Fixes checksums in Yu-Gi-Oh! 5D's World Championship 2011 (NDS) save files

YGOWC11SaveFix.c

// YGOWC11SaveFix - fixes checksums in Yu-Gi-Oh! 5D's World Championship 2011 (NDS) save files
// Copyright (C) 2014  BlackShark
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

#include <stdio.h>
#include <stdlib.h>
#include "crc32.c"

int main(int argc, char** argv)
{
    uint32_t RAW_SAV_SIZE = 0x10000;
    uint32_t DESMUME_SAV_SIZE = 0x1007A;
    uint32_t CHECKSUM_AREA_OFFSET[2] = { 0x8500, 0xB838 };
    uint32_t CHECKSUM_AREA_SIZE = 0x3334;
    uint32_t CHECKSUM_OFFSET[2] = { 0xB834, 0xEB6C };
    char WCS2011_SIGNATURE[7] = { 0x77, 0x63, 0x73, 0x32, 0x30, 0x31, 0x31 }; // wcs2011

    printf("YGOWC11SaveFix - fixes save files of Yu-Gi-Oh! 5D's WC 2011\n");

    if(argc != 2)
    {
        printf("usage: YGOWC11SaveFix.exe SAVEFILE\n");

        return 0;
    }

    FILE *fp = fopen(argv[1], "rb+");
    if (!fp)
    {
        printf("File loading failed\n");
        fclose(fp);

        return 0;
    }

    fseek (fp, 0, SEEK_END);
    uint32_t fSize = ftell(fp);

    if(fSize != RAW_SAV_SIZE && fSize != DESMUME_SAV_SIZE)
    {
        printf("Invalid file size (%d (0x%X))\n", fSize, fSize);
        fclose(fp);

        return 0;
    }

    char *signature = (char *)malloc(7);
    fseek (fp, 0, SEEK_SET);
    fread(signature, 1, 7, fp);

    int x;
    for(x = 0; x < 7; x++)
    {
        if(WCS2011_SIGNATURE[x] != signature[x])
        {
            printf("This is not a valid save file of Yu-Gi-Oh! 5D'S World Championship 2011 (NDS)\n");
            free(signature);
            fclose(fp);

            return 0;
        }
    }
    free(signature);

    char *checksumArea = (char *)malloc(CHECKSUM_AREA_SIZE);
    char *checksum = (char *)malloc(4);
    uint32_t tmp = 0;

    for(x = 0; x < 2; x++)
    {
        fseek (fp, CHECKSUM_AREA_OFFSET[x], SEEK_SET);
        fread(checksumArea, 1, CHECKSUM_AREA_SIZE, fp);

        if(checksumArea[0] == 0x53)
        {
            tmp = crc32(0, checksumArea, CHECKSUM_AREA_SIZE);

            fseek (fp, CHECKSUM_OFFSET[x], SEEK_SET);
            fread(checksum, 1, 4, fp);

            checksum[0] = (char)(tmp);
            checksum[1] = (char)((tmp >> 8));
            checksum[2] = (char)((tmp >> 16));
            checksum[3] = (char)((tmp >> 24));

            fseek (fp, CHECKSUM_OFFSET[x], SEEK_SET);
            fwrite(checksum, 1, 4, fp);
        }
    }

    free(checksumArea);
    free(checksum);
    fclose(fp);

    printf("Checksum fixed!\n");

    return 0;
}

Note: There are checksums in the "header" area (0 - 0x84FF) as well which are not fixed by this tool. Those are used for DLC stuff.