net/http: speed up ServeMux when no patterns contain hostnames

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6248053

diff --git a/src/pkg/net/http/server.go b/src/pkg/net/http/server.go
index 54eaf6a121336df7ad7d9451102914ffb632fe55..0b97de3c219c84523bb10a1b45cd7096bc1d3366 100644 (file)
--- a/src/pkg/net/http/server.go
+++ b/src/pkg/net/http/server.go
@@ -840,8 +840,9 @@ func RedirectHandler(url string, code int) Handler {
 // redirecting any request containing . or .. elements to an
 // equivalent .- and ..-free URL.
 type ServeMux struct {
-       mu sync.RWMutex
-       m  map[string]muxEntry
+       mu    sync.RWMutex
+       m     map[string]muxEntry
+       hosts bool // whether any patterns contain hostnames
 }
 
 type muxEntry struct {
@@ -903,12 +904,14 @@ func (mux *ServeMux) match(path string) Handler {
 }
 
 // handler returns the handler to use for the request r.
-func (mux *ServeMux) handler(r *Request) Handler {
+func (mux *ServeMux) handler(r *Request) (h Handler) {
        mux.mu.RLock()
        defer mux.mu.RUnlock()
 
        // Host-specific pattern takes precedence over generic ones
-       h := mux.match(r.Host + r.URL.Path)
+       if mux.hosts {
+               h = mux.match(r.Host + r.URL.Path)
+       }
        if h == nil {
                h = mux.match(r.URL.Path)
        }
@@ -950,6 +953,10 @@ func (mux *ServeMux) Handle(pattern string, handler Handler) {
 
        mux.m[pattern] = muxEntry{explicit: true, h: handler}
 
+       if pattern[0] != '/' {
+               mux.hosts = true
+       }
+
        // Helpful behavior:
        // If pattern is /tree/, insert an implicit permanent redirect for /tree.
        // It can be overridden by an explicit registration.