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< div class = "book" data-level = "8.10" data-chapter-title = "示例: 聊天服務" data-filepath = "ch8/ch8-10.md" data-basepath = ".." data-revision = "Thu Dec 24 2015 14:42:02 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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< / li >
< li class = "chapter " data-level = "1.4" data-path = "ch1/ch1-04.html" >
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< b > 1.4.< / b >
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GIF動畵
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< b > 1.5.< / b >
穫取URL
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< b > 1.6.< / b >
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併發穫取多個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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< / a >
< ul class = "articles" >
< li class = "chapter " data-level = "4.1" data-path = "ch4/ch4-01.html" >
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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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< a href = "../ch4/ch4-06.html" >
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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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< li class = "chapter " data-level = "5.3" data-path = "ch5/ch5-03.html" >
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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" >
< a href = "../ch5/ch5-04.html" >
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< b > 5.4.< / b >
錯誤
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< li class = "chapter " data-level = "5.5" data-path = "ch5/ch5-05.html" >
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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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< b > 5.8.< / b >
Deferred函數
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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" >
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< b > 5.10.< / b >
Recover捕穫異常
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< b > 6.< / b >
方法
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< li class = "chapter " data-level = "6.1" data-path = "ch6/ch6-01.html" >
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< b > 6.1.< / b >
方法聲明
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< a href = "../ch6/ch6-02.html" >
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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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< li class = "chapter " data-level = "6.5" data-path = "ch6/ch6-05.html" >
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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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< li class = "chapter " data-level = "7.2" data-path = "ch7/ch7-02.html" >
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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
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< 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 " 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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併發的退齣
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< / a >
< / li >
< li class = "chapter active" 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 >
穫取結構體字段標識
< / 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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2015-12-24 06:47:06 +00:00
< 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-" >
< h2 id = "810-示例-聊天服務" > 8.10. 示 例 : 聊 天 服 務 < / h2 >
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< p > 我 們 用 一 個 聊 天 服 務 器 來 終 結 本 章 節 的 內 容 ， 這 個 程 序 可 以 讓 一 些 用 戶 通 過 服 務 器 向 其 它 所 有 用 戶 廣 播 文 本 消 息 。 這 個 程 序 中 有 四 種 goroutine。 main和 broadcaster各 自 是 一 個 goroutine實 例 ， 每 一 個 客 戶 端 的 連 接 都 會 有 一 個 handleConn和 clientWriter的 goroutine。 broadcaster是 select用 法 的 不 錯 的 樣 例 ， 因 爲 它 需 要 處 理 三 種 不 同 類 型 的 消 息 。
下 面 演 示 的 main goroutine的 工 作 ， 是 listen和 accept(譯 註 ： 網 絡 編 程 里 的 概 念 )從 客 戶 端 過 來 的 連 接 。 對 每 一 個 連 接 ， 程 序 都 會 建 立 一 個 新 的 handleConn的 goroutine， 就 像 我 們 在 本 章 開 頭 的 併 發 的 echo服 務 器 里 所 做 的 那 樣 。 < / p >
< pre > < code class = "lang-go" > gopl.io/ch8/chat
< 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" > go< / span > broadcaster()
< 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-keyword" > continue< / span >
}
< span class = "hljs-keyword" > go< / span > handleConn(conn)
}
}
< / code > < / pre >
< p > 然 後 是 broadcaster的 goroutine。 他 的 內 部 變 量 clients會 記 録 當 前 建 立 連 接 的 客 戶 端 集 合 。 其 記 録 的 內 容 是 每 一 個 客 戶 端 的 消 息 發 齣 channel的 " 資 格 " 信 息 。 < / p >
< pre > < code class = "lang-go" > < span class = "hljs-keyword" > type< / span > client < span class = "hljs-keyword" > chan< / span > < - < span class = "hljs-typename" > string< / span > < span class = "hljs-comment" > // an outgoing message channel< / span >
< span class = "hljs-keyword" > var< / span > (
entering = < span class = "hljs-built_in" > make< / span > (< span class = "hljs-keyword" > chan< / span > client)
leaving = < span class = "hljs-built_in" > make< / span > (< span class = "hljs-keyword" > chan< / span > client)
messages = < span class = "hljs-built_in" > make< / span > (< span class = "hljs-keyword" > chan< / span > < span class = "hljs-typename" > string< / span > ) < span class = "hljs-comment" > // all incoming client messages< / span >
)
< span class = "hljs-keyword" > func< / span > broadcaster() {
clients := < span class = "hljs-built_in" > make< / span > (< span class = "hljs-keyword" > map< / span > [client]< span class = "hljs-typename" > bool< / span > ) < span class = "hljs-comment" > // all connected clients< / span >
< span class = "hljs-keyword" > for< / span > {
< span class = "hljs-keyword" > select< / span > {
< span class = "hljs-keyword" > case< / span > msg := < -messages:
< span class = "hljs-comment" > // Broadcast incoming message to all< / span >
< span class = "hljs-comment" > // clients' outgoing message channels.< / span >
< span class = "hljs-keyword" > for< / span > cli := < span class = "hljs-keyword" > range< / span > clients {
cli < - msg
}
< span class = "hljs-keyword" > case< / span > cli := < -entering:
clients[cli] = < span class = "hljs-constant" > true< / span >
< span class = "hljs-keyword" > case< / span > cli := < -leaving:
< span class = "hljs-built_in" > delete< / span > (clients, cli)
< span class = "hljs-built_in" > close< / span > (cli)
}
}
}
< / code > < / pre >
< p > broadcaster監 聽 來 自 全 局 的 entering和 leaving的 channel來 穫 知 客 戶 端 的 到 來 和 離 開 事 件 。 當 其 接 收 到 其 中 的 一 個 事 件 時 ， 會 更 新 clients集 合 ， 當 該 事 件 是 離 開 行 爲 時 ， 它 會 關 閉 客 戶 端 的 消 息 發 齣 channel。 broadcaster也 會 監 聽 全 局 的 消 息 channel， 所 有 的 客 戶 端 都 會 向 這 個 channel中 發 送 消 息 。 當 broadcaster接 收 到 什 麽 消 息 時 ， 就 會 將 其 廣 播 至 所 有 連 接 到 服 務 端 的 客 戶 端 。 < / p >
< p > 現 在 讓 我 們 看 看 每 一 個 客 戶 端 的 goroutine。 handleConn函 數 會 爲 它 的 客 戶 端 創 建 一 個 消 息 發 齣 channel併 通 過 entering channel來 通 知 客 戶 端 的 到 來 。 然 後 它 會 讀 取 客 戶 端 發 來 的 每 一 行 文 本 ， 併 通 過 全 局 的 消 息 channel來 將 這 些 文 本 發 送 齣 去 ， 併 爲 每 條 消 息 帶 上 發 送 者 的 前 綴 來 標 明 消 息 身 份 。 當 客 戶 端 發 送 完 畢 後 ， handleConn會 通 過 leaving這 個 channel來 通 知 客 戶 端 的 離 開 併 關 閉 連 接 。 < / p >
< pre > < code class = "lang-go" > < span class = "hljs-keyword" > func< / span > handleConn(conn net.Conn) {
ch := < span class = "hljs-built_in" > make< / span > (< span class = "hljs-keyword" > chan< / span > < span class = "hljs-typename" > string< / span > ) < span class = "hljs-comment" > // outgoing client messages< / span >
< span class = "hljs-keyword" > go< / span > clientWriter(conn, ch)
who := conn.RemoteAddr().String()
ch < - < span class = "hljs-string" > " You are " < / span > + who
messages < - who + < span class = "hljs-string" > " has arrived" < / span >
entering < - ch
input := bufio.NewScanner(conn)
< span class = "hljs-keyword" > for< / span > input.Scan() {
messages < - who + < span class = "hljs-string" > " : " < / span > + input.Text()
}
< span class = "hljs-comment" > // < span class = "hljs-doctag" > NOTE:< / span > ignoring potential errors from input.Err()< / span >
leaving < - ch
messages < - who + < span class = "hljs-string" > " has left" < / span >
conn.Close()
}
< span class = "hljs-keyword" > func< / span > clientWriter(conn net.Conn, ch < -< span class = "hljs-keyword" > chan< / span > < span class = "hljs-typename" > string< / span > ) {
< span class = "hljs-keyword" > for< / span > msg := < span class = "hljs-keyword" > range< / span > ch {
fmt.Fprintln(conn, msg) < span class = "hljs-comment" > // < span class = "hljs-doctag" > NOTE:< / span > ignoring network errors< / span >
}
}
< / code > < / pre >
< p > 另 外 ， handleConn爲 每 一 個 客 戶 端 創 建 了 一 個 clientWriter的 goroutine來 接 收 向 客 戶 端 發 齣 消 息 channel中 發 送 的 廣 播 消 息 ， 併 將 它 們 寫 入 到 客 戶 端 的 網 絡 連 接 。 客 戶 端 的 讀 取 方 循 環 會 在 broadcaster接 收 到 leaving通 知 併 關 閉 了 channel後 終 止 。 < / p >
< p > 下 面 演 示 的 是 當 服 務 器 有 兩 個 活 動 的 客 戶 端 連 接 ， 併 且 在 兩 個 窗 口 中 運 行 的 情 況 ， 使 用 netcat來 聊 天 ： < / p >
< pre > < code > $ go build gopl.io/ch8/chat
$ go build gopl.io/ch8/netcat3
$ ./chat &
$ ./netcat3
You are 127.0.0.1:64208 $ ./netcat3
127.0.0.1:64211 has arrived You are 127.0.0.1:64211
Hi!
127.0.0.1:64208: Hi!
127.0.0.1:64208: Hi!
Hi yourself.
127.0.0.1:64211: Hi yourself. 127.0.0.1:64211: Hi yourself.
^C
127.0.0.1:64208 has left
$ ./netcat3
You are 127.0.0.1:64216 127.0.0.1:64216 has arrived
Welcome.
127.0.0.1:64211: Welcome. 127.0.0.1:64211: Welcome.
^C
127.0.0.1:64211 has left”
< / code > < / pre > < p > 當 與 n個 客 戶 端 保 持 聊 天 session時 ， 這 個 程 序 會 有 2n+2個 併 發 的 goroutine， 然 而 這 個 程 序 卻 併 不 需 要 顯 式 的 鎖 (§ 9.2)。 clients這 個 map被 限 製 在 了 一 個 獨 立 的 goroutine中 ， broadcaster， 所 以 它 不 能 被 併 發 地 訪 問 。 多 個 goroutine共 享 的 變 量 隻 有 這 些 channel和 net.Conn的 實 例 ， 兩 個 東 西 都 是 併 發 安 全 的 。 我 們 會 在 下 一 章 中 更 多 地 解 決 約 束 ， 併 發 安 全 以 及 goroutine中 共 享 變 量 的 含 義 。 < / p >
< p > 練 習 8.12: 使 broadcaster能 夠 將 arrival事 件 通 知 當 前 所 有 的 客 戶 端 。 爲 了 達 成 這 個 目 的 ， 你 需 要 有 一 個 客 戶 端 的 集 合 ， 併 且 在 entering和 leaving的 channel中 記 録 客 戶 端 的 名 字 。
練 習 8.13: 使 聊 天 服 務 器 能 夠 斷 開 空 閒 的 客 戶 端 連 接 ， 比 如 最 近 五 分 鐘 之 後 沒 有 發 送 任 何 消 息 的 那 些 客 戶 端 。 提 示 ： 可 以 在 其 它 goroutine中 調 用 conn.Close()來 解 除 Read調 用 ， 就 像 input.Scanner()所 做 的 那 樣 。
練 習 8.14: 脩 改 聊 天 服 務 器 的 網 絡 協 議 這 樣 每 一 個 客 戶 端 就 可 以 在 entering時 可 以 提 供 它 們 的 名 字 。 將 消 息 前 綴 由 之 前 的 網 絡 地 址 改 爲 這 個 名 字 。
練 習 8.15: 如 果 一 個 客 戶 端 沒 有 及 時 地 讀 取 數 據 可 能 會 導 致 所 有 的 客 戶 端 被 阻 塞 。 脩 改 broadcaster來 跳 過 一 條 消 息 ， 而 不 是 等 待 這 個 客 戶 端 一 直 到 其 準 備 好 寫 。 或 者 爲 每 一 個 客 戶 端 的 消 息 發 齣 channel建 立 緩 衝 區 ， 這 樣 大 部 分 的 消 息 便 不 會 被 丟 掉 ； broadcaster應 該 用 一 個 非 阻 塞 的 send向 這 個 channel中 發 消 息 。 < / p >
2015-12-09 07:57:17 +00:00
< / section >
< / div >
< / div >
< / div >
2015-12-21 04:55:18 +00:00
< a href = "../ch8/ch8-09.html" class = "navigation navigation-prev " aria-label = "Previous page: 併發的退齣" > < i class = "fa fa-angle-left" > < / i > < / a >
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< a href = "../ch9/ch9.html" class = "navigation navigation-next " aria-label = "Next page: 基於共享變量的併發" > < 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-search/lunr.min.js" > < / script >
< script src = "../gitbook/plugins/gitbook-plugin-search/search.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) {
var config = {"highlight":{},"search":{},"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}};
gitbook.start(config);
});
< / script >
< / body >
< / html >
