| <!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-channel-0.3.28/src/oneshot.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>oneshot.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_channel/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_channel/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">//! A channel for sending a single message between asynchronous tasks. |
| //! |
| //! This is a single-producer, single-consumer channel. |
| |
| </span><span class="kw">use </span>alloc::sync::Arc; |
| <span class="kw">use </span>core::fmt; |
| <span class="kw">use </span>core::pin::Pin; |
| <span class="kw">use </span>core::sync::atomic::AtomicBool; |
| <span class="kw">use </span>core::sync::atomic::Ordering::SeqCst; |
| <span class="kw">use </span>futures_core::future::{FusedFuture, Future}; |
| <span class="kw">use </span>futures_core::task::{Context, Poll, Waker}; |
| |
| <span class="kw">use </span><span class="kw">crate</span>::lock::Lock; |
| |
| <span class="doccomment">/// A future for a value that will be provided by another asynchronous task. |
| /// |
| /// This is created by the [`channel`](channel) function. |
| </span><span class="attribute">#[must_use = <span class="string">"futures do nothing unless you `.await` or poll them"</span>] |
| </span><span class="kw">pub struct </span>Receiver<T> { |
| inner: Arc<Inner<T>>, |
| } |
| |
| <span class="doccomment">/// A means of transmitting a single value to another task. |
| /// |
| /// This is created by the [`channel`](channel) function. |
| </span><span class="kw">pub struct </span>Sender<T> { |
| inner: Arc<Inner<T>>, |
| } |
| |
| <span class="comment">// The channels do not ever project Pin to the inner T |
| </span><span class="kw">impl</span><T> Unpin <span class="kw">for </span>Receiver<T> {} |
| <span class="kw">impl</span><T> Unpin <span class="kw">for </span>Sender<T> {} |
| |
| <span class="doccomment">/// Internal state of the `Receiver`/`Sender` pair above. This is all used as |
| /// the internal synchronization between the two for send/recv operations. |
| </span><span class="kw">struct </span>Inner<T> { |
| <span class="doccomment">/// Indicates whether this oneshot is complete yet. This is filled in both |
| /// by `Sender::drop` and by `Receiver::drop`, and both sides interpret it |
| /// appropriately. |
| /// |
| /// For `Receiver`, if this is `true`, then it's guaranteed that `data` is |
| /// unlocked and ready to be inspected. |
| /// |
| /// For `Sender` if this is `true` then the oneshot has gone away and it |
| /// can return ready from `poll_canceled`. |
| </span>complete: AtomicBool, |
| |
| <span class="doccomment">/// The actual data being transferred as part of this `Receiver`. This is |
| /// filled in by `Sender::complete` and read by `Receiver::poll`. |
| /// |
| /// Note that this is protected by `Lock`, but it is in theory safe to |
| /// replace with an `UnsafeCell` as it's actually protected by `complete` |
| /// above. I wouldn't recommend doing this, however, unless someone is |
| /// supremely confident in the various atomic orderings here and there. |
| </span>data: Lock<<span class="prelude-ty">Option</span><T>>, |
| |
| <span class="doccomment">/// Field to store the task which is blocked in `Receiver::poll`. |
| /// |
| /// This is filled in when a oneshot is polled but not ready yet. Note that |
| /// the `Lock` here, unlike in `data` above, is important to resolve races. |
| /// Both the `Receiver` and the `Sender` halves understand that if they |
| /// can't acquire the lock then some important interference is happening. |
| </span>rx_task: Lock<<span class="prelude-ty">Option</span><Waker>>, |
| |
| <span class="doccomment">/// Like `rx_task` above, except for the task blocked in |
| /// `Sender::poll_canceled`. Additionally, `Lock` cannot be `UnsafeCell`. |
| </span>tx_task: Lock<<span class="prelude-ty">Option</span><Waker>>, |
| } |
| |
| <span class="doccomment">/// Creates a new one-shot channel for sending a single value across asynchronous tasks. |
| /// |
| /// The channel works for a spsc (single-producer, single-consumer) scheme. |
| /// |
| /// This function is similar to Rust's channel constructor found in the standard |
| /// library. Two halves are returned, the first of which is a `Sender` handle, |
| /// used to signal the end of a computation and provide its value. The second |
| /// half is a `Receiver` which implements the `Future` trait, resolving to the |
| /// value that was given to the `Sender` handle. |
| /// |
| /// Each half can be separately owned and sent across tasks. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use futures::channel::oneshot; |
| /// use std::{thread, time::Duration}; |
| /// |
| /// let (sender, receiver) = oneshot::channel::<i32>(); |
| /// |
| /// thread::spawn(|| { |
| /// println!("THREAD: sleeping zzz..."); |
| /// thread::sleep(Duration::from_millis(1000)); |
| /// println!("THREAD: i'm awake! sending."); |
| /// sender.send(3).unwrap(); |
| /// }); |
| /// |
| /// println!("MAIN: doing some useful stuff"); |
| /// |
| /// futures::executor::block_on(async { |
| /// println!("MAIN: waiting for msg..."); |
| /// println!("MAIN: got: {:?}", receiver.await) |
| /// }); |
| /// ``` |
| </span><span class="kw">pub fn </span>channel<T>() -> (Sender<T>, Receiver<T>) { |
| <span class="kw">let </span>inner = Arc::new(Inner::new()); |
| <span class="kw">let </span>receiver = Receiver { inner: inner.clone() }; |
| <span class="kw">let </span>sender = Sender { inner }; |
| (sender, receiver) |
| } |
| |
| <span class="kw">impl</span><T> Inner<T> { |
| <span class="kw">fn </span>new() -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ |
| complete: AtomicBool::new(<span class="bool-val">false</span>), |
| data: Lock::new(<span class="prelude-val">None</span>), |
| rx_task: Lock::new(<span class="prelude-val">None</span>), |
| tx_task: Lock::new(<span class="prelude-val">None</span>), |
| } |
| } |
| |
| <span class="kw">fn </span>send(<span class="kw-2">&</span><span class="self">self</span>, t: T) -> <span class="prelude-ty">Result</span><(), T> { |
| <span class="kw">if </span><span class="self">self</span>.complete.load(SeqCst) { |
| <span class="kw">return </span><span class="prelude-val">Err</span>(t); |
| } |
| |
| <span class="comment">// Note that this lock acquisition may fail if the receiver |
| // is closed and sets the `complete` flag to `true`, whereupon |
| // the receiver may call `poll()`. |
| </span><span class="kw">if let </span><span class="prelude-val">Some</span>(<span class="kw-2">mut </span>slot) = <span class="self">self</span>.data.try_lock() { |
| <span class="macro">assert!</span>(slot.is_none()); |
| <span class="kw-2">*</span>slot = <span class="prelude-val">Some</span>(t); |
| drop(slot); |
| |
| <span class="comment">// If the receiver called `close()` between the check at the |
| // start of the function, and the lock being released, then |
| // the receiver may not be around to receive it, so try to |
| // pull it back out. |
| </span><span class="kw">if </span><span class="self">self</span>.complete.load(SeqCst) { |
| <span class="comment">// If lock acquisition fails, then receiver is actually |
| // receiving it, so we're good. |
| </span><span class="kw">if let </span><span class="prelude-val">Some</span>(<span class="kw-2">mut </span>slot) = <span class="self">self</span>.data.try_lock() { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(t) = slot.take() { |
| <span class="kw">return </span><span class="prelude-val">Err</span>(t); |
| } |
| } |
| } |
| <span class="prelude-val">Ok</span>(()) |
| } <span class="kw">else </span>{ |
| <span class="comment">// Must have been closed |
| </span><span class="prelude-val">Err</span>(t) |
| } |
| } |
| |
| <span class="kw">fn </span>poll_canceled(<span class="kw-2">&</span><span class="self">self</span>, cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<()> { |
| <span class="comment">// Fast path up first, just read the flag and see if our other half is |
| // gone. This flag is set both in our destructor and the oneshot |
| // destructor, but our destructor hasn't run yet so if it's set then the |
| // oneshot is gone. |
| </span><span class="kw">if </span><span class="self">self</span>.complete.load(SeqCst) { |
| <span class="kw">return </span>Poll::Ready(()); |
| } |
| |
| <span class="comment">// If our other half is not gone then we need to park our current task |
| // and move it into the `tx_task` slot to get notified when it's |
| // actually gone. |
| // |
| // If `try_lock` fails, then the `Receiver` is in the process of using |
| // it, so we can deduce that it's now in the process of going away and |
| // hence we're canceled. If it succeeds then we just store our handle. |
| // |
| // Crucially we then check `complete` *again* before we return. |
| // While we were storing our handle inside `tx_task` the |
| // `Receiver` may have been dropped. The first thing it does is set the |
| // flag, and if it fails to acquire the lock it assumes that we'll see |
| // the flag later on. So... we then try to see the flag later on! |
| </span><span class="kw">let </span>handle = cx.waker().clone(); |
| <span class="kw">match </span><span class="self">self</span>.tx_task.try_lock() { |
| <span class="prelude-val">Some</span>(<span class="kw-2">mut </span>p) => <span class="kw-2">*</span>p = <span class="prelude-val">Some</span>(handle), |
| <span class="prelude-val">None </span>=> <span class="kw">return </span>Poll::Ready(()), |
| } |
| <span class="kw">if </span><span class="self">self</span>.complete.load(SeqCst) { |
| Poll::Ready(()) |
| } <span class="kw">else </span>{ |
| Poll::Pending |
| } |
| } |
| |
| <span class="kw">fn </span>is_canceled(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.complete.load(SeqCst) |
| } |
| |
| <span class="kw">fn </span>drop_tx(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="comment">// Flag that we're a completed `Sender` and try to wake up a receiver. |
| // Whether or not we actually stored any data will get picked up and |
| // translated to either an item or cancellation. |
| // |
| // Note that if we fail to acquire the `rx_task` lock then that means |
| // we're in one of two situations: |
| // |
| // 1. The receiver is trying to block in `poll` |
| // 2. The receiver is being dropped |
| // |
| // In the first case it'll check the `complete` flag after it's done |
| // blocking to see if it succeeded. In the latter case we don't need to |
| // wake up anyone anyway. So in both cases it's ok to ignore the `None` |
| // case of `try_lock` and bail out. |
| // |
| // The first case crucially depends on `Lock` using `SeqCst` ordering |
| // under the hood. If it instead used `Release` / `Acquire` ordering, |
| // then it would not necessarily synchronize with `inner.complete` |
| // and deadlock might be possible, as was observed in |
| // https://github.com/rust-lang/futures-rs/pull/219. |
| </span><span class="self">self</span>.complete.store(<span class="bool-val">true</span>, SeqCst); |
| |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(<span class="kw-2">mut </span>slot) = <span class="self">self</span>.rx_task.try_lock() { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(task) = slot.take() { |
| drop(slot); |
| task.wake(); |
| } |
| } |
| |
| <span class="comment">// If we registered a task for cancel notification drop it to reduce |
| // spurious wakeups |
| </span><span class="kw">if let </span><span class="prelude-val">Some</span>(<span class="kw-2">mut </span>slot) = <span class="self">self</span>.tx_task.try_lock() { |
| drop(slot.take()); |
| } |
| } |
| |
| <span class="kw">fn </span>close_rx(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="comment">// Flag our completion and then attempt to wake up the sender if it's |
| // blocked. See comments in `drop` below for more info |
| </span><span class="self">self</span>.complete.store(<span class="bool-val">true</span>, SeqCst); |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(<span class="kw-2">mut </span>handle) = <span class="self">self</span>.tx_task.try_lock() { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(task) = handle.take() { |
| drop(handle); |
| task.wake() |
| } |
| } |
| } |
| |
| <span class="kw">fn </span>try_recv(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="prelude-ty">Result</span><<span class="prelude-ty">Option</span><T>, Canceled> { |
| <span class="comment">// If we're complete, either `::close_rx` or `::drop_tx` was called. |
| // We can assume a successful send if data is present. |
| </span><span class="kw">if </span><span class="self">self</span>.complete.load(SeqCst) { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(<span class="kw-2">mut </span>slot) = <span class="self">self</span>.data.try_lock() { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(data) = slot.take() { |
| <span class="kw">return </span><span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(data)); |
| } |
| } |
| <span class="prelude-val">Err</span>(Canceled) |
| } <span class="kw">else </span>{ |
| <span class="prelude-val">Ok</span>(<span class="prelude-val">None</span>) |
| } |
| } |
| |
| <span class="kw">fn </span>recv(<span class="kw-2">&</span><span class="self">self</span>, cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<<span class="prelude-ty">Result</span><T, Canceled>> { |
| <span class="comment">// Check to see if some data has arrived. If it hasn't then we need to |
| // block our task. |
| // |
| // Note that the acquisition of the `rx_task` lock might fail below, but |
| // the only situation where this can happen is during `Sender::drop` |
| // when we are indeed completed already. If that's happening then we |
| // know we're completed so keep going. |
| </span><span class="kw">let </span>done = <span class="kw">if </span><span class="self">self</span>.complete.load(SeqCst) { |
| <span class="bool-val">true |
| </span>} <span class="kw">else </span>{ |
| <span class="kw">let </span>task = cx.waker().clone(); |
| <span class="kw">match </span><span class="self">self</span>.rx_task.try_lock() { |
| <span class="prelude-val">Some</span>(<span class="kw-2">mut </span>slot) => { |
| <span class="kw-2">*</span>slot = <span class="prelude-val">Some</span>(task); |
| <span class="bool-val">false |
| </span>} |
| <span class="prelude-val">None </span>=> <span class="bool-val">true</span>, |
| } |
| }; |
| |
| <span class="comment">// If we're `done` via one of the paths above, then look at the data and |
| // figure out what the answer is. If, however, we stored `rx_task` |
| // successfully above we need to check again if we're completed in case |
| // a message was sent while `rx_task` was locked and couldn't notify us |
| // otherwise. |
| // |
| // If we're not done, and we're not complete, though, then we've |
| // successfully blocked our task and we return `Pending`. |
| </span><span class="kw">if </span>done || <span class="self">self</span>.complete.load(SeqCst) { |
| <span class="comment">// If taking the lock fails, the sender will realise that the we're |
| // `done` when it checks the `complete` flag on the way out, and |
| // will treat the send as a failure. |
| </span><span class="kw">if let </span><span class="prelude-val">Some</span>(<span class="kw-2">mut </span>slot) = <span class="self">self</span>.data.try_lock() { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(data) = slot.take() { |
| <span class="kw">return </span>Poll::Ready(<span class="prelude-val">Ok</span>(data)); |
| } |
| } |
| Poll::Ready(<span class="prelude-val">Err</span>(Canceled)) |
| } <span class="kw">else </span>{ |
| Poll::Pending |
| } |
| } |
| |
| <span class="kw">fn </span>drop_rx(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="comment">// Indicate to the `Sender` that we're done, so any future calls to |
| // `poll_canceled` are weeded out. |
| </span><span class="self">self</span>.complete.store(<span class="bool-val">true</span>, SeqCst); |
| |
| <span class="comment">// If we've blocked a task then there's no need for it to stick around, |
| // so we need to drop it. If this lock acquisition fails, though, then |
| // it's just because our `Sender` is trying to take the task, so we |
| // let them take care of that. |
| </span><span class="kw">if let </span><span class="prelude-val">Some</span>(<span class="kw-2">mut </span>slot) = <span class="self">self</span>.rx_task.try_lock() { |
| <span class="kw">let </span>task = slot.take(); |
| drop(slot); |
| drop(task); |
| } |
| |
| <span class="comment">// Finally, if our `Sender` wants to get notified of us going away, it |
| // would have stored something in `tx_task`. Here we try to peel that |
| // out and unpark it. |
| // |
| // Note that the `try_lock` here may fail, but only if the `Sender` is |
| // in the process of filling in the task. If that happens then we |
| // already flagged `complete` and they'll pick that up above. |
| </span><span class="kw">if let </span><span class="prelude-val">Some</span>(<span class="kw-2">mut </span>handle) = <span class="self">self</span>.tx_task.try_lock() { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(task) = handle.take() { |
| drop(handle); |
| task.wake() |
| } |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><T> Sender<T> { |
| <span class="doccomment">/// Completes this oneshot with a successful result. |
| /// |
| /// This function will consume `self` and indicate to the other end, the |
| /// [`Receiver`](Receiver), that the value provided is the result of the |
| /// computation this represents. |
| /// |
| /// If the value is successfully enqueued for the remote end to receive, |
| /// then `Ok(())` is returned. If the receiving end was dropped before |
| /// this function was called, however, then `Err(t)` is returned. |
| </span><span class="kw">pub fn </span>send(<span class="self">self</span>, t: T) -> <span class="prelude-ty">Result</span><(), T> { |
| <span class="self">self</span>.inner.send(t) |
| } |
| |
| <span class="doccomment">/// Polls this `Sender` half to detect whether its associated |
| /// [`Receiver`](Receiver) has been dropped. |
| /// |
| /// # Return values |
| /// |
| /// If `Ready(())` is returned then the associated `Receiver` has been |
| /// dropped, which means any work required for sending should be canceled. |
| /// |
| /// If `Pending` is returned then the associated `Receiver` is still |
| /// alive and may be able to receive a message if sent. The current task, |
| /// however, is scheduled to receive a notification if the corresponding |
| /// `Receiver` goes away. |
| </span><span class="kw">pub fn </span>poll_canceled(<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>.inner.poll_canceled(cx) |
| } |
| |
| <span class="doccomment">/// Creates a future that resolves when this `Sender`'s corresponding |
| /// [`Receiver`](Receiver) half has hung up. |
| /// |
| /// This is a utility wrapping [`poll_canceled`](Sender::poll_canceled) |
| /// to expose a [`Future`](core::future::Future). |
| </span><span class="kw">pub fn </span>cancellation(<span class="kw-2">&mut </span><span class="self">self</span>) -> Cancellation<<span class="lifetime">'_</span>, T> { |
| Cancellation { inner: <span class="self">self </span>} |
| } |
| |
| <span class="doccomment">/// Tests to see whether this `Sender`'s corresponding `Receiver` |
| /// has been dropped. |
| /// |
| /// Unlike [`poll_canceled`](Sender::poll_canceled), this function does not |
| /// enqueue a task for wakeup upon cancellation, but merely reports the |
| /// current state, which may be subject to concurrent modification. |
| </span><span class="kw">pub fn </span>is_canceled(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.inner.is_canceled() |
| } |
| |
| <span class="doccomment">/// Tests to see whether this `Sender` is connected to the given `Receiver`. That is, whether |
| /// they were created by the same call to `channel`. |
| </span><span class="kw">pub fn </span>is_connected_to(<span class="kw-2">&</span><span class="self">self</span>, receiver: <span class="kw-2">&</span>Receiver<T>) -> bool { |
| Arc::ptr_eq(<span class="kw-2">&</span><span class="self">self</span>.inner, <span class="kw-2">&</span>receiver.inner) |
| } |
| } |
| |
| <span class="kw">impl</span><T> Drop <span class="kw">for </span>Sender<T> { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.inner.drop_tx() |
| } |
| } |
| |
| <span class="kw">impl</span><T> fmt::Debug <span class="kw">for </span>Sender<T> { |
| <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_struct(<span class="string">"Sender"</span>).field(<span class="string">"complete"</span>, <span class="kw-2">&</span><span class="self">self</span>.inner.complete).finish() |
| } |
| } |
| |
| <span class="doccomment">/// A future that resolves when the receiving end of a channel has hung up. |
| /// |
| /// This is an `.await`-friendly interface around [`poll_canceled`](Sender::poll_canceled). |
| </span><span class="attribute">#[must_use = <span class="string">"futures do nothing unless you `.await` or poll them"</span>] |
| #[derive(Debug)] |
| </span><span class="kw">pub struct </span>Cancellation<<span class="lifetime">'a</span>, T> { |
| inner: <span class="kw-2">&</span><span class="lifetime">'a </span><span class="kw-2">mut </span>Sender<T>, |
| } |
| |
| <span class="kw">impl</span><T> Future <span class="kw">for </span>Cancellation<<span class="lifetime">'_</span>, T> { |
| <span class="kw">type </span>Output = (); |
| |
| <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<()> { |
| <span class="self">self</span>.inner.poll_canceled(cx) |
| } |
| } |
| |
| <span class="doccomment">/// Error returned from a [`Receiver`](Receiver) when the corresponding |
| /// [`Sender`](Sender) is dropped. |
| </span><span class="attribute">#[derive(Clone, Copy, PartialEq, Eq, Debug)] |
| </span><span class="kw">pub struct </span>Canceled; |
| |
| <span class="kw">impl </span>fmt::Display <span class="kw">for </span>Canceled { |
| <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 { |
| <span class="macro">write!</span>(f, <span class="string">"oneshot canceled"</span>) |
| } |
| } |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">impl </span>std::error::Error <span class="kw">for </span>Canceled {} |
| |
| <span class="kw">impl</span><T> Receiver<T> { |
| <span class="doccomment">/// Gracefully close this receiver, preventing any subsequent attempts to |
| /// send to it. |
| /// |
| /// Any `send` operation which happens after this method returns is |
| /// guaranteed to fail. After calling this method, you can use |
| /// [`Receiver::poll`](core::future::Future::poll) to determine whether a |
| /// message had previously been sent. |
| </span><span class="kw">pub fn </span>close(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.inner.close_rx() |
| } |
| |
| <span class="doccomment">/// Attempts to receive a message outside of the context of a task. |
| /// |
| /// Does not schedule a task wakeup or have any other side effects. |
| /// |
| /// A return value of `None` must be considered immediately stale (out of |
| /// date) unless [`close`](Receiver::close) has been called first. |
| /// |
| /// Returns an error if the sender was dropped. |
| </span><span class="kw">pub fn </span>try_recv(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="prelude-ty">Result</span><<span class="prelude-ty">Option</span><T>, Canceled> { |
| <span class="self">self</span>.inner.try_recv() |
| } |
| } |
| |
| <span class="kw">impl</span><T> Future <span class="kw">for </span>Receiver<T> { |
| <span class="kw">type </span>Output = <span class="prelude-ty">Result</span><T, Canceled>; |
| |
| <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="prelude-ty">Result</span><T, Canceled>> { |
| <span class="self">self</span>.inner.recv(cx) |
| } |
| } |
| |
| <span class="kw">impl</span><T> FusedFuture <span class="kw">for </span>Receiver<T> { |
| <span class="kw">fn </span>is_terminated(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="kw">if </span><span class="self">self</span>.inner.complete.load(SeqCst) { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(slot) = <span class="self">self</span>.inner.data.try_lock() { |
| <span class="kw">if </span>slot.is_some() { |
| <span class="kw">return </span><span class="bool-val">false</span>; |
| } |
| } |
| <span class="bool-val">true |
| </span>} <span class="kw">else </span>{ |
| <span class="bool-val">false |
| </span>} |
| } |
| } |
| |
| <span class="kw">impl</span><T> Drop <span class="kw">for </span>Receiver<T> { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.inner.drop_rx() |
| } |
| } |
| |
| <span class="kw">impl</span><T> fmt::Debug <span class="kw">for </span>Receiver<T> { |
| <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_struct(<span class="string">"Receiver"</span>).field(<span class="string">"complete"</span>, <span class="kw-2">&</span><span class="self">self</span>.inner.complete).finish() |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="futures_channel" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
