def document_iters_to_http_response_body(ranges_iter, boundary, multipart,
                                         logger):
    """
    Takes an iterator of range iters and turns it into an appropriate
    HTTP response body, whether that's multipart/byteranges or not.

    This is almost, but not quite, the inverse of
    request_helpers.http_response_to_document_iters(). This function only
    yields chunks of the body, not any headers.

    :param ranges_iter: an iterator of dictionaries, one per range.
        Each dictionary must contain at least the following key:
        "part_iter": iterator yielding the bytes in the range

        Additionally, if multipart is True, then the following other keys
        are required:

        "start_byte": index of the first byte in the range
        "end_byte": index of the last byte in the range
        "content_type": value for the range's Content-Type header

        Finally, there is one optional key that is used in the
            multipart/byteranges case:

        "entity_length": length of the requested entity (not necessarily
            equal to the response length). If omitted, "*" will be used.

        Each part_iter will be exhausted prior to calling next(ranges_iter).

    :param boundary: MIME boundary to use, sans dashes (e.g. "boundary", not
        "--boundary").
    :param multipart: True if the response should be multipart/byteranges,
        False otherwise. This should be True if and only if you have 2 or
        more ranges.
    :param logger: a logger
    """
    if multipart:
        return document_iters_to_multipart_byteranges(ranges_iter, boundary)
    else:
        try:
            response_body_iter = next(ranges_iter)['part_iter']
        except StopIteration:
            return ''

        # We need to make sure ranges_iter does not get garbage-collected
        # before response_body_iter is exhausted. The reason is that
        # ranges_iter has a finally block that calls close_swift_conn, and
        # so if that finally block fires before we read response_body_iter,
        # there's nothing there.
        def string_along(useful_iter, useless_iter_iter, logger):
            for x in useful_iter:
                yield x

            try:
                next(useless_iter_iter)
            except __HOLE__:
                pass
            else:
                logger.warning(
                    "More than one part in a single-part response?")

        return string_along(response_body_iter, ranges_iter, logger)
dataset/ETHPy150Open openstack/swift/swift/common/utils.py/document_iters_to_http_response_body