response_writer.go

// Copyright 2014 Manu Martinez-Almeida.  All rights reserved.
// Use of this source code is governed by a MIT style
// license that can be found in the LICENSE file.

package gin

import (
	"bufio"
	"io"
	"net"
	"net/http"
)

const (
	noWritten     = -1
	defaultStatus = 200
)

type (
	ResponseWriter interface {
		http.ResponseWriter
		http.Hijacker
		http.Flusher
		http.CloseNotifier

		// Returns the HTTP response status code of the current request.
		Status() int

		// Returns the number of bytes already written into the response http body.
		// See Written()
		Size() int

		// Writes the string into the response body.
		WriteString(string) (int, error)

		// Returns true if the response body was already written.
		Written() bool

		// Forces to write the http header (status code + headers).
		WriteHeaderNow()
	}

	responseWriter struct {
		http.ResponseWriter
		size   int
		status int
	}
)

var _ ResponseWriter = &responseWriter{}

func (w *responseWriter) reset(writer http.ResponseWriter) {
	w.ResponseWriter = writer
	w.size = noWritten
	w.status = defaultStatus
}

func (w *responseWriter) WriteHeader(code int) {
	if code > 0 && w.status != code {
		if w.Written() {
			debugPrint("[WARNING] Headers were already written. Wanted to override status code %d with %d", w.status, code)
		}
		w.status = code
	}
}

func (w *responseWriter) WriteHeaderNow() {
	if !w.Written() {
		w.size = 0
		w.ResponseWriter.WriteHeader(w.status)
	}
}

func (w *responseWriter) Write(data []byte) (n int, err error) {
	w.WriteHeaderNow()
	n, err = w.ResponseWriter.Write(data)
	w.size += n
	return
}

func (w *responseWriter) WriteString(s string) (n int, err error) {
	w.WriteHeaderNow()
	n, err = io.WriteString(w.ResponseWriter, s)
	w.size += n
	return
}

func (w *responseWriter) Status() int {
	return w.status
}

func (w *responseWriter) Size() int {
	return w.size
}

func (w *responseWriter) Written() bool {
	return w.size != noWritten
}

// Implements the http.Hijacker interface
func (w *responseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
	if w.size < 0 {
		w.size = 0
	}
	return w.ResponseWriter.(http.Hijacker).Hijack()
}

// Implements the http.CloseNotify interface
func (w *responseWriter) CloseNotify() <-chan bool {
	return w.ResponseWriter.(http.CloseNotifier).CloseNotify()
}

// Implements the http.Flush interface
func (w *responseWriter) Flush() {
	w.ResponseWriter.(http.Flusher).Flush()
}