go应用专题：net/http server端

参考：

https://github.com/astaxie/build-web-application-with-golang/blob/master/zh/03.4.md（谢孟军：http包详解）

核心底层方法

启动服务

//开始
http.ListenAndServe(":3000",nil) //代理server.ListenAndServe()

l, err := net.Listen("tcp", addr)
srv.Serve(l)

//监听
for {
    rw, err := l.Accept()  //conn句柄流
    c := srv.newConn(rw)  //conn结构体
    go c.serve(connCtx) //每个连接对应一个协程处理
}    

//解析
for {
    w, err := c.readRequest(ctx) //创建请求和响应结构体
    req := w.req //请求
    serverHandler{c.server}.ServeHTTP(w, w.req) //交给http应用逻辑
}

核心接口和结构体

//tcp总连接
type TCPListener struct {
    fd *netFD
    lc ListenConfig
}
//连接处理函数
type Handler interface {
    ServeHTTP(ResponseWriter, *Request)
}
//构成一个服务
type Server struct {
    Addr string
　 Handler Handler
    mu  sync.Mutex
}

//一个具体的tcp连接
func (ln *TCPListener) accept() (*TCPConn, error) {
    fd, err := ln.fd.accept()
    if err != nil {
        return nil, err
    }
    tc := newTCPConn(fd)
    if ln.lc.KeepAlive >= 0 {
        setKeepAlive(fd, true)
        ka := ln.lc.KeepAlive
        if ln.lc.KeepAlive == 0 {
            ka = defaultTCPKeepAlive
        }
        setKeepAlivePeriod(fd, ka)
    }
    return tc, nil
}
//一个具体的http连接
type conn struct {
    server *Server
    cancelCtx context.CancelFunc

    rwc net.Conn
    remoteAddr string
    tlsState *tls.ConnectionState
    werr error

    r *connReader
    bufr *bufio.Reader
    bufw *bufio.Writer
    lastMethod string
    curReq atomic.Value // of *response (which has a Request in it)
    curState struct{ atomic uint64 } // packed (unixtime<<8|uint8(ConnState))
    mu sync.Mutex
    hijackedv bool
}

//构建一个具体的http请求
req, err := readRequest(c.bufr, keepHostHeader)
readRequest(b *bufio.Reader, deleteHostHeader bool) (req *Request, err error) {
    tp := newTextprotoReader(b)
    req = new(Request)
    s, err = tp.ReadLine()
    req.Method, req.RequestURI, req.Proto, ok = parseRequestLine(s) //首行
    mimeHeader, err := tp.ReadMIMEHeader()//头部
    req.Header = Header(mimeHeader)
    readTransfer(req, b) //请求体 ，这里弄懂需要查找专门的逻辑
}

//默认http服务器
type ServeMux struct {
   mu    sync.RWMutex
   m     map[string]muxEntry
   es    []muxEntry // slice of entries sorted from longest to shortest.
   hosts bool       // whether any patterns contain hostnames
}

func (mux *ServeMux) Handle(pattern string, handler Handler) {
　　mux.mu.Lock()
    defer mux.mu.Unlock()

    if _, exist := mux.m[pattern]; exist {
        panic("http: multiple registrations for " + pattern)
    }

    if mux.m == nil {
        mux.m = make(map[string]muxEntry)
    }
    e := muxEntry{h: handler, pattern: pattern}
    mux.m[pattern] = e
    if pattern[len(pattern)-1] == '/' {
        mux.es = appendSorted(mux.es, e)
    }

    if pattern[0] != '/' {
        mux.hosts = true
    }
}
func (mux *ServeMux) ServeHTTP(w ResponseWriter, r *Request) {
    if r.RequestURI == "*" {
        if r.ProtoAtLeast(1, 1) {
            w.Header().Set("Connection", "close")
        }
        w.WriteHeader(StatusBadRequest)
        return
    }
    h, _ := mux.Handler(r)
    h.ServeHTTP(w, r)
}

//默认兜底处理函数
type HandlerFunc func(ResponseWriter, *Request)

// ServeHTTP calls f(w, r).
func (f HandlerFunc) ServeHTTP(w ResponseWriter, r *Request) {
   f(w, r)
}

// Helper handlers
func Error(w ResponseWriter, error string, code int) {
   w.Header().Set("Content-Type", "text/plain; charset=utf-8")
   w.Header().Set("X-Content-Type-Options", "nosniff")
   w.WriteHeader(code)
   fmt.Fprintln(w, error)
}

func NotFound(w ResponseWriter, r *Request) { Error(w, "404 page not found", StatusNotFound) }

func NotFoundHandler() Handler { return HandlerFunc(NotFound) }