add method to PacketPacker to send WindowUpdate frames

work towards #19

packet_packer.go

@@ -27,8 +27,9 @@ type packetPacker struct {
 	sentPacketHandler           ackhandler.SentPacketHandler
 	connectionParametersManager *handshake.ConnectionParametersManager
 
-	streamFrameQueue StreamFrameQueue
-	controlFrames    []frames.Frame
+	streamFrameQueue   StreamFrameQueue
+	windowUpdateFrames []*frames.WindowUpdateFrame
+	controlFrames      []frames.Frame
 
 	lastPacketNumber protocol.PacketNumber
 }
@@ -41,6 +42,10 @@ func (p *packetPacker) AddHighPrioStreamFrame(f frames.StreamFrame) {
 	p.streamFrameQueue.Push(&f, true)
 }
 
+func (p *packetPacker) AddWindowUpdateFrame(f *frames.WindowUpdateFrame) {
+	p.windowUpdateFrames = append(p.windowUpdateFrames, f)
+}
+
 func (p *packetPacker) PackPacket(stopWaitingFrame *frames.StopWaitingFrame, controlFrames []frames.Frame, includeStreamFrames bool) (*packedPacket, error) {
 	// don't send out packets that only contain a StopWaitingFrame
 	if len(controlFrames) == 0 && (p.streamFrameQueue.Len() == 0 || !includeStreamFrames) {
@@ -122,9 +127,24 @@ func (p *packetPacker) getPayload(frames []frames.Frame, currentPacketNumber pro
 }
 
 func (p *packetPacker) composeNextPacket(stopWaitingFrame *frames.StopWaitingFrame, publicHeaderLength protocol.ByteCount, includeStreamFrames bool) ([]frames.Frame, error) {
-	payloadLength := protocol.ByteCount(0)
+	var payloadLength protocol.ByteCount
 	var payloadFrames []frames.Frame
 
+	maxFrameSize := protocol.MaxFrameAndPublicHeaderSize - publicHeaderLength
+
+	// TODO: handle the extremely unlikely case that there are more windowUpdateFrames than we can fit into one packet
+	for len(p.windowUpdateFrames) > 0 {
+		frame := p.windowUpdateFrames[0]
+		minLength, _ := frame.MinLength() // windowUpdateFrames.MinLength() *never* returns an error
+		payloadLength += minLength
+		payloadFrames = append(payloadFrames, frame)
+		p.windowUpdateFrames = p.windowUpdateFrames[1:]
+
+		if payloadLength > maxFrameSize {
+			panic("internal inconsistency: packet payload too large")
+		}
+	}
+
 	if stopWaitingFrame != nil {
 		payloadFrames = append(payloadFrames, stopWaitingFrame)
 		minLength, err := stopWaitingFrame.MinLength()
@@ -134,8 +154,6 @@ func (p *packetPacker) composeNextPacket(stopWaitingFrame *frames.StopWaitingFra
 		payloadLength += minLength
 	}
 
-	maxFrameSize := protocol.MaxFrameAndPublicHeaderSize - publicHeaderLength
-
 	for len(p.controlFrames) > 0 {
 		frame := p.controlFrames[0]
 		minLength, _ := frame.MinLength() // controlFrames does not contain any StopWaitingFrames. So it will *never* return an error

packet_packer_test.go

@@ -147,15 +147,14 @@ var _ = Describe("Packet packer", func() {
 	})
 
 	It("packs a lot of control frames into 2 packets if they don't fit into one", func() {
-		windowUpdateFrame := &frames.WindowUpdateFrame{
-			StreamID:   0x1337,
-			ByteOffset: 0xDECAFBAD,
+		blockedFrame := &frames.BlockedFrame{
+			StreamID: 0x1337,
 		}
-		minLength, _ := windowUpdateFrame.MinLength()
+		minLength, _ := blockedFrame.MinLength()
 		maxFramesPerPacket := int(protocol.MaxFrameAndPublicHeaderSize-publicHeaderLen) / int(minLength)
 		var controlFrames []frames.Frame
 		for i := 0; i < maxFramesPerPacket+10; i++ {
-			controlFrames = append(controlFrames, windowUpdateFrame)
+			controlFrames = append(controlFrames, blockedFrame)
 		}
 		packer.controlFrames = controlFrames
 		payloadFrames, err := packer.composeNextPacket(nil, publicHeaderLen, true)
@@ -187,6 +186,52 @@ var _ = Describe("Packet packer", func() {
 		Expect(packer.lastPacketNumber).To(Equal(protocol.PacketNumber(2)))
 	})
 
+	Context("WindowUpdate Frame handling", func() {
+		It("packs one WindowUpdateFrame", func() {
+			f := &frames.WindowUpdateFrame{
+				StreamID:   0x1337,
+				ByteOffset: 0xDECAFBAD,
+			}
+			packer.AddWindowUpdateFrame(f)
+			payloadFrames, err := packer.composeNextPacket(nil, publicHeaderLen, true)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(payloadFrames).To(HaveLen(1))
+			Expect(payloadFrames[0]).To(Equal(f))
+		})
+
+		It("packs multiple WindowUpdateFrame", func() {
+			f1 := &frames.WindowUpdateFrame{
+				StreamID:   0x1337,
+				ByteOffset: 0xDECAFBAD,
+			}
+			f2 := &frames.WindowUpdateFrame{
+				StreamID:   0x7331,
+				ByteOffset: 0xDABFACED,
+			}
+			packer.AddWindowUpdateFrame(f1)
+			packer.AddWindowUpdateFrame(f2)
+			payloadFrames, err := packer.composeNextPacket(nil, publicHeaderLen, true)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(payloadFrames).To(HaveLen(2))
+			Expect(payloadFrames).To(ContainElement(f1))
+			Expect(payloadFrames).To(ContainElement(f2))
+		})
+
+		It("only packs a WindowUpdateFrame once", func() {
+			f := &frames.WindowUpdateFrame{
+				StreamID:   0x1337,
+				ByteOffset: 0xDECAFBAD,
+			}
+			packer.AddWindowUpdateFrame(f)
+			payloadFrames, err := packer.composeNextPacket(nil, publicHeaderLen, true)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(payloadFrames).ToNot(BeNil())
+			payloadFrames, err = packer.composeNextPacket(nil, publicHeaderLen, true)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(payloadFrames).To(BeNil())
+		})
+	})
+
 	Context("Stream Frame handling", func() {
 		It("does not splits a stream frame with maximum size", func() {
 			f := frames.StreamFrame{