implement some stream ID helper functions

internal/protocol/stream_id.go

@@ -3,6 +3,19 @@ package protocol
 // A StreamID in QUIC
 type StreamID uint64
 
+// InitiatedBy says if the stream was initiated by the client or by the server
+func (s StreamID) InitiatedBy() Perspective {
+	if s%2 == 0 {
+		return PerspectiveClient
+	}
+	return PerspectiveServer
+}
+
+// IsUniDirectional says if this is a unidirectional stream (true) or not (false)
+func (s StreamID) IsUniDirectional() bool {
+	return s%4 >= 2
+}
+
 // MaxBidiStreamID is the highest stream ID that the peer is allowed to open,
 // when it is allowed to open numStreams bidirectional streams.
 func MaxBidiStreamID(numStreams int, pers Perspective) StreamID {