diff --git a/library/std/src/thread/mod.rs b/library/std/src/thread/mod.rs index e4581c2de78..7b26068c294 100644 --- a/library/std/src/thread/mod.rs +++ b/library/std/src/thread/mod.rs @@ -178,7 +178,7 @@ use crate::sys_common::thread_info; use crate::sys_common::thread_parking::Parker; use crate::sys_common::{AsInner, IntoInner}; -use crate::time::Duration; +use crate::time::{Duration, Instant}; #[stable(feature = "scoped_threads", since = "1.63.0")] mod scoped; @@ -872,6 +872,86 @@ pub fn sleep(dur: Duration) { imp::Thread::sleep(dur) } +/// Puts the current thread to sleep until the specified deadline has passed. +/// +/// The thread may still be asleep after the deadline specified due to +/// scheduling specifics or platform-dependent functionality. It will never +/// wake before. +/// +/// This function is blocking, and should not be used in `async` functions. +/// +/// # Platform-specific behavior +/// +/// This function uses [`sleep`] internally, see its platform-specific behaviour. +/// +/// +/// # Examples +/// +/// A simple game loop that limits the game to 60 frames per second. +/// +/// ```no_run +/// #![feature(thread_sleep_until)] +/// # use std::time::{Duration, Instant}; +/// # use std::thread; +/// # +/// # fn update() {} +/// # fn render() {} +/// # +/// let max_fps = 60.0; +/// let frame_time = Duration::from_secs_f32(1.0/max_fps); +/// let mut next_frame = Instant::now(); +/// loop { +/// thread::sleep_until(next_frame); +/// next_frame += frame_time; +/// update(); +/// render(); +/// } +/// ``` +/// +/// A slow api we must not call too fast and which takes a few +/// tries before succeeding. By using `sleep_until` the time the +/// api call takes does not influence when we retry or when we give up +/// +/// ```no_run +/// #![feature(thread_sleep_until)] +/// # use std::time::{Duration, Instant}; +/// # use std::thread; +/// # +/// # enum Status { +/// # Ready(usize), +/// # Waiting, +/// # } +/// # fn slow_web_api_call() -> Status { Status::Ready(42) } +/// # +/// # const MAX_DURATION: Duration = Duration::from_secs(10); +/// # +/// # fn try_api_call() -> Result { +/// let deadline = Instant::now() + MAX_DURATION; +/// let delay = Duration::from_millis(250); +/// let mut next_attempt = Instant::now(); +/// loop { +/// if Instant::now() > deadline { +/// break Err(()); +/// } +/// if let Status::Ready(data) = slow_web_api_call() { +/// break Ok(data); +/// } +/// +/// next_attempt = deadline.min(next_attempt + delay); +/// thread::sleep_until(next_attempt); +/// } +/// # } +/// # let _data = try_api_call(); +/// ``` +#[unstable(feature = "thread_sleep_until", issue = "113752")] +pub fn sleep_until(deadline: Instant) { + let now = Instant::now(); + + if let Some(delay) = deadline.checked_duration_since(now) { + sleep(delay); + } +} + /// Used to ensure that `park` and `park_timeout` do not unwind, as that can /// cause undefined behaviour if not handled correctly (see #102398 for context). struct PanicGuard;