| <!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/remote_handle.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>remote_handle.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="kw">use </span>{ |
| <span class="kw">crate</span>::future::{CatchUnwind, FutureExt}, |
| futures_channel::oneshot::{<span class="self">self</span>, Receiver, Sender}, |
| futures_core::{ |
| future::Future, |
| ready, |
| task::{Context, Poll}, |
| }, |
| pin_project_lite::pin_project, |
| std::{ |
| any::Any, |
| fmt, |
| panic::{<span class="self">self</span>, AssertUnwindSafe}, |
| pin::Pin, |
| sync::{ |
| atomic::{AtomicBool, Ordering}, |
| Arc, |
| }, |
| thread, |
| }, |
| }; |
| |
| <span class="doccomment">/// The handle to a remote future returned by |
| /// [`remote_handle`](crate::future::FutureExt::remote_handle). When you drop this, |
| /// the remote future will be woken up to be dropped by the executor. |
| /// |
| /// ## Unwind safety |
| /// |
| /// When the remote future panics, [Remote] will catch the unwind and transfer it to |
| /// the thread where `RemoteHandle` is being awaited. This is good for the common |
| /// case where [Remote] is spawned on a threadpool. It is unlikely that other code |
| /// in the executor working thread shares mutable data with the spawned future and we |
| /// preserve the executor from losing its working threads. |
| /// |
| /// If you run the future locally and send the handle of to be awaited elsewhere, you |
| /// must be careful with regard to unwind safety because the thread in which the future |
| /// is polled will keep running after the panic and the thread running the [RemoteHandle] |
| /// will unwind. |
| </span><span class="attribute">#[must_use = <span class="string">"dropping a remote handle cancels the underlying future"</span>] |
| #[derive(Debug)] |
| #[cfg_attr(docsrs, doc(cfg(feature = <span class="string">"channel"</span>)))] |
| </span><span class="kw">pub struct </span>RemoteHandle<T> { |
| rx: Receiver<thread::Result<T>>, |
| keep_running: Arc<AtomicBool>, |
| } |
| |
| <span class="kw">impl</span><T> RemoteHandle<T> { |
| <span class="doccomment">/// Drops this handle *without* canceling the underlying future. |
| /// |
| /// This method can be used if you want to drop the handle, but let the |
| /// execution continue. |
| </span><span class="kw">pub fn </span>forget(<span class="self">self</span>) { |
| <span class="self">self</span>.keep_running.store(<span class="bool-val">true</span>, Ordering::SeqCst); |
| } |
| } |
| |
| <span class="kw">impl</span><T: <span class="lifetime">'static</span>> Future <span class="kw">for </span>RemoteHandle<T> { |
| <span class="kw">type </span>Output = T; |
| |
| <span class="kw">fn </span>poll(<span class="kw-2">mut </span><span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<T> { |
| <span class="kw">match </span><span class="macro">ready!</span>(<span class="self">self</span>.rx.poll_unpin(cx)) { |
| <span class="prelude-val">Ok</span>(<span class="prelude-val">Ok</span>(output)) => Poll::Ready(output), |
| <span class="comment">// the remote future panicked. |
| </span><span class="prelude-val">Ok</span>(<span class="prelude-val">Err</span>(e)) => panic::resume_unwind(e), |
| <span class="comment">// The oneshot sender was dropped. |
| </span><span class="prelude-val">Err</span>(e) => panic::resume_unwind(Box::new(e)), |
| } |
| } |
| } |
| |
| <span class="kw">type </span>SendMsg<Fut> = <span class="prelude-ty">Result</span><<Fut <span class="kw">as </span>Future>::Output, Box<(<span class="kw">dyn </span>Any + Send + <span class="lifetime">'static</span>)>>; |
| |
| <span class="macro">pin_project! </span>{ |
| <span class="doccomment">/// A future which sends its output to the corresponding `RemoteHandle`. |
| /// Created by [`remote_handle`](crate::future::FutureExt::remote_handle). |
| </span><span class="attribute">#[must_use = <span class="string">"futures do nothing unless you `.await` or poll them"</span>] |
| #[cfg_attr(docsrs, doc(cfg(feature = <span class="string">"channel"</span>)))] |
| </span><span class="kw">pub struct </span>Remote<Fut: Future> { |
| tx: <span class="prelude-ty">Option</span><Sender<SendMsg<Fut>>>, |
| keep_running: Arc<AtomicBool>, |
| <span class="attribute">#[pin] |
| </span>future: CatchUnwind<AssertUnwindSafe<Fut>>, |
| } |
| } |
| |
| <span class="kw">impl</span><Fut: Future + fmt::Debug> fmt::Debug <span class="kw">for </span>Remote<Fut> { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| f.debug_tuple(<span class="string">"Remote"</span>).field(<span class="kw-2">&</span><span class="self">self</span>.future).finish() |
| } |
| } |
| |
| <span class="kw">impl</span><Fut: Future> Future <span class="kw">for </span>Remote<Fut> { |
| <span class="kw">type </span>Output = (); |
| |
| <span class="kw">fn </span>poll(<span class="self">self</span>: Pin<<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="kw">let </span>this = <span class="self">self</span>.project(); |
| |
| <span class="kw">if </span>this.tx.as_mut().unwrap().poll_canceled(cx).is_ready() |
| && !this.keep_running.load(Ordering::SeqCst) |
| { |
| <span class="comment">// Cancelled, bail out |
| </span><span class="kw">return </span>Poll::Ready(()); |
| } |
| |
| <span class="kw">let </span>output = <span class="macro">ready!</span>(this.future.poll(cx)); |
| |
| <span class="comment">// if the receiving end has gone away then that's ok, we just ignore the |
| // send error here. |
| </span>drop(this.tx.take().unwrap().send(output)); |
| Poll::Ready(()) |
| } |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>remote_handle<Fut: Future>(future: Fut) -> (Remote<Fut>, RemoteHandle<Fut::Output>) { |
| <span class="kw">let </span>(tx, rx) = oneshot::channel(); |
| <span class="kw">let </span>keep_running = Arc::new(AtomicBool::new(<span class="bool-val">false</span>)); |
| |
| <span class="comment">// Unwind Safety: See the docs for RemoteHandle. |
| </span><span class="kw">let </span>wrapped = Remote { |
| future: AssertUnwindSafe(future).catch_unwind(), |
| tx: <span class="prelude-val">Some</span>(tx), |
| keep_running: keep_running.clone(), |
| }; |
| |
| (wrapped, RemoteHandle { rx, keep_running }) |
| } |
| </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> |