mirror of
https://github.com/Dhghomon/easy_rust
synced 2024-11-15 18:13:23 +00:00
294 lines
20 KiB
HTML
294 lines
20 KiB
HTML
|
<!DOCTYPE HTML>
|
||
|
|
<html lang="en" class="sidebar-visible no-js light">
|
||
|
|
<head>
|
||
|
|
<!-- Book generated using mdBook -->
|
||
|
|
<meta charset="UTF-8">
|
||
|
|
<title> RwLock - Easy Rust</title>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
<!-- Custom HTML head -->
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
|
||
|
|
<meta name="description" content="">
|
||
|
|
<meta name="viewport" content="width=device-width, initial-scale=1">
|
||
|
|
<meta name="theme-color" content="#ffffff" />
|
||
|
|
|
||
|
|
|
||
|
|
<link rel="icon" href="favicon.svg">
|
||
|
|
|
||
|
|
|
||
|
|
<link rel="shortcut icon" href="favicon.png">
|
||
|
|
|
||
|
|
<link rel="stylesheet" href="css/variables.css">
|
||
|
|
<link rel="stylesheet" href="css/general.css">
|
||
|
|
<link rel="stylesheet" href="css/chrome.css">
|
||
|
|
|
||
|
|
<link rel="stylesheet" href="css/print.css" media="print">
|
||
|
|
|
||
|
|
|
||
|
|
<!-- Fonts -->
|
||
|
|
<link rel="stylesheet" href="FontAwesome/css/font-awesome.css">
|
||
|
|
|
||
|
|
<link rel="stylesheet" href="fonts/fonts.css">
|
||
|
|
|
||
|
|
|
||
|
|
<!-- Highlight.js Stylesheets -->
|
||
|
|
<link rel="stylesheet" href="highlight.css">
|
||
|
|
<link rel="stylesheet" href="tomorrow-night.css">
|
||
|
|
<link rel="stylesheet" href="ayu-highlight.css">
|
||
|
|
|
||
|
|
<!-- Custom theme stylesheets -->
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</head>
|
||
|
|
<body>
|
||
|
|
<!-- Provide site root to javascript -->
|
||
|
|
<script type="text/javascript">
|
||
|
|
var path_to_root = "";
|
||
|
|
var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? "navy" : "light";
|
||
|
|
</script>
|
||
|
|
|
||
|
|
<!-- Work around some values being stored in localStorage wrapped in quotes -->
|
||
|
|
<script type="text/javascript">
|
||
|
|
try {
|
||
|
|
var theme = localStorage.getItem('mdbook-theme');
|
||
|
|
var sidebar = localStorage.getItem('mdbook-sidebar');
|
||
|
|
|
||
|
|
if (theme.startsWith('"') && theme.endsWith('"')) {
|
||
|
|
localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1));
|
||
|
|
}
|
||
|
|
|
||
|
|
if (sidebar.startsWith('"') && sidebar.endsWith('"')) {
|
||
|
|
localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1));
|
||
|
|
}
|
||
|
|
} catch (e) { }
|
||
|
|
</script>
|
||
|
|
|
||
|
|
<!-- Set the theme before any content is loaded, prevents flash -->
|
||
|
|
<script type="text/javascript">
|
||
|
|
var theme;
|
||
|
|
try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
|
||
|
|
if (theme === null || theme === undefined) { theme = default_theme; }
|
||
|
|
var html = document.querySelector('html');
|
||
|
|
html.classList.remove('no-js')
|
||
|
|
html.classList.remove('light')
|
||
|
|
html.classList.add(theme);
|
||
|
|
html.classList.add('js');
|
||
|
|
</script>
|
||
|
|
|
||
|
|
<!-- Hide / unhide sidebar before it is displayed -->
|
||
|
|
<script type="text/javascript">
|
||
|
|
var html = document.querySelector('html');
|
||
|
|
var sidebar = 'hidden';
|
||
|
|
if (document.body.clientWidth >= 1080) {
|
||
|
|
try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
|
||
|
|
sidebar = sidebar || 'visible';
|
||
|
|
}
|
||
|
|
html.classList.remove('sidebar-visible');
|
||
|
|
html.classList.add("sidebar-" + sidebar);
|
||
|
|
</script>
|
||
|
|
|
||
|
|
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
|
||
|
|
<div class="sidebar-scrollbox">
|
||
|
|
<ol class="chapter"><li class="chapter-item expanded "><a href="Chapter_0.html"><strong aria-hidden="true">1.</strong> Update</a></li><li class="chapter-item expanded "><a href="Chapter_1.html"><strong aria-hidden="true">2.</strong> Introduction</a></li><li class="chapter-item expanded "><a href="Chapter_2.html"><strong aria-hidden="true">3.</strong> Who am I?</a></li><li class="chapter-item expanded "><a href="Chapter_3.html"><strong aria-hidden="true">4.</strong> Writing Rust in Easy English</a></li><li class="chapter-item expanded "><a href="Chapter_4.html"><strong aria-hidden="true">5.</strong> Rust Playground</a></li><li class="chapter-item expanded "><a href="Chapter_5.html"><strong aria-hidden="true">6.</strong> 🚧 and ⚠️</a></li><li class="chapter-item expanded "><a href="Chapter_6.html"><strong aria-hidden="true">7.</strong> Comments</a></li><li class="chapter-item expanded "><a href="Chapter_7.html"><strong aria-hidden="true">8.</strong> Types</a></li><li class="chapter-item expanded "><a href="Chapter_8.html"><strong aria-hidden="true">9.</strong> Type inference</a></li><li class="chapter-item expanded "><a href="Chapter_9.html"><strong aria-hidden="true">10.</strong> Printing 'hello, world!'</a></li><li class="chapter-item expanded "><a href="Chapter_10.html"><strong aria-hidden="true">11.</strong> Display and debug</a></li><li class="chapter-item expanded "><a href="Chapter_11.html"><strong aria-hidden="true">12.</strong> Mutability (changing)</a></li><li class="chapter-item expanded "><a href="Chapter_12.html"><strong aria-hidden="true">13.</strong> The stack, the heap, and pointers</a></li><li class="chapter-item expanded "><a href="Chapter_13.html"><strong aria-hidden="true">14.</strong> More about printing</a></li><li class="chapter-item expanded "><a href="Chapter_14.html"><strong aria-hidden="true">15.</strong> Strings</a></li><li class="chapter-item expanded "><a href="Chapter_15.html"><strong aria-hidden="true">16.</strong> const and static</a></li><li class="chapter-item expanded "><a href="Chapter_16.html"><strong aria-hidden="true">17.</strong> More on references</a></li><li class="chapter-item expanded "><a href="Chapter_17.html"><strong aria-hidden="true">18.</strong> Mutable references</a></li><li class="chapter-item expanded "><a href="Chapter_18.html"><strong aria-hidden="true">19.</strong> Giving references to functions</a></li><li class="chapter-item expanded "><a href="Chapter_19.html"><strong aria-hidden="true">20.</strong> Copy types</a></li><li class="chapter-item expanded "><a href="Chapter_20.html"><strong aria-hidden="true">21.</strong> Collection types</a></li><li class="chapter-item expanded "><a href="Chapter_21.html"><strong aria-hidden="true">22.</strong> Vectors</a></li><li class="chapter-item expanded "><a href="Chapter_22.html"><strong aria-hidden="true">23.</strong> Tuples</a></li><li class="chapter-item expanded "><a href="Chapter_23.html"><strong aria-hidden="true">24.</strong> Control flow</a></li><li class="chapter-item expanded "><a href="Chapter_24.html"><strong aria-hidden="true">25.</strong> Structs</a></li><li class="chapter-item expanded "><a href="Chapter_25.html"><strong aria-hidden="true">26.</strong> Enums</a></li><li class="chapter-item expanded "><a href="Chapter_26.html"><strong aria-hidden="true">27.</strong> Loops</a></li><li class="chapter-item expanded "><a href="Chapter_27.html"><strong aria-hidden="true">28.</strong> Implementing structs and enums</a></li><li class="chapter-item expanded "><a href="Chapter_28.html"><strong aria-hidden="true">29.</strong> Destructuring</a></li><li class="chapter-item expanded "><a href="Chapter_29.html"><strong aria-hidden="true">30.</strong> References and the dot operator</a></li><li class="chapter-item expanded "><a href="Chapter_30.html"><strong aria-hidden="true">31.</strong> Generics</a></li><li class="chapter-item expanded "><a href="Chapter_31.html"><strong aria-hidden="true">32.</strong> Option and Result</a></li><li class="chapter-item expanded "><a href="Chapter_32.html"><strong aria-hi
|
||
|
|
</div>
|
||
|
|
<div id="sidebar-resize-handle" class="sidebar-resize-handle"></div>
|
||
|
|
</nav>
|
||
|
|
|
||
|
|
<div id="page-wrapper" class="page-wrapper">
|
||
|
|
|
||
|
|
<div class="page">
|
||
|
|
|
||
|
|
<div id="menu-bar-hover-placeholder"></div>
|
||
|
|
<div id="menu-bar" class="menu-bar sticky bordered">
|
||
|
|
<div class="left-buttons">
|
||
|
|
<button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
|
||
|
|
<i class="fa fa-bars"></i>
|
||
|
|
</button>
|
||
|
|
<button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
|
||
|
|
<i class="fa fa-paint-brush"></i>
|
||
|
|
</button>
|
||
|
|
<ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
|
||
|
|
<li role="none"><button role="menuitem" class="theme" id="light">Light (default)</button></li>
|
||
|
|
<li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li>
|
||
|
|
<li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li>
|
||
|
|
<li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li>
|
||
|
|
<li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li>
|
||
|
|
</ul>
|
||
|
|
|
||
|
|
<button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar">
|
||
|
|
<i class="fa fa-search"></i>
|
||
|
|
</button>
|
||
|
|
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h1 class="menu-title">Easy Rust</h1>
|
||
|
|
|
||
|
|
<div class="right-buttons">
|
||
|
|
|
||
|
|
<a href="print.html" title="Print this book" aria-label="Print this book">
|
||
|
|
<i id="print-button" class="fa fa-print"></i>
|
||
|
|
</a>
|
||
|
|
|
||
|
|
|
||
|
|
</div>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
<div id="search-wrapper" class="hidden">
|
||
|
|
<form id="searchbar-outer" class="searchbar-outer">
|
||
|
|
<input type="search" name="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header">
|
||
|
|
</form>
|
||
|
|
<div id="searchresults-outer" class="searchresults-outer hidden">
|
||
|
|
<div id="searchresults-header" class="searchresults-header"></div>
|
||
|
|
<ul id="searchresults">
|
||
|
|
</ul>
|
||
|
|
</div>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
<!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
|
||
|
|
<script type="text/javascript">
|
||
|
|
document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
|
||
|
|
document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
|
||
|
|
Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
|
||
|
|
link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
|
||
|
|
});
|
||
|
|
</script>
|
||
|
|
|
||
|
|
<div id="content" class="content">
|
||
|
|
<main>
|
||
|
|
<h2><a class="header" href="#rwlock" id="rwlock">RwLock</a></h2>
|
||
|
|
<p><code>RwLock</code> means "read write lock". It is like a <code>Mutex</code> but also like a <code>RefCell</code>. You use <code>.write().unwrap()</code> instead of <code>.lock().unwrap()</code> to change it. But you can also use <code>.read().unwrap()</code> to get read access. It is like <code>RefCell</code> because it follows the rules:</p>
|
||
|
|
<ul>
|
||
|
|
<li>many <code>.read()</code> variables is okay,</li>
|
||
|
|
<li>one <code>.write()</code> variable is okay,</li>
|
||
|
|
<li>but more than one <code>.write()</code> or <code>.read()</code> together with <code>.write()</code> is not okay.</li>
|
||
|
|
</ul>
|
||
|
|
<p>The program will run forever if you try to <code>.write()</code> when you can't get access:</p>
|
||
|
|
<pre><pre class="playground"><code class="language-rust">use std::sync::RwLock;
|
||
|
|
|
||
|
|
fn main() {
|
||
|
|
let my_rwlock = RwLock::new(5);
|
||
|
|
|
||
|
|
let read1 = my_rwlock.read().unwrap(); // one .read() is fine
|
||
|
|
let read2 = my_rwlock.read().unwrap(); // two .read()s is also fine
|
||
|
|
|
||
|
|
println!("{:?}, {:?}", read1, read2);
|
||
|
|
|
||
|
|
let write1 = my_rwlock.write().unwrap(); // uh oh, now the program will wait forever
|
||
|
|
}
|
||
|
|
</code></pre></pre>
|
||
|
|
<p>So we use <code>std::mem::drop</code>, just like in a <code>Mutex</code>.</p>
|
||
|
|
<pre><pre class="playground"><code class="language-rust">use std::sync::RwLock;
|
||
|
|
use std::mem::drop; // We will use drop() many times
|
||
|
|
|
||
|
|
fn main() {
|
||
|
|
let my_rwlock = RwLock::new(5);
|
||
|
|
|
||
|
|
let read1 = my_rwlock.read().unwrap();
|
||
|
|
let read2 = my_rwlock.read().unwrap();
|
||
|
|
|
||
|
|
println!("{:?}, {:?}", read1, read2);
|
||
|
|
|
||
|
|
drop(read1);
|
||
|
|
drop(read2); // we dropped both, so we can use .write() now
|
||
|
|
|
||
|
|
let mut write1 = my_rwlock.write().unwrap();
|
||
|
|
*write1 = 6;
|
||
|
|
drop(write1);
|
||
|
|
println!("{:?}", my_rwlock);
|
||
|
|
}
|
||
|
|
</code></pre></pre>
|
||
|
|
<p>And you can use <code>try_read()</code> and <code>try_write()</code> too.</p>
|
||
|
|
<pre><pre class="playground"><code class="language-rust">use std::sync::RwLock;
|
||
|
|
|
||
|
|
fn main() {
|
||
|
|
let my_rwlock = RwLock::new(5);
|
||
|
|
|
||
|
|
let read1 = my_rwlock.read().unwrap();
|
||
|
|
let read2 = my_rwlock.read().unwrap();
|
||
|
|
|
||
|
|
if let Ok(mut number) = my_rwlock.try_write() {
|
||
|
|
*number += 10;
|
||
|
|
println!("Now the number is {}", number);
|
||
|
|
} else {
|
||
|
|
println!("Couldn't get write access, sorry!")
|
||
|
|
};
|
||
|
|
}
|
||
|
|
</code></pre></pre>
|
||
|
|
|
||
|
|
</main>
|
||
|
|
|
||
|
|
<nav class="nav-wrapper" aria-label="Page navigation">
|
||
|
|
<!-- Mobile navigation buttons -->
|
||
|
|
|
||
|
|
<a rel="prev" href="Chapter_43.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
|
||
|
|
<i class="fa fa-angle-left"></i>
|
||
|
|
</a>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
<a rel="next" href="Chapter_45.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
|
||
|
|
<i class="fa fa-angle-right"></i>
|
||
|
|
</a>
|
||
|
|
|
||
|
|
|
||
|
|
<div style="clear: both"></div>
|
||
|
|
</nav>
|
||
|
|
</div>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<nav class="nav-wide-wrapper" aria-label="Page navigation">
|
||
|
|
|
||
|
|
<a rel="prev" href="Chapter_43.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
|
||
|
|
<i class="fa fa-angle-left"></i>
|
||
|
|
</a>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
<a rel="next" href="Chapter_45.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
|
||
|
|
<i class="fa fa-angle-right"></i>
|
||
|
|
</a>
|
||
|
|
|
||
|
|
</nav>
|
||
|
|
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
<script type="text/javascript">
|
||
|
|
window.playground_copyable = true;
|
||
|
|
</script>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
<script src="elasticlunr.min.js" type="text/javascript" charset="utf-8"></script>
|
||
|
|
<script src="mark.min.js" type="text/javascript" charset="utf-8"></script>
|
||
|
|
<script src="searcher.js" type="text/javascript" charset="utf-8"></script>
|
||
|
|
|
||
|
|
|
||
|
|
<script src="clipboard.min.js" type="text/javascript" charset="utf-8"></script>
|
||
|
|
<script src="highlight.js" type="text/javascript" charset="utf-8"></script>
|
||
|
|
<script src="book.js" type="text/javascript" charset="utf-8"></script>
|
||
|
|
|
||
|
|
<!-- Custom JS scripts -->
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</body>
|
||
|
|
</html>
|