def make_footer
      footer = [
        @crc,              # bytes 0-3
        @zstream.total_in, # bytes 4-7
      ].pack 'VV'

      @io.write footer

      @zstream.flags |= Zlib::GzipFile::FOOTER_FINISHED
    end
def make_footer
      footer = [
        @crc,              # bytes 0-3
        @zstream.total_in, # bytes 4-7
      ].pack 'VV'

      @io.write footer

      @zstream.flags |= Zlib::GzipFile::FOOTER_FINISHED
    end
Writes out a gzip footer