| <!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="Getting started guide."><meta name="keywords" content="rust, rustlang, rust-lang, guide"><title>mio::guide - 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><script src="../../crates.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="icon" type="image/svg+xml" href="../../favicon.svg"> |
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| <a id="settings-menu" href="../../settings.html"><img src="../../wheel.svg" width="18" height="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class="fqn"><span class="in-band">Module <a href="../index.html">mio</a>::<wbr><a class="mod" href="">guide</a></span><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/lib.rs.html#120-264" title="goto source code">[src]</a></span></h1><div class="docblock"><h1 id="getting-started-guide" class="section-header"><a href="#getting-started-guide">Getting started guide.</a></h1> |
| <p>In this guide we’ll do the following:</p> |
| <ol> |
| <li>Create a <a href="../struct.Poll.html"><code>Poll</code></a> instance (and learn what it is).</li> |
| <li>Register an <a href="../event/trait.Source.html">event source</a>.</li> |
| <li>Create an event loop.</li> |
| </ol> |
| <p>At the end you’ll have a very small (but quick) TCP server that accepts |
| connections and then drops (disconnects) them.</p> |
| <h2 id="1-creating-a-poll-instance" class="section-header"><a href="#1-creating-a-poll-instance">1. Creating a <code>Poll</code> instance</a></h2> |
| <p>Using Mio starts by creating a <a href="../struct.Poll.html"><code>Poll</code></a> instance, which monitors events |
| from the OS and puts them into <a href="../event/struct.Events.html"><code>Events</code></a>. This allows us to execute I/O |
| operations based on what operations are ready.</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"> |
| <span class="comment">// `Poll` allows for polling of readiness events.</span> |
| <span class="kw">let</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>; |
| <span class="comment">// `Events` is collection of readiness `Event`s and can be filled by</span> |
| <span class="comment">// calling `Poll::poll`.</span> |
| <span class="kw">let</span> <span class="ident">events</span> <span class="op">=</span> <span class="ident">Events</span>::<span class="ident">with_capacity</span>(<span class="number">128</span>);</pre></div> |
| <p>For example if we’re using a <a href="../net/struct.TcpListener.html"><code>TcpListener</code></a>, we’ll only want to |
| attempt to accept an incoming connection <em>iff</em> any connections are |
| queued and ready to be accepted. We don’t want to waste our time if no |
| connections are ready.</p> |
| <h2 id="2-registering-event-source" class="section-header"><a href="#2-registering-event-source">2. Registering event source</a></h2> |
| <p>After we’ve created a <a href="../struct.Poll.html"><code>Poll</code></a> instance that monitors events from the OS |
| for us, we need to provide it with a source of events. This is done by |
| registering an <a href="../event/trait.Source.html">event source</a>. As the name “event source” suggests it is |
| a source of events which can be polled using a <code>Poll</code> instance. On Unix |
| systems this is usually a file descriptor, or a socket/handle on |
| Windows.</p> |
| <p>In the example below we’ll use a <a href="../net/struct.TcpListener.html"><code>TcpListener</code></a> for which we’ll receive |
| an event (from <a href="../struct.Poll.html"><code>Poll</code></a>) once a connection is ready to be accepted.</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"> |
| <span class="comment">// Create a `TcpListener`, binding it to `address`.</span> |
| <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">listener</span> <span class="op">=</span> <span class="ident">TcpListener</span>::<span class="ident">bind</span>(<span class="ident">address</span>)<span class="question-mark">?</span>; |
| |
| <span class="comment">// Next we register it with `Poll` to receive events for it. The `SERVER`</span> |
| <span class="comment">// `Token` is used to determine that we received an event for the listener</span> |
| <span class="comment">// later on.</span> |
| <span class="kw">const</span> <span class="ident">SERVER</span>: <span class="ident">Token</span> <span class="op">=</span> <span class="ident">Token</span>(<span class="number">0</span>); |
| <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">listener</span>, <span class="ident">SERVER</span>, <span class="ident">Interest</span>::<span class="ident">READABLE</span>)<span class="question-mark">?</span>;</pre></div> |
| <p>Multiple event sources can be <a href="../struct.Registry.html#method.register">registered</a> (concurrently), so we can |
| monitor multiple sources at a time.</p> |
| <h2 id="3-creating-the-event-loop" class="section-header"><a href="#3-creating-the-event-loop">3. Creating the event loop</a></h2> |
| <p>After we’ve created a <a href="../struct.Poll.html"><code>Poll</code></a> instance and registered one or more |
| <a href="../event/trait.Source.html">event sources</a> with it, we can <a href="../struct.Poll.html#method.poll">poll</a> it for events. Polling for events |
| is simple, we need a container to store the events: <a href="../event/struct.Events.html"><code>Events</code></a> and need |
| to do something based on the polled events (this part is up to you, we |
| can’t do it all!). If we do this in a loop we’ve got ourselves an event |
| loop.</p> |
| <p>The example below shows the event loop in action, completing our small |
| TCP server.</p> |
| |
| <div class="example-wrap"><pre class="rust rust-example-rendered"> |
| <span class="comment">// Start our event loop.</span> |
| <span class="kw">loop</span> { |
| <span class="comment">// Poll the OS for events, waiting at most 100 milliseconds.</span> |
| <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">Some</span>(<span class="ident">Duration</span>::<span class="ident">from_millis</span>(<span class="number">100</span>)))<span class="question-mark">?</span>; |
| |
| <span class="comment">// Process each event.</span> |
| <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>() { |
| <span class="comment">// We can use the token we previously provided to `register` to</span> |
| <span class="comment">// determine for which type the event is.</span> |
| <span class="kw">match</span> <span class="ident">event</span>.<span class="ident">token</span>() { |
| <span class="ident">SERVER</span> <span class="op">=</span><span class="op">></span> <span class="kw">loop</span> { |
| <span class="comment">// One or more connections are ready, so we'll attempt to</span> |
| <span class="comment">// accept them (in a loop).</span> |
| <span class="kw">match</span> <span class="ident">listener</span>.<span class="ident">accept</span>() { |
| <span class="prelude-val">Ok</span>((<span class="ident">connection</span>, <span class="ident">address</span>)) <span class="op">=</span><span class="op">></span> { |
| <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Got a connection from: {}"</span>, <span class="ident">address</span>); |
| }, |
| <span class="comment">// A "would block error" is returned if the operation</span> |
| <span class="comment">// is not ready, so we'll stop trying to accept</span> |
| <span class="comment">// connections.</span> |
| <span class="prelude-val">Err</span>(<span class="kw-2">ref</span> <span class="ident">err</span>) <span class="kw">if</span> <span class="ident">would_block</span>(<span class="ident">err</span>) <span class="op">=</span><span class="op">></span> <span class="kw">break</span>, |
| <span class="prelude-val">Err</span>(<span class="ident">err</span>) <span class="op">=</span><span class="op">></span> <span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">err</span>), |
| } |
| } |
| } |
| } |
| } |
| |
| <span class="kw">fn</span> <span class="ident">would_block</span>(<span class="ident">err</span>: <span class="kw-2">&</span><span class="ident">io</span>::<span class="ident">Error</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> { |
| <span class="ident">err</span>.<span class="ident">kind</span>() <span class="op">=</span><span class="op">=</span> <span class="ident">io</span>::<span class="ident">ErrorKind</span>::<span class="ident">WouldBlock</span> |
| }</pre></div> |
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