http: clarify use of w.conn.body in Write when sniffing.

R=gri, r, r, rsc
CC=golang-dev
https://golang.org/cl/4794047

diff --git a/src/pkg/http/server.go b/src/pkg/http/server.go
index f14ef8c04b90c0dad7436abeb03af577bb151cf1..96547c4eff0d2addb077c730cd38674c7ab0dd13 100644 (file)
--- a/src/pkg/http/server.go
+++ b/src/pkg/http/server.go
@@ -359,8 +359,7 @@ func (w *response) sniff() {
        w.needSniff = false
 
        data := w.conn.body
-       fmt.Fprintf(w.conn.buf, "Content-Type: %s\r\n", DetectContentType(data))
-       io.WriteString(w.conn.buf, "\r\n")
+       fmt.Fprintf(w.conn.buf, "Content-Type: %s\r\n\r\n", DetectContentType(data))
 
        if len(data) == 0 {
                return
@@ -408,10 +407,14 @@ func (w *response) Write(data []byte) (n int, err os.Error) {
                // We need to sniff the beginning of the output to
                // determine the content type.  Accumulate the
                // initial writes in w.conn.body.
-               body := w.conn.body
-               m = copy(body[len(body):cap(body)], data)
-               w.conn.body = body[:len(body)+m]
-               if m == len(data) {
+               // Cap m so that append won't allocate.
+               m := cap(w.conn.body) - len(w.conn.body)
+               if m > len(data) {
+                       m = len(data)
+               }
+               w.conn.body = append(w.conn.body, data[:m]...)
+               data = data[m:]
+               if len(data) == 0 {
                        // Copied everything into the buffer.
                        // Wait for next write.
                        return m, nil
@@ -423,7 +426,6 @@ func (w *response) Write(data []byte) (n int, err os.Error) {
                // of the data as a normal Write.
                // Calling sniff clears needSniff.
                w.sniff()
-               data = data[m:]
        }
 
        // TODO(rsc): if chunking happened after the buffering,