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<!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 `new` fn in crate `mio`."><meta name="keywords" content="rust, rustlang, rust-lang, new"><title>mio::unix::pipe::new - 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="../../../light.css" id="themeStyle"><link rel="stylesheet" type="text/css" href="../../../dark.css" disabled ><link rel="stylesheet" type="text/css" href="../../../ayu.css" disabled ><script id="default-settings"></script><script src="../../../storage.js"></script><noscript><link rel="stylesheet" href="../../../noscript.css"></noscript><link rel="icon" type="image/svg+xml" href="../../../favicon.svg">
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<link rel="alternate icon" type="image/png" href="../../../favicon-32x32.png"><style type="text/css">#crate-search{background-image:url("../../../down-arrow.svg");}</style></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='../../../mio/index.html'><div class='logo-container rust-logo'><img src='../../../rust-logo.png' alt='logo'></div></a><div class="sidebar-elems"><p class="location"><a href="../../index.html">mio</a>::<wbr><a href="../index.html">unix</a>::<wbr><a href="index.html">pipe</a></p><script>window.sidebarCurrent = {name: "new", 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!" aria-haspopup="menu"><img src="../../../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices" role="menu"></div></div><script src="../../../theme.js"></script><nav class="sub"><form class="search-form"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" disabled autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><span class="help-button">?</span>
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<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="out-of-band"><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/mio/sys/unix/pipe.rs.html#147-204" title="goto source code">[src]</a></span><span class="in-band">Function <a href="../../index.html">mio</a>::<wbr><a href="../index.html">unix</a>::<wbr><a href="index.html">pipe</a>::<wbr><a class="fn" href="">new</a></span></h1><pre class="rust fn">pub fn new() -> <a class="type" href="https://doc.rust-lang.org/nightly/std/io/error/type.Result.html" title="type std::io::error::Result">Result</a><<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.tuple.html">(</a><a class="struct" href="../../../mio/unix/pipe/struct.Sender.html" title="struct mio::unix::pipe::Sender">Sender</a>, <a class="struct" href="../../../mio/unix/pipe/struct.Receiver.html" title="struct mio::unix::pipe::Receiver">Receiver</a><a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.tuple.html">)</a>></pre><div class="docblock"><p>Create a new non-blocking Unix pipe.</p>
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<p>This is a wrapper around Unix's <a href="https://pubs.opengroup.org/onlinepubs/9699919799/functions/pipe.html"><code>pipe(2)</code></a> system call and can be used as
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inter-process or thread communication channel.</p>
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<p>This channel may be created before forking the process and then one end used
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in each process, e.g. the parent process has the sending end to send command
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to the child process.</p>
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<h1 id="events" class="section-header"><a href="#events">Events</a></h1>
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<p>The <a href="../../../mio/unix/pipe/struct.Sender.html" title="Sender"><code>Sender</code></a> can be registered with <a href="../../../mio/struct.Interest.html#associatedconstant.WRITABLE"><code>WRITABLE</code></a> interest to receive
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<a href="../../../mio/event/struct.Event.html#method.is_writable">writable events</a>, the <a href="../../../mio/unix/pipe/struct.Receiver.html" title="Receiver"><code>Receiver</code></a> with <a href="../../../mio/struct.Interest.html#associatedconstant.READABLE"><code>READABLE</code></a> interest. Once data is
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written to the <code>Sender</code> the <code>Receiver</code> will receive an <a href="../../../mio/event/struct.Event.html#method.is_readable">readable event</a>.</p>
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<p>In addition to those events, events will also be generated if the other side
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is dropped. To check if the <code>Sender</code> is dropped you'll need to check
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<a href="../../../mio/event/struct.Event.html#method.is_read_closed"><code>is_read_closed</code></a> on events for the <code>Receiver</code>, if it returns true the
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<code>Sender</code> is dropped. On the <code>Sender</code> end check <a href="../../../mio/event/struct.Event.html#method.is_write_closed"><code>is_write_closed</code></a>, if it
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returns true the <code>Receiver</code> was dropped. Also see the second example below.</p>
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<h1 id="deregistering" class="section-header"><a href="#deregistering">Deregistering</a></h1>
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<p>Both <code>Sender</code> and <code>Receiver</code> will deregister themselves when dropped,
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<strong>iff</strong> the file descriptors are not duplicated (via <a href="https://pubs.opengroup.org/onlinepubs/9699919799/functions/dup.html"><code>dup(2)</code></a>).</p>
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<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
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<p>Simple example that writes data into the sending end and read it from the
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receiving end.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered">
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<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>::{<span class="self">self</span>, <span class="ident">Read</span>, <span class="ident">Write</span>};
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<span class="kw">use</span> <span class="ident">mio</span>::{<span class="ident">Poll</span>, <span class="ident">Events</span>, <span class="ident">Interest</span>, <span class="ident">Token</span>};
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<span class="kw">use</span> <span class="ident">mio</span>::<span class="ident">unix</span>::<span class="ident">pipe</span>;
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<span class="comment">// Unique tokens for the two ends of the channel.</span>
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<span class="kw">const</span> <span class="ident">PIPE_RECV</span>: <span class="ident">Token</span> <span class="op">=</span> <span class="ident">Token</span>(<span class="number">0</span>);
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<span class="kw">const</span> <span class="ident">PIPE_SEND</span>: <span class="ident">Token</span> <span class="op">=</span> <span class="ident">Token</span>(<span class="number">1</span>);
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<span class="comment">// Create our `Poll` instance and the `Events` container.</span>
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">poll</span> <span class="op">=</span> <span class="ident">Poll</span>::<span class="ident">new</span>()<span class="question-mark">?</span>;
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">events</span> <span class="op">=</span> <span class="ident">Events</span>::<span class="ident">with_capacity</span>(<span class="number">8</span>);
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<span class="comment">// Create a new pipe.</span>
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<span class="kw">let</span> (<span class="kw-2">mut</span> <span class="ident">sender</span>, <span class="kw-2">mut</span> <span class="ident">receiver</span>) <span class="op">=</span> <span class="ident">pipe</span>::<span class="ident">new</span>()<span class="question-mark">?</span>;
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<span class="comment">// Register both ends of the channel.</span>
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<span class="ident">poll</span>.<span class="ident">registry</span>().<span class="ident">register</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">receiver</span>, <span class="ident">PIPE_RECV</span>, <span class="ident">Interest</span>::<span class="ident">READABLE</span>)<span class="question-mark">?</span>;
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<span class="ident">poll</span>.<span class="ident">registry</span>().<span class="ident">register</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">sender</span>, <span class="ident">PIPE_SEND</span>, <span class="ident">Interest</span>::<span class="ident">WRITABLE</span>)<span class="question-mark">?</span>;
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<span class="kw">const</span> <span class="ident">MSG</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>; <span class="number">11</span>] <span class="op">=</span> <span class="string">b"Hello world"</span>;
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<span class="kw">loop</span> {
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<span class="ident">poll</span>.<span class="ident">poll</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">events</span>, <span class="prelude-val">None</span>)<span class="question-mark">?</span>;
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<span class="kw">for</span> <span class="ident">event</span> <span class="kw">in</span> <span class="ident">events</span>.<span class="ident">iter</span>() {
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<span class="kw">match</span> <span class="ident">event</span>.<span class="ident">token</span>() {
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<span class="ident">PIPE_SEND</span> <span class="op">=</span><span class="op">></span> <span class="ident">sender</span>.<span class="ident">write</span>(<span class="ident">MSG</span>)
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.<span class="ident">and_then</span>(<span class="op">|</span><span class="ident">n</span><span class="op">|</span> <span class="kw">if</span> <span class="ident">n</span> <span class="op">!</span><span class="op">=</span> <span class="ident">MSG</span>.<span class="ident">len</span>() {
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<span class="comment">// We'll consider a short write an error in this</span>
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<span class="comment">// example. NOTE: we can't use `write_all` with</span>
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<span class="comment">// non-blocking I/O.</span>
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<span class="prelude-val">Err</span>(<span class="ident">io</span>::<span class="ident">ErrorKind</span>::<span class="ident">WriteZero</span>.<span class="ident">into</span>())
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} <span class="kw">else</span> {
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<span class="prelude-val">Ok</span>(())
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})<span class="question-mark">?</span>,
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<span class="ident">PIPE_RECV</span> <span class="op">=</span><span class="op">></span> {
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">buf</span> <span class="op">=</span> [<span class="number">0</span>; <span class="number">11</span>];
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<span class="kw">let</span> <span class="ident">n</span> <span class="op">=</span> <span class="ident">receiver</span>.<span class="ident">read</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">buf</span>)<span class="question-mark">?</span>;
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<span class="macro">println</span><span class="macro">!</span>(<span class="string">"received: {:?}"</span>, <span class="kw-2">&</span><span class="ident">buf</span>[<span class="number">0</span>..<span class="ident">n</span>]);
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">n</span>, <span class="ident">MSG</span>.<span class="ident">len</span>());
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="kw-2">&</span><span class="ident">buf</span>, <span class="kw-2">&</span><span class="kw-2">*</span><span class="ident">MSG</span>);
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<span class="kw">return</span> <span class="prelude-val">Ok</span>(());
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},
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<span class="kw">_</span> <span class="op">=</span><span class="op">></span> <span class="macro">unreachable</span><span class="macro">!</span>(),
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}
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}
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}</pre></div>
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<p>Example that receives an event once the <code>Sender</code> is dropped.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered">
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<span class="comment">// Same setup as in the example above.</span>
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">poll</span> <span class="op">=</span> <span class="ident">Poll</span>::<span class="ident">new</span>()<span class="question-mark">?</span>;
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">events</span> <span class="op">=</span> <span class="ident">Events</span>::<span class="ident">with_capacity</span>(<span class="number">8</span>);
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<span class="kw">let</span> (<span class="kw-2">mut</span> <span class="ident">sender</span>, <span class="kw-2">mut</span> <span class="ident">receiver</span>) <span class="op">=</span> <span class="ident">pipe</span>::<span class="ident">new</span>()<span class="question-mark">?</span>;
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<span class="ident">poll</span>.<span class="ident">registry</span>().<span class="ident">register</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">receiver</span>, <span class="ident">PIPE_RECV</span>, <span class="ident">Interest</span>::<span class="ident">READABLE</span>)<span class="question-mark">?</span>;
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<span class="ident">poll</span>.<span class="ident">registry</span>().<span class="ident">register</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">sender</span>, <span class="ident">PIPE_SEND</span>, <span class="ident">Interest</span>::<span class="ident">WRITABLE</span>)<span class="question-mark">?</span>;
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<span class="comment">// Drop the sender.</span>
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<span class="ident">drop</span>(<span class="ident">sender</span>);
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<span class="ident">poll</span>.<span class="ident">poll</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">events</span>, <span class="prelude-val">None</span>)<span class="question-mark">?</span>;
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<span class="kw">for</span> <span class="ident">event</span> <span class="kw">in</span> <span class="ident">events</span>.<span class="ident">iter</span>() {
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<span class="kw">match</span> <span class="ident">event</span>.<span class="ident">token</span>() {
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<span class="ident">PIPE_RECV</span> <span class="kw">if</span> <span class="ident">event</span>.<span class="ident">is_read_closed</span>() <span class="op">=</span><span class="op">></span> {
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<span class="comment">// Detected that the sender was dropped.</span>
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<span class="macro">println</span><span class="macro">!</span>(<span class="string">"Sender dropped!"</span>);
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<span class="kw">return</span> <span class="prelude-val">Ok</span>(());
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},
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<span class="kw">_</span> <span class="op">=</span><span class="op">></span> <span class="macro">unreachable</span><span class="macro">!</span>(),
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}
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}</pre></div>
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