send stream-level Blocked frames at the right time

fixes #110

blocked_manager.go

@@ -0,0 +1,42 @@
+package quic
+
+import (
+	"sync"
+
+	"github.com/lucas-clemente/quic-go/frames"
+	"github.com/lucas-clemente/quic-go/protocol"
+)
+
+type blockedManager struct {
+	blockedStreams map[protocol.StreamID]protocol.ByteCount
+	mutex          sync.RWMutex
+}
+
+func newBlockedManager() *blockedManager {
+	return &blockedManager{
+		blockedStreams: make(map[protocol.StreamID]protocol.ByteCount),
+	}
+}
+
+func (m *blockedManager) AddBlockedStream(streamID protocol.StreamID, offset protocol.ByteCount) {
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
+
+	m.blockedStreams[streamID] = offset
+}
+
+func (m *blockedManager) GetBlockedFrame(streamID protocol.StreamID, offset protocol.ByteCount) *frames.BlockedFrame {
+	m.mutex.RLock()
+	defer m.mutex.RUnlock()
+
+	blockedOffset, ok := m.blockedStreams[streamID]
+	if !ok {
+		return nil
+	}
+	if blockedOffset > offset {
+		return nil
+	}
+
+	delete(m.blockedStreams, streamID)
+	return &frames.BlockedFrame{StreamID: streamID}
+}