rust
/
rust-course
mirror of https://github.com/sunface/rust-course
5
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
Branches Tags
${ item.name }
Create tag ${ searchTerm }
Create branch ${ searchTerm }
from 'dbbf4037ca'
${ noResults }
rust-course/too-many-lists/unsafe-queue/layout.html

603 lines
70 KiB
Raw Normal View History Unescape

deploy
9 months ago
<!DOCTYPE HTML>
<html lang="zh-CN" class="light" dir="ltr">
<head>
<!-- Book generated using mdBook -->
<meta charset="UTF-8">
<title>数据布局 - Rust语言圣经(Rust Course)</title>
<!-- Custom HTML head -->
<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 -->
<link rel="stylesheet" href="../../theme/style.css">
</head>
<body class="sidebar-visible no-js">
<div id="body-container">
<!-- Provide site root to javascript -->
<script>
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>
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>
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('light')
html.classList.add(theme);
var body = document.querySelector('body');
body.classList.remove('no-js')
body.classList.add('js');
</script>
<input type="checkbox" id="sidebar-toggle-anchor" class="hidden">
<!-- Hide / unhide sidebar before it is displayed -->
<script>
var body = document.querySelector('body');
var sidebar = null;
var sidebar_toggle = document.getElementById("sidebar-toggle-anchor");
if (document.body.clientWidth >= 1080) {
try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
sidebar = sidebar || 'visible';
} else {
sidebar = 'hidden';
}
sidebar_toggle.checked = sidebar === 'visible';
body.classList.remove('sidebar-visible');
body.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 affix "><a href="../../about-book.html">关于本书</a></li><li class="chapter-item affix "><a href="../../into-rust.html">进入 Rust 编程世界</a></li><li class="chapter-item affix "><a href="../../first-try/sth-you-should-not-do.html">避免从入门到放弃</a></li><li class="chapter-item affix "><a href="../../community.html">社区和锈书</a></li><li class="spacer"></li><li class="chapter-item affix "><a href="../../some-thoughts.html">Datav: 可编程的数据可视化平台和可观测性平台</a></li><li class="chapter-item affix "><li class="part-title">Rust 语言基础学习</li><li class="spacer"></li><li class="chapter-item "><a href="../../first-try/intro.html"><strong aria-hidden="true">1.</strong> 寻找牛刀，以便小试</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../../first-try/installation.html"><strong aria-hidden="true">1.1.</strong> 安装 Rust 环境</a></li><li class="chapter-item "><a href="../../first-try/editor.html"><strong aria-hidden="true">1.2.</strong> 墙推 VSCode!</a></li><li class="chapter-item "><a href="../../first-try/cargo.html"><strong aria-hidden="true">1.3.</strong> 认识 Cargo</a></li><li class="chapter-item "><a href="../../first-try/hello-world.html"><strong aria-hidden="true">1.4.</strong> 不仅仅是 Hello world</a></li><li class="chapter-item "><a href="../../first-try/slowly-downloading.html"><strong aria-hidden="true">1.5.</strong> 下载依赖太慢了？</a></li></ol></li><li class="chapter-item "><a href="../../basic/intro.html"><strong aria-hidden="true">2.</strong> Rust 基础入门</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../../basic/variable.html"><strong aria-hidden="true">2.1.</strong> 变量绑定与解构</a></li><li class="chapter-item "><a href="../../basic/base-type/index.html"><strong aria-hidden="true">2.2.</strong> 基本类型</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../../basic/base-type/numbers.html"><strong aria-hidden="true">2.2.1.</strong> 数值类型</a></li><li class="chapter-item "><a href="../../basic/base-type/char-bool.html"><strong aria-hidden="true">2.2.2.</strong> 字符、布尔、单元类型</a></li><li class="chapter-item "><a href="../../basic/base-type/statement-expression.html"><strong aria-hidden="true">2.2.3.</strong> 语句与表达式</a></li><li class="chapter-item "><a href="../../basic/base-type/function.html"><strong aria-hidden="true">2.2.4.</strong> 函数</a></li></ol></li><li class="chapter-item "><a href="../../basic/ownership/index.html"><strong aria-hidden="true">2.3.</strong> 所有权和借用</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../../basic/ownership/ownership.html"><strong aria-hidden="true">2.3.1.</strong> 所有权</a></li><li class="chapter-item "><a href="../../basic/ownership/borrowing.html"><strong aria-hidden="true">2.3.2.</strong> 引用与借用</a></li></ol></li><li class="chapter-item "><a href="../../basic/compound-type/intro.html"><strong aria-hidden="true">2.4.</strong> 复合类型</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item "><a href="../../basic/compound-type/string-slice.html"><strong aria-hidden="true">2.4.1.</strong> 字符串与切片</a></li><li class="chapter-item "><a href="../../basic/compound-type/tuple.html"><strong aria-hidden="true">2.4.2.</strong> 元组</a></li><li class="chapter-item "><a href="../../basic/compound-type/struct.html"><strong aria-hidden="true">2.4.3.</strong> 结构体</a></li><li class="chapter-item "><a href="../../basic/compound-type/enum.html"><strong aria-hidden="true">2.4.4.</strong> 枚举</a></li><li class="chapter-item "><a href="../../basic/compound-type/array.html"><strong aria-hidden="true">2.4.5.</strong> 数组</a></li></ol></li><li class="chapter-item "><a href="../../basic/flow-contro
</div>
<div id="sidebar-resize-handle" class="sidebar-resize-handle">
<div class="sidebar-resize-indicator"></div>
</div>
</nav>
<!-- Track and set sidebar scroll position -->
<script>
var sidebarScrollbox = document.querySelector('#sidebar .sidebar-scrollbox');
sidebarScrollbox.addEventListener('click', function(e) {
if (e.target.tagName === 'A') {
sessionStorage.setItem('sidebar-scroll', sidebarScrollbox.scrollTop);
}
}, { passive: true });
var sidebarScrollTop = sessionStorage.getItem('sidebar-scroll');
sessionStorage.removeItem('sidebar-scroll');
if (sidebarScrollTop) {
// preserve sidebar scroll position when navigating via links within sidebar
sidebarScrollbox.scrollTop = sidebarScrollTop;
} else {
// scroll sidebar to current active section when navigating via "next/previous chapter" buttons
var activeSection = document.querySelector('#sidebar .active');
if (activeSection) {
activeSection.scrollIntoView({ block: 'center' });
}
}
</script>
<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">
<div class="left-buttons">
<label id="sidebar-toggle" class="icon-button" for="sidebar-toggle-anchor" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
<i class="fa fa-bars"></i>
</label>
<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</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">Rust语言圣经(Rust Course)</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>
<a href="https://github.com/sunface/rust-course" title="Git repository" aria-label="Git repository">
<i id="git-repository-button" class="fa fa-github"></i>
</a>
<a href="https://github.com/sunface/rust-course/edit/main/src/too-many-lists/unsafe-queue/layout.md" title="Suggest an edit" aria-label="Suggest an edit">
<i id="git-edit-button" class="fa fa-edit"></i>
</a>
</div>
</div>
<div id="search-wrapper" class="hidden">
<form id="searchbar-outer" class="searchbar-outer">
<input type="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>
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">
<!-- Page table of contents -->
<div class="sidetoc"><nav class="pagetoc"></nav></div>
<main>
<h1 id="数据布局"><a class="header" href="#数据布局">数据布局</a></h1>
<p>那么单向链表的队列长什么样？对于栈来说，我们向一端推入( push )元素，然后再从同一端弹出( pop )。对于栈和队列而言，唯一的区别在于队列从末端弹出。</p>
<p>栈的实现类似于下图：</p>
<pre><code class="language-shell">input list:
[Some(ptr)] -&gt; (A, Some(ptr)) -&gt; (B, None)
stack push X:
[Some(ptr)] -&gt; (X, Some(ptr)) -&gt; (A, Some(ptr)) -&gt; (B, None)
stack pop:
[Some(ptr)] -&gt; (A, Some(ptr)) -&gt; (B, None)
</code></pre>
<p>由于队列是首端进，末端出，因此我们需要决定将 <code>push</code> 和 <code>pop</code> 中的哪个放到末端去操作，如果将 <code>push</code> 放在末端操作:</p>
<pre><code class="language-shell">input list:
[Some(ptr)] -&gt; (A, Some(ptr)) -&gt; (B, None)
flipped push X:
[Some(ptr)] -&gt; (A, Some(ptr)) -&gt; (B, Some(ptr)) -&gt; (X, None)
</code></pre>
<p>而如果将 <code>pop</code> 放在末端:</p>
<pre><code class="language-shell">input list:
[Some(ptr)] -&gt; (A, Some(ptr)) -&gt; (B, Some(ptr)) -&gt; (X, None)
flipped pop:
[Some(ptr)] -&gt; (A, Some(ptr)) -&gt; (B, None)
</code></pre>
<p>但是这样实现有一个很糟糕的地方：两个操作都需要遍历整个链表后才能完成。队列要求 <code>push</code> 和 <code>pop</code> 操作需要高效，但是遍历整个链表才能完成的操作怎么看都谈不上高效！</p>
<p>其中一个解决办法就是保存一个指针指向末端:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>use std::mem;
pub struct List&lt;T&gt; {
head: Link&lt;T&gt;,
tail: Link&lt;T&gt;, // NEW!
}
type Link&lt;T&gt; = Option&lt;Box&lt;Node&lt;T&gt;&gt;&gt;;
struct Node&lt;T&gt; {
elem: T,
next: Link&lt;T&gt;,
}
impl&lt;T&gt; List&lt;T&gt; {
pub fn new() -&gt; Self {
List { head: None, tail: None }
}
pub fn push(&amp;mut self, elem: T) {
let new_tail = Box::new(Node {
elem: elem,
// 在尾端推入一个新节点时，新节点的下一个节点永远是 None
next: None,
});
// 让 tail 指向新的节点，并返回之前的 old tail
let old_tail = mem::replace(&amp;mut self.tail, Some(new_tail));
match old_tail {
Some(mut old_tail) =&gt; {
// 若 old tail 存在，则让该节点指向新的节点
old_tail.next = Some(new_tail);
}
None =&gt; {
// 否则，将 head 指向新的节点
self.head = Some(new_tail);
}
}
}
}
<span class="boring">}</span></code></pre></pre>
<p>在之前的各种链表锤炼下，我们对于相关代码应该相当熟悉了，因此可以适当提提速 - 在写的过程中，事实上我碰到了很多错误，这些错误就不再一一列举。</p>
<p>但是如果你担心不再能看到错误，那就纯属多余了:</p>
<pre><code class="language-shell">$ cargo build
error[E0382]: use of moved value: `new_tail`
--&gt; src/fifth.rs:38:38
|
26 | let new_tail = Box::new(Node {
| -------- move occurs because `new_tail` has type `std::boxed::Box&lt;fifth::Node&lt;T&gt;&gt;`, which does not implement the `Copy` trait
...
33 | let old_tail = mem::replace(&amp;mut self.tail, Some(new_tail));
| -------- value moved here
...
38 | old_tail.next = Some(new_tail);
| ^^^^^^^^ value used here after move
</code></pre>
<p>新鲜出炉的错误，接好！<code>Box</code> 并没有实现 <code>Copy</code> 特征，因此我们不能在两个地方进行赋值。好在，可以使用没有所有权的引用类型:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>pub struct List&lt;T&gt; {
head: Link&lt;T&gt;,
tail: Option&lt;&amp;mut Node&lt;T&gt;&gt;, // NEW!
}
type Link&lt;T&gt; = Option&lt;Box&lt;Node&lt;T&gt;&gt;&gt;;
struct Node&lt;T&gt; {
elem: T,
next: Link&lt;T&gt;,
}
impl&lt;T&gt; List&lt;T&gt; {
pub fn new() -&gt; Self {
List { head: None, tail: None }
}
pub fn push(&amp;mut self, elem: T) {
let new_tail = Box::new(Node {
elem: elem,
next: None,
});
let new_tail = match self.tail.take() {
Some(old_tail) =&gt; {
old_tail.next = Some(new_tail);
old_tail.next.as_deref_mut()
}
None =&gt; {
self.head = Some(new_tail);
self.head.as_deref_mut()
}
};
self.tail = new_tail;
}
}
<span class="boring">}</span></code></pre></pre>
<pre><code class="language-shell">$ cargo build
error[E0106]: missing lifetime specifier
--&gt; src/fifth.rs:3:18
|
3 | tail: Option&lt;&amp;mut Node&lt;T&gt;&gt;, // NEW!
| ^ expected lifetime parameter
</code></pre>
<p>好吧，结构体中的引用类型需要显式的标注生命周期，先加一个 <code>'a</code> 吧:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>pub struct List&lt;'a, T&gt; {
head: Link&lt;T&gt;,
tail: Option&lt;&amp;'a mut Node&lt;T&gt;&gt;, // NEW!
}
type Link&lt;T&gt; = Option&lt;Box&lt;Node&lt;T&gt;&gt;&gt;;
struct Node&lt;T&gt; {
elem: T,
next: Link&lt;T&gt;,
}
impl&lt;'a, T&gt; List&lt;'a, T&gt; {
pub fn new() -&gt; Self {
List { head: None, tail: None }
}
pub fn push(&amp;mut self, elem: T) {
let new_tail = Box::new(Node {
elem: elem,
next: None,
});
let new_tail = match self.tail.take() {
Some(old_tail) =&gt; {
old_tail.next = Some(new_tail);
old_tail.next.as_deref_mut()
}
None =&gt; {
self.head = Some(new_tail);
self.head.as_deref_mut()
}
};
self.tail = new_tail;
}
}
<span class="boring">}</span></code></pre></pre>
<pre><code class="language-shell">$ cargo build
error[E0495]: cannot infer an appropriate lifetime for autoref due to conflicting requirements
--&gt; src/fifth.rs:35:27
|
35 | self.head.as_deref_mut()
| ^^^^^^^^^^^^
|
note: first, the lifetime cannot outlive the anonymous lifetime #1 defined on the method body at 18:5...
--&gt; src/fifth.rs:18:5
|
18 | / pub fn push(&amp;mut self, elem: T) {
19 | | let new_tail = Box::new(Node {
20 | | elem: elem,
21 | | // When you push onto the tail, your next is always None
... |
39 | | self.tail = new_tail;
40 | | }
| |_____^
note: ...so that reference does not outlive borrowed content
--&gt; src/fifth.rs:35:17
|
35 | self.head.as_deref_mut()
| ^^^^^^^^^
note: but, the lifetime must be valid for the lifetime 'a as defined on the impl at 13:6...
--&gt; src/fifth.rs:13:6
|
13 | impl&lt;'a, T&gt; List&lt;'a, T&gt; {
| ^^
= note: ...so that the expression is assignable:
expected std::option::Option&lt;&amp;'a mut fifth::Node&lt;T&gt;&gt;
found std::option::Option&lt;&amp;mut fifth::Node&lt;T&gt;&gt;
</code></pre>
<p>好长... Rust 为啥这么难... 但是，这里有一句重点:</p>
<blockquote>
<p>the lifetime must be valid for the lifetime 'a as defined on the impl</p>
</blockquote>
<p>意思是说生命周期至少要和 <code>'a</code> 一样长，是不是因为编译器为 <code>self</code> 推导的生命周期不够长呢？我们试着来手动标注下:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>pub fn push(&amp;'a mut self, elem: T) {
<span class="boring">}</span></code></pre></pre>
<p>当当当当，成功通过编译:</p>
<pre><code class="language-shell">$ cargo build
warning: field is never used: `elem`
--&gt; src/fifth.rs:9:5
|
9 | elem: T,
| ^^^^^^^
|
= note: #[warn(dead_code)] on by default
</code></pre>
<p>这个错误可以称之为错误之王，但是我们依然成功的解决了它，太棒了！再来实现下 <code>pop</code>:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>pub fn pop(&amp;'a mut self) -&gt; Option&lt;T&gt; {
self.head.take().map(|head| {
let head = *head;
self.head = head.next;
if self.head.is_none() {
self.tail = None;
}
head.elem
})
}
<span class="boring">}</span></code></pre></pre>
<p>看起来不错，写几个测试用例溜一溜:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>mod test {
use super::List;
#[test]
fn basics() {
let mut list = List::new();
// Check empty list behaves right
assert_eq!(list.pop(), None);
// Populate list
list.push(1);
list.push(2);
list.push(3);
// Check normal removal
assert_eq!(list.pop(), Some(1));
assert_eq!(list.pop(), Some(2));
// Push some more just to make sure nothing's corrupted
list.push(4);
list.push(5);
// Check normal removal
assert_eq!(list.pop(), Some(3));
assert_eq!(list.pop(), Some(4));
// Check exhaustion
assert_eq!(list.pop(), Some(5));
assert_eq!(list.pop(), None);
}
}
<span class="boring">}</span></code></pre></pre>
<pre><code class="language-shell">$ cargo test
error[E0499]: cannot borrow `list` as mutable more than once at a time
--&gt; src/fifth.rs:68:9
|
65 | assert_eq!(list.pop(), None);
| ---- first mutable borrow occurs here
...
68 | list.push(1);
| ^^^^
| |
| second mutable borrow occurs here
| first borrow later used here
error[E0499]: cannot borrow `list` as mutable more than once at a time
--&gt; src/fifth.rs:69:9
|
65 | assert_eq!(list.pop(), None);
| ---- first mutable borrow occurs here
...
69 | list.push(2);
| ^^^^
| |
| second mutable borrow occurs here
| first borrow later used here
error[E0499]: cannot borrow `list` as mutable more than once at a time
--&gt; src/fifth.rs:70:9
|
65 | assert_eq!(list.pop(), None);
| ---- first mutable borrow occurs here
...
70 | list.push(3);
| ^^^^
| |
| second mutable borrow occurs here
| first borrow later used here
....
** WAY MORE LINES OF ERRORS **
....
error: aborting due to 11 previous errors
</code></pre>
<p>🙀🙀🙀，震惊！但编译器真的没错，因为都是我们刚才那个标记惹的祸。</p>
<p>我们为 <code>self</code> 标记了 <code>'a</code>，意味着在 <code>'a</code> 结束前，无法再去使用 <code>self</code>，大家可以自己推断下 <code>'a</code> 的生命周期是多长。</p>
<p>那么该怎么办？回到老路 <code>RefCell</code> 上？显然不可能，那只能祭出大杀器：裸指针。</p>
<blockquote>
<p>事实上，上文的问题主要是自引用引起的，感兴趣的同学可以查看<a href="https://course.rs/advance/circle-self-ref/intro.html">这里</a>深入阅读。</p>
</blockquote>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>pub struct List&lt;T&gt; {
head: Link&lt;T&gt;,
tail: *mut Node&lt;T&gt;, // DANGER DANGER
}
type Link&lt;T&gt; = Option&lt;Box&lt;Node&lt;T&gt;&gt;&gt;;
struct Node&lt;T&gt; {
elem: T,
next: Link&lt;T&gt;,
}
<span class="boring">}</span></code></pre></pre>
<p>如上所示，当使用裸指针后， <code>head</code> 和 <code>tail</code> 就不会形成自引用的问题，也不再违反 Rust 严苛的借用规则。</p>
<blockquote>
<p>注意！当前的实现依然是有严重问题的，在后面我们会修复</p>
</blockquote>
<p>果然，编程的最高境界就是回归本质：使用 C 语言的东东。</p>
<div id="giscus-container"></div>
</main>
<nav class="nav-wrapper" aria-label="Page navigation">
<!-- Mobile navigation buttons -->
<a rel="prev" href="../../too-many-lists/unsafe-queue/intro.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 prefetch" href="../../too-many-lists/unsafe-queue/basics.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="../../too-many-lists/unsafe-queue/intro.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 prefetch" href="../../too-many-lists/unsafe-queue/basics.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>
window.playground_copyable = true;
</script>
<script src="../../ace.js"></script>
<script src="../../editor.js"></script>
<script src="../../mode-rust.js"></script>
<script src="../../theme-dawn.js"></script>
<script src="../../theme-tomorrow_night.js"></script>
<script src="../../elasticlunr.min.js"></script>
<script src="../../mark.min.js"></script>
<script src="../../searcher.js"></script>
<script src="../../clipboard.min.js"></script>
<script src="../../highlight.js"></script>
<script src="../../book.js"></script>
<script type="text/javascript" charset="utf-8">
var pagePath = "too-many-lists/unsafe-queue/layout.md"
</script>
<!-- Custom JS scripts -->
<script src="../../assets/custom.js"></script>
<script src="../../assets/bigPicture.js"></script>
</div>
</body>
</html>