Use deques for frame queues.

Python lists make bad queues. Rather than being linked-lists they're
actually fancy arrays. This means popping from the left (which frame
queues do) requires that the array be resized and potentially
reallocated. We should avoid some of that memory churn.

Author: Lukasa

hyper/http20/stream.py

@@ -18,6 +18,7 @@
     ContinuationFrame,
 )
 from .response import HTTP20Response
+import collections
 
 
 # Define a set of states for a HTTP/2.0 stream.
@@ -52,7 +53,7 @@ def __init__(self,
         self.stream_id = stream_id
         self.state = STATE_IDLE
         self.headers = []
-        self._queued_frames = []
+        self._queued_frames = collections.deque()
 
         # There are two flow control windows: one for data we're sending,
         # one for data being sent to us.
@@ -118,7 +119,7 @@ def listlen(list):
         # Begin by processing frames off the queue.
         while amt is None or listlen(data) < amt:
             try:
-                frame = self._queued_frames.pop(0)
+                frame = self._queued_frames.popleft()
             except IndexError:
                 # No frames on the queue. Try to read one and try again.
                 self._recv_cb()
@@ -204,7 +205,7 @@ def getresponse(self):
         # connection if necessary.
         while True:
             try:
-                frame = self._queued_frames.pop(0)
+                frame = self._queued_frames.popleft()
             except IndexError:
                 self._recv_cb()
                 continue