/************************************************************************
 *									*
 *  KL_API.C   KEYBIT Lite API access module				*
 *  Public Domain 1996 Pino Navato					*
 *									*
 ************************************************************************/

#include <dos.h>
#include <string.h>
#include "kl_api.h"

#define AMIS_INSTCHECK	  0   	       /* installation check */
#define KLAPI_GET_SB_PTR  0x10	       /* get pointer to status byte */

#define AMIS_SUCCESSFUL	  0xFF


static int mpx;
static union REGS regs;


/*
  +-----  search4keybit()  ---------------------------------------------+
  |  Purpose:	Search for KEYBIT Lite v5+ in memory.			|
  |  Note:	This function sets the global variable mpx used		|
  |		by get_sb_ptr().					|
  |  Return:	Full version number if found, 0 if not found.		|
  +---------------------------------------------------------------------+
*/
unsigned search4keybit(void)
   {
   char far *sig;				/* generic AMIS signature */
   const char far *KL_sig = "Pino NavKeybit  "; /* KEYBIT's AMIS signature */

   for (mpx = 0; mpx <= 255; mpx++)
      {
      regs.h.ah = mpx;
      regs.h.al = AMIS_INSTCHECK;		/* installation check */
      int86(0x2D, &regs, &regs);
      if (regs.h.al == AMIS_SUCCESSFUL)		/* installed? */
	 {
	 sig = (char far *) MK_FP(regs.x.dx, regs.x.di);
	 if (_fstrcmp(sig, KL_sig) == 0)  /* KEYBIT Lite? */
	    if (regs.h.ch >= 5) 	  /* v5+ ? */
	       return regs.x.cx;	  /* YES! Return full version number */
	    else
	       break;			  /* NO, it's an older version. Stop searching */
	 }
      }
   return 0;
   }


/*
  +-----  get_sb_ptr()	------------------------------------------------+
  |  Purpose:	Get a far pointer to KEYBIT Lite status byte.		|
  |  Return:	Far pointer to KEYBIT Lite status byte			|
  |		or NULL if KEYBIT Lite v5+ not installed.		|
  +---------------------------------------------------------------------+
*/
unsigned char far *get_sb_ptr(void)
   {
   if (search4keybit() == 0)
      return NULL;

   regs.h.ah = mpx;
   regs.h.al = KLAPI_GET_SB_PTR;
   int86(0x2D, &regs, &regs);
   return (unsigned char far *) MK_FP(regs.x.dx, regs.x.bx);
   }


static unsigned char far *status_ptr;
static unsigned char old_status;

/*
  +-----  enable_emailsupport()  ---------------------------------------+
  |  Purpose:	Set e-mail support flag to 1 and save original status	|
  |		in the global variable old_status.			|
  |  Note:	This function has no effect if KEYBIT Lite isn't in	|
  |		memory.							|
  |  Return:	Nothing.						|
  +---------------------------------------------------------------------+
*/
void enable_emailsupport(void)
   {
   if ((status_ptr = get_sb_ptr()) != NULL)
      {   
      old_status = *status_ptr;
      *status_ptr |= EMAILSUPPORT_FLAG;
      }
   }


/*
  +-----  restore_keybit_status()  -------------------------------------+
  |  Purpose:	Restore KEYBIT Lite's original status from the global	|
  |		variable old_status.					|
  |  Note:	This function has no effect if KEYBIT Lite isn't in	|
  |		memory or if enable_emailsupport() hasn't been called.	|
  |  Return:	Nothing.						|
  +---------------------------------------------------------------------+
*/
void restore_keybit_status(void)
   {
   if (status_ptr != NULL)
      *status_ptr = old_status;
   }