move the packet number generator to the ackhandler package

internal/ackhandler/packet_number_generator_test.go

@@ -0,0 +1,100 @@
+package ackhandler
+
+import (
+	"math"
+
+	"github.com/lucas-clemente/quic-go/internal/protocol"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Packet Number Generator", func() {
+	var png *packetNumberGenerator
+
+	BeforeEach(func() {
+		png = newPacketNumberGenerator(1, 100)
+	})
+
+	It("can be initialized to return any first packet number", func() {
+		png = newPacketNumberGenerator(12345, 100)
+		Expect(png.Pop()).To(Equal(protocol.PacketNumber(12345)))
+	})
+
+	It("gets 1 as the first packet number", func() {
+		num := png.Pop()
+		Expect(num).To(Equal(protocol.PacketNumber(1)))
+	})
+
+	It("allows peeking", func() {
+		png.nextToSkip = 1000
+		Expect(png.Peek()).To(Equal(protocol.PacketNumber(1)))
+		Expect(png.Peek()).To(Equal(protocol.PacketNumber(1)))
+		num := png.Pop()
+		Expect(num).To(Equal(protocol.PacketNumber(1)))
+		Expect(png.Peek()).To(Equal(protocol.PacketNumber(2)))
+		Expect(png.Peek()).To(Equal(protocol.PacketNumber(2)))
+	})
+
+	It("skips a packet number", func() {
+		var last protocol.PacketNumber
+		var skipped bool
+		for i := 0; i < 1000; i++ {
+			num := png.Pop()
+			if num > last+1 {
+				skipped = true
+				break
+			}
+			last = num
+		}
+		Expect(skipped).To(BeTrue())
+	})
+
+	It("skips a specific packet number", func() {
+		png.nextToSkip = 2
+		num := png.Pop()
+		Expect(num).To(Equal(protocol.PacketNumber(1)))
+		Expect(png.Peek()).To(Equal(protocol.PacketNumber(3)))
+		num = png.Pop()
+		Expect(num).To(Equal(protocol.PacketNumber(3)))
+	})
+
+	It("generates a new packet number to skip", func() {
+		png.next = 100
+		png.averagePeriod = 100
+
+		rep := 5000
+		var sum protocol.PacketNumber
+
+		for i := 0; i < rep; i++ {
+			png.generateNewSkip()
+			Expect(png.nextToSkip).ToNot(Equal(protocol.PacketNumber(101)))
+			sum += png.nextToSkip
+		}
+
+		average := sum / protocol.PacketNumber(rep)
+		Expect(average).To(BeNumerically("==", protocol.PacketNumber(200), 4))
+	})
+
+	It("uses random numbers", func() {
+		var smallest uint16 = math.MaxUint16
+		var largest uint16
+		var sum uint64
+
+		rep := 10000
+
+		for i := 0; i < rep; i++ {
+			num := png.getRandomNumber()
+			sum += uint64(num)
+			if num > largest {
+				largest = num
+			}
+			if num < smallest {
+				smallest = num
+			}
+		}
+
+		Expect(smallest).To(BeNumerically("<", 300))
+		Expect(largest).To(BeNumerically(">", math.MaxUint16-300))
+		Expect(sum / uint64(rep)).To(BeNumerically("==", uint64(math.MaxUint16/2), 1000))
+	})
+})