/* correct-i386-2.c
   Corrects the Debian 2.2 rev0 i386 Binary-2 CD for a single-bit error.

   COMPILE: gcc -Wall -O2 -o correct-i386-2 correct-i386-2.c
   USAGE:   ./correct-i386-2 binary-i386-2.iso
   NOTE: This is an in-place correction - it doesn't require any disk space.

   Old md5sum: c4a8591b64efe58e0acd39f7eac30ac6  binary-i386-2.iso
   New md5sum: be04cd6d17159d66978ad227b26ed17d  binary-i386-2.iso

   Copyright (C) 2000 J.A. Bezemer
   Licensed under GNU GPL -- NO WARRANTY WHATSOEVER -- USE AT YOUR OWN RISK!
 */

#include <stdio.h>

#define POS 0x148554de
/* Or 0x64de to correct pdksh_5.2.14-1.deb when copied from the CD */

#define OLD 0xc8
#define NEW 0xc0

int
main (int argc, char *argv[])
{
  FILE *f;
  unsigned char o, n = NEW;

  if (argc == 2 &&
      (f = fopen (argv[1], "r+")) != NULL &&
      fseek (f, POS, SEEK_SET) == 0 &&
      fread (&o, 1, 1, f) == 1 &&
      o == OLD &&
      fseek (f, POS, SEEK_SET) == 0 &&
      fwrite (&n, 1, 1, f) == 1 &&
      fclose (f) == 0)
    {
      fprintf (stderr, "Correction successful\n");
      return 0;
    }
  else
    {
      fprintf (stderr, "Usage error, file error, wrong file or already "
	       "converted file\n");
      perror ("This may be the error message");
      return 1;
    }
}