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// Copyright 2018-2020 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::permissions::Permissions;
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::serde_json;
use deno_core::serde_json::json;
use deno_core::serde_json::Value;
use deno_core::BufVec;
use deno_core::OpState;
use deno_core::ZeroCopyBuf;
use serde::Deserialize;
use std::cell::RefCell;
use std::future::Future;
use std::rc::Rc;
use std::time::Duration;
use std::time::Instant;
pub type StartTime = Instant;
#[derive(Default)]
pub struct GlobalTimer {
tx: Option<oneshot::Sender<()>>,
}
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,
) -> impl Future<Output = Result<(), ()>> {
if self.tx.is_some() {
self.cancel();
}
assert!(self.tx.is_none());
let (tx, rx) = oneshot::channel();
self.tx = Some(tx);
let delay = tokio::time::delay_until(deadline.into());
let rx = rx
.map_err(|err| panic!("Unexpected error in receiving channel {:?}", err));
futures::future::select(delay, rx).then(|_| futures::future::ok(()))
}
}
pub fn init(rt: &mut deno_core::JsRuntime) {
super::reg_json_sync(rt, "op_global_timer_stop", op_global_timer_stop);
super::reg_json_async(rt, "op_global_timer", op_global_timer);
super::reg_json_sync(rt, "op_now", op_now);
}
fn op_global_timer_stop(
state: &mut OpState,
_args: Value,
_zero_copy: &mut [ZeroCopyBuf],
) -> Result<Value, AnyError> {
let global_timer = state.borrow_mut::<GlobalTimer>();
global_timer.cancel();
Ok(json!({}))
}
#[derive(Deserialize)]
struct GlobalTimerArgs {
timeout: u64,
}
async fn op_global_timer(
state: Rc<RefCell<OpState>>,
args: Value,
_zero_copy: BufVec,
) -> Result<Value, AnyError> {
let args: GlobalTimerArgs = serde_json::from_value(args)?;
let val = args.timeout;
let deadline = Instant::now() + Duration::from_millis(val);
let timer_fut = {
let mut s = state.borrow_mut();
let global_timer = s.borrow_mut::<GlobalTimer>();
global_timer.new_timeout(deadline).boxed_local()
};
let _ = timer_fut.await;
Ok(json!({}))
}
// 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.
fn op_now(
state: &mut OpState,
_args: Value,
_zero_copy: &mut [ZeroCopyBuf],
) -> Result<Value, AnyError> {
let start_time = state.borrow::<StartTime>();
let seconds = start_time.elapsed().as_secs();
let mut subsec_nanos = start_time.elapsed().subsec_nanos();
let reduced_time_precision = 2_000_000; // 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::<Permissions>().check_hrtime().is_err() {
subsec_nanos -= subsec_nanos % reduced_time_precision;
}
Ok(json!({
"seconds": seconds,
"subsecNanos": subsec_nanos,
}))
}
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