add a function to tell if there's app data in the retransmission queue

retransmission_queue.go

@@ -47,6 +47,10 @@ func (q *retransmissionQueue) HasHandshakeData() bool {
 	return len(q.handshakeCryptoData) > 0 || len(q.handshake) > 0
 }
 
+func (q *retransmissionQueue) HasAppData() bool {
+	return len(q.appData) > 0
+}
+
 func (q *retransmissionQueue) AddAppData(f wire.Frame) {
 	if _, ok := f.(*wire.StreamFrame); ok {
 		panic("STREAM frames are handled with their respective streams.")

retransmission_queue_test.go

@@ -176,9 +176,12 @@ var _ = Describe("Retransmission queue", func() {
 
 		It("queues and retrieves a control frame", func() {
 			f := &wire.MaxDataFrame{ByteOffset: 0x42}
+			Expect(q.HasAppData()).To(BeFalse())
 			q.AddAppData(f)
+			Expect(q.HasAppData()).To(BeTrue())
 			Expect(q.GetAppDataFrame(f.Length(version) - 1)).To(BeNil())
 			Expect(q.GetAppDataFrame(f.Length(version))).To(Equal(f))
+			Expect(q.HasAppData()).To(BeFalse())
 		})
 	})
 })