sims.c

/*
The Sims 3 save game checksum fix
*/

#include <stdio.h>
#include <stdlib.h>


// the sims 3 code: sub_20935D0
unsigned int checksum(unsigned char *savegame, size_t size)
{
  unsigned int i = 0; // r4@1
  unsigned int v3; // r2@2

  for (i = 19; size; --size )
  {
    v3 = *savegame++;
    i = (i + (v3 * size & 0xFFFF)) & 0xFFFF;
  }
  return i;
}


int main(int argc, char **argv) {
	unsigned char *saveFile = NULL;
	FILE *save = fopen(argv[1], "rb");

	if (save != NULL) {
		unsigned int saveSize = 0;

		fseek(save, 0L, SEEK_END);
		saveSize = ftell(save);
		rewind(save);

		saveFile = (unsigned char*) malloc (sizeof(unsigned char) * saveSize);

		fread(saveFile, sizeof(unsigned char), saveSize, save);

		printf("value: 0x%X\n", *(unsigned int*)(saveFile+0x28));

		unsigned short data = checksum((saveFile+0x28), 0x6C);

		printf("value: 0x%X\n", data);

		fclose(save);
		free(saveFile);
		saveFile = NULL;
	} else {
		printf("Failed to open save game file");
	}


	return 0;
}