<!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="API documentation for the Rust `sync_channel` fn in crate `std`."><meta name="keywords" content="rust, rustlang, rust-lang, sync_channel"><title>std::sync::mpsc::sync_channel - Rust</title><link rel="stylesheet" type="text/css" href="../../../normalize.css"><link rel="stylesheet" type="text/css" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../../dark.css"><link rel="stylesheet" type="text/css" href="../../../light.css" id="themeStyle"><script src="../../../storage.js"></script><link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"></head><body class="rustdoc fn"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../../../std/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a><div class="sidebar-elems"><p class='location'><a href='../../index.html'>std</a>::<wbr><a href='../index.html'>sync</a>::<wbr><a href='index.html'>mpsc</a></p><script>window.sidebarCurrent = {name: 'sync_channel', ty: 'fn', relpath: ''};</script><script defer src="sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../../../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../../../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><a id="settings-menu" href="../../../settings.html"><img src="../../../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><span class='in-band'>Function <a href='../../index.html'>std</a>::<wbr><a href='../index.html'>sync</a>::<wbr><a href='index.html'>mpsc</a>::<wbr><a class="fn" href=''>sync_channel</a></span><span class='out-of-band'><span class='since' title='Stable since Rust version 1.0.0'>1.0.0</span><span id='render-detail'><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class='inner'>−</span>]</a></span><a class='srclink' href='../../../src/std/sync/mpsc/mod.rs.html#777-780' title='goto source code'>[src]</a></span></h1><pre class='rust fn'>pub fn sync_channel<T>(bound: <a class="primitive" href="../../primitive.usize.html">usize</a>) -> <a class="primitive" href="../../primitive.tuple.html">(</a><a class="struct" href="../../../std/sync/mpsc/struct.SyncSender.html" title="struct std::sync::mpsc::SyncSender">SyncSender</a><T>, <a class="struct" href="../../../std/sync/mpsc/struct.Receiver.html" title="struct std::sync::mpsc::Receiver">Receiver</a><T><a class="primitive" href="../../primitive.tuple.html">)</a></pre><div class='docblock'><p>Creates a new synchronous, bounded channel.
All data sent on the <a href="struct.SyncSender.html"><code>SyncSender</code></a> will become available on the <a href="struct.Receiver.html"><code>Receiver</code></a>
in the same order as it was sent. Like asynchronous <a href="fn.channel.html"><code>channel</code></a>s, the
<a href="struct.Receiver.html"><code>Receiver</code></a> will block until a message becomes available. <code>sync_channel</code>
differs greatly in the semantics of the sender, however.</p>
<p>This channel has an internal buffer on which messages will be queued.
<code>bound</code> specifies the buffer size. When the internal buffer becomes full,
future sends will <em>block</em> waiting for the buffer to open up. Note that a
buffer size of 0 is valid, in which case this becomes "rendezvous channel"
where each <a href="struct.SyncSender.html#method.send"><code>send</code></a> will not return until a <a href="struct.Receiver.html#method.recv"><code>recv</code></a> is paired with it.</p>
<p>The <a href="struct.SyncSender.html"><code>SyncSender</code></a> can be cloned to <a href="struct.SyncSender.html#method.send"><code>send</code></a> to the same channel multiple
times, but only one <a href="struct.Receiver.html"><code>Receiver</code></a> is supported.</p>
<p>Like asynchronous channels, if the <a href="struct.Receiver.html"><code>Receiver</code></a> is disconnected while trying
to <a href="struct.SyncSender.html#method.send"><code>send</code></a> with the <a href="struct.SyncSender.html"><code>SyncSender</code></a>, the <a href="struct.SyncSender.html#method.send"><code>send</code></a> method will return a
<a href="struct.SendError.html"><code>SendError</code></a>. Similarly, If the <a href="struct.SyncSender.html"><code>SyncSender</code></a> is disconnected while trying
to <a href="struct.Receiver.html#method.recv"><code>recv</code></a>, the <a href="struct.Receiver.html#method.recv"><code>recv</code></a> method will return a <a href="struct.RecvError.html"><code>RecvError</code></a>.</p>
<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">sync</span>::<span class="ident">mpsc</span>::<span class="ident">sync_channel</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">thread</span>;
<span class="kw">let</span> (<span class="ident">sender</span>, <span class="ident">receiver</span>) <span class="op">=</span> <span class="ident">sync_channel</span>(<span class="number">1</span>);
<span class="comment">// this returns immediately</span>
<span class="ident">sender</span>.<span class="ident">send</span>(<span class="number">1</span>).<span class="ident">unwrap</span>();
<span class="ident">thread</span>::<span class="ident">spawn</span>(<span class="kw">move</span><span class="op">||</span> {
<span class="comment">// this will block until the previous message has been received</span>
<span class="ident">sender</span>.<span class="ident">send</span>(<span class="number">2</span>).<span class="ident">unwrap</span>();
});
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">receiver</span>.<span class="ident">recv</span>().<span class="ident">unwrap</span>(), <span class="number">1</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">receiver</span>.<span class="ident">recv</span>().<span class="ident">unwrap</span>(), <span class="number">2</span>);<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Async%3A%3Ampsc%3A%3Async_channel%3B%0Ause%20std%3A%3Athread%3B%0A%0Alet%20(sender%2C%20receiver)%20%3D%20sync_channel(1)%3B%0A%0A%2F%2F%20this%20returns%20immediately%0Asender.send(1).unwrap()%3B%0A%0Athread%3A%3Aspawn(move%7C%7C%20%7B%0A%20%20%20%20%2F%2F%20this%20will%20block%20until%20the%20previous%20message%20has%20been%20received%0A%20%20%20%20sender.send(2).unwrap()%3B%0A%7D)%3B%0A%0Aassert_eq!(receiver.recv().unwrap()%2C%201)%3B%0Aassert_eq!(receiver.recv().unwrap()%2C%202)%3B%0A%7D">Run</a></pre>
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