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127 lines
3.6 KiB
Rust
127 lines
3.6 KiB
Rust
// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
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//! This module helps deno implement timers.
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//!
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//! As an optimization, we want to avoid an expensive calls into rust for every
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//! setTimeout in JavaScript. Thus in //js/timers.ts a data structure is
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//! implemented that calls into Rust for only the smallest timeout. Thus we
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//! only need to be able to start and cancel a single timer (or Delay, as Tokio
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//! calls it) for an entire Isolate. This is what is implemented here.
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use crate::permissions::Permissions;
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use deno_core::error::AnyError;
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use deno_core::futures;
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use deno_core::futures::channel::oneshot;
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use deno_core::futures::FutureExt;
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use deno_core::futures::TryFutureExt;
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use deno_core::serde_json;
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use deno_core::serde_json::json;
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use deno_core::serde_json::Value;
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use deno_core::BufVec;
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use deno_core::OpState;
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use deno_core::ZeroCopyBuf;
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use serde::Deserialize;
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use std::cell::RefCell;
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use std::future::Future;
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use std::rc::Rc;
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use std::time::Duration;
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use std::time::Instant;
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pub type StartTime = Instant;
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#[derive(Default)]
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pub struct GlobalTimer {
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tx: Option<oneshot::Sender<()>>,
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}
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impl GlobalTimer {
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pub fn cancel(&mut self) {
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if let Some(tx) = self.tx.take() {
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tx.send(()).ok();
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}
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}
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pub fn new_timeout(
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&mut self,
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deadline: Instant,
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) -> impl Future<Output = Result<(), ()>> {
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if self.tx.is_some() {
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self.cancel();
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}
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assert!(self.tx.is_none());
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let (tx, rx) = oneshot::channel();
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self.tx = Some(tx);
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let delay = tokio::time::delay_until(deadline.into());
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let rx = rx
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.map_err(|err| panic!("Unexpected error in receiving channel {:?}", err));
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futures::future::select(delay, rx).then(|_| futures::future::ok(()))
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}
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}
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pub fn init(rt: &mut deno_core::JsRuntime) {
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super::reg_json_sync(rt, "op_global_timer_stop", op_global_timer_stop);
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super::reg_json_async(rt, "op_global_timer", op_global_timer);
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super::reg_json_sync(rt, "op_now", op_now);
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}
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fn op_global_timer_stop(
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state: &mut OpState,
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_args: Value,
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_zero_copy: &mut [ZeroCopyBuf],
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) -> Result<Value, AnyError> {
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let global_timer = state.borrow_mut::<GlobalTimer>();
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global_timer.cancel();
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Ok(json!({}))
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}
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#[derive(Deserialize)]
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struct GlobalTimerArgs {
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timeout: u64,
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}
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async fn op_global_timer(
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state: Rc<RefCell<OpState>>,
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args: Value,
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_zero_copy: BufVec,
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) -> Result<Value, AnyError> {
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let args: GlobalTimerArgs = serde_json::from_value(args)?;
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let val = args.timeout;
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let deadline = Instant::now() + Duration::from_millis(val);
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let timer_fut = {
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let mut s = state.borrow_mut();
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let global_timer = s.borrow_mut::<GlobalTimer>();
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global_timer.new_timeout(deadline).boxed_local()
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};
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let _ = timer_fut.await;
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Ok(json!({}))
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}
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// Returns a milliseconds and nanoseconds subsec
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// since the start time of the deno runtime.
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// If the High precision flag is not set, the
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// nanoseconds are rounded on 2ms.
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fn op_now(
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state: &mut OpState,
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_args: Value,
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_zero_copy: &mut [ZeroCopyBuf],
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) -> Result<Value, AnyError> {
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let start_time = state.borrow::<StartTime>();
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let seconds = start_time.elapsed().as_secs();
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let mut subsec_nanos = start_time.elapsed().subsec_nanos();
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let reduced_time_precision = 2_000_000; // 2ms in nanoseconds
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// If the permission is not enabled
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// Round the nano result on 2 milliseconds
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// see: https://developer.mozilla.org/en-US/docs/Web/API/DOMHighResTimeStamp#Reduced_time_precision
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if state.borrow::<Permissions>().check_hrtime().is_err() {
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subsec_nanos -= subsec_nanos % reduced_time_precision;
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}
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Ok(json!({
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"seconds": seconds,
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"subsecNanos": subsec_nanos,
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}))
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}
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