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Golang websocket

WBOY

发布： 2024-02-05 21:18:03

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golang websocket

问题内容

谁能帮忙解释一下下面的代码片段的含义吗？

var partner = make(chan io.ReadWriteCloser)

func match(c io.ReadWriteCloser) {
    fmt.Fprintln(c, "Waiting for a partner...")
    select {
    case partner <- c:
        // handled by the other goroutine
    case p := <-partner:
        chat(p, c)
    }
}

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完整版：

package main

import (
    "fmt"
    "golang.org/x/net/websocket"
    "html/template"
    "io"
    "log"
    "net/http"
)

const listenAddr = "localhost:4000"

type socket struct {
    conn *websocket.Conn
    done chan bool
}

func (s socket) Read(b []byte) (int, error) {
    return s.conn.Read(b)
}

func (s socket) Write(b []byte) (int, error) {
    return s.conn.Write(b)
}

func (s socket) Close() error {
    s.done <- true
    return nil
}

var rootTemplate = template.Must(template.New("root").Parse(`
<!DOCTYPE html>
<html>
    <head>
        <title>Websocket Chat - Golang</title>
        <meta charset="UTF-8"/>
        <script>
            var input, output, websocket;

            function showMessage(msg) {
                var p = document.createElement("p");
                p.innerHTML = msg;
                output.appendChild(p);
            }
        
            function onMessage(e) {
                showMessage(e.data);
            }
            
            function onClose() {
                showMessage("Connection closed.");
            }
            
            function onKeyUp(e) {
                if (e.keyCode === 13) {
                    sendMessage();
                }
            }
            
            function sendMessage() {
                var msg = input.value;
                input.value = "";
                websocket.send(msg + "\n");
                showMessage(msg);
            }
            
            function init() {
                input = document.getElementById("input");
                input.addEventListener("keyup", onKeyUp, false);
                output = document.getElementById("output");
                websocket = new WebSocket("ws://{{.}}/socket");
                websocket.onmessage = onMessage;
                websocket.onclose = onClose;
            }
            
            window.addEventListener("load", init);
        </script>
    </head>
    <body>
        Say: <input id="input" type="text"/>
        <div id="output"></div>
    </body>
</html>
`))

func rootHandler(w http.ResponseWriter, r *http.Request) {
    rootTemplate.Execute(w, listenAddr)
}

func socketHandler(conn *websocket.Conn) {
    s := socket{conn: conn, done: make(chan bool)}
    go match(s)
    <-s.done
}

var partner = make(chan io.ReadWriteCloser)

func match(c io.ReadWriteCloser) {
    fmt.Fprintln(c, "Waiting for a partner...")
    select {
    case partner <- c:
        // handled by the other goroutine
    case p := <-partner:
        chat(p, c)
    }
}

func chat(a, b io.ReadWriteCloser) {
    fmt.Fprintln(a, "Found one! Say hi.")
    fmt.Fprintln(b, "Found one! Say hi.")
    errc := make(chan error, 1)
    go cp(a, b, errc)
    go cp(b, a, errc)
    if err := <-errc; err != nil {
        log.Println(err)
    }
    a.Close()
    b.Close()
    go io.Copy(b, a)
    io.Copy(a, b)
}

func cp(w io.Writer, r io.Reader, errc chan<- error) {
    _, err := io.Copy(w, r)
    errc <- err
}

func main() {
    http.HandleFunc("/", rootHandler)
    http.Handle("/socket", websocket.Handler(socketHandler))
    err := http.ListenAndServe(listenAddr, nil)
    if err != nil {
        log.Fatal(err)
    }
}

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不太明白为什么当第二个加入者加入聊天频道时可以执行这个聊天功能。