| <!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/stream/poll_immediate.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>poll_immediate.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>core::pin::Pin; |
| <span class="kw">use </span>futures_core::task::{Context, Poll}; |
| <span class="kw">use </span>futures_core::Stream; |
| <span class="kw">use </span>pin_project_lite::pin_project; |
| |
| <span class="macro">pin_project! </span>{ |
| <span class="doccomment">/// Stream for the [poll_immediate](poll_immediate()) function. |
| /// |
| /// It will never return [Poll::Pending](core::task::Poll::Pending) |
| </span><span class="attribute">#[derive(Debug, Clone)] |
| #[must_use = <span class="string">"futures do nothing unless you `.await` or poll them"</span>] |
| </span><span class="kw">pub struct </span>PollImmediate<S> { |
| <span class="attribute">#[pin] |
| </span>stream: <span class="prelude-ty">Option</span><S> |
| } |
| } |
| |
| <span class="kw">impl</span><T, S> Stream <span class="kw">for </span>PollImmediate<S> |
| <span class="kw">where |
| </span>S: Stream<Item = T>, |
| { |
| <span class="kw">type </span>Item = Poll<T>; |
| |
| <span class="kw">fn </span>poll_next(<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="prelude-ty">Option</span><<span class="self">Self</span>::Item>> { |
| <span class="kw">let </span><span class="kw-2">mut </span>this = <span class="self">self</span>.project(); |
| <span class="kw">let </span>stream = <span class="kw">match </span>this.stream.as_mut().as_pin_mut() { |
| <span class="comment">// inner is gone, so we can continue to signal that the stream is closed. |
| </span><span class="prelude-val">None </span>=> <span class="kw">return </span>Poll::Ready(<span class="prelude-val">None</span>), |
| <span class="prelude-val">Some</span>(inner) => inner, |
| }; |
| |
| <span class="kw">match </span>stream.poll_next(cx) { |
| Poll::Ready(<span class="prelude-val">Some</span>(t)) => Poll::Ready(<span class="prelude-val">Some</span>(Poll::Ready(t))), |
| Poll::Ready(<span class="prelude-val">None</span>) => { |
| this.stream.set(<span class="prelude-val">None</span>); |
| Poll::Ready(<span class="prelude-val">None</span>) |
| } |
| Poll::Pending => Poll::Ready(<span class="prelude-val">Some</span>(Poll::Pending)), |
| } |
| } |
| |
| <span class="kw">fn </span>size_hint(<span class="kw-2">&</span><span class="self">self</span>) -> (usize, <span class="prelude-ty">Option</span><usize>) { |
| <span class="self">self</span>.stream.as_ref().map_or((<span class="number">0</span>, <span class="prelude-val">Some</span>(<span class="number">0</span>)), Stream::size_hint) |
| } |
| } |
| |
| <span class="kw">impl</span><S: Stream> <span class="kw">super</span>::FusedStream <span class="kw">for </span>PollImmediate<S> { |
| <span class="kw">fn </span>is_terminated(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.stream.is_none() |
| } |
| } |
| |
| <span class="doccomment">/// Creates a new stream that always immediately returns [Poll::Ready](core::task::Poll::Ready) when awaiting it. |
| /// |
| /// This is useful when immediacy is more important than waiting for the next item to be ready. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # futures::executor::block_on(async { |
| /// use futures::stream::{self, StreamExt}; |
| /// use futures::task::Poll; |
| /// |
| /// let mut r = stream::poll_immediate(Box::pin(stream::iter(1_u32..3))); |
| /// assert_eq!(r.next().await, Some(Poll::Ready(1))); |
| /// assert_eq!(r.next().await, Some(Poll::Ready(2))); |
| /// assert_eq!(r.next().await, None); |
| /// |
| /// let mut p = stream::poll_immediate(Box::pin(stream::once(async { |
| /// futures::pending!(); |
| /// 42_u8 |
| /// }))); |
| /// assert_eq!(p.next().await, Some(Poll::Pending)); |
| /// assert_eq!(p.next().await, Some(Poll::Ready(42))); |
| /// assert_eq!(p.next().await, None); |
| /// # }); |
| /// ``` |
| </span><span class="kw">pub fn </span>poll_immediate<S: Stream>(s: S) -> PollImmediate<S> { |
| <span class="kw">super</span>::assert_stream::<Poll<S::Item>, PollImmediate<S>>(PollImmediate { stream: <span class="prelude-val">Some</span>(s) }) |
| } |
| </code></pre></div> |
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