go http 服务器编程(1)

package main

import (
	"io"
	"net/http"
)

type helloHandler struct{}

func (h *helloHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	w.Write([]byte("Hello, world!"))
}

func main() {
	http.Handle("/", &helloHandler{})
	http.ListenAndServe(":12345", nil)
}

type Handler interface {
    ServeHTTP(ResponseWriter, *Request)
}

package main

import (
	"io"
	"net/http"
)

func helloHandler(w http.ResponseWriter, req *http.Request) {
	io.WriteString(w, "hello, world!\n")
}

func main() {
	http.HandleFunc("/", helloHandler)
	http.ListenAndServe(":12345", nil)
}

// The HandlerFunc type is an adapter to allow the use of
// ordinary functions as HTTP handlers.  If f is a function
// with the appropriate signature, HandlerFunc(f) is a
// Handler object that calls f.
type HandlerFunc func(ResponseWriter, *Request)

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

package main

import (
	"io"
	"net/http"
)

func helloHandler(w http.ResponseWriter, req *http.Request) {
	io.WriteString(w, "hello, world!\n")
}

func main() {
    // 通过 HandlerFunc 把函数转换成 Handler 接口的实现对象
    hh := http.HandlerFunc(helloHandler)
	http.Handle("/", hh)
	http.ListenAndServe(":12345", nil)
}

package main

import (
	"net/http"
)

func main() {
	http.ListenAndServe(":12345", http.FileServer(http.Dir(".")))
}

package main

import (
	"io"
	"net/http"
)

func helloHandler(w http.ResponseWriter, r *http.Request) {
	io.WriteString(w, "Hello, world!\n")
}

func echoHandler(w http.ResponseWriter, r *http.Request) {
	io.WriteString(w, r.URL.Path)
}

func main() {
	mux := http.NewServeMux()
	mux.HandleFunc("/hello", helloHandler)
	mux.HandleFunc("/", echoHandler)

	http.ListenAndServe(":12345", mux)
}

type ServeMux struct {
        // contains filtered or unexported fields
}

func NewServeMux() *ServeMux
func (mux *ServeMux) Handle(pattern string, handler Handler)
func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Request))
func (mux *ServeMux) Handler(r *Request) (h Handler, pattern string)
func (mux *ServeMux) ServeHTTP(w ResponseWriter, r *Request)

func ListenAndServe(addr string, handler Handler) error {
	server := &Server{Addr: addr, Handler: handler}
	return server.ListenAndServe()
}

// A Server defines parameters for running an HTTP server.
// The zero value for Server is a valid configuration.
type Server struct {
	Addr           string        // TCP address to listen on, ":http" if empty
	Handler        Handler       // handler to invoke, http.DefaultServeMux if nil
	......
}

// ListenAndServe listens on the TCP network address srv.Addr and then
// calls Serve to handle requests on incoming connections.  If
// srv.Addr is blank, ":http" is used.
func (srv *Server) ListenAndServe() error {
	addr := srv.Addr
	if addr == "" {
		addr = ":http"
	}
	ln, err := net.Listen("tcp", addr)
	if err != nil {
		return err
	}
	return srv.Serve(tcpKeepAliveListener{ln.(*net.TCPListener)})
}

// Serve accepts incoming connections on the Listener l, creating a
// new service goroutine for each.  The service goroutines read requests and
// then call srv.Handler to reply to them.
func (srv *Server) Serve(l net.Listener) error {
	defer l.Close()
	var tempDelay time.Duration // how long to sleep on accept failure
    // 循环逻辑，接受请求并处理
	for {
         // 有新的连接
		rw, e := l.Accept()
		if e != nil {
			if ne, ok := e.(net.Error); ok && ne.Temporary() {
				if tempDelay == 0 {
					tempDelay = 5 * time.Millisecond
				} else {
					tempDelay *= 2
				}
				if max := 1 * time.Second; tempDelay > max {
					tempDelay = max
				}
				srv.logf("http: Accept error: %v; retrying in %v", e, tempDelay)
				time.Sleep(tempDelay)
				continue
			}
			return e
		}
		tempDelay = 0
         // 创建 Conn 连接
		c, err := srv.newConn(rw)
		if err != nil {
			continue
		}
		c.setState(c.rwc, StateNew) // before Serve can return
         // 启动新的 goroutine 进行处理
		go c.serve()
	}
}

func (c *conn) serve() {
	origConn := c.rwc // copy it before it's set nil on Close or Hijack

  	...

	for {
		w, err := c.readRequest()
		if c.lr.N != c.server.initialLimitedReaderSize() {
			// If we read any bytes off the wire, we're active.
			c.setState(c.rwc, StateActive)
		}

         ...

		// HTTP cannot have multiple simultaneous active requests.[*]
		// Until the server replies to this request, it can't read another,
		// so we might as well run the handler in this goroutine.
		// [*] Not strictly true: HTTP pipelining.  We could let them all process
		// in parallel even if their responses need to be serialized.
		serverHandler{c.server}.ServeHTTP(w, w.req)

		w.finishRequest()
		if w.closeAfterReply {
			if w.requestBodyLimitHit {
				c.closeWriteAndWait()
			}
			break
		}
		c.setState(c.rwc, StateIdle)
	}
}

func (sh serverHandler) ServeHTTP(rw ResponseWriter, req *Request) {
	handler := sh.srv.Handler
	if handler == nil {
		handler = DefaultServeMux
	}
	if req.RequestURI == "*" && req.Method == "OPTIONS" {
		handler = globalOptionsHandler{}
	}
	handler.ServeHTTP(rw, req)
}

type ServeMux struct {
	mu    sync.RWMutex
    m     map[string]muxEntry  // 存放路由信息的字典！\(^o^)/
	hosts bool // whether any patterns contain hostnames
}

type muxEntry struct {
	explicit bool
	h        Handler
	pattern  string
}

// Handle registers the handler for the given pattern.
// If a handler already exists for pattern, Handle panics.
func (mux *ServeMux) Handle(pattern string, handler Handler) {
	mux.mu.Lock()
	defer mux.mu.Unlock()

    // 边界情况处理
	if pattern == "" {
		panic("http: invalid pattern " + pattern)
	}
	if handler == nil {
		panic("http: nil handler")
	}
	if mux.m[pattern].explicit {
		panic("http: multiple registrations for " + pattern)
	}

    // 创建 `muxEntry` 并添加到路由字典中
	mux.m[pattern] = muxEntry{explicit: true, h: handler, pattern: pattern}

	if pattern[0] != '/' {
		mux.hosts = true
	}

    // 这是一个很有用的小技巧，如果注册了 `/tree/`， `serveMux` 会自动添加一个 `/tree` 的路径并重定向到 `/tree/`。当然这个 `/tree` 路径会被用户显示的路由信息覆盖。
	// Helpful behavior:
	// If pattern is /tree/, insert an implicit permanent redirect for /tree.
	// It can be overridden by an explicit registration.
	n := len(pattern)
	if n > 0 && pattern[n-1] == '/' && !mux.m[pattern[0:n-1]].explicit {
		// If pattern contains a host name, strip it and use remaining
		// path for redirect.
		path := pattern
		if pattern[0] != '/' {
			// In pattern, at least the last character is a '/', so
			// strings.Index can't be -1.
			path = pattern[strings.Index(pattern, "/"):]
		}
		mux.m[pattern[0:n-1]] = muxEntry{h: RedirectHandler(path, StatusMovedPermanently), pattern: pattern}
	}
}

// ServeHTTP dispatches the request to the handler whose
// pattern most closely matches the request URL.
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)
}

// Does path match pattern?
func pathMatch(pattern, path string) bool {
	if len(pattern) == 0 {
		// should not happen
		return false
	}
	n := len(pattern)
	if pattern[n-1] != '/' {
		return pattern == path
	}
    // 匹配的逻辑很简单，path 前面的字符和 pattern 一样就是匹配
	return len(path) >= n && path[0:n] == pattern
}

// Find a handler on a handler map given a path string
// Most-specific (longest) pattern wins
func (mux *ServeMux) match(path string) (h Handler, pattern string) {
	var n = 0
	for k, v := range mux.m {
		if !pathMatch(k, path) {
			continue
		}
         // 最长匹配的逻辑在这里
		if h == nil || len(k) > n {
			n = len(k)
			h = v.h
			pattern = v.pattern
		}
	}
	return
}