// Copyright 2018 Gin Core Team.  All rights reserved.
  // Use of this source code is governed by a MIT style
  // license that can be found in the LICENSE file.
  
  package render
  
  import (
  	"io"
  	"net/http"
  	"strconv"
  )
  
  // Reader contains the IO reader and its length, and custom ContentType and other headers.
  type Reader struct {
  	ContentType   string
  	ContentLength int64
  	Reader        io.Reader
  	Headers       map[string]string
  }
  
  // Render (Reader) writes data with custom ContentType and headers.
  func (r Reader) Render(w http.ResponseWriter) (err error) {
  	r.WriteContentType(w)
  	r.Headers["Content-Length"] = strconv.FormatInt(r.ContentLength, 10)
  	r.writeHeaders(w, r.Headers)
  	_, err = io.Copy(w, r.Reader)
  	return
  }
  
  // WriteContentType (Reader) writes custom ContentType.
  func (r Reader) WriteContentType(w http.ResponseWriter) {
  	writeContentType(w, []string{r.ContentType})
  }
  
  // writeHeaders writes custom Header.
  func (r Reader) writeHeaders(w http.ResponseWriter, headers map[string]string) {
  	header := w.Header()
  	for k, v := range headers {
  		if header.Get(k) == "" {
  			header.Set(k, v)
  		}
  	}
  }