selectors.py 文件源码

def select(self, timeout=None):
            if timeout is not None:
                if timeout <= 0:
                    timeout = 0.0
                else:
                    # select.epoll.poll() has a resolution of 1 millisecond
                    # but luckily takes seconds so we don't need a wrapper
                    # like PollSelector. Just for better rounding.
                    timeout = math.ceil(timeout * 1e3) * 1e-3
                timeout = float(timeout)
            else:
                timeout = -1.0  # epoll.poll() must have a float.

            # We always want at least 1 to ensure that select can be called
            # with no file descriptors registered. Otherwise will fail.
            max_events = max(len(self._fd_to_key), 1)

            ready = []
            fd_events = _syscall_wrapper(self._epoll.poll, True,
                                         timeout=timeout,
                                         maxevents=max_events)
            for fd, event_mask in fd_events:
                events = 0
                if event_mask & ~select.EPOLLIN:
                    events |= EVENT_WRITE
                if event_mask & ~select.EPOLLOUT:
                    events |= EVENT_READ

                key = self._key_from_fd(fd)
                if key:
                    ready.append((key, events & key.events))
            return ready