| <!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/futures_unordered/task.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>task.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>alloc::sync::{Arc, Weak}; |
| <span class="kw">use </span>core::cell::UnsafeCell; |
| <span class="kw">use </span>core::sync::atomic::Ordering::{<span class="self">self</span>, Relaxed, SeqCst}; |
| <span class="kw">use </span>core::sync::atomic::{AtomicBool, AtomicPtr}; |
| |
| <span class="kw">use </span><span class="kw">super</span>::abort::abort; |
| <span class="kw">use </span><span class="kw">super</span>::ReadyToRunQueue; |
| <span class="kw">use </span><span class="kw">crate</span>::task::{waker_ref, ArcWake, WakerRef}; |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>Task<Fut> { |
| <span class="comment">// The future |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) future: UnsafeCell<<span class="prelude-ty">Option</span><Fut>>, |
| |
| <span class="comment">// Next pointer for linked list tracking all active tasks (use |
| // `spin_next_all` to read when access is shared across threads) |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) next_all: AtomicPtr<Task<Fut>>, |
| |
| <span class="comment">// Previous task in linked list tracking all active tasks |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) prev_all: UnsafeCell<<span class="kw-2">*const </span>Task<Fut>>, |
| |
| <span class="comment">// Length of the linked list tracking all active tasks when this node was |
| // inserted (use `spin_next_all` to synchronize before reading when access |
| // is shared across threads) |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) len_all: UnsafeCell<usize>, |
| |
| <span class="comment">// Next pointer in ready to run queue |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) next_ready_to_run: AtomicPtr<Task<Fut>>, |
| |
| <span class="comment">// Queue that we'll be enqueued to when woken |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) ready_to_run_queue: Weak<ReadyToRunQueue<Fut>>, |
| |
| <span class="comment">// Whether or not this task is currently in the ready to run queue |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) queued: AtomicBool, |
| |
| <span class="comment">// Whether the future was awoken during polling |
| // It is possible for this flag to be set to true after the polling, |
| // but it will be ignored. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) woken: AtomicBool, |
| } |
| |
| <span class="comment">// `Task` can be sent across threads safely because it ensures that |
| // the underlying `Fut` type isn't touched from any of its methods. |
| // |
| // The parent (`super`) module is trusted not to access `future` |
| // across different threads. |
| </span><span class="kw">unsafe impl</span><Fut> Send <span class="kw">for </span>Task<Fut> {} |
| <span class="kw">unsafe impl</span><Fut> Sync <span class="kw">for </span>Task<Fut> {} |
| |
| <span class="kw">impl</span><Fut> ArcWake <span class="kw">for </span>Task<Fut> { |
| <span class="kw">fn </span>wake_by_ref(arc_self: <span class="kw-2">&</span>Arc<<span class="self">Self</span>>) { |
| <span class="kw">let </span>inner = <span class="kw">match </span>arc_self.ready_to_run_queue.upgrade() { |
| <span class="prelude-val">Some</span>(inner) => inner, |
| <span class="prelude-val">None </span>=> <span class="kw">return</span>, |
| }; |
| |
| arc_self.woken.store(<span class="bool-val">true</span>, Relaxed); |
| |
| <span class="comment">// It's our job to enqueue this task it into the ready to run queue. To |
| // do this we set the `queued` flag, and if successful we then do the |
| // actual queueing operation, ensuring that we're only queued once. |
| // |
| // Once the task is inserted call `wake` to notify the parent task, |
| // as it'll want to come along and run our task later. |
| // |
| // Note that we don't change the reference count of the task here, |
| // we merely enqueue the raw pointer. The `FuturesUnordered` |
| // implementation guarantees that if we set the `queued` flag that |
| // there's a reference count held by the main `FuturesUnordered` queue |
| // still. |
| </span><span class="kw">let </span>prev = arc_self.queued.swap(<span class="bool-val">true</span>, SeqCst); |
| <span class="kw">if </span>!prev { |
| inner.enqueue(Arc::as_ptr(arc_self)); |
| inner.waker.wake(); |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><Fut> Task<Fut> { |
| <span class="doccomment">/// Returns a waker reference for this task without cloning the Arc. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>waker_ref(this: <span class="kw-2">&</span>Arc<<span class="self">Self</span>>) -> WakerRef<<span class="lifetime">'_</span>> { |
| waker_ref(this) |
| } |
| |
| <span class="doccomment">/// Spins until `next_all` is no longer set to `pending_next_all`. |
| /// |
| /// The temporary `pending_next_all` value is typically overwritten fairly |
| /// quickly after a node is inserted into the list of all futures, so this |
| /// should rarely spin much. |
| /// |
| /// When it returns, the correct `next_all` value is returned. |
| /// |
| /// `Relaxed` or `Acquire` ordering can be used. `Acquire` ordering must be |
| /// used before `len_all` can be safely read. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>spin_next_all( |
| <span class="kw-2">&</span><span class="self">self</span>, |
| pending_next_all: <span class="kw-2">*mut </span><span class="self">Self</span>, |
| ordering: Ordering, |
| ) -> <span class="kw-2">*const </span><span class="self">Self </span>{ |
| <span class="kw">loop </span>{ |
| <span class="kw">let </span>next = <span class="self">self</span>.next_all.load(ordering); |
| <span class="kw">if </span>next != pending_next_all { |
| <span class="kw">return </span>next; |
| } |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><Fut> Drop <span class="kw">for </span>Task<Fut> { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="comment">// Since `Task<Fut>` is sent across all threads for any lifetime, |
| // regardless of `Fut`, we, to guarantee memory safety, can't actually |
| // touch `Fut` at any time except when we have a reference to the |
| // `FuturesUnordered` itself . |
| // |
| // Consequently it *should* be the case that we always drop futures from |
| // the `FuturesUnordered` instance. This is a bomb, just in case there's |
| // a bug in that logic. |
| </span><span class="kw">unsafe </span>{ |
| <span class="kw">if </span>(<span class="kw-2">*</span><span class="self">self</span>.future.get()).is_some() { |
| abort(<span class="string">"future still here when dropping"</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> |
