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/* ┌────────────────────────────────────────────────────────────────────────────────────────────┐ *\ * │ │ * * │ This Source Code Form is subject to the terms of the Mozilla Public │ * * │ License, v. 2.0. If a copy of the MPL was not distributed with this │ * * │ file, You can obtain one at http://mozilla.org/MPL/2.0/. │ * * │ │ * \* └────────────────────────────────────────────────────────────────────────────────────────────┘ */ /* ┌────────────────────────────────────────────────────────────────────────────────────────────┐ *\ * │ Configuration │ * \* └────────────────────────────────────────────────────────────────────────────────────────────┘ */ #![no_std] /* ┌────────────────────────────────────────────────────────────────────────────────────────────┐ *\ * │ Documentation │ * \* └────────────────────────────────────────────────────────────────────────────────────────────┘ */ //! A way to poll a future until it or a timer completes. //! //! ## Example //! //! ```rust //! use async_io::Timer; //! # use futures_lite::future; //! use smol_timeout::TimeoutExt; //! use std::time::Duration; //! //! # future::block_on(async { //! # //! let foo = async { //! Timer::after(Duration::from_millis(250)).await; //! 24 //! }; //! //! let foo = foo.timeout(Duration::from_millis(100)); //! assert_eq!(foo.await, None); //! //! let bar = async { //! Timer::after(Duration::from_millis(100)).await; //! 42 //! }; //! //! let bar = bar.timeout(Duration::from_millis(250)); //! assert_eq!(bar.await, Some(42)); //! # //! # }); //! ``` /* ┌────────────────────────────────────────────────────────────────────────────────────────────┐ *\ * │ Imports │ * \* └────────────────────────────────────────────────────────────────────────────────────────────┘ */ use async_io::Timer; use core::future::Future; use core::pin::Pin; use core::task::{Context, Poll}; use core::time::Duration; use pin_project_lite::pin_project; /* ┌────────────────────────────────────────────────────────────────────────────────────────────┐ *\ * │ struct Timeout<Fut> │ * \* └────────────────────────────────────────────────────────────────────────────────────────────┘ */ pin_project! { #[derive(Debug)] /// A future polling both another future and a [`Timer`] that will complete after a specified /// timeout, and returning the future's output or [`None`] if the timer completes first. /// /// ## Example /// /// ```rust /// use async_io::Timer; /// # use futures_lite::future; /// use smol_timeout::TimeoutExt; /// use std::time::Duration; /// /// # future::block_on(async { /// # /// let foo = async { /// Timer::after(Duration::from_millis(250)).await; /// 24 /// }; /// /// let foo = foo.timeout(Duration::from_millis(100)); /// assert_eq!(foo.await, None); /// /// let bar = async { /// Timer::after(Duration::from_millis(100)).await; /// 42 /// }; /// /// let bar = bar.timeout(Duration::from_millis(250)); /// assert_eq!(bar.await, Some(42)); /// # /// # }) /// ``` pub struct Timeout<Fut: Future> { #[pin] future: Fut, #[pin] timer: Timer, } } /* ┌────────────────────────────────────────────────────────────────────────────────────────────┐ *\ * │ trait TimeoutExt: Future │ * \* └────────────────────────────────────────────────────────────────────────────────────────────┘ */ /// An extension trait for [`Future`]s that provides a way to create [`Timeout`]s. pub trait TimeoutExt: Future { /// Given a [`Duration`], creates and returns a new [`Timeout`] that will poll both the future /// and a [`Timer`] that will complete after the provided duration, and return the future's /// output or [`None`] if the timer completes first. /// /// ## Example /// /// ```rust /// use async_io::Timer; /// # use futures_lite::future; /// use smol_timeout::TimeoutExt; /// use std::time::Duration; /// /// # future::block_on(async { /// # /// let foo = async { /// Timer::after(Duration::from_millis(250)).await; /// 24 /// }; /// /// let foo = foo.timeout(Duration::from_millis(100)); /// assert_eq!(foo.await, None); /// /// let bar = async { /// Timer::after(Duration::from_millis(100)).await; /// 42 /// }; /// /// let bar = bar.timeout(Duration::from_millis(250)); /// assert_eq!(bar.await, Some(42)); /// # /// # }) /// ``` fn timeout(self, after: Duration) -> Timeout<Self> where Self: Sized, { Timeout { future: self, timer: Timer::after(after), } } } impl<Fut: Future> TimeoutExt for Fut {} /* ┌────────────────────────────────────────────────────────────────────────────────────────────┐ *\ * │ impl Future for Timeout<Fut> │ * \* └────────────────────────────────────────────────────────────────────────────────────────────┘ */ impl<Fut: Future> Future for Timeout<Fut> { type Output = Option<Fut::Output>; fn poll(self: Pin<&mut Self>, ctx: &mut Context) -> Poll<Self::Output> { let this = self.project(); if this.timer.poll(ctx).is_ready() { return Poll::Ready(None); } if let Poll::Ready(output) = this.future.poll(ctx) { return Poll::Ready(Some(output)); } Poll::Pending } }