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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package http
// This file implements ServeMux behavior as in Go 1.21.
// The behavior is controlled by a GODEBUG setting.
// Most of this code is derived from commit 08e35cc334.
// Changes are minimal: aside from the different receiver type,
// they mostly involve renaming functions, usually by unexporting them.
import (
"internal/godebug"
"net/url"
"sort"
"strings"
"sync"
)
var httpmuxgo121 = godebug.New("httpmuxgo121")
var use121 bool
// Read httpmuxgo121 once at startup, since dealing with changes to it during
// program execution is too complex and error-prone.
func init() {
if httpmuxgo121.Value() == "1" {
use121 = true
httpmuxgo121.IncNonDefault()
}
}
// serveMux121 holds the state of a ServeMux needed for Go 1.21 behavior.
type serveMux121 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
}
type muxEntry struct {
h Handler
pattern string
}
// Formerly ServeMux.Handle.
func (mux *serveMux121) handle(pattern string, handler Handler) {
mux.mu.Lock()
defer mux.mu.Unlock()
if pattern == "" {
panic("http: invalid pattern")
}
if handler == nil {
panic("http: nil handler")
}
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 appendSorted(es []muxEntry, e muxEntry) []muxEntry {
n := len(es)
i := sort.Search(n, func(i int) bool {
return len(es[i].pattern) < len(e.pattern)
})
if i == n {
return append(es, e)
}
// we now know that i points at where we want to insert
es = append(es, muxEntry{}) // try to grow the slice in place, any entry works.
copy(es[i+1:], es[i:]) // Move shorter entries down
es[i] = e
return es
}
// Formerly ServeMux.HandleFunc.
func (mux *serveMux121) handleFunc(pattern string, handler func(ResponseWriter, *Request)) {
if handler == nil {
panic("http: nil handler")
}
mux.handle(pattern, HandlerFunc(handler))
}
// Formerly ServeMux.Handler.
func (mux *serveMux121) findHandler(r *Request) (h Handler, pattern string) {
// CONNECT requests are not canonicalized.
if r.Method == "CONNECT" {
// If r.URL.Path is /tree and its handler is not registered,
// the /tree -> /tree/ redirect applies to CONNECT requests
// but the path canonicalization does not.
if u, ok := mux.redirectToPathSlash(r.URL.Host, r.URL.Path, r.URL); ok {
return RedirectHandler(u.String(), StatusMovedPermanently), u.Path
}
return mux.handler(r.Host, r.URL.Path)
}
// All other requests have any port stripped and path cleaned
// before passing to mux.handler.
host := stripHostPort(r.Host)
path := cleanPath(r.URL.Path)
// If the given path is /tree and its handler is not registered,
// redirect for /tree/.
if u, ok := mux.redirectToPathSlash(host, path, r.URL); ok {
return RedirectHandler(u.String(), StatusMovedPermanently), u.Path
}
if path != r.URL.Path {
_, pattern = mux.handler(host, path)
u := &url.URL{Path: path, RawQuery: r.URL.RawQuery}
return RedirectHandler(u.String(), StatusMovedPermanently), pattern
}
return mux.handler(host, r.URL.Path)
}
// handler is the main implementation of findHandler.
// The path is known to be in canonical form, except for CONNECT methods.
func (mux *serveMux121) handler(host, path string) (h Handler, pattern string) {
mux.mu.RLock()
defer mux.mu.RUnlock()
// Host-specific pattern takes precedence over generic ones
if mux.hosts {
h, pattern = mux.match(host + path)
}
if h == nil {
h, pattern = mux.match(path)
}
if h == nil {
h, pattern = NotFoundHandler(), ""
}
return
}
// Find a handler on a handler map given a path string.
// Most-specific (longest) pattern wins.
func (mux *serveMux121) match(path string) (h Handler, pattern string) {
// Check for exact match first.
v, ok := mux.m[path]
if ok {
return v.h, v.pattern
}
// Check for longest valid match. mux.es contains all patterns
// that end in / sorted from longest to shortest.
for _, e := range mux.es {
if strings.HasPrefix(path, e.pattern) {
return e.h, e.pattern
}
}
return nil, ""
}
// redirectToPathSlash determines if the given path needs appending "/" to it.
// This occurs when a handler for path + "/" was already registered, but
// not for path itself. If the path needs appending to, it creates a new
// URL, setting the path to u.Path + "/" and returning true to indicate so.
func (mux *serveMux121) redirectToPathSlash(host, path string, u *url.URL) (*url.URL, bool) {
mux.mu.RLock()
shouldRedirect := mux.shouldRedirectRLocked(host, path)
mux.mu.RUnlock()
if !shouldRedirect {
return u, false
}
path = path + "/"
u = &url.URL{Path: path, RawQuery: u.RawQuery}
return u, true
}
// shouldRedirectRLocked reports whether the given path and host should be redirected to
// path+"/". This should happen if a handler is registered for path+"/" but
// not path -- see comments at ServeMux.
func (mux *serveMux121) shouldRedirectRLocked(host, path string) bool {
p := []string{path, host + path}
for _, c := range p {
if _, exist := mux.m[c]; exist {
return false
}
}
n := len(path)
if n == 0 {
return false
}
for _, c := range p {
if _, exist := mux.m[c+"/"]; exist {
return path[n-1] != '/'
}
}
return false
}
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