add SetWriteDelay

sess.go

@@ -90,6 +90,7 @@ type (
 		headerSize     int           // the overall header size added before KCP frame
 		updateInterval time.Duration // interval in seconds to call kcp.flush()
 		ackNoDelay     bool          // send ack immediately for each incoming packet
+		writeDelay     bool          // delay kcp.flush() for Write() for bulk transfer
 
 		// notifications
 		die          chan struct{} // notify session has Closed
@@ -256,7 +257,9 @@ func (s *UDPSession) Write(b []byte) (n int, err error) {
 				}
 			}
 
-			s.kcp.flush(false)
+			if !s.writeDelay {
+				s.kcp.flush(false)
+			}
 			s.mu.Unlock()
 			atomic.AddUint64(&DefaultSnmp.BytesSent, uint64(n))
 			return n, nil
@@ -336,6 +339,13 @@ func (s *UDPSession) SetWriteDeadline(t time.Time) error {
 	return nil
 }
 
+// SetWriteDelay delays write for bulk transfer until the next update interval
+func (s *UDPSession) SetWriteDelay(delay bool) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.writeDelay = delay
+}
+
 // SetWindowSize set maximum window size
 func (s *UDPSession) SetWindowSize(sndwnd, rcvwnd int) {
 	s.mu.Lock()

sess_test.go

@@ -270,6 +270,7 @@ func TestSendRecv(t *testing.T) {
 	if err != nil {
 		panic(err)
 	}
+	cli.SetWriteDelay(true)
 	const N = 100
 	buf := make([]byte, 10)
 	for i := 0; i < N; i++ {