http: add docs/warning on incorrect use of NewChunkedWriter
R=golang-dev, adg, r
CC=golang-dev
https://golang.org/cl/4536075
diff --git a/src/pkg/http/chunked.go b/src/pkg/http/chunked.go
index bfd68a4..59121c5 100644
--- a/src/pkg/http/chunked.go
+++ b/src/pkg/http/chunked.go
@@ -6,14 +6,24 @@
import (
"io"
+ "log"
"os"
"strconv"
)
// NewChunkedWriter returns a new writer that translates writes into HTTP
-// "chunked" format before writing them to w. Closing the returned writer
+// "chunked" format before writing them to w. Closing the returned writer
// sends the final 0-length chunk that marks the end of the stream.
+//
+// NewChunkedWriter is not needed by normal applications. The http
+// package adds chunking automatically if handlers don't set a
+// Content-Length header. Using NewChunkedWriter inside a handler
+// would result in double chunking or chunking with a Content-Length
+// length, both of which are wrong.
func NewChunkedWriter(w io.Writer) io.WriteCloser {
+ if _, bad := w.(*response); bad {
+ log.Printf("warning: using NewChunkedWriter in an http.Handler; expect corrupt output")
+ }
return &chunkedWriter{w}
}
