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package iris
import (
// Recorder the middleware to enable response writer recording ( *responseWriter -> *ResponseRecorder)
var Recorder = HandlerFunc(func(ctx *Context) {
var rrpool = sync.Pool{New: func() interface{} { return &ResponseRecorder{} }}
func acquireResponseRecorder(underline *responseWriter) *ResponseRecorder {
w := rrpool.Get().(*ResponseRecorder)
w.responseWriter = underline
w.headers = underline.Header()
return w
func releaseResponseRecorder(w *ResponseRecorder) {
if w.responseWriter != nil {
// A ResponseRecorder is used mostly by context's transactions
// in order to record and change if needed the body, status code and headers.
// You are NOT limited to use that too:
// just call context.ResponseWriter.Recorder()/Record() and
// response writer will act like context.ResponseWriter.(*iris.ResponseRecorder)
type ResponseRecorder struct {
// these three fields are setted on flushBody which runs only once on the end of the handler execution.
// this helps the performance on multi-write and keep tracks the body, status code and headers in order to run each transaction
// on its own
chunks []byte // keep track of the body in order to be resetable and useful inside custom transactions
headers http.Header // the saved headers
var _ ResponseWriter = &ResponseRecorder{}
// Header returns the header map that will be sent by
// WriteHeader. Changing the header after a call to
// WriteHeader (or Write) has no effect unless the modified
// headers were declared as trailers by setting the
// "Trailer" header before the call to WriteHeader (see example).
// To suppress implicit response headers, set their value to nil.
func (w *ResponseRecorder) Header() http.Header {
return w.headers
// Writef formats according to a format specifier and writes to the response.
// Returns the number of bytes written and any write error encountered
func (w *ResponseRecorder) Writef(format string, a ...interface{}) (n int, err error) {
return fmt.Fprintf(w, format, a...)
// WriteString writes a simple string to the response.
// Returns the number of bytes written and any write error encountered
func (w *ResponseRecorder) WriteString(s string) (n int, err error) {
return w.Write([]byte(s))
// Adds the contents to the body reply, it writes the contents temporarily
// to a value in order to be flushed at the end of the request,
// this method give us the opportunity to reset the body if needed.
// If WriteHeader has not yet been called, Write calls
// WriteHeader(http.StatusOK) before writing the data. If the Header
// does not contain a Content-Type line, Write adds a Content-Type set
// to the result of passing the initial 512 bytes of written data to
// DetectContentType.
// Depending on the HTTP protocol version and the client, calling
// Write or WriteHeader may prevent future reads on the
// Request.Body. For HTTP/1.x requests, handlers should read any
// needed request body data before writing the response. Once the
// headers have been flushed (due to either an explicit Flusher.Flush
// call or writing enough data to trigger a flush), the request body
// may be unavailable. For HTTP/2 requests, the Go HTTP server permits
// handlers to continue to read the request body while concurrently
// writing the response. However, such behavior may not be supported
// by all HTTP/2 clients. Handlers should read before writing if
// possible to maximize compatibility.
func (w *ResponseRecorder) Write(contents []byte) (int, error) {
w.chunks = append(w.chunks, contents...)
return len(w.chunks), nil
// Body returns the body tracked from the writer so far
// do not use this for edit.
func (w *ResponseRecorder) Body() []byte {
return w.chunks
// SetBodyString overrides the body and sets it to a string value
func (w *ResponseRecorder) SetBodyString(s string) {
w.chunks = []byte(s)
// SetBody overrides the body and sets it to a slice of bytes value
func (w *ResponseRecorder) SetBody(b []byte) {
w.chunks = b
// ResetBody resets the response body
func (w *ResponseRecorder) ResetBody() {
w.chunks = w.chunks[0:0]
// ResetHeaders clears the temp headers
func (w *ResponseRecorder) ResetHeaders() {
// original response writer's headers are empty.
w.headers = w.responseWriter.Header()
// Reset resets the response body, headers and the status code header
func (w *ResponseRecorder) Reset() {
w.statusCode = StatusOK
// flushResponse the full body, headers and status code to the underline response writer
// called automatically at the end of each request, see ReleaseCtx
func (w *ResponseRecorder) flushResponse() {
if w.headers != nil {
for k, values := range w.headers {
for i := range values {
w.responseWriter.Header().Add(k, values[i])
// NOTE: before the responseWriter.Writer in order to:
// 1. execute the beforeFlush if != nil
// 2. set the status code before the .Write method overides that
if len(w.chunks) > 0 {
// Flush sends any buffered data to the client.
func (w *ResponseRecorder) Flush() {
// NOTE: Users: Uncomment the below code if you are already using Go from master branch.
// HTTP/2 Go 1.8 Push feature,
// as described in the source code(master):
// .
// I have already tested the feature on my machine, but
// in order to avoid breaking the users' workspace:
// Uncomment these when 1.8 released (I guess in the middle of February)
// TODO:
// // Push initiates an HTTP/2 server push. This constructs a synthetic
// // request using the given target and options, serializes that request
// // into a PUSH_PROMISE frame, then dispatches that request using the
// // server's request handler. If opts is nil, default options are used.
// //
// // The target must either be an absolute path (like "/path") or an absolute
// // URL that contains a valid host and the same scheme as the parent request.
// // If the target is a path, it will inherit the scheme and host of the
// // parent request.
// //
// // The HTTP/2 spec disallows recursive pushes and cross-authority pushes.
// // Push may or may not detect these invalid pushes; however, invalid
// // pushes will be detected and canceled by conforming clients.
// //
// // Handlers that wish to push URL X should call Push before sending any
// // data that may trigger a request for URL X. This avoids a race where the
// // client issues requests for X before receiving the PUSH_PROMISE for X.
// //
// // Push returns ErrNotSupported if the client has disabled push or if push
// // is not supported on the underlying connection.
// func (w *ResponseRecorder) Push(target string, opts *http.PushOptions) error {
// w.flushResponse()
// err := w.responseWriter.Push(target, opts)
// // NOTE: we have to reset them even if the push failed.
// w.ResetBody()
// w.ResetHeaders()
// return err
// }
// clone returns a clone of this response writer
// it copies the header, status code, headers and the beforeFlush finally returns a new ResponseRecorder
func (w *ResponseRecorder) clone() ResponseWriter {
wc := &ResponseRecorder{}
wc.headers = w.headers
wc.chunks = w.chunks[0:]
wc.responseWriter = &(*w.responseWriter) // w.responseWriter.clone().(*responseWriter) //
return wc
// writeTo writes a response writer (temp: status code, headers and body) to another response writer
func (w *ResponseRecorder) writeTo(res ResponseWriter) {
if to, ok := res.(*ResponseRecorder); ok {
// set the status code, to is first ( probably an error >=400)
if w.statusCode == StatusOK {
to.statusCode = w.statusCode
if w.beforeFlush != nil {
// if to had a before flush, lets combine them
if to.beforeFlush != nil {
nextBeforeFlush := w.beforeFlush
prevBeforeFlush := to.beforeFlush
to.beforeFlush = func() {
} else {
to.beforeFlush = w.beforeFlush
if !to.statusCodeSent {
to.statusCodeSent = w.statusCodeSent
// append the headers
if w.headers != nil {
for k, values := range w.headers {
for _, v := range values {
if to.headers.Get(v) == "" {
to.headers.Add(k, v)
// append the body
if len(w.chunks) > 0 {
func (w *ResponseRecorder) releaseMe() {