| <!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-executor-0.3.28/src/local_pool.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>local_pool.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_executor/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_executor/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>::enter; |
| <span class="kw">use </span>futures_core::future::Future; |
| <span class="kw">use </span>futures_core::stream::Stream; |
| <span class="kw">use </span>futures_core::task::{Context, Poll}; |
| <span class="kw">use </span>futures_task::{waker_ref, ArcWake}; |
| <span class="kw">use </span>futures_task::{FutureObj, LocalFutureObj, LocalSpawn, Spawn, SpawnError}; |
| <span class="kw">use </span>futures_util::pin_mut; |
| <span class="kw">use </span>futures_util::stream::FuturesUnordered; |
| <span class="kw">use </span>futures_util::stream::StreamExt; |
| <span class="kw">use </span>std::cell::RefCell; |
| <span class="kw">use </span>std::ops::{Deref, DerefMut}; |
| <span class="kw">use </span>std::rc::{Rc, Weak}; |
| <span class="kw">use </span>std::sync::{ |
| atomic::{AtomicBool, Ordering}, |
| Arc, |
| }; |
| <span class="kw">use </span>std::thread::{<span class="self">self</span>, Thread}; |
| |
| <span class="doccomment">/// A single-threaded task pool for polling futures to completion. |
| /// |
| /// This executor allows you to multiplex any number of tasks onto a single |
| /// thread. It's appropriate to poll strictly I/O-bound futures that do very |
| /// little work in between I/O actions. |
| /// |
| /// To get a handle to the pool that implements |
| /// [`Spawn`](futures_task::Spawn), use the |
| /// [`spawner()`](LocalPool::spawner) method. Because the executor is |
| /// single-threaded, it supports a special form of task spawning for non-`Send` |
| /// futures, via [`spawn_local_obj`](futures_task::LocalSpawn::spawn_local_obj). |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub struct </span>LocalPool { |
| pool: FuturesUnordered<LocalFutureObj<<span class="lifetime">'static</span>, ()>>, |
| incoming: Rc<Incoming>, |
| } |
| |
| <span class="doccomment">/// A handle to a [`LocalPool`](LocalPool) that implements |
| /// [`Spawn`](futures_task::Spawn). |
| </span><span class="attribute">#[derive(Clone, Debug)] |
| </span><span class="kw">pub struct </span>LocalSpawner { |
| incoming: Weak<Incoming>, |
| } |
| |
| <span class="kw">type </span>Incoming = RefCell<Vec<LocalFutureObj<<span class="lifetime">'static</span>, ()>>>; |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>ThreadNotify { |
| <span class="doccomment">/// The (single) executor thread. |
| </span>thread: Thread, |
| <span class="doccomment">/// A flag to ensure a wakeup (i.e. `unpark()`) is not "forgotten" |
| /// before the next `park()`, which may otherwise happen if the code |
| /// being executed as part of the future(s) being polled makes use of |
| /// park / unpark calls of its own, i.e. we cannot assume that no other |
| /// code uses park / unpark on the executing `thread`. |
| </span>unparked: AtomicBool, |
| } |
| |
| <span class="macro">thread_local! </span>{ |
| <span class="kw">static </span>CURRENT_THREAD_NOTIFY: Arc<ThreadNotify> = Arc::new(ThreadNotify { |
| thread: thread::current(), |
| unparked: AtomicBool::new(<span class="bool-val">false</span>), |
| }); |
| } |
| |
| <span class="kw">impl </span>ArcWake <span class="kw">for </span>ThreadNotify { |
| <span class="kw">fn </span>wake_by_ref(arc_self: <span class="kw-2">&</span>Arc<<span class="self">Self</span>>) { |
| <span class="comment">// Make sure the wakeup is remembered until the next `park()`. |
| </span><span class="kw">let </span>unparked = arc_self.unparked.swap(<span class="bool-val">true</span>, Ordering::Release); |
| <span class="kw">if </span>!unparked { |
| <span class="comment">// If the thread has not been unparked yet, it must be done |
| // now. If it was actually parked, it will run again, |
| // otherwise the token made available by `unpark` |
| // may be consumed before reaching `park()`, but `unparked` |
| // ensures it is not forgotten. |
| </span>arc_self.thread.unpark(); |
| } |
| } |
| } |
| |
| <span class="comment">// Set up and run a basic single-threaded spawner loop, invoking `f` on each |
| // turn. |
| </span><span class="kw">fn </span>run_executor<T, F: FnMut(<span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<T>>(<span class="kw-2">mut </span>f: F) -> T { |
| <span class="kw">let </span>_enter = enter().expect( |
| <span class="string">"cannot execute `LocalPool` executor from within \ |
| another executor"</span>, |
| ); |
| |
| CURRENT_THREAD_NOTIFY.with(|thread_notify| { |
| <span class="kw">let </span>waker = waker_ref(thread_notify); |
| <span class="kw">let </span><span class="kw-2">mut </span>cx = Context::from_waker(<span class="kw-2">&</span>waker); |
| <span class="kw">loop </span>{ |
| <span class="kw">if let </span>Poll::Ready(t) = f(<span class="kw-2">&mut </span>cx) { |
| <span class="kw">return </span>t; |
| } |
| |
| <span class="comment">// Wait for a wakeup. |
| </span><span class="kw">while </span>!thread_notify.unparked.swap(<span class="bool-val">false</span>, Ordering::Acquire) { |
| <span class="comment">// No wakeup occurred. It may occur now, right before parking, |
| // but in that case the token made available by `unpark()` |
| // is guaranteed to still be available and `park()` is a no-op. |
| </span>thread::park(); |
| } |
| } |
| }) |
| } |
| |
| <span class="doccomment">/// Check for a wakeup, but don't consume it. |
| </span><span class="kw">fn </span>woken() -> bool { |
| CURRENT_THREAD_NOTIFY.with(|thread_notify| thread_notify.unparked.load(Ordering::Acquire)) |
| } |
| |
| <span class="kw">impl </span>LocalPool { |
| <span class="doccomment">/// Create a new, empty pool of tasks. |
| </span><span class="kw">pub fn </span>new() -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ pool: FuturesUnordered::new(), incoming: Default::default() } |
| } |
| |
| <span class="doccomment">/// Get a clonable handle to the pool as a [`Spawn`]. |
| </span><span class="kw">pub fn </span>spawner(<span class="kw-2">&</span><span class="self">self</span>) -> LocalSpawner { |
| LocalSpawner { incoming: Rc::downgrade(<span class="kw-2">&</span><span class="self">self</span>.incoming) } |
| } |
| |
| <span class="doccomment">/// Run all tasks in the pool to completion. |
| /// |
| /// ``` |
| /// use futures::executor::LocalPool; |
| /// |
| /// let mut pool = LocalPool::new(); |
| /// |
| /// // ... spawn some initial tasks using `spawn.spawn()` or `spawn.spawn_local()` |
| /// |
| /// // run *all* tasks in the pool to completion, including any newly-spawned ones. |
| /// pool.run(); |
| /// ``` |
| /// |
| /// The function will block the calling thread until *all* tasks in the pool |
| /// are complete, including any spawned while running existing tasks. |
| </span><span class="kw">pub fn </span>run(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| run_executor(|cx| <span class="self">self</span>.poll_pool(cx)) |
| } |
| |
| <span class="doccomment">/// Runs all the tasks in the pool until the given future completes. |
| /// |
| /// ``` |
| /// use futures::executor::LocalPool; |
| /// |
| /// let mut pool = LocalPool::new(); |
| /// # let my_app = async {}; |
| /// |
| /// // run tasks in the pool until `my_app` completes |
| /// pool.run_until(my_app); |
| /// ``` |
| /// |
| /// The function will block the calling thread *only* until the future `f` |
| /// completes; there may still be incomplete tasks in the pool, which will |
| /// be inert after the call completes, but can continue with further use of |
| /// one of the pool's run or poll methods. While the function is running, |
| /// however, all tasks in the pool will try to make progress. |
| </span><span class="kw">pub fn </span>run_until<F: Future>(<span class="kw-2">&mut </span><span class="self">self</span>, future: F) -> F::Output { |
| <span class="macro">pin_mut!</span>(future); |
| |
| run_executor(|cx| { |
| { |
| <span class="comment">// if our main task is done, so are we |
| </span><span class="kw">let </span>result = future.as_mut().poll(cx); |
| <span class="kw">if let </span>Poll::Ready(output) = result { |
| <span class="kw">return </span>Poll::Ready(output); |
| } |
| } |
| |
| <span class="kw">let _ </span>= <span class="self">self</span>.poll_pool(cx); |
| Poll::Pending |
| }) |
| } |
| |
| <span class="doccomment">/// Runs all tasks and returns after completing one future or until no more progress |
| /// can be made. Returns `true` if one future was completed, `false` otherwise. |
| /// |
| /// ``` |
| /// use futures::executor::LocalPool; |
| /// use futures::task::LocalSpawnExt; |
| /// use futures::future::{ready, pending}; |
| /// |
| /// let mut pool = LocalPool::new(); |
| /// let spawner = pool.spawner(); |
| /// |
| /// spawner.spawn_local(ready(())).unwrap(); |
| /// spawner.spawn_local(ready(())).unwrap(); |
| /// spawner.spawn_local(pending()).unwrap(); |
| /// |
| /// // Run the two ready tasks and return true for them. |
| /// pool.try_run_one(); // returns true after completing one of the ready futures |
| /// pool.try_run_one(); // returns true after completing the other ready future |
| /// |
| /// // the remaining task can not be completed |
| /// assert!(!pool.try_run_one()); // returns false |
| /// ``` |
| /// |
| /// This function will not block the calling thread and will return the moment |
| /// that there are no tasks left for which progress can be made or after exactly one |
| /// task was completed; Remaining incomplete tasks in the pool can continue with |
| /// further use of one of the pool's run or poll methods. |
| /// Though only one task will be completed, progress may be made on multiple tasks. |
| </span><span class="kw">pub fn </span>try_run_one(<span class="kw-2">&mut </span><span class="self">self</span>) -> bool { |
| run_executor(|cx| { |
| <span class="kw">loop </span>{ |
| <span class="self">self</span>.drain_incoming(); |
| |
| <span class="kw">match </span><span class="self">self</span>.pool.poll_next_unpin(cx) { |
| <span class="comment">// Success! |
| </span>Poll::Ready(<span class="prelude-val">Some</span>(())) => <span class="kw">return </span>Poll::Ready(<span class="bool-val">true</span>), |
| <span class="comment">// The pool was empty. |
| </span>Poll::Ready(<span class="prelude-val">None</span>) => <span class="kw">return </span>Poll::Ready(<span class="bool-val">false</span>), |
| Poll::Pending => (), |
| } |
| |
| <span class="kw">if </span>!<span class="self">self</span>.incoming.borrow().is_empty() { |
| <span class="comment">// New tasks were spawned; try again. |
| </span><span class="kw">continue</span>; |
| } <span class="kw">else if </span>woken() { |
| <span class="comment">// The pool yielded to us, but there's more progress to be made. |
| </span><span class="kw">return </span>Poll::Pending; |
| } <span class="kw">else </span>{ |
| <span class="kw">return </span>Poll::Ready(<span class="bool-val">false</span>); |
| } |
| } |
| }) |
| } |
| |
| <span class="doccomment">/// Runs all tasks in the pool and returns if no more progress can be made |
| /// on any task. |
| /// |
| /// ``` |
| /// use futures::executor::LocalPool; |
| /// use futures::task::LocalSpawnExt; |
| /// use futures::future::{ready, pending}; |
| /// |
| /// let mut pool = LocalPool::new(); |
| /// let spawner = pool.spawner(); |
| /// |
| /// spawner.spawn_local(ready(())).unwrap(); |
| /// spawner.spawn_local(ready(())).unwrap(); |
| /// spawner.spawn_local(pending()).unwrap(); |
| /// |
| /// // Runs the two ready task and returns. |
| /// // The empty task remains in the pool. |
| /// pool.run_until_stalled(); |
| /// ``` |
| /// |
| /// This function will not block the calling thread and will return the moment |
| /// that there are no tasks left for which progress can be made; |
| /// remaining incomplete tasks in the pool can continue with further use of one |
| /// of the pool's run or poll methods. While the function is running, all tasks |
| /// in the pool will try to make progress. |
| </span><span class="kw">pub fn </span>run_until_stalled(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| run_executor(|cx| <span class="kw">match </span><span class="self">self</span>.poll_pool(cx) { |
| <span class="comment">// The pool is empty. |
| </span>Poll::Ready(()) => Poll::Ready(()), |
| Poll::Pending => { |
| <span class="kw">if </span>woken() { |
| Poll::Pending |
| } <span class="kw">else </span>{ |
| <span class="comment">// We're stalled for now. |
| </span>Poll::Ready(()) |
| } |
| } |
| }); |
| } |
| |
| <span class="doccomment">/// Poll `self.pool`, re-filling it with any newly-spawned tasks. |
| /// Repeat until either the pool is empty, or it returns `Pending`. |
| /// |
| /// Returns `Ready` if the pool was empty, and `Pending` otherwise. |
| /// |
| /// NOTE: the pool may call `wake`, so `Pending` doesn't necessarily |
| /// mean that the pool can't make progress. |
| </span><span class="kw">fn </span>poll_pool(<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">loop </span>{ |
| <span class="self">self</span>.drain_incoming(); |
| |
| <span class="kw">let </span>pool_ret = <span class="self">self</span>.pool.poll_next_unpin(cx); |
| |
| <span class="comment">// We queued up some new tasks; add them and poll again. |
| </span><span class="kw">if </span>!<span class="self">self</span>.incoming.borrow().is_empty() { |
| <span class="kw">continue</span>; |
| } |
| |
| <span class="kw">match </span>pool_ret { |
| Poll::Ready(<span class="prelude-val">Some</span>(())) => <span class="kw">continue</span>, |
| Poll::Ready(<span class="prelude-val">None</span>) => <span class="kw">return </span>Poll::Ready(()), |
| Poll::Pending => <span class="kw">return </span>Poll::Pending, |
| } |
| } |
| } |
| |
| <span class="doccomment">/// Empty the incoming queue of newly-spawned tasks. |
| </span><span class="kw">fn </span>drain_incoming(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="kw">let </span><span class="kw-2">mut </span>incoming = <span class="self">self</span>.incoming.borrow_mut(); |
| <span class="kw">for </span>task <span class="kw">in </span>incoming.drain(..) { |
| <span class="self">self</span>.pool.push(task) |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>Default <span class="kw">for </span>LocalPool { |
| <span class="kw">fn </span>default() -> <span class="self">Self </span>{ |
| <span class="self">Self</span>::new() |
| } |
| } |
| |
| <span class="doccomment">/// Run a future to completion on the current thread. |
| /// |
| /// This function will block the caller until the given future has completed. |
| /// |
| /// Use a [`LocalPool`](LocalPool) if you need finer-grained control over |
| /// spawned tasks. |
| </span><span class="kw">pub fn </span>block_on<F: Future>(f: F) -> F::Output { |
| <span class="macro">pin_mut!</span>(f); |
| run_executor(|cx| f.as_mut().poll(cx)) |
| } |
| |
| <span class="doccomment">/// Turn a stream into a blocking iterator. |
| /// |
| /// When `next` is called on the resulting `BlockingStream`, the caller |
| /// will be blocked until the next element of the `Stream` becomes available. |
| </span><span class="kw">pub fn </span>block_on_stream<S: Stream + Unpin>(stream: S) -> BlockingStream<S> { |
| BlockingStream { stream } |
| } |
| |
| <span class="doccomment">/// An iterator which blocks on values from a stream until they become available. |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub struct </span>BlockingStream<S: Stream + Unpin> { |
| stream: S, |
| } |
| |
| <span class="kw">impl</span><S: Stream + Unpin> Deref <span class="kw">for </span>BlockingStream<S> { |
| <span class="kw">type </span>Target = S; |
| <span class="kw">fn </span>deref(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw-2">&</span><span class="self">Self</span>::Target { |
| <span class="kw-2">&</span><span class="self">self</span>.stream |
| } |
| } |
| |
| <span class="kw">impl</span><S: Stream + Unpin> DerefMut <span class="kw">for </span>BlockingStream<S> { |
| <span class="kw">fn </span>deref_mut(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="kw-2">&mut </span><span class="self">Self</span>::Target { |
| <span class="kw-2">&mut </span><span class="self">self</span>.stream |
| } |
| } |
| |
| <span class="kw">impl</span><S: Stream + Unpin> BlockingStream<S> { |
| <span class="doccomment">/// Convert this `BlockingStream` into the inner `Stream` type. |
| </span><span class="kw">pub fn </span>into_inner(<span class="self">self</span>) -> S { |
| <span class="self">self</span>.stream |
| } |
| } |
| |
| <span class="kw">impl</span><S: Stream + Unpin> Iterator <span class="kw">for </span>BlockingStream<S> { |
| <span class="kw">type </span>Item = S::Item; |
| |
| <span class="kw">fn </span>next(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>::Item> { |
| LocalPool::new().run_until(<span class="self">self</span>.stream.next()) |
| } |
| |
| <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.size_hint() |
| } |
| } |
| |
| <span class="kw">impl </span>Spawn <span class="kw">for </span>LocalSpawner { |
| <span class="kw">fn </span>spawn_obj(<span class="kw-2">&</span><span class="self">self</span>, future: FutureObj<<span class="lifetime">'static</span>, ()>) -> <span class="prelude-ty">Result</span><(), SpawnError> { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(incoming) = <span class="self">self</span>.incoming.upgrade() { |
| incoming.borrow_mut().push(future.into()); |
| <span class="prelude-val">Ok</span>(()) |
| } <span class="kw">else </span>{ |
| <span class="prelude-val">Err</span>(SpawnError::shutdown()) |
| } |
| } |
| |
| <span class="kw">fn </span>status(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="prelude-ty">Result</span><(), SpawnError> { |
| <span class="kw">if </span><span class="self">self</span>.incoming.upgrade().is_some() { |
| <span class="prelude-val">Ok</span>(()) |
| } <span class="kw">else </span>{ |
| <span class="prelude-val">Err</span>(SpawnError::shutdown()) |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>LocalSpawn <span class="kw">for </span>LocalSpawner { |
| <span class="kw">fn </span>spawn_local_obj(<span class="kw-2">&</span><span class="self">self</span>, future: LocalFutureObj<<span class="lifetime">'static</span>, ()>) -> <span class="prelude-ty">Result</span><(), SpawnError> { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(incoming) = <span class="self">self</span>.incoming.upgrade() { |
| incoming.borrow_mut().push(future); |
| <span class="prelude-val">Ok</span>(()) |
| } <span class="kw">else </span>{ |
| <span class="prelude-val">Err</span>(SpawnError::shutdown()) |
| } |
| } |
| |
| <span class="kw">fn </span>status_local(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="prelude-ty">Result</span><(), SpawnError> { |
| <span class="kw">if </span><span class="self">self</span>.incoming.upgrade().is_some() { |
| <span class="prelude-val">Ok</span>(()) |
| } <span class="kw">else </span>{ |
| <span class="prelude-val">Err</span>(SpawnError::shutdown()) |
| } |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="futures_executor" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |