code: def fill_rawq(self):
          
          if self.irawq >= len(self.rawq):
              self.rawq = b''
              self.irawq = 0
          # The buffer size should be fairly small so as to avoid quadratic
          # behavior in process_rawq() above
          buf = yield from self._reader.read(50)
          self.eof = (not buf)
          self.rawq = self.rawq + buf
docs: Fill raw queue from exactly one recv() system call.
  
          Set self.eof when connection is closed.