Hi guys out there,
I am not shure if this is the right forum for my Question.
Have a problem using my own Keyboard interrupt handler. The handler
works
fine as long as i do not press keys like pause, arrow keys etc. My
system
returns with a stack overflow.
Is there something i have overseen in my keyboard Interrupt Service
Routine?
I just want to get the key pressed and store it in a variable for
later processing. This comprises all keys available on the keyboard.
Can't use a while( !_bios_keybrd(_NKEYBRD_READY) ) construct, because
this
keeps my program in a trap. See code ready-for-compile code below
Sorry, that the code is written in C++ ;-)
My System:
Pentium II-MMX 233MHz
Award BIS v4.51PG
Pure MS-DS 6.2 (no MFC or WinX.X installed)
MS C700 optimizing compiler (PWB)
//
#include <dos.h>
#include <bios.h>
#include <iostream.h>
#include <stdlib>
#define _DEBUG
#define TRUE (1==1)
#define FALSE (1==0)
typedef int INT;
typedef unsigned int UINT;
typedef unsigned char BL;
typedef void (__far __interrupt *KEYBARDISR)(void);
class EventHandler
{
public:
EventHandler();
~EventHandler();
public:
static void (__far __interrupt *old_KeyboardISR)(); /* ptr. to old
keybrd int handler */
static void __far __interrupt KeyboardISR(void);
BL KeyboardSetHandler( KEYBARDISR pISRfunc );
static INT iEventCounter;
static UINT m_siKeyStroke;
void RestoreKeyboard(void);
};
// initializing class members
INT EventHandler::iEventCounter = 0;
UINT EventHandler::m_siKeyStroke = 0;
void (__far __interrupt *EventHandler::old_KeyboardISR)() = NULL;
// constructor
EventHandler::EventHandler()
{
KeyboardSetHandler( KeyboardISR );
}
EventHandler::~EventHandler()
{
RestoreKeyboard();
}
// sets keyb ISR
BL ( KEYBARDISR pISRfunc )
{
if(pISRfunc == NULL) return(FALSE);
EventHandler::old_KeyboardISR = _dos_getvect(0x09);
_dos_setvect( 0x09, pISRfunc );
return(TRUE);
}
// the Keyboard Interrupt Service Routine
void __far __interrupt EventHandler::KeyboardISR()
{
(*EventHandler::old_KeyboardISR)(); /* call old interrupt handler */
/
My intention to call the old interrupt handler is to fill the
AX register value of INT16h with the desired keystroke.
_bios_keybrd
should exactly return this value, but it does not (always)
/
EventHandler::m_siKeyStroke = (UINT)_bios_keybrd( _NKEYBRD_READ );
EventHandler::iEventCounter++;
#ifdef _DEBUG
// ok, i know we schould not call low level I/ stuff
// in a interrupt handler, but for debugging its ok ;-)
cout << "Event Counter = " << EventHandler::iEventCounter
<< " Key: " << EventHandler::m_siKeyStroke << endl;
#endif
}
void EventHandler::RestoreKeyboard(void)
{
_dos_setvect( 0x09, EventHandler::old_KeyboardISR );
}
int main(void)
{
EventHandler kbdEvent;
while(TRUE) // sorry, needs a reboot
;
return(0);
}
//

"Hartmut" <free.fly@gmx.dewrote in message
news:43DA8B7A.F68BF457@gmx.de
Hi guys out there,

I am not shure if this is the right forum for my Question.

Have a problem using my own Keyboard interrupt handler. The handler
works

Same answer as when you posted this to 'alt.comp.lang.learn.c-c++'

Find a newsgroup about your *platform* (your combination
of hardware/operating system, etc). C is a *language*,
not a platform. If you keep going from one language group
to another, you won't get anywhere.
-Mike