[connection] Use constant-time stream ID allocation

Instead of running over all the created streams, keep track of the next
ID for unidirectional and bidirectional streams.

Co-authored-by: Jeremy Lainé <[email protected]>

src/aioquic/quic/connection.py

@@ -303,6 +303,8 @@ def __init__(
         self._local_max_streams_uni = Limit(
             frame_type=QuicFrameType.MAX_STREAMS_UNI, name="max_streams_uni", value=128
         )
+        self._local_next_stream_id_bidi = 0 if self._is_client else 1
+        self._local_next_stream_id_uni = 2 if self._is_client else 3
         self._loss_at: Optional[float] = None
         self._network_paths: List[QuicNetworkPath] = []
         self._pacing_at: Optional[float] = None
@@ -623,10 +625,10 @@ def get_next_available_stream_id(self, is_unidirectional=False) -> int:
         """
         Return the stream ID for the next stream created by this endpoint.
         """
-        stream_id = (int(is_unidirectional) << 1) | int(not self._is_client)
-        while stream_id in self._streams or stream_id in self._streams_finished:
-            stream_id += 4
-        return stream_id
+        if is_unidirectional:
+            return self._local_next_stream_id_uni
+        else:
+            return self._local_next_stream_id_bidi
 
     def get_timer(self) -> Optional[float]:
         """
@@ -1291,12 +1293,17 @@ def _get_or_create_stream_for_send(self, stream_id: int) -> QuicStream:
                 streams_blocked = self._streams_blocked_bidi
 
             # create stream
+            is_unidirectional = stream_is_unidirectional(stream_id)
             stream = self._streams[stream_id] = QuicStream(
                 stream_id=stream_id,
                 max_stream_data_local=max_stream_data_local,
                 max_stream_data_remote=max_stream_data_remote,
-                readable=not stream_is_unidirectional(stream_id),
+                readable=not is_unidirectional,
             )
+            if is_unidirectional:
+                self._local_next_stream_id_uni = stream_id + 4
+            else:
+                self._local_next_stream_id_bidi = stream_id + 4
 
             # mark stream as blocked if needed
             if stream_id // 4 >= max_streams: