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denoland-deno/ext/web/timers.rs
Divy Srivastava 4c9dd33e27
perf(ext/web): optimize timer cancellation (#16316)
Towards #16315 

It created a bunch of Error objects and rejected the promise. This patch
changes `op_sleep` to resolve with `true` if it was cancelled.
2022-10-17 16:59:16 +05:30

93 lines
2.6 KiB
Rust

// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
//! This module helps deno implement timers and performance APIs.
use deno_core::error::AnyError;
use deno_core::op;
use deno_core::CancelFuture;
use deno_core::CancelHandle;
use deno_core::OpState;
use deno_core::Resource;
use deno_core::ResourceId;
use std::borrow::Cow;
use std::cell::RefCell;
use std::rc::Rc;
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 type StartTime = Instant;
// 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.
#[op(fast)]
pub fn op_now<TP>(state: &mut OpState, buf: &mut [u8])
where
TP: TimersPermission + 'static,
{
let start_time = state.borrow::<StartTime>();
let elapsed = start_time.elapsed();
let seconds = elapsed.as_secs();
let mut subsec_nanos = elapsed.subsec_nanos();
// 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() {
let reduced_time_precision = 2_000_000; // 2ms in nanoseconds
subsec_nanos -= subsec_nanos % reduced_time_precision;
}
if buf.len() < 8 {
return;
}
let buf: &mut [u32] =
// SAFETY: buffer is at least 8 bytes long.
unsafe { std::slice::from_raw_parts_mut(buf.as_mut_ptr() as _, 2) };
buf[0] = seconds as u32;
buf[1] = subsec_nanos as u32;
}
pub struct TimerHandle(Rc<CancelHandle>);
impl Resource for TimerHandle {
fn name(&self) -> Cow<str> {
"timer".into()
}
fn close(self: Rc<Self>) {
self.0.cancel();
}
}
/// Creates a [`TimerHandle`] resource that can be used to cancel invocations of
/// [`op_sleep`].
#[op]
pub fn op_timer_handle(state: &mut OpState) -> ResourceId {
state
.resource_table
.add(TimerHandle(CancelHandle::new_rc()))
}
/// Waits asynchronously until either `millis` milliseconds have passed or the
/// [`TimerHandle`] resource given by `rid` has been canceled.
///
/// If the timer is canceled, this returns `false`. Otherwise, it returns `true`.
#[op(deferred)]
pub async fn op_sleep(
state: Rc<RefCell<OpState>>,
millis: u64,
rid: ResourceId,
) -> Result<bool, AnyError> {
let handle = state.borrow().resource_table.get::<TimerHandle>(rid)?;
let res = tokio::time::sleep(Duration::from_millis(millis))
.or_cancel(handle.0.clone())
.await;
Ok(res.is_ok())
}