write_or_die(output_fd, header, n);
obj[0].idx.crc32 = crc32(0, Z_NULL, 0);
obj[0].idx.crc32 = crc32(obj[0].idx.crc32, header, n);
write_or_die(output_fd, header, n);
obj[0].idx.crc32 = crc32(0, Z_NULL, 0);
obj[0].idx.crc32 = crc32(obj[0].idx.crc32, header, n);