http.py 文件源码

def next_chunk(self, num_retries=0):
    """Get the next chunk of the download.

    Args:
      num_retries: Integer, number of times to retry with randomized
            exponential backoff. If all retries fail, the raised HttpError
            represents the last request. If zero (default), we attempt the
            request only once.

    Returns:
      (status, done): (MediaDownloadStatus, boolean)
         The value of 'done' will be True when the media has been fully
         downloaded.

    Raises:
      googleapiclient.errors.HttpError if the response was not a 2xx.
      httplib2.HttpLib2Error if a transport error has occured.
    """
    headers = {
        'range': 'bytes=%d-%d' % (
            self._progress, self._progress + self._chunksize)
        }
    http = self._request.http

    resp, content = _retry_request(
        http, num_retries, 'media download', self._sleep, self._rand, self._uri,
        'GET', headers=headers)

    if resp.status in [200, 206]:
      if 'content-location' in resp and resp['content-location'] != self._uri:
        self._uri = resp['content-location']
      self._progress += len(content)
      self._fd.write(content)

      if 'content-range' in resp:
        content_range = resp['content-range']
        length = content_range.rsplit('/', 1)[1]
        self._total_size = int(length)
      elif 'content-length' in resp:
        self._total_size = int(resp['content-length'])

      if self._progress == self._total_size:
        self._done = True
      return MediaDownloadProgress(self._progress, self._total_size), self._done
    else:
      raise HttpError(resp, content, uri=self._uri)