| <!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/git/checkouts/tokio-377c595163f99a10/dfe252d/tokio/src/sync/mpsc/mod.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>mod.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/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/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="attribute">#![cfg_attr(not(feature = <span class="string">"sync"</span>), allow(dead_code, unreachable_pub))] |
| |
| </span><span class="doccomment">//! A multi-producer, single-consumer queue for sending values between |
| //! asynchronous tasks. |
| //! |
| //! This module provides two variants of the channel: bounded and unbounded. The |
| //! bounded variant has a limit on the number of messages that the channel can |
| //! store, and if this limit is reached, trying to send another message will |
| //! wait until a message is received from the channel. An unbounded channel has |
| //! an infinite capacity, so the `send` method will always complete immediately. |
| //! This makes the [`UnboundedSender`] usable from both synchronous and |
| //! asynchronous code. |
| //! |
| //! Similar to the `mpsc` channels provided by `std`, the channel constructor |
| //! functions provide separate send and receive handles, [`Sender`] and |
| //! [`Receiver`] for the bounded channel, [`UnboundedSender`] and |
| //! [`UnboundedReceiver`] for the unbounded channel. If there is no message to read, |
| //! the current task will be notified when a new value is sent. [`Sender`] and |
| //! [`UnboundedSender`] allow sending values into the channel. If the bounded |
| //! channel is at capacity, the send is rejected and the task will be notified |
| //! when additional capacity is available. In other words, the channel provides |
| //! backpressure. |
| //! |
| //! This channel is also suitable for the single-producer single-consumer |
| //! use-case. (Unless you only need to send one message, in which case you |
| //! should use the [oneshot] channel.) |
| //! |
| //! # Disconnection |
| //! |
| //! When all [`Sender`] handles have been dropped, it is no longer |
| //! possible to send values into the channel. This is considered the termination |
| //! event of the stream. As such, `Receiver::poll` returns `Ok(Ready(None))`. |
| //! |
| //! If the [`Receiver`] handle is dropped, then messages can no longer |
| //! be read out of the channel. In this case, all further attempts to send will |
| //! result in an error. |
| //! |
| //! # Clean Shutdown |
| //! |
| //! When the [`Receiver`] is dropped, it is possible for unprocessed messages to |
| //! remain in the channel. Instead, it is usually desirable to perform a "clean" |
| //! shutdown. To do this, the receiver first calls `close`, which will prevent |
| //! any further messages to be sent into the channel. Then, the receiver |
| //! consumes the channel to completion, at which point the receiver can be |
| //! dropped. |
| //! |
| //! # Communicating between sync and async code |
| //! |
| //! When you want to communicate between synchronous and asynchronous code, there |
| //! are two situations to consider: |
| //! |
| //! **Bounded channel**: If you need a bounded channel, you should use a bounded |
| //! Tokio `mpsc` channel for both directions of communication. Instead of calling |
| //! the async [`send`][bounded-send] or [`recv`][bounded-recv] methods, in |
| //! synchronous code you will need to use the [`blocking_send`][blocking-send] or |
| //! [`blocking_recv`][blocking-recv] methods. |
| //! |
| //! **Unbounded channel**: You should use the kind of channel that matches where |
| //! the receiver is. So for sending a message _from async to sync_, you should |
| //! use [the standard library unbounded channel][std-unbounded] or |
| //! [crossbeam][crossbeam-unbounded]. Similarly, for sending a message _from sync |
| //! to async_, you should use an unbounded Tokio `mpsc` channel. |
| //! |
| //! Please be aware that the above remarks were written with the `mpsc` channel |
| //! in mind, but they can also be generalized to other kinds of channels. In |
| //! general, any channel method that isn't marked async can be called anywhere, |
| //! including outside of the runtime. For example, sending a message on a |
| //! [oneshot] channel from outside the runtime is perfectly fine. |
| //! |
| //! # Multiple runtimes |
| //! |
| //! The mpsc channel does not care about which runtime you use it in, and can be |
| //! used to send messages from one runtime to another. It can also be used in |
| //! non-Tokio runtimes. |
| //! |
| //! There is one exception to the above: the [`send_timeout`] must be used from |
| //! within a Tokio runtime, however it is still not tied to one specific Tokio |
| //! runtime, and the sender may be moved from one Tokio runtime to another. |
| //! |
| //! [`Sender`]: crate::sync::mpsc::Sender |
| //! [`Receiver`]: crate::sync::mpsc::Receiver |
| //! [bounded-send]: crate::sync::mpsc::Sender::send() |
| //! [bounded-recv]: crate::sync::mpsc::Receiver::recv() |
| //! [blocking-send]: crate::sync::mpsc::Sender::blocking_send() |
| //! [blocking-recv]: crate::sync::mpsc::Receiver::blocking_recv() |
| //! [`UnboundedSender`]: crate::sync::mpsc::UnboundedSender |
| //! [`UnboundedReceiver`]: crate::sync::mpsc::UnboundedReceiver |
| //! [oneshot]: crate::sync::oneshot |
| //! [`Handle::block_on`]: crate::runtime::Handle::block_on() |
| //! [std-unbounded]: std::sync::mpsc::channel |
| //! [crossbeam-unbounded]: https://docs.rs/crossbeam/*/crossbeam/channel/fn.unbounded.html |
| //! [`send_timeout`]: crate::sync::mpsc::Sender::send_timeout |
| |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">mod </span>block; |
| |
| <span class="kw">mod </span>bounded; |
| <span class="kw">pub use </span><span class="self">self</span>::bounded::{channel, OwnedPermit, Permit, Receiver, Sender, WeakSender}; |
| |
| <span class="kw">mod </span>chan; |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">mod </span>list; |
| |
| <span class="kw">mod </span>unbounded; |
| <span class="kw">pub use </span><span class="self">self</span>::unbounded::{ |
| unbounded_channel, UnboundedReceiver, UnboundedSender, WeakUnboundedSender, |
| }; |
| |
| <span class="kw">pub mod </span>error; |
| |
| <span class="doccomment">/// The number of values a block can contain. |
| /// |
| /// This value must be a power of 2. It also must be smaller than the number of |
| /// bits in `usize`. |
| </span><span class="attribute">#[cfg(all(target_pointer_width = <span class="string">"64"</span>, not(loom)))] |
| </span><span class="kw">const </span>BLOCK_CAP: usize = <span class="number">32</span>; |
| |
| <span class="attribute">#[cfg(all(not(target_pointer_width = <span class="string">"64"</span>), not(loom)))] |
| </span><span class="kw">const </span>BLOCK_CAP: usize = <span class="number">16</span>; |
| |
| <span class="attribute">#[cfg(loom)] |
| </span><span class="kw">const </span>BLOCK_CAP: usize = <span class="number">2</span>; |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../../" data-current-crate="tokio" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
