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< title > 示例: 併發的Clock服務 | Go编程语言< / title >
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< div class = "book" data-level = "8.2" data-chapter-title = "示例: 併發的Clock服務" data-filepath = "ch8/ch8-02.md" data-basepath = ".." data-revision = "Mon Dec 28 2015 16:03:52 GMT+0800 (中国标准时间)" >
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前言
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< b > 0.1.< / b >
Go語言起源
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< b > 0.2.< / b >
Go語言項目
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< b > 0.3.< / b >
本書的組織
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< b > 0.4.< / b >
更多的信息
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< b > 0.5.< / b >
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致謝
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< b > 1.< / b >
入門
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< b > 1.1.< / b >
Hello, World
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< b > 1.2.< / b >
命令行參數
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< b > 1.3.< / b >
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査找重複的行
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< b > 1.4.< / b >
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GIF動畵
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< b > 1.5.< / b >
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獲取URL
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< b > 1.6.< / b >
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併發獲取多個URL
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< b > 1.7.< / b >
Web服務
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< b > 1.8.< / b >
本章要點
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< b > 2.< / b >
程序結構
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< b > 2.1.< / b >
命名
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< b > 2.2.< / b >
聲明
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< b > 2.3.< / b >
變量
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< b > 2.4.< / b >
賦值
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< b > 2.5.< / b >
類型
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< b > 2.6.< / b >
包和文件
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< b > 2.7.< / b >
作用域
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< b > 3.< / b >
基礎數據類型
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< b > 3.1.< / b >
整型
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< b > 3.2.< / b >
浮點數
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< b > 3.3.< / b >
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複數
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< b > 3.4.< / b >
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布爾型
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< b > 3.5.< / b >
字符串
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< b > 3.6.< / b >
常量
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< b > 4.< / b >
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複合數據類型
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< ul class = "articles" >
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< b > 4.1.< / b >
數組
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< b > 4.2.< / b >
切片
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< b > 4.3.< / b >
字典
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< b > 4.4.< / b >
結構體
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< b > 4.5.< / b >
JSON
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< b > 4.6.< / b >
文本和HTML模闆
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< li class = "chapter " data-level = "5" data-path = "ch5/ch5.html" >
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< b > 5.< / b >
函數
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< b > 5.1.< / b >
函數聲明
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< li class = "chapter " data-level = "5.2" data-path = "ch5/ch5-02.html" >
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< b > 5.2.< / b >
遞歸
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< b > 5.3.< / b >
多返迴值
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< li class = "chapter " data-level = "5.4" data-path = "ch5/ch5-04.html" >
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< b > 5.4.< / b >
錯誤
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< b > 5.5.< / b >
函數值
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< li class = "chapter " data-level = "5.6" data-path = "ch5/ch5-06.html" >
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< b > 5.6.< / b >
匿名函數
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< li class = "chapter " data-level = "5.7" data-path = "ch5/ch5-07.html" >
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< b > 5.7.< / b >
可變參數
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< li class = "chapter " data-level = "5.8" data-path = "ch5/ch5-08.html" >
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< b > 5.8.< / b >
Deferred函數
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< li class = "chapter " data-level = "5.9" data-path = "ch5/ch5-09.html" >
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< b > 5.9.< / b >
Panic異常
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< li class = "chapter " data-level = "5.10" data-path = "ch5/ch5-10.html" >
< a href = "../ch5/ch5-10.html" >
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< b > 5.10.< / b >
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Recover捕獲異常
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< b > 6.< / b >
方法
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< b > 6.1.< / b >
方法聲明
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< b > 6.2.< / b >
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基於指針對象的方法
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< li class = "chapter " data-level = "6.3" data-path = "ch6/ch6-03.html" >
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< b > 6.3.< / b >
通過嵌入結構體來擴展類型
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< li class = "chapter " data-level = "6.4" data-path = "ch6/ch6-04.html" >
< a href = "../ch6/ch6-04.html" >
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< b > 6.4.< / b >
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方法值和方法表達式
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< b > 6.5.< / b >
示例: Bit數組
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< b > 6.6.< / b >
封裝
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< b > 7.< / b >
接口
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< b > 7.1.< / b >
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接口是合約
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< b > 7.2.< / b >
接口類型
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< li class = "chapter " data-level = "7.3" data-path = "ch7/ch7-03.html" >
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< b > 7.3.< / b >
實現接口的條件
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< b > 7.4.< / b >
flag.Value接口
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< b > 7.5.< / b >
接口值
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< b > 7.6.< / b >
sort.Interface接口
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< b > 7.7.< / b >
http.Handler接口
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< b > 7.8.< / b >
error接口
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< b > 7.9.< / b >
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示例: 表達式求值
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< b > 7.10.< / b >
類型斷言
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< b > 7.11.< / b >
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基於類型斷言識别錯誤類型
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< b > 7.12.< / b >
通過類型斷言査詢接口
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< b > 7.13.< / b >
類型分支
< / a >
< / li >
< li class = "chapter " data-level = "7.14" data-path = "ch7/ch7-14.html" >
< a href = "../ch7/ch7-14.html" >
< i class = "fa fa-check" > < / i >
< b > 7.14.< / b >
示例: 基於標記的XML解碼
< / a >
< / li >
< li class = "chapter " data-level = "7.15" data-path = "ch7/ch7-15.html" >
< a href = "../ch7/ch7-15.html" >
< i class = "fa fa-check" > < / i >
< b > 7.15.< / b >
補充幾點
< / a >
< / li >
< / ul >
< / li >
< li class = "chapter " data-level = "8" data-path = "ch8/ch8.html" >
< a href = "../ch8/ch8.html" >
< i class = "fa fa-check" > < / i >
< b > 8.< / b >
Goroutines和Channels
< / a >
< ul class = "articles" >
< li class = "chapter " data-level = "8.1" data-path = "ch8/ch8-01.html" >
< a href = "../ch8/ch8-01.html" >
< i class = "fa fa-check" > < / i >
< b > 8.1.< / b >
Goroutines
< / a >
< / li >
< li class = "chapter active" data-level = "8.2" data-path = "ch8/ch8-02.html" >
< a href = "../ch8/ch8-02.html" >
< i class = "fa fa-check" > < / i >
< b > 8.2.< / b >
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示例: 併發的Clock服務
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< / a >
< / li >
< li class = "chapter " data-level = "8.3" data-path = "ch8/ch8-03.html" >
< a href = "../ch8/ch8-03.html" >
< i class = "fa fa-check" > < / i >
< b > 8.3.< / b >
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示例: 併發的Echo服務
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< / a >
< / li >
< li class = "chapter " data-level = "8.4" data-path = "ch8/ch8-04.html" >
< a href = "../ch8/ch8-04.html" >
< i class = "fa fa-check" > < / i >
< b > 8.4.< / b >
Channels
< / a >
< / li >
< li class = "chapter " data-level = "8.5" data-path = "ch8/ch8-05.html" >
< a href = "../ch8/ch8-05.html" >
< i class = "fa fa-check" > < / i >
< b > 8.5.< / b >
併行的循環
< / a >
< / li >
< li class = "chapter " data-level = "8.6" data-path = "ch8/ch8-06.html" >
< a href = "../ch8/ch8-06.html" >
< i class = "fa fa-check" > < / i >
< b > 8.6.< / b >
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示例: 併發的Web爬蟲
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< / a >
< / li >
< li class = "chapter " data-level = "8.7" data-path = "ch8/ch8-07.html" >
< a href = "../ch8/ch8-07.html" >
< i class = "fa fa-check" > < / i >
< b > 8.7.< / b >
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基於select的多路複用
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< / a >
< / li >
< li class = "chapter " data-level = "8.8" data-path = "ch8/ch8-08.html" >
< a href = "../ch8/ch8-08.html" >
< i class = "fa fa-check" > < / i >
< b > 8.8.< / b >
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示例: 併發的字典遍歷
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< / a >
< / li >
< li class = "chapter " data-level = "8.9" data-path = "ch8/ch8-09.html" >
< a href = "../ch8/ch8-09.html" >
< i class = "fa fa-check" > < / i >
< b > 8.9.< / b >
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併發的退出
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< / a >
< / li >
< li class = "chapter " data-level = "8.10" data-path = "ch8/ch8-10.html" >
< a href = "../ch8/ch8-10.html" >
< i class = "fa fa-check" > < / i >
< b > 8.10.< / b >
示例: 聊天服務
< / a >
< / li >
< / ul >
< / li >
< li class = "chapter " data-level = "9" data-path = "ch9/ch9.html" >
< a href = "../ch9/ch9.html" >
< i class = "fa fa-check" > < / i >
< b > 9.< / b >
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基於共享變量的併發
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< / a >
< ul class = "articles" >
< li class = "chapter " data-level = "9.1" data-path = "ch9/ch9-01.html" >
< a href = "../ch9/ch9-01.html" >
< i class = "fa fa-check" > < / i >
< b > 9.1.< / b >
競爭條件
< / a >
< / li >
< li class = "chapter " data-level = "9.2" data-path = "ch9/ch9-02.html" >
< a href = "../ch9/ch9-02.html" >
< i class = "fa fa-check" > < / i >
< b > 9.2.< / b >
sync.Mutex互斥鎖
< / a >
< / li >
< li class = "chapter " data-level = "9.3" data-path = "ch9/ch9-03.html" >
< a href = "../ch9/ch9-03.html" >
< i class = "fa fa-check" > < / i >
< b > 9.3.< / b >
sync.RWMutex讀寫鎖
< / a >
< / li >
< li class = "chapter " data-level = "9.4" data-path = "ch9/ch9-04.html" >
< a href = "../ch9/ch9-04.html" >
< i class = "fa fa-check" > < / i >
< b > 9.4.< / b >
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內存同步
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< / a >
< / li >
< li class = "chapter " data-level = "9.5" data-path = "ch9/ch9-05.html" >
< a href = "../ch9/ch9-05.html" >
< i class = "fa fa-check" > < / i >
< b > 9.5.< / b >
sync.Once初始化
< / a >
< / li >
< li class = "chapter " data-level = "9.6" data-path = "ch9/ch9-06.html" >
< a href = "../ch9/ch9-06.html" >
< i class = "fa fa-check" > < / i >
< b > 9.6.< / b >
競爭條件檢測
< / a >
< / li >
< li class = "chapter " data-level = "9.7" data-path = "ch9/ch9-07.html" >
< a href = "../ch9/ch9-07.html" >
< i class = "fa fa-check" > < / i >
< b > 9.7.< / b >
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示例: 併發的非阻塞緩存
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< / a >
< / li >
< li class = "chapter " data-level = "9.8" data-path = "ch9/ch9-08.html" >
< a href = "../ch9/ch9-08.html" >
< i class = "fa fa-check" > < / i >
< b > 9.8.< / b >
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Goroutines和線程
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< / a >
< / li >
< / ul >
< / li >
< li class = "chapter " data-level = "10" data-path = "ch10/ch10.html" >
< a href = "../ch10/ch10.html" >
< i class = "fa fa-check" > < / i >
< b > 10.< / b >
包和工具
< / a >
< ul class = "articles" >
< li class = "chapter " data-level = "10.1" data-path = "ch10/ch10-01.html" >
< a href = "../ch10/ch10-01.html" >
< i class = "fa fa-check" > < / i >
< b > 10.1.< / b >
簡介
< / a >
< / li >
< li class = "chapter " data-level = "10.2" data-path = "ch10/ch10-02.html" >
< a href = "../ch10/ch10-02.html" >
< i class = "fa fa-check" > < / i >
< b > 10.2.< / b >
導入路徑
< / a >
< / li >
< li class = "chapter " data-level = "10.3" data-path = "ch10/ch10-03.html" >
< a href = "../ch10/ch10-03.html" >
< i class = "fa fa-check" > < / i >
< b > 10.3.< / b >
包聲明
< / a >
< / li >
< li class = "chapter " data-level = "10.4" data-path = "ch10/ch10-04.html" >
< a href = "../ch10/ch10-04.html" >
< i class = "fa fa-check" > < / i >
< b > 10.4.< / b >
導入聲明
< / a >
< / li >
< li class = "chapter " data-level = "10.5" data-path = "ch10/ch10-05.html" >
< a href = "../ch10/ch10-05.html" >
< i class = "fa fa-check" > < / i >
< b > 10.5.< / b >
匿名導入
< / a >
< / li >
< li class = "chapter " data-level = "10.6" data-path = "ch10/ch10-06.html" >
< a href = "../ch10/ch10-06.html" >
< i class = "fa fa-check" > < / i >
< b > 10.6.< / b >
包和命名
< / a >
< / li >
< li class = "chapter " data-level = "10.7" data-path = "ch10/ch10-07.html" >
< a href = "../ch10/ch10-07.html" >
< i class = "fa fa-check" > < / i >
< b > 10.7.< / b >
工具
< / a >
< / li >
< / ul >
< / li >
< li class = "chapter " data-level = "11" data-path = "ch11/ch11.html" >
< a href = "../ch11/ch11.html" >
< i class = "fa fa-check" > < / i >
< b > 11.< / b >
測試
< / a >
< ul class = "articles" >
< li class = "chapter " data-level = "11.1" data-path = "ch11/ch11-01.html" >
< a href = "../ch11/ch11-01.html" >
< i class = "fa fa-check" > < / i >
< b > 11.1.< / b >
go test
< / a >
< / li >
< li class = "chapter " data-level = "11.2" data-path = "ch11/ch11-02.html" >
< a href = "../ch11/ch11-02.html" >
< i class = "fa fa-check" > < / i >
< b > 11.2.< / b >
測試函數
< / a >
< / li >
< li class = "chapter " data-level = "11.3" data-path = "ch11/ch11-03.html" >
< a href = "../ch11/ch11-03.html" >
< i class = "fa fa-check" > < / i >
< b > 11.3.< / b >
測試覆蓋率
< / a >
< / li >
< li class = "chapter " data-level = "11.4" data-path = "ch11/ch11-04.html" >
< a href = "../ch11/ch11-04.html" >
< i class = "fa fa-check" > < / i >
< b > 11.4.< / b >
基準測試
< / a >
< / li >
< li class = "chapter " data-level = "11.5" data-path = "ch11/ch11-05.html" >
< a href = "../ch11/ch11-05.html" >
< i class = "fa fa-check" > < / i >
< b > 11.5.< / b >
剖析
< / a >
< / li >
< li class = "chapter " data-level = "11.6" data-path = "ch11/ch11-06.html" >
< a href = "../ch11/ch11-06.html" >
< i class = "fa fa-check" > < / i >
< b > 11.6.< / b >
示例函數
< / a >
< / li >
< / ul >
< / li >
< li class = "chapter " data-level = "12" data-path = "ch12/ch12.html" >
< a href = "../ch12/ch12.html" >
< i class = "fa fa-check" > < / i >
< b > 12.< / b >
反射
< / a >
< ul class = "articles" >
< li class = "chapter " data-level = "12.1" data-path = "ch12/ch12-01.html" >
< a href = "../ch12/ch12-01.html" >
< i class = "fa fa-check" > < / i >
< b > 12.1.< / b >
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爲何需要反射?
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< / a >
< / li >
< li class = "chapter " data-level = "12.2" data-path = "ch12/ch12-02.html" >
< a href = "../ch12/ch12-02.html" >
< i class = "fa fa-check" > < / i >
< b > 12.2.< / b >
reflect.Type和reflect.Value
< / a >
< / li >
< li class = "chapter " data-level = "12.3" data-path = "ch12/ch12-03.html" >
< a href = "../ch12/ch12-03.html" >
< i class = "fa fa-check" > < / i >
< b > 12.3.< / b >
Display遞歸打印
< / a >
< / li >
< li class = "chapter " data-level = "12.4" data-path = "ch12/ch12-04.html" >
< a href = "../ch12/ch12-04.html" >
< i class = "fa fa-check" > < / i >
< b > 12.4.< / b >
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示例: 編碼S表達式
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< / a >
< / li >
< li class = "chapter " data-level = "12.5" data-path = "ch12/ch12-05.html" >
< a href = "../ch12/ch12-05.html" >
< i class = "fa fa-check" > < / i >
< b > 12.5.< / b >
通過reflect.Value脩改值
< / a >
< / li >
< li class = "chapter " data-level = "12.6" data-path = "ch12/ch12-06.html" >
< a href = "../ch12/ch12-06.html" >
< i class = "fa fa-check" > < / i >
< b > 12.6.< / b >
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示例: 解碼S表達式
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< / a >
< / li >
< li class = "chapter " data-level = "12.7" data-path = "ch12/ch12-07.html" >
< a href = "../ch12/ch12-07.html" >
< i class = "fa fa-check" > < / i >
< b > 12.7.< / b >
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獲取結構體字段標識
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< / a >
< / li >
< li class = "chapter " data-level = "12.8" data-path = "ch12/ch12-08.html" >
< a href = "../ch12/ch12-08.html" >
< i class = "fa fa-check" > < / i >
< b > 12.8.< / b >
顯示一個類型的方法集
< / a >
< / li >
< li class = "chapter " data-level = "12.9" data-path = "ch12/ch12-09.html" >
< a href = "../ch12/ch12-09.html" >
< i class = "fa fa-check" > < / i >
< b > 12.9.< / b >
幾點忠告
< / a >
< / li >
< / ul >
< / li >
< li class = "chapter " data-level = "13" data-path = "ch13/ch13.html" >
< a href = "../ch13/ch13.html" >
< i class = "fa fa-check" > < / i >
< b > 13.< / b >
底層編程
< / a >
< ul class = "articles" >
< li class = "chapter " data-level = "13.1" data-path = "ch13/ch13-01.html" >
< a href = "../ch13/ch13-01.html" >
< i class = "fa fa-check" > < / i >
< b > 13.1.< / b >
unsafe.Sizeof, Alignof 和 Offsetof
< / a >
< / li >
< li class = "chapter " data-level = "13.2" data-path = "ch13/ch13-02.html" >
< a href = "../ch13/ch13-02.html" >
< i class = "fa fa-check" > < / i >
< b > 13.2.< / b >
unsafe.Pointer
< / a >
< / li >
< li class = "chapter " data-level = "13.3" data-path = "ch13/ch13-03.html" >
< a href = "../ch13/ch13-03.html" >
< i class = "fa fa-check" > < / i >
< b > 13.3.< / b >
示例: 深度相等判斷
< / a >
< / li >
< li class = "chapter " data-level = "13.4" data-path = "ch13/ch13-04.html" >
< a href = "../ch13/ch13-04.html" >
< i class = "fa fa-check" > < / i >
< b > 13.4.< / b >
通過cgo調用C代碼
< / a >
< / li >
< li class = "chapter " data-level = "13.5" data-path = "ch13/ch13-05.html" >
< a href = "../ch13/ch13-05.html" >
< i class = "fa fa-check" > < / i >
< b > 13.5.< / b >
幾點忠告
< / a >
< / li >
< / ul >
< / li >
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< li class = "chapter " data-level = "14" data-path = "CONTRIBUTORS.html" >
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< a href = "../CONTRIBUTORS.html" >
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< i class = "fa fa-check" > < / i >
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< b > 14.< / b >
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附録
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< / a >
< / li >
< li class = "divider" > < / li >
< li >
< a href = "https://www.gitbook.com" target = "blank" class = "gitbook-link" >
本書使用 GitBook 釋出
< / a >
< / li >
< / ul >
< / nav >
< / div >
< div class = "book-body" >
< div class = "body-inner" >
< div class = "book-header" role = "navigation" >
<!-- Actions Left -->
<!-- Title -->
< h1 >
< i class = "fa fa-circle-o-notch fa-spin" > < / i >
< a href = "../" > Go编程语言< / a >
< / h1 >
< / div >
< div class = "page-wrapper" tabindex = "-1" role = "main" >
< div class = "page-inner" >
< section class = "normal" id = "section-" >
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< h2 id = "82-示例-併發的clock服務" > 8.2. 示 例 : 併 發 的 Clock服 務 < / h2 >
< p > 網 絡 編 程 是 併 發 大 顯 身 手 的 一 個 領 域 ， 由 於 服 務 器 是 最 典 型 的 需 要 同 時 處 理 很 多 連 接 的 程 序 ， 這 些 連 接 一 般 來 自 遠 彼 此 獨 立 的 客 戶 端 。 在 本 小 節 中 ， 我 們 會 講 解 go語 言 的 net包 ， 這 個 包 提 供 編 寫 一 個 網 絡 客 戶 端 或 者 服 務 器 程 序 的 基 本 組 件 ， 無 論 兩 者 間 通 信 是 使 用 TCP， UDP或 者 Unix domain sockets。 在 第 一 章 中 我 們 已 經 使 用 過 的 net/http包 里 的 方 法 ， 也 算 是 net包 的 一 部 分 。 < / p >
< p > 我 們 的 第 一 個 例 子 是 一 個 順 序 執 行 的 時 鐘 服 務 器 ， 它 會 每 隔 一 秒 鐘 將 當 前 時 間 寫 到 客 戶 端 ： < / p >
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< pre > < code class = "lang-go" > gopl.io/ch8/clock1
< span class = "hljs-comment" > // Clock1 is a TCP server that periodically writes the time.< / span >
< span class = "hljs-keyword" > package< / span > main
< span class = "hljs-keyword" > import< / span > (
< span class = "hljs-string" > " io" < / span >
< span class = "hljs-string" > " log" < / span >
< span class = "hljs-string" > " net" < / span >
< span class = "hljs-string" > " time" < / span >
)
< span class = "hljs-keyword" > func< / span > main() {
listener, err := net.Listen(< span class = "hljs-string" > " tcp" < / span > , < span class = "hljs-string" > " localhost:8000" < / span > )
< span class = "hljs-keyword" > if< / span > err != < span class = "hljs-constant" > nil< / span > {
log.Fatal(err)
}
< span class = "hljs-keyword" > for< / span > {
conn, err := listener.Accept()
< span class = "hljs-keyword" > if< / span > err != < span class = "hljs-constant" > nil< / span > {
log.Print(err) < span class = "hljs-comment" > // e.g., connection aborted< / span >
< span class = "hljs-keyword" > continue< / span >
}
handleConn(conn) < span class = "hljs-comment" > // handle one connection at a time< / span >
}
}
< span class = "hljs-keyword" > func< / span > handleConn(c net.Conn) {
< span class = "hljs-keyword" > defer< / span > c.Close()
< span class = "hljs-keyword" > for< / span > {
_, err := io.WriteString(c, time.Now().Format(< span class = "hljs-string" > " 15:04:05\n" < / span > ))
< span class = "hljs-keyword" > if< / span > err != < span class = "hljs-constant" > nil< / span > {
< span class = "hljs-keyword" > return< / span > < span class = "hljs-comment" > // e.g., client disconnected< / span >
}
time.Sleep(< span class = "hljs-number" > 1< / span > * time.Second)
}
}
< / code > < / pre >
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< p > Listen函 數 創 建 了 一 個 net.Listener的 對 象 ， 這 個 對 象 會 監 聽 一 個 網 絡 端 口 上 到 來 的 連 接 ， 在 這 個 例 子 里 我 們 用 的 是 TCP的 localhost:8000端 口 。 listener對 象 的 Accept方 法 會 直 接 阻 塞 ， 直 到 一 個 新 的 連 接 被 創 建 ， 然 後 會 返 迴 一 個 net.Conn對 象 來 表 示 這 個 連 接 。 < / p >
< p > handleConn函 數 會 處 理 一 個 完 整 的 客 戶 端 連 接 。 在 一 個 for死 循 環 中 ， 將 當 前 的 時 候 用 time.Now()函 數 得 到 ， 然 後 寫 到 客 戶 端 。 由 於 net.Conn實 現 了 io.Writer接 口 ， 我 們 可 以 直 接 向 其 寫 入 內 容 。 這 個 死 循 環 會 一 直 執 行 ， 直 到 寫 入 失 敗 。 最 可 能 的 原 因 是 客 戶 端 主 動 斷 開 連 接 。 這 種 情 況 下 handleConn函 數 會 用 defer調 用 關 閉 服 務 器 側 的 連 接 ， 然 後 返 迴 到 主 函 數 ， 繼 續 等 待 下 一 個 連 接 請 求 。 < / p >
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< p > time.Time.Format方 法 提 供 了 一 種 格 式 化 日 期 和 時 間 信 息 的 方 式 。 它 的 參 數 是 一 個 格 式 化 模 闆 標 識 如 何 來 格 式 化 時 間 ， 而 這 個 格 式 化 模 闆 限 定 爲 Mon Jan 2 03:04:05PM 2006 UTC-0700。 有 8個 部 分 (週 幾 ， 月 份 ， 一 個 月 的 第 幾 天 ， 等 等 )。 可 以 以 任 意 的 形 式 來 組 合 前 面 這 個 模 闆 ； 出 現 在 模 闆 中 的 部 分 會 作 爲 參 考 來 對 時 間 格 式 進 行 輸 出 。 在 上 面 的 例 子 中 我 們 隻 用 到 了 小 時 、 分 鐘 和 秒 。 time包 里 定 義 了 很 多 標 準 時 間 格 式 ， 比 如 time.RFC1123。 在 進 行 格 式 化 的 逆 向 操 作 time.Parse時 ， 也 會 用 到 同 樣 的 策 略 。 (譯 註 ： 這 是 go語 言 和 其 它 語 言 相 比 比 較 奇 葩 的 一 個 地 方 。 。 你 需 要 記 住 格 式 化 字 符 串 是 1月 2日 下 午 3點 4分 5秒 零 六 年 UTC-0700， 而 不 像 其 它 語 言 那 樣 Y-m-d H:i:s一 樣 ， 當 然 了 這 里 可 以 用 1234567的 方 式 來 記 憶 ， 倒 是 也 不 麻 煩 )< / p >
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< p > 爲 了 連 接 例 子 里 的 服 務 器 ， 我 們 需 要 一 個 客 戶 端 程 序 ， 比 如 netcat這 個 工 具 (nc命 令 )， 這 個 工 具 可 以 用 來 執 行 網 絡 連 接 操 作 。 < / p >
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< pre > < code > $ go build gopl.io/ch8/clock1
$ ./clock1 &
$ nc localhost 8000
13:58:54
13:58:55
13:58:56
13:58:57
^C
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< / code > < / pre > < p > 客 戶 端 將 服 務 器 發 來 的 時 間 顯 示 了 出 來 ， 我 們 用 Control+C來 中 斷 客 戶 端 的 執 行 ， 在 Unix繫 統 上 ， 你 會 看 到 ^C這 樣 的 響 應 。 如 果 你 的 繫 統 沒 有 裝 nc這 個 工 具 ， 你 可 以 用 telnet來 實 現 同 樣 的 效 果 ， 或 者 也 可 以 用 我 們 下 面 的 這 個 用 go寫 的 簡 單 的 telnet程 序 ， 用 net.Dial就 可 以 簡 單 地 創 建 一 個 TCP連 接 ： < / p >
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< pre > < code class = "lang-go" > gopl.io/ch8/netcat1
< span class = "hljs-comment" > // Netcat1 is a read-only TCP client.< / span >
< span class = "hljs-keyword" > package< / span > main
< span class = "hljs-keyword" > import< / span > (
< span class = "hljs-string" > " io" < / span >
< span class = "hljs-string" > " log" < / span >
< span class = "hljs-string" > " net" < / span >
< span class = "hljs-string" > " os" < / span >
)
< span class = "hljs-keyword" > func< / span > main() {
conn, err := net.Dial(< span class = "hljs-string" > " tcp" < / span > , < span class = "hljs-string" > " localhost:8000" < / span > )
< span class = "hljs-keyword" > if< / span > err != < span class = "hljs-constant" > nil< / span > {
log.Fatal(err)
}
< span class = "hljs-keyword" > defer< / span > conn.Close()
mustCopy(os.Stdout, conn)
}
< span class = "hljs-keyword" > func< / span > mustCopy(dst io.Writer, src io.Reader) {
< span class = "hljs-keyword" > if< / span > _, err := io.Copy(dst, src); err != < span class = "hljs-constant" > nil< / span > {
log.Fatal(err)
}
}
< / code > < / pre >
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< p > 這 個 程 序 會 從 連 接 中 讀 取 數 據 ， 併 將 讀 到 的 內 容 寫 到 標 準 輸 出 中 ， 直 到 遇 到 end of file的 條 件 或 者 發 生 錯 誤 。 mustCopy這 個 函 數 我 們 在 本 節 的 幾 個 例 子 中 都 會 用 到 。 讓 我 們 同 時 運 行 兩 個 客 戶 端 來 進 行 一 個 測 試 ， 這 里 可 以 開 兩 個 終 端 窗 口 ， 下 面 左 邊 的 是 其 中 的 一 個 的 輸 出 ， 右 邊 的 是 另 一 個 的 輸 出 ： < / p >
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< 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
< / code > < / pre > < p > killall命 令 是 一 個 Unix命 令 行 工 具 ， 可 以 用 給 定 的 進 程 名 來 殺 掉 所 有 名 字 匹 配 的 進 程 。 < / p >
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< p > 第 二 個 客 戶 端 必 鬚 等 待 第 一 個 客 戶 端 完 成 工 作 ， 這 樣 服 務 端 才 能 繼 續 向 後 執 行 ； 因 爲 我 們 這 里 的 服 務 器 程 序 同 一 時 間 隻 能 處 理 一 個 客 戶 端 連 接 。 我 們 這 里 對 服 務 端 程 序 做 一 點 小 改 動 ， 使 其 支 持 併 發 ： 在 handleConn函 數 調 用 的 地 方 增 加 go關 鍵 字 ， 讓 每 一 次 handleConn的 調 用 都 進 入 一 個 獨 立 的 goroutine。 < / p >
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< pre > < code class = "lang-go" > gopl.io/ch8/clock2
< span class = "hljs-keyword" > for< / span > {
conn, err := listener.Accept()
< span class = "hljs-keyword" > if< / span > err != < span class = "hljs-constant" > nil< / span > {
log.Print(err) < span class = "hljs-comment" > // e.g., connection aborted< / span >
< span class = "hljs-keyword" > continue< / span >
}
< span class = "hljs-keyword" > go< / span > handleConn(conn) < span class = "hljs-comment" > // handle connections concurrently< / span >
}
< / code > < / pre >
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< p > 現 在 多 個 客 戶 端 可 以 同 時 接 收 到 時 間 了 ： < / p >
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< pre > < code > $ go build gopl.io/ch8/clock2
$ ./clock2 &
$ 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
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< / code > < / pre > < p > 練 習 8.1: 脩 改 clock2來 支 持 傳 入 參 數 作 爲 端 口 號 ， 然 後 寫 一 個 clockwall的 程 序 ， 這 個 程 序 可 以 同 時 與 多 個 clock服 務 器 通 信 ， 從 多 服 務 器 中 讀 取 時 間 ， 併 且 在 一 個 表 格 中 一 次 顯 示 所 有 服 務 傳 迴 的 結 果 ， 類 似 於 你 在 某 些 辦 公 室 里 看 到 的 時 鐘 牆 。 如 果 你 有 地 理 學 上 分 布 式 的 服 務 器 可 以 用 的 話 ， 讓 這 些 服 務 器 跑 在 不 同 的 機 器 上 面 ； 或 者 在 同 一 台 機 器 上 跑 多 個 不 同 的 實 例 ， 這 些 實 例 監 聽 不 同 的 端 口 ， 假 裝 自 己 在 不 同 的 時 區 。 像 下 面 這 樣 ： < / p >
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< pre > < code > $ TZ=US/Eastern ./clock2 -port 8010 &
$ TZ=Asia/Tokyo ./clock2 -port 8020 &
$ TZ=Europe/London ./clock2 -port 8030 &
$ clockwall NewYork=localhost:8010 London=localhost:8020 Tokyo=localhost:8030
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< / code > < / pre > < p > 練 習 8.2: 實 現 一 個 併 發 FTP服 務 器 。 服 務 器 應 該 解 析 客 戶 端 來 的 一 些 命 令 ， 比 如 cd命 令 來 切 換 目 録 ， ls來 列 出 目 録 內 文 件 ， get和 send來 傳 輸 文 件 ， close來 關 閉 連 接 。 你 可 以 用 標 準 的 ftp命 令 來 作 爲 客 戶 端 ， 或 者 也 可 以 自 己 實 現 一 個 。 < / p >
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< / section >
< / div >
< / div >
< / div >
< a href = "../ch8/ch8-01.html" class = "navigation navigation-prev " aria-label = "Previous page: Goroutines" > < i class = "fa fa-angle-left" > < / i > < / a >
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< a href = "../ch8/ch8-03.html" class = "navigation navigation-next " aria-label = "Next page: 示例: 併發的Echo服務" > < i class = "fa fa-angle-right" > < / i > < / a >
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< / div >
< / div >
< script src = "../gitbook/app.js" > < / script >
< script src = "../gitbook/plugins/gitbook-plugin-sharing/buttons.js" > < / script >
< script src = "../gitbook/plugins/gitbook-plugin-fontsettings/buttons.js" > < / script >
< script >
require(["gitbook"], function(gitbook) {
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var config = {"katex":{},"highlight":{},"sharing":{"facebook":true,"twitter":true,"google":false,"weibo":false,"instapaper":false,"vk":false,"all":["facebook","google","twitter","weibo","instapaper"]},"fontsettings":{"theme":"white","family":"sans","size":2}};
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gitbook.start(config);
});
< / script >
< / body >
< / html >
