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// Copyright 2015 The Tango 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 tango
import (
// ResponseWriter is a wrapper around http.ResponseWriter that provides extra information about
// the response. It is recommended that middleware handlers use this construct to wrap a responsewriter
// if the functionality calls for it.
type ResponseWriter interface {
// Status returns the status code of the response or 0 if the response has not been written.
Status() int
// Written returns whether or not the ResponseWriter has been written.
Written() bool
// Size returns the size of the response body.
Size() int
type responseWriter struct {
status int
size int
func (rw *responseWriter) reset(w http.ResponseWriter) {
rw.ResponseWriter = w
rw.status = 0
rw.size = 0
func (rw *responseWriter) WriteHeader(s int) {
rw.status = s
func (rw *responseWriter) Write(b []byte) (int, error) {
if !rw.Written() {
// The status will be StatusOK if WriteHeader has not been called yet
size, err := rw.ResponseWriter.Write(b)
rw.size += size
return size, err
func (rw *responseWriter) Status() int {
return rw.status
func (rw *responseWriter) Size() int {
return rw.size
func (rw *responseWriter) Written() bool {
return rw.status != 0
func (rw *responseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
hijacker, ok := rw.ResponseWriter.(http.Hijacker)
if !ok {
return nil, nil, fmt.Errorf("the ResponseWriter doesn't support the Hijacker interface")
return hijacker.Hijack()
func (rw *responseWriter) CloseNotify() <-chan bool {
return rw.ResponseWriter.(http.CloseNotifier).CloseNotify()
func (rw *responseWriter) Flush() {
flusher, ok := rw.ResponseWriter.(http.Flusher)
if ok {