/*
 *  vtest.acc
 *
 *  this accessory tests a disk to see if it is a possible boot virus-
 *  infected disk.
 *
 *  version 1.0, 3/31/88
 *
 *  greg lindahl
 *
 *  this program is in the public domain. it may be copied freely,
 *  distributed, and even sold if you can find a sucker who's willing
 *  to buy it.
 *
 */

#include <define.h>
#include <gemdefs.h>
#include <osbind.h>

#define Getbpb(a) bios(7,a) /* missing from my osbind.h */

#define WORD int	 /* alcyon version of these */
#define BYTE char
#define LONG long

extern WORD gl_apid; /* declared extern to work around Alcyon binding bug */

WORD	menu_id ;	/* our menu id */

WORD 	phys_handle;	/* physical workstation handle */
WORD 	handle;		/* virtual workstation handle */

WORD	foo;

WORD	contrl[12];
WORD	intin[128];
WORD	ptsin[128];
WORD	intout[128];
WORD	ptsout[128];

WORD work_in[11];	/* Input to GSX parameter array */
WORD work_out[57];	/* Output from GSX parameter array */
WORD pxyarray[10];	/* input point array */

open_vwork()
{
	int i;

	for( i = 0 ; i < 10 ; work_in[i++] = 1 )
	   ;
	work_in[10] = 2;
	handle = phys_handle;

	v_opnvwk( work_in, &handle, work_out );
}

main()
{
	appl_init(); /* result returned as global */

	phys_handle = graf_handle(&foo,&foo,&foo,&foo);

	open_vwork();

	menu_id = menu_register(gl_apid,"  Virus Test");

	if( menu_id == -1 )	/* too many accessories */
	    return;

	multi(); /* never returns */
}


multi()
{
	WORD msgbuf[8]; /* 16 byte buffer */

	while (TRUE) {

	   evnt_mesag( msgbuf );

	   if( msgbuf[0] == AC_OPEN ) {
	      if( msgbuf[4] == menu_id ) {
		 test_disk();
	      }
	   }
	}
}

test_disk()
{
  char  buf[512];
  register  int   dno;
  register  long  reply;

  dno = form_alert( 3,
"[0][Virus Test 1.0 (3/31/88)| |Test which floppy drive?][A|B|Cancel]"
  );

  if( ( dno == 3 ) || ( dno == 0 ) )
     return;

  dno--;

  reply = Rwabs( 0, buf, 1, 0, dno );

#define AE_CHNG (-14)

  if( reply == AE_CHNG ) {
      reply = Getbpb( dno );
      reply = Rwabs( 0, buf, 1, 0, dno );
  }

  if( reply ) {
     form_alert( 1, "[2][Error reading floppy disk!][Cancel]" );
     return;
  }

/*
 *  GEMDOS disks are bootable if they checksum to the magic number 0x1234.
 *  This is more accurate than looking for a bsr in the first byte.
 */

  if( checksum( buf, 0x100 ) != 0x1234 ) {
     form_alert( 1,
"[1][Disk is not bootable...|Probably not infected.][Whew!]"
     );
  } else {
     form_alert( 1,
"[2][Disk is bootable...|Could be infected by boot virus.][Oh No!]"
      );
  }
}

int checksum( ptr, cnt )
register WORD *ptr;
register int cnt;
{
	register i;

	for( i = 0 ; cnt-- ; )
	   i += *ptr++;

	return( i );
}