| <!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/tokio-util-0.7.8/src/sync/mpsc.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>mpsc.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="../../../tokio_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="../../../tokio_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>futures_sink::Sink; |
| <span class="kw">use </span>std::pin::Pin; |
| <span class="kw">use </span>std::task::{Context, Poll}; |
| <span class="kw">use </span>std::{fmt, mem}; |
| <span class="kw">use </span>tokio::sync::mpsc::OwnedPermit; |
| <span class="kw">use </span>tokio::sync::mpsc::Sender; |
| |
| <span class="kw">use </span><span class="kw">super</span>::ReusableBoxFuture; |
| |
| <span class="doccomment">/// Error returned by the `PollSender` when the channel is closed. |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub struct </span>PollSendError<T>(<span class="prelude-ty">Option</span><T>); |
| |
| <span class="kw">impl</span><T> PollSendError<T> { |
| <span class="doccomment">/// Consumes the stored value, if any. |
| /// |
| /// If this error was encountered when calling `start_send`/`send_item`, this will be the item |
| /// that the caller attempted to send. Otherwise, it will be `None`. |
| </span><span class="kw">pub fn </span>into_inner(<span class="self">self</span>) -> <span class="prelude-ty">Option</span><T> { |
| <span class="self">self</span>.<span class="number">0 |
| </span>} |
| } |
| |
| <span class="kw">impl</span><T> fmt::Display <span class="kw">for </span>PollSendError<T> { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, fmt: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| <span class="macro">write!</span>(fmt, <span class="string">"channel closed"</span>) |
| } |
| } |
| |
| <span class="kw">impl</span><T: fmt::Debug> std::error::Error <span class="kw">for </span>PollSendError<T> {} |
| |
| <span class="attribute">#[derive(Debug)] |
| </span><span class="kw">enum </span>State<T> { |
| Idle(Sender<T>), |
| Acquiring, |
| ReadyToSend(OwnedPermit<T>), |
| Closed, |
| } |
| |
| <span class="doccomment">/// A wrapper around [`mpsc::Sender`] that can be polled. |
| /// |
| /// [`mpsc::Sender`]: tokio::sync::mpsc::Sender |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub struct </span>PollSender<T> { |
| sender: <span class="prelude-ty">Option</span><Sender<T>>, |
| state: State<T>, |
| acquire: ReusableBoxFuture<<span class="lifetime">'static</span>, <span class="prelude-ty">Result</span><OwnedPermit<T>, PollSendError<T>>>, |
| } |
| |
| <span class="comment">// Creates a future for acquiring a permit from the underlying channel. This is used to ensure |
| // there's capacity for a send to complete. |
| // |
| // By reusing the same async fn for both `Some` and `None`, we make sure every future passed to |
| // ReusableBoxFuture has the same underlying type, and hence the same size and alignment. |
| </span><span class="kw">async fn </span>make_acquire_future<T>( |
| data: <span class="prelude-ty">Option</span><Sender<T>>, |
| ) -> <span class="prelude-ty">Result</span><OwnedPermit<T>, PollSendError<T>> { |
| <span class="kw">match </span>data { |
| <span class="prelude-val">Some</span>(sender) => sender |
| .reserve_owned() |
| .<span class="kw">await |
| </span>.map_err(|<span class="kw">_</span>| PollSendError(<span class="prelude-val">None</span>)), |
| <span class="prelude-val">None </span>=> <span class="macro">unreachable!</span>(<span class="string">"this future should not be pollable in this state"</span>), |
| } |
| } |
| |
| <span class="kw">impl</span><T: Send + <span class="lifetime">'static</span>> PollSender<T> { |
| <span class="doccomment">/// Creates a new `PollSender`. |
| </span><span class="kw">pub fn </span>new(sender: Sender<T>) -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ |
| sender: <span class="prelude-val">Some</span>(sender.clone()), |
| state: State::Idle(sender), |
| acquire: ReusableBoxFuture::new(make_acquire_future(<span class="prelude-val">None</span>)), |
| } |
| } |
| |
| <span class="kw">fn </span>take_state(<span class="kw-2">&mut </span><span class="self">self</span>) -> State<T> { |
| mem::replace(<span class="kw-2">&mut </span><span class="self">self</span>.state, State::Closed) |
| } |
| |
| <span class="doccomment">/// Attempts to prepare the sender to receive a value. |
| /// |
| /// This method must be called and return `Poll::Ready(Ok(()))` prior to each call to |
| /// `send_item`. |
| /// |
| /// This method returns `Poll::Ready` once the underlying channel is ready to receive a value, |
| /// by reserving a slot in the channel for the item to be sent. If this method returns |
| /// `Poll::Pending`, the current task is registered to be notified (via |
| /// `cx.waker().wake_by_ref()`) when `poll_reserve` should be called again. |
| /// |
| /// # Errors |
| /// |
| /// If the channel is closed, an error will be returned. This is a permanent state. |
| </span><span class="kw">pub fn </span>poll_reserve(<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><(), PollSendError<T>>> { |
| <span class="kw">loop </span>{ |
| <span class="kw">let </span>(result, next_state) = <span class="kw">match </span><span class="self">self</span>.take_state() { |
| State::Idle(sender) => { |
| <span class="comment">// Start trying to acquire a permit to reserve a slot for our send, and |
| // immediately loop back around to poll it the first time. |
| </span><span class="self">self</span>.acquire.set(make_acquire_future(<span class="prelude-val">Some</span>(sender))); |
| (<span class="prelude-val">None</span>, State::Acquiring) |
| } |
| State::Acquiring => <span class="kw">match </span><span class="self">self</span>.acquire.poll(cx) { |
| <span class="comment">// Channel has capacity. |
| </span>Poll::Ready(<span class="prelude-val">Ok</span>(permit)) => { |
| (<span class="prelude-val">Some</span>(Poll::Ready(<span class="prelude-val">Ok</span>(()))), State::ReadyToSend(permit)) |
| } |
| <span class="comment">// Channel is closed. |
| </span>Poll::Ready(<span class="prelude-val">Err</span>(e)) => (<span class="prelude-val">Some</span>(Poll::Ready(<span class="prelude-val">Err</span>(e))), State::Closed), |
| <span class="comment">// Channel doesn't have capacity yet, so we need to wait. |
| </span>Poll::Pending => (<span class="prelude-val">Some</span>(Poll::Pending), State::Acquiring), |
| }, |
| <span class="comment">// We're closed, either by choice or because the underlying sender was closed. |
| </span>s @ State::Closed => (<span class="prelude-val">Some</span>(Poll::Ready(<span class="prelude-val">Err</span>(PollSendError(<span class="prelude-val">None</span>)))), s), |
| <span class="comment">// We're already ready to send an item. |
| </span>s @ State::ReadyToSend(<span class="kw">_</span>) => (<span class="prelude-val">Some</span>(Poll::Ready(<span class="prelude-val">Ok</span>(()))), s), |
| }; |
| |
| <span class="self">self</span>.state = next_state; |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(result) = result { |
| <span class="kw">return </span>result; |
| } |
| } |
| } |
| |
| <span class="doccomment">/// Sends an item to the channel. |
| /// |
| /// Before calling `send_item`, `poll_reserve` must be called with a successful return |
| /// value of `Poll::Ready(Ok(()))`. |
| /// |
| /// # Errors |
| /// |
| /// If the channel is closed, an error will be returned. This is a permanent state. |
| /// |
| /// # Panics |
| /// |
| /// If `poll_reserve` was not successfully called prior to calling `send_item`, then this method |
| /// will panic. |
| </span><span class="attribute">#[track_caller] |
| </span><span class="kw">pub fn </span>send_item(<span class="kw-2">&mut </span><span class="self">self</span>, value: T) -> <span class="prelude-ty">Result</span><(), PollSendError<T>> { |
| <span class="kw">let </span>(result, next_state) = <span class="kw">match </span><span class="self">self</span>.take_state() { |
| State::Idle(<span class="kw">_</span>) | State::Acquiring => { |
| <span class="macro">panic!</span>(<span class="string">"`send_item` called without first calling `poll_reserve`"</span>) |
| } |
| <span class="comment">// We have a permit to send our item, so go ahead, which gets us our sender back. |
| </span>State::ReadyToSend(permit) => (<span class="prelude-val">Ok</span>(()), State::Idle(permit.send(value))), |
| <span class="comment">// We're closed, either by choice or because the underlying sender was closed. |
| </span>State::Closed => (<span class="prelude-val">Err</span>(PollSendError(<span class="prelude-val">Some</span>(value))), State::Closed), |
| }; |
| |
| <span class="comment">// Handle deferred closing if `close` was called between `poll_reserve` and `send_item`. |
| </span><span class="self">self</span>.state = <span class="kw">if </span><span class="self">self</span>.sender.is_some() { |
| next_state |
| } <span class="kw">else </span>{ |
| State::Closed |
| }; |
| result |
| } |
| |
| <span class="doccomment">/// Checks whether this sender is been closed. |
| /// |
| /// The underlying channel that this sender was wrapping may still be open. |
| </span><span class="kw">pub fn </span>is_closed(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="macro">matches!</span>(<span class="self">self</span>.state, State::Closed) || <span class="self">self</span>.sender.is_none() |
| } |
| |
| <span class="doccomment">/// Gets a reference to the `Sender` of the underlying channel. |
| /// |
| /// If `PollSender` has been closed, `None` is returned. The underlying channel that this sender |
| /// was wrapping may still be open. |
| </span><span class="kw">pub fn </span>get_ref(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="prelude-ty">Option</span><<span class="kw-2">&</span>Sender<T>> { |
| <span class="self">self</span>.sender.as_ref() |
| } |
| |
| <span class="doccomment">/// Closes this sender. |
| /// |
| /// No more messages will be able to be sent from this sender, but the underlying channel will |
| /// remain open until all senders have dropped, or until the [`Receiver`] closes the channel. |
| /// |
| /// If a slot was previously reserved by calling `poll_reserve`, then a final call can be made |
| /// to `send_item` in order to consume the reserved slot. After that, no further sends will be |
| /// possible. If you do not intend to send another item, you can release the reserved slot back |
| /// to the underlying sender by calling [`abort_send`]. |
| /// |
| /// [`abort_send`]: crate::sync::PollSender::abort_send |
| /// [`Receiver`]: tokio::sync::mpsc::Receiver |
| </span><span class="kw">pub fn </span>close(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="comment">// Mark ourselves officially closed by dropping our main sender. |
| </span><span class="self">self</span>.sender = <span class="prelude-val">None</span>; |
| |
| <span class="comment">// If we're already idle, closed, or we haven't yet reserved a slot, we can quickly |
| // transition to the closed state. Otherwise, leave the existing permit in place for the |
| // caller if they want to complete the send. |
| </span><span class="kw">match </span><span class="self">self</span>.state { |
| State::Idle(<span class="kw">_</span>) => <span class="self">self</span>.state = State::Closed, |
| State::Acquiring => { |
| <span class="self">self</span>.acquire.set(make_acquire_future(<span class="prelude-val">None</span>)); |
| <span class="self">self</span>.state = State::Closed; |
| } |
| <span class="kw">_ </span>=> {} |
| } |
| } |
| |
| <span class="doccomment">/// Aborts the current in-progress send, if any. |
| /// |
| /// Returns `true` if a send was aborted. If the sender was closed prior to calling |
| /// `abort_send`, then the sender will remain in the closed state, otherwise the sender will be |
| /// ready to attempt another send. |
| </span><span class="kw">pub fn </span>abort_send(<span class="kw-2">&mut </span><span class="self">self</span>) -> bool { |
| <span class="comment">// We may have been closed in the meantime, after a call to `poll_reserve` already |
| // succeeded. We'll check if `self.sender` is `None` to see if we should transition to the |
| // closed state when we actually abort a send, rather than resetting ourselves back to idle. |
| |
| </span><span class="kw">let </span>(result, next_state) = <span class="kw">match </span><span class="self">self</span>.take_state() { |
| <span class="comment">// We're currently trying to reserve a slot to send into. |
| </span>State::Acquiring => { |
| <span class="comment">// Replacing the future drops the in-flight one. |
| </span><span class="self">self</span>.acquire.set(make_acquire_future(<span class="prelude-val">None</span>)); |
| |
| <span class="comment">// If we haven't closed yet, we have to clone our stored sender since we have no way |
| // to get it back from the acquire future we just dropped. |
| </span><span class="kw">let </span>state = <span class="kw">match </span><span class="self">self</span>.sender.clone() { |
| <span class="prelude-val">Some</span>(sender) => State::Idle(sender), |
| <span class="prelude-val">None </span>=> State::Closed, |
| }; |
| (<span class="bool-val">true</span>, state) |
| } |
| <span class="comment">// We got the permit. If we haven't closed yet, get the sender back. |
| </span>State::ReadyToSend(permit) => { |
| <span class="kw">let </span>state = <span class="kw">if </span><span class="self">self</span>.sender.is_some() { |
| State::Idle(permit.release()) |
| } <span class="kw">else </span>{ |
| State::Closed |
| }; |
| (<span class="bool-val">true</span>, state) |
| } |
| s => (<span class="bool-val">false</span>, s), |
| }; |
| |
| <span class="self">self</span>.state = next_state; |
| result |
| } |
| } |
| |
| <span class="kw">impl</span><T> Clone <span class="kw">for </span>PollSender<T> { |
| <span class="doccomment">/// Clones this `PollSender`. |
| /// |
| /// The resulting `PollSender` will have an initial state identical to calling `PollSender::new`. |
| </span><span class="kw">fn </span>clone(<span class="kw-2">&</span><span class="self">self</span>) -> PollSender<T> { |
| <span class="kw">let </span>(sender, state) = <span class="kw">match </span><span class="self">self</span>.sender.clone() { |
| <span class="prelude-val">Some</span>(sender) => (<span class="prelude-val">Some</span>(sender.clone()), State::Idle(sender)), |
| <span class="prelude-val">None </span>=> (<span class="prelude-val">None</span>, State::Closed), |
| }; |
| |
| <span class="self">Self </span>{ |
| sender, |
| state, |
| <span class="comment">// We don't use `make_acquire_future` here because our relaxed bounds on `T` are not |
| // compatible with the transitive bounds required by `Sender<T>`. |
| </span>acquire: ReusableBoxFuture::new(<span class="kw">async </span>{ <span class="macro">unreachable!</span>() }), |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><T: Send + <span class="lifetime">'static</span>> Sink<T> <span class="kw">for </span>PollSender<T> { |
| <span class="kw">type </span>Error = PollSendError<T>; |
| |
| <span class="kw">fn </span>poll_ready(<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><(), <span class="self">Self</span>::Error>> { |
| Pin::into_inner(<span class="self">self</span>).poll_reserve(cx) |
| } |
| |
| <span class="kw">fn </span>poll_flush(<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><(), <span class="self">Self</span>::Error>> { |
| Poll::Ready(<span class="prelude-val">Ok</span>(())) |
| } |
| |
| <span class="kw">fn </span>start_send(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, item: T) -> <span class="prelude-ty">Result</span><(), <span class="self">Self</span>::Error> { |
| Pin::into_inner(<span class="self">self</span>).send_item(item) |
| } |
| |
| <span class="kw">fn </span>poll_close(<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><(), <span class="self">Self</span>::Error>> { |
| Pin::into_inner(<span class="self">self</span>).close(); |
| Poll::Ready(<span class="prelude-val">Ok</span>(())) |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="tokio_util" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
