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2023-06-26 17:30:52 +00:00
< ol class = "chapter" > < li class = "chapter-item expanded affix " > < a href = "../index.html" > Go语言圣经< / a > < / li > < li class = "chapter-item expanded affix " > < a href = "../preface-zh.html" > 译者序< / a > < / li > < li class = "chapter-item expanded affix " > < 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 > < 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 > < li class = "chapter-item expanded " > < a href = "../ch2/ch2.html" > < strong aria-hidden = "true" > 2.< / strong > 程序结构< / a > < / li > < 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 > < li class = "chapter-item expanded " > < a href = "../ch3/ch3.html" > < strong aria-hidden = "true" > 3.< / strong > 基础数据类型< / a > < / li > < 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 > < li class = "chapter-item expanded " > < a href = "../ch4/ch4.html" > < strong aria-hidden = "true" > 4.< / strong > 复合数据类型< / a > < / li > < 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< /
2022-08-04 06:59:33 +00:00
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2023-06-26 17:46:27 +00:00
< li > < em > 凹语言(专为 WebAssembly 设计): < a href = "https://github.com/wa-lang/wa" > https://github.com/wa-lang/wa< / a > < / em > < / li >
< li > < em > KCL 配置语言(Rust): < a href = "https://github.com/kcl-lang/kcl" > https://github.com/kcl-lang/kcl< / a > < / em > < / li >
< / ul >
2022-08-04 06:59:33 +00:00
< hr >
< h2 id = "83-示例-并发的echo服务" > < a class = "header" href = "#83-示例-并发的echo服务" > 8.3. 示例: 并发的Echo服务< / a > < / h2 >
< p > clock服务器每一个连接都会起一个goroutine。在本节中我们会创建一个echo服务器, 这个服务在每个连接中会有多个goroutine。大多数echo服务仅仅会返回他们读取到的内容, 就像下面这个简单的handleConn函数所做的一样: < / p >
< pre > < code class = "language-go" > func handleConn(c net.Conn) {
io.Copy(c, c) // NOTE: ignoring errors
c.Close()
}
< / code > < / pre >
< p > 一个更有意思的echo服务应该模拟一个实际的echo的“回响”, 并且一开始要用大写HELLO来表示“声音很大”, 之后经过一小段延迟返回一个有所缓和的Hello, 然后一个全小写字母的hello表示声音渐渐变小直至消失, 像下面这个版本的handleConn(译注:笑看作者脑洞大开): < / p >
< p > < u > < i > gopl.io/ch8/reverb1< / i > < / u > < / p >
< pre > < code class = "language-go" > func echo(c net.Conn, shout string, delay time.Duration) {
fmt.Fprintln(c, " \t" , strings.ToUpper(shout))
time.Sleep(delay)
fmt.Fprintln(c, " \t" , shout)
time.Sleep(delay)
fmt.Fprintln(c, " \t" , strings.ToLower(shout))
}
func handleConn(c net.Conn) {
input := bufio.NewScanner(c)
for input.Scan() {
echo(c, input.Text(), 1*time.Second)
}
// NOTE: ignoring potential errors from input.Err()
c.Close()
}
< / code > < / pre >
< p > 我们需要升级我们的客户端程序,这样它就可以发送终端的输入到服务器,并把服务端的返回输出到终端上,这使我们有了使用并发的另一个好机会:< / p >
< p > < u > < i > gopl.io/ch8/netcat2< / i > < / u > < / p >
< pre > < code class = "language-go" > func main() {
conn, err := net.Dial(" tcp" , " localhost:8000" )
if err != nil {
log.Fatal(err)
}
defer conn.Close()
go mustCopy(os.Stdout, conn)
mustCopy(conn, os.Stdin)
}
< / code > < / pre >
< p > 当main goroutine从标准输入流中读取内容并将其发送给服务器时, 另一个goroutine会读取并打印服务端的响应。当main goroutine碰到输入终止时, 例如, 用户在终端中按了Control-D(^D), 在windows上是Control-Z, 这时程序就会被终止, 尽管其它goroutine中还有进行中的任务。( 在8.4.1中引入了channels后我们会明白如何让程序等待两边都结束。) < / p >
< p > 下面这个会话中,客户端的输入是左对齐的,服务端的响应会用缩进来区别显示。
客户端会向服务器“喊三次话”:< / p >
< pre > < code > $ go build gopl.io/ch8/reverb1
$ ./reverb1 &
$ go build gopl.io/ch8/netcat2
$ ./netcat2
Hello?
HELLO?
Hello?
hello?
Is there anybody there?
IS THERE ANYBODY THERE?
Yooo-hooo!
Is there anybody there?
is there anybody there?
YOOO-HOOO!
Yooo-hooo!
yooo-hooo!
^D
$ killall reverb1
< / code > < / pre >
< p > 注意客户端的第三次shout在前一个shout处理完成之前一直没有被处理, 这貌似看起来不是特别“现实”。真实世界里的回响应该是会由三次shout的回声组合而成的。为了模拟真实世界的回响, 我们需要更多的goroutine来做这件事情。这样我们就再一次地需要go这个关键词了, 这次我们用它来调用echo: < / p >
< p > < u > < i > gopl.io/ch8/reverb2< / i > < / u > < / p >
< pre > < code class = "language-go" > func handleConn(c net.Conn) {
input := bufio.NewScanner(c)
for input.Scan() {
go echo(c, input.Text(), 1*time.Second)
}
// NOTE: ignoring potential errors from input.Err()
c.Close()
}
< / code > < / pre >
< p > go后跟的函数的参数会在go语句自身执行时被求值; 因此input.Text()会在main goroutine中被求值。
现在回响是并发并且会按时间来覆盖掉其它响应了:< / p >
< pre > < code > $ go build gopl.io/ch8/reverb2
$ ./reverb2 &
$ ./netcat2
Is there anybody there?
IS THERE ANYBODY THERE?
Yooo-hooo!
Is there anybody there?
YOOO-HOOO!
is there anybody there?
Yooo-hooo!
yooo-hooo!
^D
$ killall reverb2
< / code > < / pre >
< p > 让服务使用并发不只是处理多个客户端的请求, 甚至在处理单个连接时也可能会用到, 就像我们上面的两个go关键词的用法。然而在我们使用go关键词的同时, 需要慎重地考虑net.Conn中的方法在并发地调用时是否安全, 事实上对于大多数类型来说也确实不安全。我们会在下一章中详细地探讨并发安全性。< / p >
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