Add support for driving BufferedProtocol instances using `sock_recv…

…_into`

Support for this feature is emulated for the `Pipe{Read,Write}Transport`
however, since `glib.IOChannel` does not appear to expose anything similar
to the `recvinto` syscall in its APIs. The emulation at least makes it possible
to use `BufferedProtocol` instances without causing crashes due to API
differences versus the classic `Protocol` interface at least.

src/gbulb/transports.py

@@ -154,9 +154,9 @@ def _submit_read_data(self, data):
     def _loop_reading(self, fut=None):
         if self._paused:
             return
-        data = None
 
         try:
+            data = None
             if fut is not None:
                 assert self._read_fut is fut or (
                     self._read_fut is None and self._closing
@@ -171,7 +171,7 @@ def _loop_reading(self, fut=None):
                 data = None
                 return
 
-            if data == b"" or data == 0:
+            if data == b"":
                 # No need to reschedule on end-of-file
                 return
 
@@ -193,9 +193,6 @@ def _loop_reading(self, fut=None):
             self._cancelable.add(self._read_fut)
         else:
             self._read_fut.add_done_callback(self._loop_reading)
-        finally:
-            if data is not None:
-                self._submit_read_data(data)
 
 
 class WriteTransport(BaseTransport, transports._FlowControlMixin):