http: do not cache CanonicalHeaderKey

Fixes #1080.

R=rsc
CC=golang-dev
https://golang.org/cl/2158043

diff --git a/src/pkg/http/request.go b/src/pkg/http/request.go
index 76ed05706b97953f71a59c44a1b10fbb3d2a8c17..a602fd52c0e28fa44f51733f9cb7d29c36a128e2 100644 (file)
--- a/src/pkg/http/request.go
+++ b/src/pkg/http/request.go
@@ -382,29 +382,30 @@ func parseHTTPVersion(vers string) (int, int, bool) {
        return major, minor, true
 }
 
-var cmap = make(map[string]string)
-
 // CanonicalHeaderKey returns the canonical format of the
 // HTTP header key s.  The canonicalization converts the first
 // letter and any letter following a hyphen to upper case;
 // the rest are converted to lowercase.  For example, the
 // canonical key for "accept-encoding" is "Accept-Encoding".
 func CanonicalHeaderKey(s string) string {
-       if t, ok := cmap[s]; ok {
-               return t
-       }
-
        // canonicalize: first letter upper case
        // and upper case after each dash.
        // (Host, User-Agent, If-Modified-Since).
        // HTTP headers are ASCII only, so no Unicode issues.
-       a := []byte(s)
+       var a []byte
        upper := true
-       for i, v := range a {
+       for i := 0; i < len(s); i++ {
+               v := s[i]
                if upper && 'a' <= v && v <= 'z' {
+                       if a == nil {
+                               a = []byte(s)
+                       }
                        a[i] = v + 'A' - 'a'
                }
                if !upper && 'A' <= v && v <= 'Z' {
+                       if a == nil {
+                               a = []byte(s)
+                       }
                        a[i] = v + 'a' - 'A'
                }
                upper = false
@@ -412,9 +413,10 @@ func CanonicalHeaderKey(s string) string {
                        upper = true
                }
        }
-       t := string(a)
-       cmap[s] = t
-       return t
+       if a != nil {
+               return string(a)
+       }
+       return s
 }
 
 type chunkedReader struct {