#include <stdio.h>
#include <conio.h>
#include <dos.h>

//In C++, ISRs take (...) arguments
#ifdef __cplusplus
  #define __CPPARGS ...
#else
  #define __CPPARGS
#endif

//Kills the current interrupt, no matter where it is
void sendEOI(void);


void interrupt far (*oldisr[16])(__CPPARGS);  //global to store old handler pointer

void sendEOI(void)
{
   outportb(0xA0, 0x20);
   outportb(0x20, 0x20);
}

unsigned char initirq(char IRQnumber,void interrupt (*ISR)(__CPPARGS))
{
   unsigned char intmask, oldmask;

   if (IRQnumber <=7) {
      oldmask = inportb(0x21);
      oldisr[IRQnumber] = getvect(IRQnumber + 8);
      setvect(IRQnumber + 8,ISR);
      intmask = oldmask & (~(1 << IRQnumber));
      outportb(0x21,intmask);
   } else {
      oldmask = inportb(0xA1);
      oldisr[IRQnumber] = getvect(IRQnumber + 0x70 - 8);
      setvect(IRQnumber - 8 + 0x70, ISR);
      intmask = oldmask & (~(1 << (IRQnumber - 8)));
      outportb(0xA1, intmask);
   }
   return(oldmask);
}

void restoreirq(char IRQnumber)
{
   unsigned char intmask;

   if (IRQnumber <=7 ){
      intmask = inportb(0x21);
      intmask |= (1 << IRQnumber);
      setvect(IRQnumber + 8,oldisr[IRQnumber]);
      outportb(0x21, intmask);
   } else {
      intmask = inportb(0xA1);
      intmask |= (1 << (IRQnumber - 8));
      setvect(IRQnumber - 8 + 0x70, oldisr[IRQnumber]);
      outportb(0xA1, intmask);
   }
}







// sets ISR to IRQnumber service routine
// returns the old PIC mask
unsigned char initirq(char IRQnumber,void interrupt (*ISR)(__CPPARGS));

// restores IRQnumber service routine
void restoreirq(char IRQnumber);


int IRQoccurred;
unsigned int BASE;
int IRQ;


void interrupt far newisr(__CPPARGS)
{

  IRQoccurred++;
  outportb(BASE + 0xF, 0);
  sendEOI();
}


unsigned AskForBaseAddress(unsigned int OldOne)
{
	char msg[7];
	int NewOne = 0, Success = 0, Dummy;
	int AddrInputPosX, AddrInputPosY;

	puts("\nPlease enter the Base Address for your card (in hex)");
	printf("or press ENTER for %X.\n>", OldOne);
	AddrInputPosX = wherex(); AddrInputPosY = wherey();
	do {
      gotoxy(AddrInputPosX, AddrInputPosY);
      clreol();
      msg[0] = 5; msg[1] = 0;
	  cgets(msg);
      sscanf(msg + 2, "%x", &NewOne);
      Success = 1;
      Dummy = NewOne;
		if (msg[1] == 0) {
        gotoxy(AddrInputPosX, AddrInputPosY);
        printf("%X", OldOne);
        Success = 1;
        Dummy = OldOne;
      }
	} while(!Success);
	return (Dummy);
} /* end of AskForBaseAddress */


int getIRQnum(int defIRQ)
{

    char line[8];
    int IRQ;

    clrscr();
    printf("Please enter the IRQ number or press <enter> for %d\n=>", defIRQ);

    gets(line);

    if (sscanf(line, "%d", &IRQ) == 0)
       IRQ = defIRQ;


    return IRQ;
}



void doIO ()
{
    int done = 0;
    char stroke;
    unsigned int portA;

    //set up  Ports A and B for input
    //set up Port C for output so we can generate interrupts with it.

    outportb(BASE + 0x3, 0x92);

    outportb(BASE + 0xE, 0); //enable the card to generate interrupts


    while (!done)
    {
        printf("Press 'q' to quit. Any other key to generate an interrupt\n");
        printf("and read the digital bits on Port A\n");
        while(!kbhit());
        stroke = getch();

        if (stroke == 'q' || stroke == 'Q')
           return;


        outportb(BASE + 0x2, 0);
        delay(0);
        outportb(BASE + 0x2, 0x8);

        delay(1); //1 millisecond should be more than enough time for the card to
                  //create an interrupt;

        if (IRQoccurred)
        {
            portA = inportb(BASE);

            printf("Reading from PortA is: %02x Hex\n", portA);

            IRQoccurred = 0;
        }
        else
        {
            printf("No interrupt occurred\n");
        }
    }
}


void main (void)
{

    //init global variables
    BASE = 0xE000;
    IRQ = 11;

    //get the cards base address and current IRQ

    clrscr();

    BASE = AskForBaseAddress(BASE);
    IRQ = getIRQnum(IRQ);


    //set up our new IRQ handler, but don't enable the card to
    //generate them just yet
    initirq(IRQ, newisr);


    //do the interrupts

    doIO();


    //disable interrupts on the card
    outportb(BASE + 0xD, 0);

    //restore the old IRQ and allow the program to exit

    restoreirq(IRQ);

}