patchbin.c

/* patchbin.c, Patch a binary file, by Lionello Lunesu, placed in the public domain */
struct FILE;
extern struct FILE* fopen(char*, char*);
extern int fwrite(void*, int, int, struct FILE*);
extern int fread(void*, int, int, struct FILE*);
extern int fseek(struct FILE*, long int, int);
#define SEEK_SET 0
extern int memcmp(void*, void*, int);

int main(int argc, char** argv)
{
  long int OFFSET = 0x0002de70;
  unsigned TEST[] = { 0xe5903010, 0xe92d4070, 0xe3530000, 0xe1a04000, 0xe590500c, 0x1a00000a };
  unsigned PATCH[] = { 0xe3a00000 };

  struct FILE * f = fopen(argv[1], "r+");
  if (!f)
    return 1;
  if (fseek(f, OFFSET, SEEK_SET))
    return 2;
  char buf[sizeof(TEST)];
  if (1 != fread(buf, sizeof(TEST), 1, f))
    return 3;
  if (memcmp(buf, TEST, sizeof(TEST)))
    return 4;
  if (1 != fwrite(PATCH, sizeof(PATCH), 1, f))
    return 5;
  return 0;
}