perf: Write file data to local while transferring

Before, the download was started after all file data were sent from the device to the browser.
Now, the download starts when the file data begins to transfer.

Signed-off-by: Jianhui Zhao <zhaojh329@gmail.com>

device.go

@@ -11,6 +11,7 @@ import (
 	"io"
 	"io/ioutil"
 	"net"
+	"rttys/client"
 	"strings"
 	"sync/atomic"
 	"time"
@@ -32,6 +33,15 @@ const (
 	msgTypeMax = msgTypeAck
 )
 
+const (
+	msgTypeFileSend = iota
+	msgTypeFileRecv
+	msgTypeFileInfo
+	msgTypeFileData
+	msgTypeFileAck
+	msgTypeFileAbort
+)
+
 const rttyProto uint8 = 3
 const heartbeatInterval = time.Second * 5
 
@@ -56,6 +66,50 @@ type termMessage struct {
 	data []byte
 }
 
+type fileMessage struct {
+	sid  string
+	data []byte
+}
+
+type fileProxy struct {
+	reader *io.PipeReader
+	writer *io.PipeWriter
+}
+
+func (fp *fileProxy) Read(b []byte) (int, error) {
+	return fp.reader.Read(b)
+}
+
+func (fp *fileProxy) Write(dev client.Client, sid string, b []byte) {
+	go func() {
+		_, err := fp.writer.Write(b)
+		if err != nil {
+			fp.Cancel(dev, sid)
+			dev.(*device).br.fileProxy.Delete(sid)
+			return
+		}
+		fp.Ack(dev, sid)
+	}()
+}
+
+func (fp *fileProxy) Close() {
+	fp.writer.Close()
+}
+
+func (fp *fileProxy) Cancel(dev client.Client, sid string) {
+	b := make([]byte, 33)
+	copy(b, sid)
+	b[32] = msgTypeFileAbort
+	dev.WriteMsg(msgTypeFile, b)
+}
+
+func (fp *fileProxy) Ack(dev client.Client, sid string) {
+	b := make([]byte, 33)
+	copy(b, sid)
+	b[32] = msgTypeFileAck
+	dev.WriteMsg(msgTypeFile, b)
+}
+
 type loginAckMsg struct {
 	devid  string
 	sid    string
@@ -251,16 +305,12 @@ func (dev *device) readLoop() {
 
 			sid := string(b[:32])
 
-			b = b[31:]
-
 			if typ == msgTypeFile {
-				b[0] = 1
+				dev.br.fileMessage <- &fileMessage{sid, b[32:]}
 			} else {
-				b[0] = 0
+				dev.br.termMessage <- &termMessage{sid, b[32:]}
 			}
 
-			dev.br.termMessage <- &termMessage{sid, b}
-
 		case msgTypeCmd:
 			if msgLen < 1 {
 				log.Error().Msg("msgTypeCmd: invalid")