improve sending of WindowUpdate frames

fixes #96

window_update_manager.go

@@ -0,0 +1,66 @@
+package quic
+
+import (
+	"sync"
+
+	"github.com/lucas-clemente/quic-go/frames"
+	"github.com/lucas-clemente/quic-go/protocol"
+)
+
+type windowUpdateItem struct {
+	Offset  protocol.ByteCount
+	Counter uint8
+}
+
+// WindowUpdateManager manages window update frames for receiving data
+type WindowUpdateManager struct {
+	streamOffsets map[protocol.StreamID]*windowUpdateItem
+	mutex         sync.RWMutex
+}
+
+// NewWindowUpdateManager returns a new WindowUpdateManager
+func NewWindowUpdateManager() *WindowUpdateManager {
+	return &WindowUpdateManager{
+		streamOffsets: make(map[protocol.StreamID]*windowUpdateItem),
+	}
+}
+
+// SetStreamOffset sets an offset for a stream
+func (m *WindowUpdateManager) SetStreamOffset(streamID protocol.StreamID, n protocol.ByteCount) {
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
+
+	entry, ok := m.streamOffsets[streamID]
+	if !ok {
+		m.streamOffsets[streamID] = &windowUpdateItem{Offset: n}
+		return
+	}
+
+	if n > entry.Offset {
+		entry.Offset = n
+		entry.Counter = 0
+	}
+}
+
+// GetWindowUpdateFrames gets all the WindowUpdate frames that need to be sent
+func (m *WindowUpdateManager) GetWindowUpdateFrames() []*frames.WindowUpdateFrame {
+	m.mutex.RLock()
+	defer m.mutex.RUnlock()
+
+	var wuf []*frames.WindowUpdateFrame
+
+	for key, value := range m.streamOffsets {
+		if value.Counter >= protocol.WindowUpdateNumRepitions {
+			continue
+		}
+
+		frame := frames.WindowUpdateFrame{
+			StreamID:   key,
+			ByteOffset: value.Offset,
+		}
+		value.Counter++
+		wuf = append(wuf, &frame)
+	}
+
+	return wuf
+}