implement a basic flow controller

needed for #39, #100, #106

flow_controller_test.go

@@ -0,0 +1,86 @@
+package quic
+
+import (
+	"github.com/lucas-clemente/quic-go/protocol"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Flow controller", func() {
+	var controller *flowController
+
+	BeforeEach(func() {
+		controller = &flowController{}
+	})
+
+	Context("send flow control", func() {
+		It("adds bytes sent", func() {
+			controller.bytesSent = 5
+			controller.AddBytesSent(6)
+			Expect(controller.bytesSent).To(Equal(protocol.ByteCount(5 + 6)))
+		})
+
+		It("gets the size of the remaining flow control window", func() {
+			controller.bytesSent = 5
+			controller.sendFlowControlWindow = 12
+			Expect(controller.SendWindowSize()).To(Equal(protocol.ByteCount(12 - 5)))
+		})
+
+		It("updates the size of the flow control window", func() {
+			controller.bytesSent = 5
+			updateSuccessful := controller.UpdateSendWindow(15)
+			Expect(updateSuccessful).To(BeTrue())
+			Expect(controller.SendWindowSize()).To(Equal(protocol.ByteCount(15 - 5)))
+		})
+
+		It("does not decrease the flow control window", func() {
+			updateSuccessful := controller.UpdateSendWindow(20)
+			Expect(updateSuccessful).To(BeTrue())
+			Expect(controller.SendWindowSize()).To(Equal(protocol.ByteCount(20)))
+			updateSuccessful = controller.UpdateSendWindow(10)
+			Expect(updateSuccessful).To(BeFalse())
+			Expect(controller.SendWindowSize()).To(Equal(protocol.ByteCount(20)))
+		})
+	})
+
+	Context("receive flow control", func() {
+		var receiveFlowControlWindow protocol.ByteCount = 1337
+		var receiveWindowUpdateThreshold protocol.ByteCount = 500
+		var receiveFlowControlWindowIncrement protocol.ByteCount = 600
+
+		BeforeEach(func() {
+			controller.receiveFlowControlWindow = receiveFlowControlWindow
+			controller.receiveWindowUpdateThreshold = receiveWindowUpdateThreshold
+			controller.receiveFlowControlWindowIncrement = receiveFlowControlWindowIncrement
+		})
+
+		It("adds bytes read", func() {
+			controller.bytesRead = 5
+			controller.AddBytesRead(6)
+			Expect(controller.bytesRead).To(Equal(protocol.ByteCount(5 + 6)))
+		})
+
+		It("triggers a window update when necessary", func() {
+			readPosition := receiveFlowControlWindow - receiveWindowUpdateThreshold + 1
+			controller.bytesRead = readPosition
+			updateNecessary, offset := controller.MaybeTriggerWindowUpdate()
+			Expect(updateNecessary).To(BeTrue())
+			Expect(offset).To(Equal(readPosition + receiveFlowControlWindowIncrement))
+		})
+
+		It("triggers a window update when not necessary", func() {
+			readPosition := receiveFlowControlWindow - receiveWindowUpdateThreshold - 1
+			controller.bytesRead = readPosition
+			updateNecessary, _ := controller.MaybeTriggerWindowUpdate()
+			Expect(updateNecessary).To(BeFalse())
+		})
+
+		It("detects a flow control violation", func() {
+			Expect(controller.CheckFlowControlViolation(receiveFlowControlWindow + 1)).To(BeTrue())
+		})
+
+		It("does not give a flow control violation when using the window completely", func() {
+			Expect(controller.CheckFlowControlViolation(receiveFlowControlWindow)).To(BeFalse())
+		})
+	})
+})