calculate the EntropyByte of every sent packet

ackhandler/outgoing_packet_ack_handler.go

@@ -9,9 +9,11 @@ import (
 )
 
 type outgoingPacketAckHandler struct {
-	lastSentPacketNumber protocol.PacketNumber
-	packetHistory        map[protocol.PacketNumber]*Packet
-	packetHistoryMutex   sync.Mutex
+	lastSentPacketNumber            protocol.PacketNumber
+	highestInOrderAckedPacketNumber protocol.PacketNumber
+	highestInOrderAckedEntropy      EntropyAccumulator
+	packetHistory                   map[protocol.PacketNumber]*Packet
+	packetHistoryMutex              sync.Mutex
 }
 
 // NewOutgoingPacketAckHandler creates a new outgoingPacketAckHandler
@@ -31,6 +33,20 @@ func (h *outgoingPacketAckHandler) SentPacket(packet *Packet) error {
 	if h.lastSentPacketNumber+1 != packet.PacketNumber {
 		return errors.New("Packet number must be increased by exactly 1")
 	}
+
+	var lastPacketEntropy EntropyAccumulator
+	// ToDo: write tests for this
+	if packet.PacketNumber == 0 {
+		lastPacketEntropy = EntropyAccumulator(0)
+	} else {
+		if h.highestInOrderAckedPacketNumber == packet.PacketNumber-1 {
+			lastPacketEntropy = h.highestInOrderAckedEntropy
+		} else {
+			lastPacketEntropy = h.packetHistory[packet.PacketNumber-1].Entropy
+		}
+	}
+	lastPacketEntropy.Add(packet.PacketNumber, packet.EntropyBit)
+	packet.Entropy = lastPacketEntropy
 	h.lastSentPacketNumber = packet.PacketNumber
 	h.packetHistory[packet.PacketNumber] = packet
 	return nil

ackhandler/outgoing_packet_ack_handler_test.go

@@ -13,9 +13,10 @@ var _ = Describe("AckHandler", func() {
 	})
 
 	Context("SentPacket", func() {
-		It("accepts two consecutive packets", func() {
+		It("accepts three consecutive packets", func() {
+			entropy := EntropyAccumulator(0)
 			packet1 := Packet{PacketNumber: 1, Plaintext: []byte{0x13, 0x37}, EntropyBit: true}
-			packet2 := Packet{PacketNumber: 2, Plaintext: []byte{0xBE, 0xEF}, EntropyBit: false}
+			packet2 := Packet{PacketNumber: 2, Plaintext: []byte{0xBE, 0xEF}, EntropyBit: true}
 			err := handler.SentPacket(&packet1)
 			Expect(err).ToNot(HaveOccurred())
 			err = handler.SentPacket(&packet2)
@@ -23,6 +24,12 @@ var _ = Describe("AckHandler", func() {
 			Expect(handler.lastSentPacketNumber).To(Equal(protocol.PacketNumber(2)))
 			Expect(handler.packetHistory).To(HaveKey(protocol.PacketNumber(1)))
 			Expect(handler.packetHistory).To(HaveKey(protocol.PacketNumber(2)))
+			entropy.Add(packet1.PacketNumber, packet1.EntropyBit)
+			Expect(handler.packetHistory[1].PacketNumber).To(Equal(protocol.PacketNumber(1)))
+			Expect(handler.packetHistory[1].Entropy).To(Equal(entropy))
+			entropy.Add(packet2.PacketNumber, packet2.EntropyBit)
+			Expect(handler.packetHistory[2].PacketNumber).To(Equal(protocol.PacketNumber(2)))
+			Expect(handler.packetHistory[2].Entropy).To(Equal(entropy))
 		})
 
 		It("rejects packets with the same packet number", func() {

ackhandler/packet.go

@@ -7,6 +7,7 @@ type Packet struct {
 	PacketNumber protocol.PacketNumber
 	Plaintext    []byte
 	EntropyBit   bool
+	Entropy      EntropyAccumulator
 
 	MissingReports uint8
 }