Decode bson data from a file to multiple documents as a generator.

    Works similarly to the decode_all function, but reads from the file object
    in chunks and parses bson in chunks, yielding one document at a time.

    :Parameters:
      - `file_obj`: A file object containing BSON data.
      - `codec_options` (optional): An instance of
        :class:`~bson.codec_options.CodecOptions`.

    .. versionchanged:: 3.0
       Replaced `as_class`, `tz_aware`, and `uuid_subtype` options with
       `codec_options`.

    .. versionadded:: 2.8

def decode_file_iter(file_obj, codec_options=DEFAULT_CODEC_OPTIONS):
    """Decode bson data from a file to multiple documents as a generator.

    Works similarly to the decode_all function, but reads from the file object
    in chunks and parses bson in chunks, yielding one document at a time.

    :Parameters:
      - `file_obj`: A file object containing BSON data.
      - `codec_options` (optional): An instance of
        :class:`~bson.codec_options.CodecOptions`.

    .. versionchanged:: 3.0
       Replaced `as_class`, `tz_aware`, and `uuid_subtype` options with
       `codec_options`.

    .. versionadded:: 2.8
    """
    while True:
        # Read size of next object.
        size_data = file_obj.read(4)
        if len(size_data) == 0:
            break  # Finished with file normaly.
        elif len(size_data) != 4:
            raise InvalidBSON("cut off in middle of objsize")
        obj_size = _UNPACK_INT(size_data)[0] - 4
        elements = size_data + file_obj.read(obj_size)
        yield _bson_to_dict(elements, codec_options)