| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.28/src/future/future/mod.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>mod.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../../../normalize.css"><link rel="stylesheet" href="../../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../../ayu.css" disabled><link rel="stylesheet" href="../../../../dark.css" disabled><link rel="stylesheet" href="../../../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../../../storage.js"></script><script defer src="../../../../source-script.js"></script><script defer src="../../../../source-files.js"></script><script defer src="../../../../main.js"></script><noscript><link rel="stylesheet" href="../../../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../../../futures_util/index.html"><div class="logo-container"><img class="rust-logo" src="../../../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../../futures_util/index.html"><img class="rust-logo" src="../../../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="doccomment">//! Futures |
| //! |
| //! This module contains a number of functions for working with `Future`s, |
| //! including the `FutureExt` trait which adds methods to `Future` types. |
| |
| </span><span class="attribute">#[cfg(feature = <span class="string">"alloc"</span>)] |
| </span><span class="kw">use </span>alloc::boxed::Box; |
| <span class="kw">use </span>core::pin::Pin; |
| |
| <span class="kw">use </span><span class="kw">crate</span>::fns::{inspect_fn, into_fn, ok_fn, InspectFn, IntoFn, OkFn}; |
| <span class="kw">use </span><span class="kw">crate</span>::future::{assert_future, Either}; |
| <span class="kw">use </span><span class="kw">crate</span>::never::Never; |
| <span class="kw">use </span><span class="kw">crate</span>::stream::assert_stream; |
| <span class="attribute">#[cfg(feature = <span class="string">"alloc"</span>)] |
| </span><span class="kw">use </span>futures_core::future::{BoxFuture, LocalBoxFuture}; |
| <span class="kw">use </span>futures_core::{ |
| future::Future, |
| stream::Stream, |
| task::{Context, Poll}, |
| }; |
| <span class="kw">use </span>pin_utils::pin_mut; |
| |
| <span class="comment">// Combinators |
| |
| </span><span class="kw">mod </span>flatten; |
| <span class="kw">mod </span>fuse; |
| <span class="kw">mod </span>map; |
| |
| <span class="macro">delegate_all!</span>( |
| <span class="doccomment">/// Future for the [`flatten`](super::FutureExt::flatten) method. |
| </span>Flatten<F>( |
| flatten::Flatten<F, <F <span class="kw">as </span>Future>::Output> |
| ): Debug + Future + FusedFuture + New[|x: F| flatten::Flatten::new(x)] |
| <span class="kw">where </span>F: Future |
| ); |
| |
| <span class="macro">delegate_all!</span>( |
| <span class="doccomment">/// Stream for the [`flatten_stream`](FutureExt::flatten_stream) method. |
| </span>FlattenStream<F>( |
| flatten::Flatten<F, <F <span class="kw">as </span>Future>::Output> |
| ): Debug + Sink + Stream + FusedStream + New[|x: F| flatten::Flatten::new(x)] |
| <span class="kw">where </span>F: Future |
| ); |
| |
| <span class="attribute">#[allow(unreachable_pub)] </span><span class="comment">// https://github.com/rust-lang/rust/issues/57411 |
| </span><span class="kw">pub use </span>fuse::Fuse; |
| |
| <span class="macro">delegate_all!</span>( |
| <span class="doccomment">/// Future for the [`map`](super::FutureExt::map) method. |
| </span>Map<Fut, F>( |
| map::Map<Fut, F> |
| ): Debug + Future + FusedFuture + New[|x: Fut, f: F| map::Map::new(x, f)] |
| ); |
| |
| <span class="macro">delegate_all!</span>( |
| <span class="doccomment">/// Stream for the [`into_stream`](FutureExt::into_stream) method. |
| </span>IntoStream<F>( |
| <span class="kw">crate</span>::stream::Once<F> |
| ): Debug + Stream + FusedStream + New[|x: F| <span class="kw">crate</span>::stream::Once::new(x)] |
| ); |
| |
| <span class="macro">delegate_all!</span>( |
| <span class="doccomment">/// Future for the [`map_into`](FutureExt::map_into) combinator. |
| </span>MapInto<Fut, T>( |
| Map<Fut, IntoFn<T>> |
| ): Debug + Future + FusedFuture + New[|x: Fut| Map::new(x, into_fn())] |
| ); |
| |
| <span class="macro">delegate_all!</span>( |
| <span class="doccomment">/// Future for the [`then`](FutureExt::then) method. |
| </span>Then<Fut1, Fut2, F>( |
| flatten::Flatten<Map<Fut1, F>, Fut2> |
| ): Debug + Future + FusedFuture + New[|x: Fut1, y: F| flatten::Flatten::new(Map::new(x, y))] |
| ); |
| |
| <span class="macro">delegate_all!</span>( |
| <span class="doccomment">/// Future for the [`inspect`](FutureExt::inspect) method. |
| </span>Inspect<Fut, F>( |
| map::Map<Fut, InspectFn<F>> |
| ): Debug + Future + FusedFuture + New[|x: Fut, f: F| map::Map::new(x, inspect_fn(f))] |
| ); |
| |
| <span class="macro">delegate_all!</span>( |
| <span class="doccomment">/// Future for the [`never_error`](super::FutureExt::never_error) combinator. |
| </span>NeverError<Fut>( |
| Map<Fut, OkFn<Never>> |
| ): Debug + Future + FusedFuture + New[|x: Fut| Map::new(x, ok_fn())] |
| ); |
| |
| <span class="macro">delegate_all!</span>( |
| <span class="doccomment">/// Future for the [`unit_error`](super::FutureExt::unit_error) combinator. |
| </span>UnitError<Fut>( |
| Map<Fut, OkFn<()>> |
| ): Debug + Future + FusedFuture + New[|x: Fut| Map::new(x, ok_fn())] |
| ); |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">mod </span>catch_unwind; |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| #[allow(unreachable_pub)] </span><span class="comment">// https://github.com/rust-lang/rust/issues/57411 |
| </span><span class="kw">pub use </span><span class="self">self</span>::catch_unwind::CatchUnwind; |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"channel"</span>)] |
| #[cfg_attr(docsrs, doc(cfg(feature = <span class="string">"channel"</span>)))] |
| #[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">mod </span>remote_handle; |
| <span class="attribute">#[cfg(feature = <span class="string">"channel"</span>)] |
| #[cfg_attr(docsrs, doc(cfg(feature = <span class="string">"channel"</span>)))] |
| #[cfg(feature = <span class="string">"std"</span>)] |
| #[allow(unreachable_pub)] </span><span class="comment">// https://github.com/rust-lang/rust/issues/57411 |
| </span><span class="kw">pub use </span><span class="self">self</span>::remote_handle::{Remote, RemoteHandle}; |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">mod </span>shared; |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| #[allow(unreachable_pub)] </span><span class="comment">// https://github.com/rust-lang/rust/issues/57411 |
| </span><span class="kw">pub use </span><span class="self">self</span>::shared::{Shared, WeakShared}; |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized> FutureExt <span class="kw">for </span>T <span class="kw">where </span>T: Future {} |
| |
| <span class="doccomment">/// An extension trait for `Future`s that provides a variety of convenient |
| /// adapters. |
| </span><span class="kw">pub trait </span>FutureExt: Future { |
| <span class="doccomment">/// Map this future's output to a different type, returning a new future of |
| /// the resulting type. |
| /// |
| /// This function is similar to the `Option::map` or `Iterator::map` where |
| /// it will change the type of the underlying future. This is useful to |
| /// chain along a computation once a future has been resolved. |
| /// |
| /// Note that this function consumes the receiving future and returns a |
| /// wrapped version of it, similar to the existing `map` methods in the |
| /// standard library. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # futures::executor::block_on(async { |
| /// use futures::future::FutureExt; |
| /// |
| /// let future = async { 1 }; |
| /// let new_future = future.map(|x| x + 3); |
| /// assert_eq!(new_future.await, 4); |
| /// # }); |
| /// ``` |
| </span><span class="kw">fn </span>map<U, F>(<span class="self">self</span>, f: F) -> Map<<span class="self">Self</span>, F> |
| <span class="kw">where |
| </span>F: FnOnce(<span class="self">Self</span>::Output) -> U, |
| <span class="self">Self</span>: Sized, |
| { |
| assert_future::<U, <span class="kw">_</span>>(Map::new(<span class="self">self</span>, f)) |
| } |
| |
| <span class="doccomment">/// Map this future's output to a different type, returning a new future of |
| /// the resulting type. |
| /// |
| /// This function is equivalent to calling `map(Into::into)` but allows naming |
| /// the return type. |
| </span><span class="kw">fn </span>map_into<U>(<span class="self">self</span>) -> MapInto<<span class="self">Self</span>, U> |
| <span class="kw">where |
| </span><span class="self">Self</span>::Output: Into<U>, |
| <span class="self">Self</span>: Sized, |
| { |
| assert_future::<U, <span class="kw">_</span>>(MapInto::new(<span class="self">self</span>)) |
| } |
| |
| <span class="doccomment">/// Chain on a computation for when a future finished, passing the result of |
| /// the future to the provided closure `f`. |
| /// |
| /// The returned value of the closure must implement the `Future` trait |
| /// and can represent some more work to be done before the composed future |
| /// is finished. |
| /// |
| /// The closure `f` is only run *after* successful completion of the `self` |
| /// future. |
| /// |
| /// Note that this function consumes the receiving future and returns a |
| /// wrapped version of it. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # futures::executor::block_on(async { |
| /// use futures::future::FutureExt; |
| /// |
| /// let future_of_1 = async { 1 }; |
| /// let future_of_4 = future_of_1.then(|x| async move { x + 3 }); |
| /// assert_eq!(future_of_4.await, 4); |
| /// # }); |
| /// ``` |
| </span><span class="kw">fn </span>then<Fut, F>(<span class="self">self</span>, f: F) -> Then<<span class="self">Self</span>, Fut, F> |
| <span class="kw">where |
| </span>F: FnOnce(<span class="self">Self</span>::Output) -> Fut, |
| Fut: Future, |
| <span class="self">Self</span>: Sized, |
| { |
| assert_future::<Fut::Output, <span class="kw">_</span>>(Then::new(<span class="self">self</span>, f)) |
| } |
| |
| <span class="doccomment">/// Wrap this future in an `Either` future, making it the left-hand variant |
| /// of that `Either`. |
| /// |
| /// This can be used in combination with the `right_future` method to write `if` |
| /// statements that evaluate to different futures in different branches. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # futures::executor::block_on(async { |
| /// use futures::future::FutureExt; |
| /// |
| /// let x = 6; |
| /// let future = if x < 10 { |
| /// async { true }.left_future() |
| /// } else { |
| /// async { false }.right_future() |
| /// }; |
| /// |
| /// assert_eq!(future.await, true); |
| /// # }); |
| /// ``` |
| </span><span class="kw">fn </span>left_future<B>(<span class="self">self</span>) -> Either<<span class="self">Self</span>, B> |
| <span class="kw">where |
| </span>B: Future<Output = <span class="self">Self</span>::Output>, |
| <span class="self">Self</span>: Sized, |
| { |
| assert_future::<<span class="self">Self</span>::Output, <span class="kw">_</span>>(Either::Left(<span class="self">self</span>)) |
| } |
| |
| <span class="doccomment">/// Wrap this future in an `Either` future, making it the right-hand variant |
| /// of that `Either`. |
| /// |
| /// This can be used in combination with the `left_future` method to write `if` |
| /// statements that evaluate to different futures in different branches. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # futures::executor::block_on(async { |
| /// use futures::future::FutureExt; |
| /// |
| /// let x = 6; |
| /// let future = if x > 10 { |
| /// async { true }.left_future() |
| /// } else { |
| /// async { false }.right_future() |
| /// }; |
| /// |
| /// assert_eq!(future.await, false); |
| /// # }); |
| /// ``` |
| </span><span class="kw">fn </span>right_future<A>(<span class="self">self</span>) -> Either<A, <span class="self">Self</span>> |
| <span class="kw">where |
| </span>A: Future<Output = <span class="self">Self</span>::Output>, |
| <span class="self">Self</span>: Sized, |
| { |
| assert_future::<<span class="self">Self</span>::Output, <span class="kw">_</span>>(Either::Right(<span class="self">self</span>)) |
| } |
| |
| <span class="doccomment">/// Convert this future into a single element stream. |
| /// |
| /// The returned stream contains single success if this future resolves to |
| /// success or single error if this future resolves into error. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # futures::executor::block_on(async { |
| /// use futures::future::FutureExt; |
| /// use futures::stream::StreamExt; |
| /// |
| /// let future = async { 17 }; |
| /// let stream = future.into_stream(); |
| /// let collected: Vec<_> = stream.collect().await; |
| /// assert_eq!(collected, vec![17]); |
| /// # }); |
| /// ``` |
| </span><span class="kw">fn </span>into_stream(<span class="self">self</span>) -> IntoStream<<span class="self">Self</span>> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| { |
| assert_stream::<<span class="self">Self</span>::Output, <span class="kw">_</span>>(IntoStream::new(<span class="self">self</span>)) |
| } |
| |
| <span class="doccomment">/// Flatten the execution of this future when the output of this |
| /// future is itself another future. |
| /// |
| /// This can be useful when combining futures together to flatten the |
| /// computation out the final result. |
| /// |
| /// This method is roughly equivalent to `self.then(|x| x)`. |
| /// |
| /// Note that this function consumes the receiving future and returns a |
| /// wrapped version of it. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # futures::executor::block_on(async { |
| /// use futures::future::FutureExt; |
| /// |
| /// let nested_future = async { async { 1 } }; |
| /// let future = nested_future.flatten(); |
| /// assert_eq!(future.await, 1); |
| /// # }); |
| /// ``` |
| </span><span class="kw">fn </span>flatten(<span class="self">self</span>) -> Flatten<<span class="self">Self</span>> |
| <span class="kw">where |
| </span><span class="self">Self</span>::Output: Future, |
| <span class="self">Self</span>: Sized, |
| { |
| <span class="kw">let </span>f = Flatten::new(<span class="self">self</span>); |
| assert_future::<<<<span class="self">Self </span><span class="kw">as </span>Future>::Output <span class="kw">as </span>Future>::Output, <span class="kw">_</span>>(f) |
| } |
| |
| <span class="doccomment">/// Flatten the execution of this future when the successful result of this |
| /// future is a stream. |
| /// |
| /// This can be useful when stream initialization is deferred, and it is |
| /// convenient to work with that stream as if stream was available at the |
| /// call site. |
| /// |
| /// Note that this function consumes this future and returns a wrapped |
| /// version of it. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # futures::executor::block_on(async { |
| /// use futures::future::FutureExt; |
| /// use futures::stream::{self, StreamExt}; |
| /// |
| /// let stream_items = vec![17, 18, 19]; |
| /// let future_of_a_stream = async { stream::iter(stream_items) }; |
| /// |
| /// let stream = future_of_a_stream.flatten_stream(); |
| /// let list: Vec<_> = stream.collect().await; |
| /// assert_eq!(list, vec![17, 18, 19]); |
| /// # }); |
| /// ``` |
| </span><span class="kw">fn </span>flatten_stream(<span class="self">self</span>) -> FlattenStream<<span class="self">Self</span>> |
| <span class="kw">where |
| </span><span class="self">Self</span>::Output: Stream, |
| <span class="self">Self</span>: Sized, |
| { |
| assert_stream::<<<span class="self">Self</span>::Output <span class="kw">as </span>Stream>::Item, <span class="kw">_</span>>(FlattenStream::new(<span class="self">self</span>)) |
| } |
| |
| <span class="doccomment">/// Fuse a future such that `poll` will never again be called once it has |
| /// completed. This method can be used to turn any `Future` into a |
| /// `FusedFuture`. |
| /// |
| /// Normally, once a future has returned `Poll::Ready` from `poll`, |
| /// any further calls could exhibit bad behavior such as blocking |
| /// forever, panicking, never returning, etc. If it is known that `poll` |
| /// may be called too often then this method can be used to ensure that it |
| /// has defined semantics. |
| /// |
| /// If a `fuse`d future is `poll`ed after having returned `Poll::Ready` |
| /// previously, it will return `Poll::Pending`, from `poll` again (and will |
| /// continue to do so for all future calls to `poll`). |
| /// |
| /// This combinator will drop the underlying future as soon as it has been |
| /// completed to ensure resources are reclaimed as soon as possible. |
| </span><span class="kw">fn </span>fuse(<span class="self">self</span>) -> Fuse<<span class="self">Self</span>> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| { |
| <span class="kw">let </span>f = Fuse::new(<span class="self">self</span>); |
| assert_future::<<span class="self">Self</span>::Output, <span class="kw">_</span>>(f) |
| } |
| |
| <span class="doccomment">/// Do something with the output of a future before passing it on. |
| /// |
| /// When using futures, you'll often chain several of them together. While |
| /// working on such code, you might want to check out what's happening at |
| /// various parts in the pipeline, without consuming the intermediate |
| /// value. To do that, insert a call to `inspect`. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # futures::executor::block_on(async { |
| /// use futures::future::FutureExt; |
| /// |
| /// let future = async { 1 }; |
| /// let new_future = future.inspect(|&x| println!("about to resolve: {}", x)); |
| /// assert_eq!(new_future.await, 1); |
| /// # }); |
| /// ``` |
| </span><span class="kw">fn </span>inspect<F>(<span class="self">self</span>, f: F) -> Inspect<<span class="self">Self</span>, F> |
| <span class="kw">where |
| </span>F: FnOnce(<span class="kw-2">&</span><span class="self">Self</span>::Output), |
| <span class="self">Self</span>: Sized, |
| { |
| assert_future::<<span class="self">Self</span>::Output, <span class="kw">_</span>>(Inspect::new(<span class="self">self</span>, f)) |
| } |
| |
| <span class="doccomment">/// Catches unwinding panics while polling the future. |
| /// |
| /// In general, panics within a future can propagate all the way out to the |
| /// task level. This combinator makes it possible to halt unwinding within |
| /// the future itself. It's most commonly used within task executors. It's |
| /// not recommended to use this for error handling. |
| /// |
| /// Note that this method requires the `UnwindSafe` bound from the standard |
| /// library. This isn't always applied automatically, and the standard |
| /// library provides an `AssertUnwindSafe` wrapper type to apply it |
| /// after-the fact. To assist using this method, the `Future` trait is also |
| /// implemented for `AssertUnwindSafe<F>` where `F` implements `Future`. |
| /// |
| /// This method is only available when the `std` feature of this |
| /// library is activated, and it is activated by default. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # futures::executor::block_on(async { |
| /// use futures::future::{self, FutureExt, Ready}; |
| /// |
| /// let future = future::ready(2); |
| /// assert!(future.catch_unwind().await.is_ok()); |
| /// |
| /// let future = future::lazy(|_| -> Ready<i32> { |
| /// unimplemented!() |
| /// }); |
| /// assert!(future.catch_unwind().await.is_err()); |
| /// # }); |
| /// ``` |
| </span><span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">fn </span>catch_unwind(<span class="self">self</span>) -> CatchUnwind<<span class="self">Self</span>> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized + ::std::panic::UnwindSafe, |
| { |
| assert_future::<<span class="prelude-ty">Result</span><<span class="self">Self</span>::Output, Box<<span class="kw">dyn </span>std::any::Any + Send>>, <span class="kw">_</span>>(CatchUnwind::new( |
| <span class="self">self</span>, |
| )) |
| } |
| |
| <span class="doccomment">/// Create a cloneable handle to this future where all handles will resolve |
| /// to the same result. |
| /// |
| /// The `shared` combinator method provides a method to convert any future |
| /// into a cloneable future. It enables a future to be polled by multiple |
| /// threads. |
| /// |
| /// This method is only available when the `std` feature of this |
| /// library is activated, and it is activated by default. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # futures::executor::block_on(async { |
| /// use futures::future::FutureExt; |
| /// |
| /// let future = async { 6 }; |
| /// let shared1 = future.shared(); |
| /// let shared2 = shared1.clone(); |
| /// |
| /// assert_eq!(6, shared1.await); |
| /// assert_eq!(6, shared2.await); |
| /// # }); |
| /// ``` |
| /// |
| /// ``` |
| /// // Note, unlike most examples this is written in the context of a |
| /// // synchronous function to better illustrate the cross-thread aspect of |
| /// // the `shared` combinator. |
| /// |
| /// # futures::executor::block_on(async { |
| /// use futures::future::FutureExt; |
| /// use futures::executor::block_on; |
| /// use std::thread; |
| /// |
| /// let future = async { 6 }; |
| /// let shared1 = future.shared(); |
| /// let shared2 = shared1.clone(); |
| /// let join_handle = thread::spawn(move || { |
| /// assert_eq!(6, block_on(shared2)); |
| /// }); |
| /// assert_eq!(6, shared1.await); |
| /// join_handle.join().unwrap(); |
| /// # }); |
| /// ``` |
| </span><span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">fn </span>shared(<span class="self">self</span>) -> Shared<<span class="self">Self</span>> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| <span class="self">Self</span>::Output: Clone, |
| { |
| assert_future::<<span class="self">Self</span>::Output, <span class="kw">_</span>>(Shared::new(<span class="self">self</span>)) |
| } |
| |
| <span class="doccomment">/// Turn this future into a future that yields `()` on completion and sends |
| /// its output to another future on a separate task. |
| /// |
| /// This can be used with spawning executors to easily retrieve the result |
| /// of a future executing on a separate task or thread. |
| /// |
| /// This method is only available when the `std` feature of this |
| /// library is activated, and it is activated by default. |
| </span><span class="attribute">#[cfg(feature = <span class="string">"channel"</span>)] |
| #[cfg_attr(docsrs, doc(cfg(feature = <span class="string">"channel"</span>)))] |
| #[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">fn </span>remote_handle(<span class="self">self</span>) -> (Remote<<span class="self">Self</span>>, RemoteHandle<<span class="self">Self</span>::Output>) |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| { |
| <span class="kw">let </span>(wrapped, handle) = remote_handle::remote_handle(<span class="self">self</span>); |
| (assert_future::<(), <span class="kw">_</span>>(wrapped), handle) |
| } |
| |
| <span class="doccomment">/// Wrap the future in a Box, pinning it. |
| /// |
| /// This method is only available when the `std` or `alloc` feature of this |
| /// library is activated, and it is activated by default. |
| </span><span class="attribute">#[cfg(feature = <span class="string">"alloc"</span>)] |
| </span><span class="kw">fn </span>boxed<<span class="lifetime">'a</span>>(<span class="self">self</span>) -> BoxFuture<<span class="lifetime">'a</span>, <span class="self">Self</span>::Output> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized + Send + <span class="lifetime">'a</span>, |
| { |
| assert_future::<<span class="self">Self</span>::Output, <span class="kw">_</span>>(Box::pin(<span class="self">self</span>)) |
| } |
| |
| <span class="doccomment">/// Wrap the future in a Box, pinning it. |
| /// |
| /// Similar to `boxed`, but without the `Send` requirement. |
| /// |
| /// This method is only available when the `std` or `alloc` feature of this |
| /// library is activated, and it is activated by default. |
| </span><span class="attribute">#[cfg(feature = <span class="string">"alloc"</span>)] |
| </span><span class="kw">fn </span>boxed_local<<span class="lifetime">'a</span>>(<span class="self">self</span>) -> LocalBoxFuture<<span class="lifetime">'a</span>, <span class="self">Self</span>::Output> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized + <span class="lifetime">'a</span>, |
| { |
| assert_future::<<span class="self">Self</span>::Output, <span class="kw">_</span>>(Box::pin(<span class="self">self</span>)) |
| } |
| |
| <span class="doccomment">/// Turns a [`Future<Output = T>`](Future) into a |
| /// [`TryFuture<Ok = T, Error = ()`>](futures_core::future::TryFuture). |
| </span><span class="kw">fn </span>unit_error(<span class="self">self</span>) -> UnitError<<span class="self">Self</span>> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| { |
| assert_future::<<span class="prelude-ty">Result</span><<span class="self">Self</span>::Output, ()>, <span class="kw">_</span>>(UnitError::new(<span class="self">self</span>)) |
| } |
| |
| <span class="doccomment">/// Turns a [`Future<Output = T>`](Future) into a |
| /// [`TryFuture<Ok = T, Error = Never`>](futures_core::future::TryFuture). |
| </span><span class="kw">fn </span>never_error(<span class="self">self</span>) -> NeverError<<span class="self">Self</span>> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| { |
| assert_future::<<span class="prelude-ty">Result</span><<span class="self">Self</span>::Output, Never>, <span class="kw">_</span>>(NeverError::new(<span class="self">self</span>)) |
| } |
| |
| <span class="doccomment">/// A convenience for calling `Future::poll` on `Unpin` future types. |
| </span><span class="kw">fn </span>poll_unpin(<span class="kw-2">&mut </span><span class="self">self</span>, cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<<span class="self">Self</span>::Output> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Unpin, |
| { |
| Pin::new(<span class="self">self</span>).poll(cx) |
| } |
| |
| <span class="doccomment">/// Evaluates and consumes the future, returning the resulting output if |
| /// the future is ready after the first call to `Future::poll`. |
| /// |
| /// If `poll` instead returns `Poll::Pending`, `None` is returned. |
| /// |
| /// This method is useful in cases where immediacy is more important than |
| /// waiting for a result. It is also convenient for quickly obtaining |
| /// the value of a future that is known to always resolve immediately. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # use futures::prelude::*; |
| /// use futures::{future::ready, future::pending}; |
| /// let future_ready = ready("foobar"); |
| /// let future_pending = pending::<&'static str>(); |
| /// |
| /// assert_eq!(future_ready.now_or_never(), Some("foobar")); |
| /// assert_eq!(future_pending.now_or_never(), None); |
| /// ``` |
| /// |
| /// In cases where it is absolutely known that a future should always |
| /// resolve immediately and never return `Poll::Pending`, this method can |
| /// be combined with `expect()`: |
| /// |
| /// ``` |
| /// # use futures::{prelude::*, future::ready}; |
| /// let future_ready = ready("foobar"); |
| /// |
| /// assert_eq!(future_ready.now_or_never().expect("Future not ready"), "foobar"); |
| /// ``` |
| </span><span class="kw">fn </span>now_or_never(<span class="self">self</span>) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>::Output> |
| <span class="kw">where |
| </span><span class="self">Self</span>: Sized, |
| { |
| <span class="kw">let </span>noop_waker = <span class="kw">crate</span>::task::noop_waker(); |
| <span class="kw">let </span><span class="kw-2">mut </span>cx = Context::from_waker(<span class="kw-2">&</span>noop_waker); |
| |
| <span class="kw">let </span>this = <span class="self">self</span>; |
| <span class="macro">pin_mut!</span>(this); |
| <span class="kw">match </span>this.poll(<span class="kw-2">&mut </span>cx) { |
| Poll::Ready(x) => <span class="prelude-val">Some</span>(x), |
| <span class="kw">_ </span>=> <span class="prelude-val">None</span>, |
| } |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../../" data-current-crate="futures_util" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
