support chunked mode

context.go

@@ -5,6 +5,7 @@
 package gin
 
 import (
+	"bytes"
 	"errors"
 	"io"
 	"io/ioutil"
@@ -820,6 +821,26 @@ func (c *Context) DataFromReader(code int, contentLength int64, contentType stri
 	})
 }
 
+func (c *Context) DataFromReaderStream(code int, offset int, contentType string, reader io.Reader, extraHeaders map[string]string) {
+	p := make([]byte, offset)
+	for {
+		n, err := reader.Read(p)
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			panic(err)
+		}
+
+		c.Render(code, render.ReaderStream{
+			Headers:     extraHeaders,
+			ContentType: contentType,
+			Reader:      bytes.NewReader(p[:n]),
+		})
+		c.Writer.Flush()
+	}
+}
+
 // File writes the specified file into the body stream in a efficient way.
 func (c *Context) File(filepath string) {
 	http.ServeFile(c.Writer, c.Request, filepath)

render/reader.go

@@ -38,3 +38,30 @@ func (r Reader) writeHeaders(w http.ResponseWriter, headers map[string]string) {
 		}
 	}
 }
+
+type ReaderStream struct {
+	ContentType string
+	Reader      io.Reader
+	Headers     map[string]string
+}
+
+// Render (ReaderStream) writes data with custom ContentType and headers.
+func (r ReaderStream) Render(w http.ResponseWriter) (err error) {
+	r.WriteContentType(w)
+	r.writeHeaders(w, r.Headers)
+	_, err = io.Copy(w, r.Reader)
+	return
+}
+
+func (r ReaderStream) WriteContentType(w http.ResponseWriter) {
+	writeContentType(w, []string{r.ContentType})
+}
+
+func (r ReaderStream) writeHeaders(w http.ResponseWriter, headers map[string]string) {
+	header := w.Header()
+	for k, v := range headers {
+		if val := header[k]; len(val) == 0 {
+			header[k] = []string{v}
+		}
+	}
+}

render/render.go

@@ -26,6 +26,7 @@ var (
 	_ Render     = YAML{}
 	_ Render     = MsgPack{}
 	_ Render     = Reader{}
+	_ Render     = ReaderStream{}
 	_ Render     = AsciiJSON{}
 	_ Render     = ProtoBuf{}
 )