卓越飞翔博客
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)
}
}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"/>
</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)
}
}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。
正确答案
看起来 HTTP 处理程序创建了一个 Web 套接字并开始等待另一方连接。这是因为当处理HTTP请求时，处理程序调用match，这将在select上阻塞，因为partner通道既不可读也不可写。没有 goroutine 监听它，或者发送给它。
当第二个请求到来时，match 会再次从另一个 goroutine 中调用。现在有两个 goroutine，并且它们可以匹配。其中一个 goroutine 可以发送到 partner 通道，另一个 goroutine 接收它。传输的对象是读写器，然后用于两个伙伴之间的通信。
