ehlxr/gopl-zh.github.com
1
0
Fork 0
mirror of https://github.com/gopl-zh/gopl-zh.github.com.git synced 2024-12-27 07:16:22 +00:00
Code Issues Projects Releases Wiki Activity
26da315c57
gopl-zh.github.com/ch8/ch8-02.html

732 lines
36 KiB
HTML
Raw Normal View History

deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<!DOCTYPE HTML>
<html lang="zh" class="sidebar-visible no-js light">
<head>
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
<!-- Book generated using https://github.com/wa-lang/wabook -->
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<meta charset="UTF-8">
<title>示例: 并发的Clock服务 - Go语言圣经</title>
<!-- Custom HTML head -->
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<meta name="description" content="">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="theme-color" content="#ffffff" />
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<link rel="icon" href="../favicon.svg">
<link rel="shortcut icon" href="../favicon.png">
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
<link rel="stylesheet" href="../static/wabook/css/variables.css">
<link rel="stylesheet" href="../static/wabook/css/general.css">
<link rel="stylesheet" href="../static/wabook/css/chrome.css">
<link rel="stylesheet" href="../static/wabook/css/print.css" media="print">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<!-- Fonts -->
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
<link rel="stylesheet" href="../static/wabook/FontAwesome/css/font-awesome.css">
<link rel="stylesheet" href="../static/wabook/fonts/fonts.css">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<!-- Highlight.js Stylesheets -->
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
<link rel="stylesheet" href="../static/wabook/highlight.css">
<link rel="stylesheet" href="../static/wabook/tomorrow-night.css">
<link rel="stylesheet" href="../static/wabook/ayu-highlight.css">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<!-- 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 {
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
var theme = localStorage.getItem('wabook-theme');
var sidebar = localStorage.getItem('wabook-sidebar');
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
if (theme.startsWith('"') && theme.endsWith('"')) {
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
localStorage.setItem('wabook-theme', theme.slice(1, theme.length - 1));
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
}
if (sidebar.startsWith('"') && sidebar.endsWith('"')) {
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
localStorage.setItem('wabook-sidebar', sidebar.slice(1, sidebar.length - 1));
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
}
} catch (e) { }
</script>
<!-- Set the theme before any content is loaded, prevents flash -->
<script type="text/javascript">
var theme;
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
try { theme = localStorage.getItem('wabook-theme'); } catch(e) { }
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
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) {
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
try { sidebar = localStorage.getItem('wabook-sidebar'); } catch(e) { }
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
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">
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<ol class="chapter">
<li class="chapter-item expanded ">
<a href="../index.html" >Go语言圣经</a>
</li>
<li class="chapter-item expanded ">
<a href="../preface-zh.html" >译者序</a>
</li>
<li class="chapter-item expanded ">
<a href="../preface.html" >前言</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch1/ch1.html" ><strong aria-hidden="true">1.</strong> 入门</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch1/ch1-01.html" ><strong aria-hidden="true">1.1.</strong> Hello, World</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch1/ch1-02.html" ><strong aria-hidden="true">1.2.</strong> 命令行参数</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch1/ch1-03.html" ><strong aria-hidden="true">1.3.</strong> 查找重复的行</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch1/ch1-04.html" ><strong aria-hidden="true">1.4.</strong> GIF动画</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch1/ch1-05.html" ><strong aria-hidden="true">1.5.</strong> 获取URL</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch1/ch1-06.html" ><strong aria-hidden="true">1.6.</strong> 并发获取多个URL</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch1/ch1-07.html" ><strong aria-hidden="true">1.7.</strong> Web服务</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch1/ch1-08.html" ><strong aria-hidden="true">1.8.</strong> 本章要点</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch2/ch2.html" ><strong aria-hidden="true">2.</strong> 程序结构</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch2/ch2-01.html" ><strong aria-hidden="true">2.1.</strong> 命名</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch2/ch2-02.html" ><strong aria-hidden="true">2.2.</strong> 声明</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch2/ch2-03.html" ><strong aria-hidden="true">2.3.</strong> 变量</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch2/ch2-04.html" ><strong aria-hidden="true">2.4.</strong> 赋值</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch2/ch2-05.html" ><strong aria-hidden="true">2.5.</strong> 类型</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch2/ch2-06.html" ><strong aria-hidden="true">2.6.</strong> 包和文件</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch2/ch2-07.html" ><strong aria-hidden="true">2.7.</strong> 作用域</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch3/ch3.html" ><strong aria-hidden="true">3.</strong> 基础数据类型</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch3/ch3-01.html" ><strong aria-hidden="true">3.1.</strong> 整型</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch3/ch3-02.html" ><strong aria-hidden="true">3.2.</strong> 浮点数</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch3/ch3-03.html" ><strong aria-hidden="true">3.3.</strong> 复数</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch3/ch3-04.html" ><strong aria-hidden="true">3.4.</strong> 布尔型</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch3/ch3-05.html" ><strong aria-hidden="true">3.5.</strong> 字符串</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch3/ch3-06.html" ><strong aria-hidden="true">3.6.</strong> 常量</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch4/ch4.html" ><strong aria-hidden="true">4.</strong> 复合数据类型</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch4/ch4-01.html" ><strong aria-hidden="true">4.1.</strong> 数组</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch4/ch4-02.html" ><strong aria-hidden="true">4.2.</strong> Slice</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch4/ch4-03.html" ><strong aria-hidden="true">4.3.</strong> Map</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch4/ch4-04.html" ><strong aria-hidden="true">4.4.</strong> 结构体</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch4/ch4-05.html" ><strong aria-hidden="true">4.5.</strong> JSON</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch4/ch4-06.html" ><strong aria-hidden="true">4.6.</strong> 文本和HTML模板</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch5/ch5.html" ><strong aria-hidden="true">5.</strong> 函数</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch5/ch5-01.html" ><strong aria-hidden="true">5.1.</strong> 函数声明</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-02.html" ><strong aria-hidden="true">5.2.</strong> 递归</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-03.html" ><strong aria-hidden="true">5.3.</strong> 多返回值</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-04.html" ><strong aria-hidden="true">5.4.</strong> 错误</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-05.html" ><strong aria-hidden="true">5.5.</strong> 函数值</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-06.html" ><strong aria-hidden="true">5.6.</strong> 匿名函数</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-07.html" ><strong aria-hidden="true">5.7.</strong> 可变参数</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-08.html" ><strong aria-hidden="true">5.8.</strong> Deferred函数</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-09.html" ><strong aria-hidden="true">5.9.</strong> Panic异常</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch5/ch5-10.html" ><strong aria-hidden="true">5.10.</strong> Recover捕获异常</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch6/ch6.html" ><strong aria-hidden="true">6.</strong> 方法</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch6/ch6-01.html" ><strong aria-hidden="true">6.1.</strong> 方法声明</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch6/ch6-02.html" ><strong aria-hidden="true">6.2.</strong> 基于指针对象的方法</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch6/ch6-03.html" ><strong aria-hidden="true">6.3.</strong> 通过嵌入结构体来扩展类型</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch6/ch6-04.html" ><strong aria-hidden="true">6.4.</strong> 方法值和方法表达式</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch6/ch6-05.html" ><strong aria-hidden="true">6.5.</strong> 示例: Bit数组</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch6/ch6-06.html" ><strong aria-hidden="true">6.6.</strong> 封装</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch7/ch7.html" ><strong aria-hidden="true">7.</strong> 接口</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch7/ch7-01.html" ><strong aria-hidden="true">7.1.</strong> 接口是合约</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-02.html" ><strong aria-hidden="true">7.2.</strong> 接口类型</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-03.html" ><strong aria-hidden="true">7.3.</strong> 实现接口的条件</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-04.html" ><strong aria-hidden="true">7.4.</strong> flag.Value接口</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-05.html" ><strong aria-hidden="true">7.5.</strong> 接口值</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-06.html" ><strong aria-hidden="true">7.6.</strong> sort.Interface接口</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-07.html" ><strong aria-hidden="true">7.7.</strong> http.Handler接口</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-08.html" ><strong aria-hidden="true">7.8.</strong> error接口</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-09.html" ><strong aria-hidden="true">7.9.</strong> 示例: 表达式求值</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-10.html" ><strong aria-hidden="true">7.10.</strong> 类型断言</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-11.html" ><strong aria-hidden="true">7.11.</strong> 基于类型断言识别错误类型</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-12.html" ><strong aria-hidden="true">7.12.</strong> 通过类型断言查询接口</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-13.html" ><strong aria-hidden="true">7.13.</strong> 类型分支</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-14.html" ><strong aria-hidden="true">7.14.</strong> 示例: 基于标记的XML解码</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch7/ch7-15.html" ><strong aria-hidden="true">7.15.</strong> 补充几点</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch8/ch8.html" ><strong aria-hidden="true">8.</strong> Goroutines和Channels</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch8/ch8-01.html" ><strong aria-hidden="true">8.1.</strong> Goroutines</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-02.html" class="active"><strong aria-hidden="true">8.2.</strong> 示例: 并发的Clock服务</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-03.html" ><strong aria-hidden="true">8.3.</strong> 示例: 并发的Echo服务</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-04.html" ><strong aria-hidden="true">8.4.</strong> Channels</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-05.html" ><strong aria-hidden="true">8.5.</strong> 并发的循环</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-06.html" ><strong aria-hidden="true">8.6.</strong> 示例: 并发的Web爬虫</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-07.html" ><strong aria-hidden="true">8.7.</strong> 基于select的多路复用</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-08.html" ><strong aria-hidden="true">8.8.</strong> 示例: 并发的目录遍历</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-09.html" ><strong aria-hidden="true">8.9.</strong> 并发的退出</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch8/ch8-10.html" ><strong aria-hidden="true">8.10.</strong> 示例: 聊天服务</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch9/ch9.html" ><strong aria-hidden="true">9.</strong> 基于共享变量的并发</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch9/ch9-01.html" ><strong aria-hidden="true">9.1.</strong> 竞争条件</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch9/ch9-02.html" ><strong aria-hidden="true">9.2.</strong> sync.Mutex互斥锁</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch9/ch9-03.html" ><strong aria-hidden="true">9.3.</strong> sync.RWMutex读写锁</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch9/ch9-04.html" ><strong aria-hidden="true">9.4.</strong> 内存同步</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch9/ch9-05.html" ><strong aria-hidden="true">9.5.</strong> sync.Once惰性初始化</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch9/ch9-06.html" ><strong aria-hidden="true">9.6.</strong> 竞争条件检测</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch9/ch9-07.html" ><strong aria-hidden="true">9.7.</strong> 示例: 并发的非阻塞缓存</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch9/ch9-08.html" ><strong aria-hidden="true">9.8.</strong> Goroutines和线程</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch10/ch10.html" ><strong aria-hidden="true">10.</strong> 包和工具</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch10/ch10-01.html" ><strong aria-hidden="true">10.1.</strong> 包简介</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch10/ch10-02.html" ><strong aria-hidden="true">10.2.</strong> 导入路径</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch10/ch10-03.html" ><strong aria-hidden="true">10.3.</strong> 包声明</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch10/ch10-04.html" ><strong aria-hidden="true">10.4.</strong> 导入声明</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch10/ch10-05.html" ><strong aria-hidden="true">10.5.</strong> 包的匿名导入</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch10/ch10-06.html" ><strong aria-hidden="true">10.6.</strong> 包和命名</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch10/ch10-07.html" ><strong aria-hidden="true">10.7.</strong> 工具</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch11/ch11.html" ><strong aria-hidden="true">11.</strong> 测试</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch11/ch11-01.html" ><strong aria-hidden="true">11.1.</strong> go test</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch11/ch11-02.html" ><strong aria-hidden="true">11.2.</strong> 测试函数</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch11/ch11-03.html" ><strong aria-hidden="true">11.3.</strong> 测试覆盖率</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch11/ch11-04.html" ><strong aria-hidden="true">11.4.</strong> 基准测试</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch11/ch11-05.html" ><strong aria-hidden="true">11.5.</strong> 剖析</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch11/ch11-06.html" ><strong aria-hidden="true">11.6.</strong> 示例函数</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch12/ch12.html" ><strong aria-hidden="true">12.</strong> 反射</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch12/ch12-01.html" ><strong aria-hidden="true">12.1.</strong> 为何需要反射?</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch12/ch12-02.html" ><strong aria-hidden="true">12.2.</strong> reflect.Type和reflect.Value</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch12/ch12-03.html" ><strong aria-hidden="true">12.3.</strong> Display递归打印</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch12/ch12-04.html" ><strong aria-hidden="true">12.4.</strong> 示例: 编码S表达式</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch12/ch12-05.html" ><strong aria-hidden="true">12.5.</strong> 通过reflect.Value修改值</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch12/ch12-06.html" ><strong aria-hidden="true">12.6.</strong> 示例: 解码S表达式</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch12/ch12-07.html" ><strong aria-hidden="true">12.7.</strong> 获取结构体字段标签</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch12/ch12-08.html" ><strong aria-hidden="true">12.8.</strong> 显示一个类型的方法集</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch12/ch12-09.html" ><strong aria-hidden="true">12.9.</strong> 几点忠告</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../ch13/ch13.html" ><strong aria-hidden="true">13.</strong> 底层编程</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../ch13/ch13-01.html" ><strong aria-hidden="true">13.1.</strong> unsafe.Sizeof, Alignof 和 Offsetof</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch13/ch13-02.html" ><strong aria-hidden="true">13.2.</strong> unsafe.Pointer</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch13/ch13-03.html" ><strong aria-hidden="true">13.3.</strong> 示例: 深度相等判断</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch13/ch13-04.html" ><strong aria-hidden="true">13.4.</strong> 通过cgo调用C代码</a>
</li>
<li class="chapter-item expanded ">
<a href="../ch13/ch13-05.html" ><strong aria-hidden="true">13.5.</strong> 几点忠告</a>
</li>
</ol>
<li class="chapter-item expanded ">
<a href="../appendix/appendix.html" ><strong aria-hidden="true">14.</strong> 附录</a>
</li>
<ol class="section">
<li class="chapter-item expanded ">
<a href="../appendix/appendix-a-errata.html" ><strong aria-hidden="true">14.1.</strong> 附录A：原文勘误</a>
</li>
<li class="chapter-item expanded ">
<a href="../appendix/appendix-b-author.html" ><strong aria-hidden="true">14.2.</strong> 附录B：作者译者</a>
</li>
<li class="chapter-item expanded ">
<a href="../appendix/appendix-c-cpoyright.html" ><strong aria-hidden="true">14.3.</strong> 附录C：译文授权</a>
</li>
<li class="chapter-item expanded ">
<a href="../appendix/appendix-d-translations.html" ><strong aria-hidden="true">14.4.</strong> 附录D：其它语言</a>
</li>
</ol>
</ol>
</div>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<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="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>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
</div>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<h1 class="menu-title"><a href="../index.html">Go语言圣经</a></h1>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<div class="right-buttons">
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<a href="https://github.com/gopl-zh/gopl-zh.github.com" title="Git repository" aria-label="Git repository">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<i id="git-repository-button" class="fa fa-github"></i>
</a>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<a href="https://github.com/gopl-zh/gopl-zh.github.com/edit/master/ch8/ch8-02.md" title="Suggest an edit" aria-label="Suggest an edit">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<i id="git-edit-button" class="fa fa-edit"></i>
</a>
</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">
<!-- Page table of contents -->
<div class="sidetoc"><nav class="pagetoc"></nav></div>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<main>
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
<ul dir="auto"><li><em>凹语言(Go实现, 面向WASM设计): <a href="https://github.com/wa-lang/wa">https://github.com/wa-lang/wa</a></em></li><li><em>WaBook(Go语言实现的MD电子书构建工具): <a href="https://github.com/wa-lang/wabook">https://github.com/wa-lang/wabook</a></em></li></ul><hr>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<h2>8.2. 示例: 并发的Clock服务</h2>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<p>网络编程是并发大显身手的一个领域，由于服务器是最典型的需要同时处理很多连接的程序，这些连接一般来自于彼此独立的客户端。在本小节中，我们会讲解go语言的net包，这个包提供编写一个网络客户端或者服务器程序的基本组件，无论两者间通信是使用TCP、UDP或者Unix domain sockets。在第一章中我们使用过的net/http包里的方法，也算是net包的一部分。</p>
<p>我们的第一个例子是一个顺序执行的时钟服务器，它会每隔一秒钟将当前时间写到客户端：</p>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<p><!-- raw HTML omitted --><!-- raw HTML omitted -->gopl.io/ch8/clock1<!-- raw HTML omitted --><!-- raw HTML omitted --></p>
<pre><code class="language-go">// Clock1 is a TCP server that periodically writes the time.
package main
import (
&quot;io&quot;
&quot;log&quot;
&quot;net&quot;
&quot;time&quot;
)
func main() {
listener, err := net.Listen(&quot;tcp&quot;, &quot;localhost:8000&quot;)
if err != nil {
log.Fatal(err)
}
for {
conn, err := listener.Accept()
if err != nil {
log.Print(err) // e.g., connection aborted
continue
}
handleConn(conn) // handle one connection at a time
}
}
func handleConn(c net.Conn) {
defer c.Close()
for {
_, err := io.WriteString(c, time.Now().Format(&quot;15:04:05\n&quot;))
if err != nil {
return // e.g., client disconnected
}
time.Sleep(1 * time.Second)
}
}
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</code></pre>
<p>Listen函数创建了一个net.Listener的对象，这个对象会监听一个网络端口上到来的连接，在这个例子里我们用的是TCP的localhost:8000端口。listener对象的Accept方法会直接阻塞，直到一个新的连接被创建，然后会返回一个net.Conn对象来表示这个连接。</p>
<p>handleConn函数会处理一个完整的客户端连接。在一个for死循环中，用time.Now()获取当前时刻，然后写到客户端。由于net.Conn实现了io.Writer接口，我们可以直接向其写入内容。这个死循环会一直执行，直到写入失败。最可能的原因是客户端主动断开连接。这种情况下handleConn函数会用defer调用关闭服务器侧的连接，然后返回到主函数，继续等待下一个连接请求。</p>
<p>time.Time.Format方法提供了一种格式化日期和时间信息的方式。它的参数是一个格式化模板，标识如何来格式化时间，而这个格式化模板限定为Mon Jan 2 03:04:05PM 2006 UTC-0700。有8个部分（周几、月份、一个月的第几天……）。可以以任意的形式来组合前面这个模板；出现在模板中的部分会作为参考来对时间格式进行输出。在上面的例子中我们只用到了小时、分钟和秒。time包里定义了很多标准时间格式，比如time.RFC1123。在进行格式化的逆向操作time.Parse时，也会用到同样的策略。（译注：这是go语言和其它语言相比比较奇葩的一个地方。你需要记住格式化字符串是1月2日下午3点4分5秒零六年UTC-0700，而不像其它语言那样Y-m-d H:i:s一样，当然了这里可以用1234567的方式来记忆，倒是也不麻烦。）</p>
<p>为了连接例子里的服务器，我们需要一个客户端程序，比如netcat这个工具（nc命令），这个工具可以用来执行网络连接操作。</p>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<pre><code>$ go build gopl.io/ch8/clock1
$ ./clock1 &amp;
$ nc localhost 8000
13:58:54
13:58:55
13:58:56
13:58:57
^C
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</code></pre>
<p>客户端将服务器发来的时间显示了出来，我们用Control+C来中断客户端的执行，在Unix系统上，你会看到^C这样的响应。如果你的系统没有装nc这个工具，你可以用telnet来实现同样的效果，或者也可以用我们下面的这个用go写的简单的telnet程序，用net.Dial就可以简单地创建一个TCP连接：</p>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<p><!-- raw HTML omitted --><!-- raw HTML omitted -->gopl.io/ch8/netcat1<!-- raw HTML omitted --><!-- raw HTML omitted --></p>
<pre><code class="language-go">// Netcat1 is a read-only TCP client.
package main
import (
&quot;io&quot;
&quot;log&quot;
&quot;net&quot;
&quot;os&quot;
)
func main() {
conn, err := net.Dial(&quot;tcp&quot;, &quot;localhost:8000&quot;)
if err != nil {
log.Fatal(err)
}
defer conn.Close()
mustCopy(os.Stdout, conn)
}
func mustCopy(dst io.Writer, src io.Reader) {
if _, err := io.Copy(dst, src); err != nil {
log.Fatal(err)
}
}
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</code></pre>
<p>这个程序会从连接中读取数据，并将读到的内容写到标准输出中，直到遇到end of file的条件或者发生错误。mustCopy这个函数我们在本节的几个例子中都会用到。让我们同时运行两个客户端来进行一个测试，这里可以开两个终端窗口，下面左边的是其中的一个的输出，右边的是另一个的输出：</p>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<pre><code>$ go build gopl.io/ch8/netcat1
$ ./netcat1
13:58:54 $ ./netcat1
13:58:55
13:58:56
^C
13:58:57
13:58:58
13:58:59
^C
$ killall clock1
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</code></pre>
<p>killall命令是一个Unix命令行工具，可以用给定的进程名来杀掉所有名字匹配的进程。</p>
<p>第二个客户端必须等待第一个客户端完成工作，这样服务端才能继续向后执行；因为我们这里的服务器程序同一时间只能处理一个客户端连接。我们这里对服务端程序做一点小改动，使其支持并发：在handleConn函数调用的地方增加go关键字，让每一次handleConn的调用都进入一个独立的goroutine。</p>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<p><!-- raw HTML omitted --><!-- raw HTML omitted -->gopl.io/ch8/clock2<!-- raw HTML omitted --><!-- raw HTML omitted --></p>
<pre><code class="language-go">for {
conn, err := listener.Accept()
if err != nil {
log.Print(err) // e.g., connection aborted
continue
}
go handleConn(conn) // handle connections concurrently
}
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</code></pre>
<p>现在多个客户端可以同时接收到时间了：</p>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<pre><code>$ go build gopl.io/ch8/clock2
$ ./clock2 &amp;
$ go build gopl.io/ch8/netcat1
$ ./netcat1
14:02:54 $ ./netcat1
14:02:55 14:02:55
14:02:56 14:02:56
14:02:57 ^C
14:02:58
14:02:59 $ ./netcat1
14:03:00 14:03:00
14:03:01 14:03:01
^C 14:03:02
^C
$ killall clock2
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</code></pre>
<p><strong>练习 8.1：</strong> 修改clock2来支持传入参数作为端口号，然后写一个clockwall的程序，这个程序可以同时与多个clock服务器通信，从多个服务器中读取时间，并且在一个表格中一次显示所有服务器传回的结果，类似于你在某些办公室里看到的时钟墙。如果你有地理学上分布式的服务器可以用的话，让这些服务器跑在不同的机器上面；或者在同一台机器上跑多个不同的实例，这些实例监听不同的端口，假装自己在不同的时区。像下面这样：</p>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<pre><code>$ TZ=US/Eastern ./clock2 -port 8010 &amp;
$ TZ=Asia/Tokyo ./clock2 -port 8020 &amp;
$ TZ=Europe/London ./clock2 -port 8030 &amp;
$ clockwall NewYork=localhost:8010 Tokyo=localhost:8020 London=localhost:8030
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</code></pre>
<p><strong>练习 8.2：</strong> 实现一个并发FTP服务器。服务器应该解析客户端发来的一些命令，比如cd命令来切换目录，ls来列出目录内文件，get和send来传输文件，close来关闭连接。你可以用标准的ftp命令来作为客户端，或者也可以自己实现一个。</p>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<hr><table><tr><td><img width="222px" src="https://chai2010.cn/advanced-go-programming-book/css.png"></td><td><img width="222px" src="https://chai2010.cn/advanced-go-programming-book/cch.png"></td></tr></table>
<div id="giscus-container"></div>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<footer class="page-footer">
<span>© 2015-2016 | <a href="https://github.com/gopl-zh"> Go语言圣经中文版</a>, 仅学习交流使用</span>
</footer>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</main>
<nav class="nav-wrapper" aria-label="Page navigation">
<!-- Mobile navigation buttons -->
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<a rel="prev" href="../ch8/ch8-01.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<i class="fa fa-angle-left"></i>
</a>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<!-- ../ch8/ch8-03.html -->
<a rel="next" href="../ch8/ch8-03.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<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">
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<a rel="prev" href="../ch8/ch8-01.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<i class="fa fa-angle-left"></i>
</a>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<a rel="next" href="../ch8/ch8-03.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<i class="fa fa-angle-right"></i>
</a>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
</nav>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</div>
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
<script type="text/javascript">
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
window.playground_copyable = true;
</script>
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
<script src="../static/wabook/mark.min.js" type="text/javascript" charset="utf-8"></script>
<script src="../static/wabook/clipboard.min.js" type="text/javascript" charset="utf-8"></script>
<script src="../static/wabook/highlight.js" type="text/javascript" charset="utf-8"></script>
<script src="../static/wabook/book.js" type="text/javascript" charset="utf-8"></script>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
<script type="text/javascript" charset="utf-8">
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
var pagePath = "ch8/ch8-02.md"
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</script>
<!-- Custom JS scripts -->
deploy: 56bbafbd084510732427c1af2fe0c7528c8cb53c
2024-08-13 00:15:53 +00:00
<script src="../static/wabook/giscus.js" type="text/javascript" charset="utf-8"></script>
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
deploy: b76e3beb2c9759038e6deee4214d9d977a5729a4
2024-08-08 07:47:03 +00:00
deploy: 06a1bdf7353d7ab131c932b22e155c41f763dde3
2022-08-04 06:59:33 +00:00
</body>
</html>
Reference in New Issue Copy Permalink