result<(), ()>>>>;
+
+#[derive(Default)]
+pub struct GlobalTimer {
+  tx: Option<oneshot::Sender<()>>,
+  pub future: Option<TimerFuture>,
+}
+
+impl GlobalTimer {
+  pub fn cancel(&mut self) {
+    if let Some(tx) = self.tx.take() {
+      tx.send(()).ok();
+    }
+  }
+
+  pub fn new_timeout(&mut self, deadline: Instant) {
+    if self.tx.is_some() {
+      self.cancel();
+    }
+    assert!(self.tx.is_none());
+    self.future.take();
+
+    let (tx, rx) = oneshot::channel();
+    self.tx = Some(tx);
+
+    let delay = tokio::time::sleep_until(deadline.into()).boxed_local();
+    let rx = rx
+      .map_err(|err| panic!("Unexpected error in receiving channel {:?}", err));
+
+    let fut = futures::future::select(delay, rx)
+      .then(|_| futures::future::ok(()))
+      .boxed_local();
+    self.future = Some(fut);
+  }
+}
+
+pub fn op_global_timer_stop(
+  state: &mut OpState,
+  _args: (),
+  _: (),
+) -> Result<(), AnyError> {
+  let global_timer = state.borrow_mut::<GlobalTimer>();
+  global_timer.cancel();
+  Ok(())
+}
+
+// Set up a timer that will be later awaited by JS promise.
+// It's a separate op, because canceling a timeout immediately
+// after setting it caused a race condition (because Tokio timeout)
+// might have been registered after next event loop tick.
+//
+// See https://github.com/denoland/deno/issues/7599 for more
+// details.
+pub fn op_global_timer_start(
+  state: &mut OpState,
+  timeout: u64,
+  _: (),
+) -> Result<(), AnyError> {
+  // According to spec, minimum allowed timeout is 4 ms.
+  // https://html.spec.whatwg.org/multipage/timers-and-user-prompts.html#timers
+  // TODO(#10974) Per spec this is actually a little more complicated than this.
+  // The minimum timeout depends on the nesting level of the timeout.
+  let timeout = std::cmp::max(timeout, 4);
+
+  let deadline = Instant::now() + Duration::from_millis(timeout);
+  let global_timer = state.borrow_mut::<GlobalTimer>();
+  global_timer.new_timeout(deadline);
+  Ok(())
+}
+
+pub async fn op_global_timer(
+  state: Rc<RefCell<OpState>>,
+  _args: (),
+  _: (),
+) -> Result<(), AnyError> {
+  let maybe_timer_fut = {
+    let mut s = state.borrow_mut();
+    let global_timer = s.borrow_mut::<GlobalTimer>();
+    global_timer.future.take()
+  };
+  if let Some(timer_fut) = maybe_timer_fut {
+    let _ = timer_fut.await;
+  }
+  Ok(())
+}
+
+// Returns a milliseconds and nanoseconds subsec
+// since the start time of the deno runtime.
+// If the High precision flag is not set, the
+// nanoseconds are rounded on 2ms.
+pub fn op_now<TP>(
+  state: &mut OpState,
+  _argument: (),
+  _: (),
+) -> Result<f64, AnyError>
+where
+  TP: TimersPermission + 'static,
+{
+  let start_time = state.borrow::<StartTime>();
+  let seconds = start_time.elapsed().as_secs();
+  let mut subsec_nanos = start_time.elapsed().subsec_nanos() as f64;
+  let reduced_time_precision = 2_000_000.0; // 2ms in nanoseconds
+
+  // If the permission is not enabled
+  // Round the nano result on 2 milliseconds
+  // see: https://developer.mozilla.org/en-US/docs/Web/API/DOMHighResTimeStamp#Reduced_time_precision
+  if !state.borrow_mut::<TP>().allow_hrtime() {
+    subsec_nanos -= subsec_nanos % reduced_time_precision;
+  }
+
+  let result = (seconds * 1_000) as f64 + (subsec_nanos / 1_000_000.0);
+
+  Ok(result)
+}
+
+pub fn op_sleep_sync<TP>(
+  state: &mut OpState,
+  millis: u64,
+  _: (),
+) -> Result<(), AnyError>
+where
+  TP: TimersPermission + 'static,
+{
+  state.borrow::<TP>().check_unstable(state, "Deno.sleepSync");
+  sleep(Duration::from_millis(millis));
+  Ok(())
+}