iostream.py 文件源码

def read_from_fd(self):
        try:
            chunk = os.read(self.fd, self.read_chunk_size)
        except (IOError, OSError) as e:
            if errno_from_exception(e) in _ERRNO_WOULDBLOCK:
                return None
            elif errno_from_exception(e) == errno.EBADF:
                # If the writing half of a pipe is closed, select will
                # report it as readable but reads will fail with EBADF.
                self.close(exc_info=True)
                return None
            else:
                raise
        if not chunk:
            self.close()
            return None
        return chunk