sphinx_gci_gamecube.1sc

//------------------------------------------------
//--- 010 Editor v12.0.1 Script File
//
//      File: Sphinx and the Cursed Mummy - GameCube save data (CRC32 regen script)
//   Authors: Swyter
//   Version: 2022.08.04
//   Purpose: Recompute the CRC32 checksum that the Sphinx GameCube savedata seems to use for error correction.
//            This will probably work for any other GCI saves, I think.
//  Category: Game
//------------------------------------------------

Printf("\n\n--\n[+] Checksumming «%s»\n", GetFileName());

BigEndian();

uint64 data_end_offset = FileSize();

 int64    old_checksum = ReadUInt(0x40); /* swy: the checksum is at offset 0x40, right at the end of the main header, there's some padding afterwards */
 int64    new_checksum = Checksum(CHECKSUM_CRC32, 0x1c0, data_end_offset); /* swy: right after the header padding starts the verified chunk, right until the end */

Printf(
    "\n[i] Old: %06X,\n    New: %6X (%smatch)\n", old_checksum, new_checksum,
    (old_checksum == new_checksum) ? "" : "didn't "
);

if (old_checksum != new_checksum)
    WriteUInt(0x40, new_checksum); /* swy: overwrite it in place */

Printf("\n[+] Done\n");