// capture interrupts and change time resolution
#include <dos.h>
#include "millisec.h"

void interrupt far my_timer (...);
void interrupt far ctrl_brk (...);
void interrupt far ctrl_c (...);

extern unsigned breakflag;
extern long clockticks;

static void interrupt (far *oldint08) (...);

millisec::millisec () {
breakflag = 0; clockticks = 0;
oldint08 = getvect (8);
oldint27 = getvect (27);
oldint35 = getvect (35);
disable(); // now install our handlers
setvect (8, my_timer);
outportb (67, 52); // change to millisecond timing
outportb (64, 168); // 168 = low order byte of 1192
outportb (64, 4); // 4 = high order byte of 1192
setvect (27, ctrl_brk);
setvect (35, ctrl_c);
enable(); // ready to process
}

millisec::~millisec () {
disable(); // restore original handlers
setvect (8, oldint08);
outportb (67, 52); // restore standard time
outportb (64, 0);
outportb (64, 0);
setvect (27, oldint27);
setvect (35, oldint35);
enable(); // ready to exit
}

void interrupt far my_timer (...) {
static int count = 0;
clockticks++; count++;
if (count < 55) outportb (32, 32);
else { count=0; (oldint08)(); } }

void interrupt far ctrl_brk (...) {
breakflag++; }

void interrupt far ctrl_c (...) {
breakflag++; }