Writes the file footer (finished the file).

def WriteFileFooter(self):
    """Writes the file footer (finished the file)."""

    if not self._stream:
      raise ArchiveAlreadyClosedError(
          "Attempting to write to a ZIP archive that was already closed.")

    if self.cur_cmpr:
      buf = self.cur_cmpr.flush()
      self.cur_compress_size += len(buf)
      self.cur_zinfo.compress_size = self.cur_compress_size

      self._stream.write(buf)
    else:
      self.cur_zinfo.compress_size = self.cur_file_size

    self.cur_zinfo.CRC = self.cur_crc
    self.cur_zinfo.file_size = self.cur_file_size

    # The zip footer has a 8 bytes limit for sizes so if we compress a
    # file larger than 4 GB, the code below will not work. The ZIP64
    # convention is to write 0xffffffff for compressed and
    # uncompressed size in those cases. The actual size is written by
    # the library for us anyways so those fields are redundant.
    cur_file_size = min(0xffffffff, self.cur_file_size)
    cur_compress_size = min(0xffffffff, self.cur_compress_size)

    # Writing data descriptor ZIP64-way by default. We never know how large
    # the archive may become as we're generating it dynamically.
    #
    # crc-32                          8 bytes (little endian)
    # compressed size                 8 bytes (little endian)
    # uncompressed size               8 bytes (little endian)
    self._stream.write(
        struct.pack("<LLL", self.cur_crc, cur_compress_size, cur_file_size))

    # Register the file in the zip file, so that central directory gets
    # written correctly.
    self._zip_fd.filelist.append(self.cur_zinfo)
    self._zip_fd.NameToInfo[self.cur_zinfo.filename] = self.cur_zinfo

    self._ResetState()

    return self._stream.GetValueAndReset()