iostream.py 文件源码

def read_from_fd(self):
        if self._ssl_accepting:
            return None
        try:
            chunk = self.socket.read(self.read_chunk_size)
        except SSL.WantReadError:
            return None

        except SSL.ZeroReturnError:
            self.close(exc_info=True)
            return None

        except SSL.SysCallError as e:
            err_num = abs(e[0])
            if err_num in (errno.EWOULDBLOCK, errno.EAGAIN):
                return None

            # NOTE: We will handle the self.close in here.
            # _read_to_buffer of BaseIOStream will not chceck SSL.SysCallError
            if err_num == errno.EPERM:
                self.close(exc_info=True)
                return None

            self.close(exc_info=True)
            raise

        # NOTE: Just in case we missed some SSL Error type.
        except SSL.Error as e:
            raise

        if not chunk:
            self.close()
            return None
        return chunk