file.py 文件源码

def _create_files(self, filename):
        # XXX this is racy
        assert filename
        logger.debug('Opening files for ‘%s’', filename)

        mkdir_p(os.path.dirname(filename))
        self._part_filename = '%s.part' % (filename, )
        self._part_fd = os.open(
            self._part_filename, os.O_CREAT | os.O_WRONLY | os.O_NONBLOCK, 0o600)

        try:
            self._segments_file.lock()
        except IOError as e:
            # Clean up.
            os.close(self._part_fd)
            self._part_fd = -1
            self._part_filename = None

            if e.errno == errno.EAGAIN:
                # Cannot acquire lock: some other process (or part of this
                # process) is already downloading it. Clean up and watch that
                # file for completion.
                logger.debug('File ‘%s.sgt’ is locked: waiting on completion.',
                             filename)
                self._watch_for_completion(filename)
                return False
            else:
                raise

        # XXX hack
        return True

        # Reserve space for the full file and truncate any existing content to
        # the start of the final chunk (because it might be smaller than the
        # chunk size).
        size = self.chunk_size * (self._num_segments - 1)
        try:
            fallocate.fallocate(self._part_fd, 0, size)
        except IOError as e:  # if it fails, we might get surprises later, but it's ok.
            logger.debug('Error calling fallocate(%u, 0, %u): %s' %
                         (self._part_fd, self._size, e.message))
        try:
            os.ftruncate(self._part_fd, size)
        except IOError as e:
            logger.debug('Error calling ftruncate(%u, %u): %s' %
                         (self._part_fd, size, e.message))

        return True