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//! This is a safe Rust library providing async `sleep_for` and `sleep_until` functions. //! These functions return futures that complete at the specified time. //! //! It works well with [`safina`](https://crates.io/crates/safina). //! //! # Features //! - `forbid(unsafe_code)` //! - Depends only on `std` //! - Good test coverage (95%) //! - Source of time is //! [`std::thread::park_timeout`](https://doc.rust-lang.org/std/thread/fn.park_timeout.html) //! via //! [`std::sync::mpsc::Receiver::recv_timeout`](https://doc.rust-lang.org/std/sync/mpsc/struct.Receiver.html#method.recv_timeout). //! //! # Limitations //! - Requires Rust `nightly`, for [OnceCell](https://doc.rust-lang.org/std/lazy/struct.OnceCell.html) //! - Timers complete around 2ms late, but never early //! - Allocates memory //! //! # Examples //! ```rust //! # use std::time::Duration; //! # async fn f() { //! safina_timer::start_timer_thread(); //! safina_timer::sleep_for(Duration::from_secs(10)).await; //! # } //! ``` //! //! ```rust //! # use std::time::{Duration, Instant}; //! # async fn f() { //! safina_timer::start_timer_thread(); //! let deadline = //! Instant::now() + Duration::from_millis(500); //! safina_timer::sleep_until(deadline).await; //! # } //! ``` //! //! ```rust //! # use std::time::{Duration, Instant}; //! # async fn read_request() -> Result<(), std::io::Error> { Ok(()) } //! # async fn read_data(id: ()) -> Result<(), std::io::Error> { Ok(()) } //! # fn process_data(data: ()) -> Result<(), std::io::Error> { Ok(()) } //! # async fn write_data(data: ()) -> Result<(), std::io::Error> { Ok(()) } //! # async fn send_response(response: ()) -> Result<(), std::io::Error> { Ok(()) } //! # async fn f() -> Result<(), std::io::Error> { //! use safina_timer::with_deadline; //! safina_timer::start_timer_thread(); //! let deadline = //! Instant::now() + Duration::from_millis(500); //! let req = //! with_deadline(read_request(), deadline).await??; //! let data = //! with_deadline(read_data(req), deadline).await??; //! with_deadline(write_data(data), deadline).await??; //! with_deadline(send_response(data), deadline).await??; //! # Ok(()) //! # } //! ``` //! //! ```rust //! # use std::time::{Duration, Instant}; //! # async fn read_request() -> Result<(), std::io::Error> { Ok(()) } //! # async fn read_data(id: ()) -> Result<(), std::io::Error> { Ok(()) } //! # fn process_data(data: ()) -> Result<(), std::io::Error> { Ok(()) } //! # async fn write_data(data: ()) -> Result<(), std::io::Error> { Ok(()) } //! # async fn send_response(response: ()) -> Result<(), std::io::Error> { Ok(()) } //! # async fn f() -> Result<(), std::io::Error> { //! use safina_timer::with_timeout; //! safina_timer::start_timer_thread(); //! let req = with_timeout( //! read_request(), Duration::from_millis(500) //! ).await??; //! let data = with_timeout( //! read_data(req), Duration::from_millis(1000) //! ).await??; //! with_timeout( //! write_data(data), Duration::from_millis(1000) //! ).await??; //! with_timeout( //! send_response(data), Duration::from_millis(5000) //! ).await??; //! # Ok(()) //! # } //! ``` //! //! # Documentation //! https://docs.rs/safina-timer //! //! # Alternatives //! - [futures-timer](https://crates.io/crates/futures-timer) //! - popular //! - Supports: Wasm, Linux, Windows, macOS //! - Contains generous amounts of `unsafe` code //! - Uses `std::thread::park_timeout` as its source of time //! - [async-io](https://crates.io/crates/async-io) //! - popular //! - single and repeating timers //! - Supports: Linux, Windows, macOS, iOS, Android, and many others. //! - Uses [polling](https://crates.io/crates/polling) crate //! which makes unsafe calls to OS. //! - [async-timer](https://crates.io/crates/async-timer) //! - Supports: Linux & Android //! - Makes unsafe calls to OS //! - [tokio](https://crates.io/crates/tokio) //! - very popular //! - single and repeating timers //! - Supports: Linux, macOS, other unix-like OSes, Windows //! - Fast, internally complicated, and full of `unsafe` //! - [embedded-async-timer](https://crates.io/crates/embedded-async-timer) //! - no_std //! - Supports: bare_metal //! # Release Process //! 1. Edit `Cargo.toml` and bump version number. //! 1. Run `./release.sh` //! //! # Changelog //! - v0.1.2 //! - Update [`with_deadline`](https://docs.rs/safina-timer/latest/safina_timer/fn.with_deadline.html) //! and [`with_timeout`](https://docs.rs/safina-timer/latest/safina_timer/fn.with_timeout.html): //! - Make them panic on TimerThreadNotStarted error and //! return new [`DeadlineExceeded`](https://docs.rs/safina-timer/latest/safina_timer/struct.DeadlineExceeded.html) //! struct instead of DeadlineError enum. //! This allows callers to write a match clause like `Err(DeadlineExceeded)`. //! - Make them use //! [`std::boxed::Box::pin`](https://doc.rust-lang.org/stable/std/boxed/struct.Box.html#method.pin) //! so callers don't have to. //! - Make [`sleep_until`](https://docs.rs/safina-timer/latest/safina_timer/fn.sleep_until.html) //! and [`sleep_for`](https://docs.rs/safina-timer/latest/safina_timer/fn.sleep_for.html) //! return `()` and //! panic if [`start_timer_thread()`](fn.start_timer_thread.html) has not been called. //! - v0.1.1 //! - Use most recent waker passed to `SleepFuture::poll`, as required by the //! [`std::future::Future::poll`](https://doc.rust-lang.org/stable/std/future/trait.Future.html#tymethod.poll) //! contract. //! - Add [`with_deadline`](https://docs.rs/safina-timer/latest/safina_timer/fn.with_deadline.html) //! and [`with_timeout`](https://docs.rs/safina-timer/latest/safina_timer/fn.with_timeout.html) //! functions. //! - v0.1.0 - First published version //! //! # TO DO //! - DONE - Implement `sleep_until` //! - DONE - Implement `sleep_for` //! - DONE - Add tests //! - Add docs //! - Publish on crates.io #![forbid(unsafe_code)] #![feature(once_cell)] #![feature(wake_trait)] mod deadline_future; pub use deadline_future::*; mod sleep_future; pub use sleep_future::*; #[cfg(test)] pub use tests::*; use core::cmp::Reverse; use core::fmt::{Debug, Display, Formatter}; use core::task::Waker; use std::collections::BinaryHeap; use std::error::Error; use std::lazy::SyncOnceCell; use std::sync::mpsc::{Receiver, RecvTimeoutError, SyncSender}; use std::sync::{Arc, Mutex}; use std::time::Instant; #[derive(Debug)] pub(crate) struct ScheduledWake { instant: Instant, waker: Arc<Mutex<Option<Waker>>>, } impl ScheduledWake { pub fn wake(&self) { if let Some(waker) = self.waker.lock().unwrap().take() { waker.wake(); } } } impl PartialEq for ScheduledWake { fn eq(&self, other: &Self) -> bool { std::cmp::PartialEq::eq(&self.instant, &other.instant) } } impl Eq for ScheduledWake {} impl PartialOrd for ScheduledWake { fn partial_cmp(&self, other: &Self) -> Option<core::cmp::Ordering> { core::cmp::PartialOrd::partial_cmp(&self.instant, &other.instant) } } impl Ord for ScheduledWake { fn cmp(&self, other: &Self) -> core::cmp::Ordering { std::cmp::Ord::cmp(&self.instant, &other.instant) } } static TIMER_THREAD_SENDER: SyncOnceCell<SyncSender<ScheduledWake>> = SyncOnceCell::new(); /// Starts the worker thread, if it's not already started. /// You must call this before calling [`sleep_until`] or [`sleep_for`]. pub fn start_timer_thread() { TIMER_THREAD_SENDER.get_or_init(|| { let (sender, receiver) = std::sync::mpsc::sync_channel(0); std::thread::spawn(|| timer_thread(receiver)); sender }); } fn timer_thread(receiver: Receiver<ScheduledWake>) { let mut heap: BinaryHeap<Reverse<ScheduledWake>> = BinaryHeap::new(); loop { if let Some(Reverse(peeked_wake)) = heap.peek() { let now = Instant::now(); if peeked_wake.instant < now { heap.pop().unwrap().0.wake(); } else { // We can switch to recv_deadline once it is stable: // https://github.com/rust-lang/rust/issues/46316 match receiver.recv_timeout(peeked_wake.instant - now) { Ok(new_wake) => { heap.push(Reverse(new_wake)); } Err(RecvTimeoutError::Timeout) => {} Err(RecvTimeoutError::Disconnected) => unreachable!(), } } } else { heap.push(Reverse(receiver.recv().unwrap())); } } } /// Call [`start_timer_thread`] to prevent this error. #[derive(Debug, Eq, PartialEq)] pub struct TimerThreadNotStarted {} impl Display for TimerThreadNotStarted { fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), std::fmt::Error> { std::fmt::Debug::fmt(self, f) } } impl Error for TimerThreadNotStarted {} fn schedule_wake( instant: Instant, waker: Arc<Mutex<Option<Waker>>>, ) -> Result<(), TimerThreadNotStarted> { let sender = TIMER_THREAD_SENDER.get().ok_or(TimerThreadNotStarted {})?; sender.send(ScheduledWake { instant, waker }).unwrap(); Ok(()) } #[cfg(test)] mod tests { use super::*; use core::ops::Range; use core::time::Duration; use std::sync::atomic::AtomicBool; use std::sync::Arc; use std::time::Instant; #[derive(Clone)] pub struct FakeWaker { called_flag: Arc<AtomicBool>, } impl FakeWaker { pub fn new(called_flag: &Arc<AtomicBool>) -> Self { Self { called_flag: called_flag.clone(), } } pub fn into_waker(self) -> Waker { std::task::Waker::from(Arc::new(self)) } } impl std::task::Wake for FakeWaker { fn wake(self: Arc<Self>) { if self .called_flag .fetch_or(true, std::sync::atomic::Ordering::AcqRel) { panic!("wake already called"); } } } pub fn expect_elapsed(before: Instant, range_ms: Range<u64>) { if range_ms.is_empty() { panic!("invalid range {:?}", range_ms) } let elapsed = before.elapsed(); let duration_range = Duration::from_millis(range_ms.start)..Duration::from_millis(range_ms.end); if !duration_range.contains(&elapsed) { panic!("{:?} elapsed, out of range {:?}", elapsed, duration_range); } } fn make_scheduled_wakes() -> (ScheduledWake, ScheduledWake, ScheduledWake, ScheduledWake) { let now = Instant::now(); ( ScheduledWake { instant: now - Duration::from_millis(1), waker: Arc::new(Mutex::new(None)), }, ScheduledWake { instant: now, waker: Arc::new(Mutex::new(None)), }, ScheduledWake { instant: now + Duration::from_millis(1), waker: Arc::new(Mutex::new(None)), }, ScheduledWake { instant: now + Duration::from_millis(1), waker: Arc::new(Mutex::new(None)), }, ) } #[test] fn test_scheduled() { use core::cmp::Ordering; let (sw1, sw2, sw3, sw3b) = make_scheduled_wakes(); assert!(format!("{:?}", sw1).starts_with("ScheduledWake {")); assert_eq!(sw3, sw3b); assert_ne!(sw3, sw2); assert_eq!(Some(Ordering::Less), PartialOrd::partial_cmp(&sw1, &sw2)); assert_eq!(Some(Ordering::Equal), PartialOrd::partial_cmp(&sw1, &sw1)); assert_eq!(Some(Ordering::Greater), PartialOrd::partial_cmp(&sw2, &sw1)); assert_eq!(Ordering::Less, Ord::cmp(&sw1, &sw2)); assert_eq!(Ordering::Equal, Ord::cmp(&sw1, &sw1)); assert_eq!(Ordering::Greater, Ord::cmp(&sw2, &sw1)); } #[test] fn test_error() { let e1 = TimerThreadNotStarted {}; let e2 = TimerThreadNotStarted {}; assert_eq!("TimerThreadNotStarted", format!("{:?}", e1)); assert_eq!(e1, e2); assert_eq!("TimerThreadNotStarted", format!("{}", e1)); } }