keep track of highest byte received in FlowController

ref #39

flow_controller.go

@@ -15,6 +15,7 @@ type flowController struct {
 	lastBlockedSentForOffset protocol.ByteCount
 
 	bytesRead                         protocol.ByteCount
+	highestReceived                   protocol.ByteCount
 	receiveWindowUpdateThreshold      protocol.ByteCount
 	receiveFlowControlWindow          protocol.ByteCount
 	receiveFlowControlWindowIncrement protocol.ByteCount
@@ -61,6 +62,15 @@ func (c *flowController) SendWindowSize() protocol.ByteCount {
 	return c.sendFlowControlWindow - c.bytesSent
 }
 
+func (c *flowController) UpdateHighestReceived(n protocol.ByteCount) {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+
+	if n > c.highestReceived {
+		c.highestReceived = n
+	}
+}
+
 func (c *flowController) AddBytesRead(n protocol.ByteCount) {
 	c.mutex.Lock()
 	defer c.mutex.Unlock()
@@ -100,11 +110,11 @@ func (c *flowController) MaybeTriggerWindowUpdate() (bool, protocol.ByteCount) {
 	return false, 0
 }
 
-func (c *flowController) CheckFlowControlViolation(highestByte protocol.ByteCount) bool {
+func (c *flowController) CheckFlowControlViolation() bool {
 	c.mutex.Lock()
 	defer c.mutex.Unlock()
 
-	if highestByte > c.receiveFlowControlWindow {
+	if c.highestReceived > c.receiveFlowControlWindow {
 		return true
 	}
 	return false

flow_controller_test.go

@@ -103,12 +103,26 @@ var _ = Describe("Flow controller", func() {
 			Expect(updateNecessary).To(BeFalse())
 		})
 
+		It("updates the highestReceived", func() {
+			controller.highestReceived = 1337
+			controller.UpdateHighestReceived(1338)
+			Expect(controller.highestReceived).To(Equal(protocol.ByteCount(1338)))
+		})
+
+		It("does not decrease the highestReceived", func() {
+			controller.highestReceived = 1337
+			controller.UpdateHighestReceived(1000)
+			Expect(controller.highestReceived).To(Equal(protocol.ByteCount(1337)))
+		})
+
 		It("detects a flow control violation", func() {
-			Expect(controller.CheckFlowControlViolation(receiveFlowControlWindow + 1)).To(BeTrue())
+			controller.UpdateHighestReceived(receiveFlowControlWindow + 1)
+			Expect(controller.CheckFlowControlViolation()).To(BeTrue())
 		})
 
 		It("does not give a flow control violation when using the window completely", func() {
-			Expect(controller.CheckFlowControlViolation(receiveFlowControlWindow)).To(BeFalse())
+			controller.UpdateHighestReceived(receiveFlowControlWindow)
+			Expect(controller.CheckFlowControlViolation()).To(BeFalse())
 		})
 	})
 })

stream.go

@@ -203,7 +203,8 @@ func (s *stream) Close() error {
 // AddStreamFrame adds a new stream frame
 func (s *stream) AddStreamFrame(frame *frames.StreamFrame) error {
 	maxOffset := frame.Offset + protocol.ByteCount(len(frame.Data))
-	if s.flowController.CheckFlowControlViolation(maxOffset) {
+	s.flowController.UpdateHighestReceived(maxOffset)
+	if s.flowController.CheckFlowControlViolation() {
 		return errFlowControlViolation
 	}