//  v1_zad4.cpp
//  prevodjenje iz komandne linije: bcc -ms -Ic:\bc31\include -Lc:\bc31\lib v1_zad4.cpp

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

struct PCB{
    unsigned sp;
    unsigned* stack;
};

PCB *p[3];
PCB* running; 

int nextThread;

//makro
#define dispatch(x) { \
   nextThread = x; \
   _dispatch(); \
 }
void _dispatch(){
  asm {    // Cuva registre na steku.
	push ax // Sta bi se desilo da ne cuvamo AX?
	push bx
	push cx
	push dx
	mov bx, running // upisuje adresu mem. lok.
 	mov [bx], sp    // cuva sp
  }
  running = p[nextThread];
  asm {
	mov bx, running
	mov sp, [bx]   // restauira sp
     	
	 pop dx        // restauira podatke
	 pop cx
	 pop bx
	 pop ax
  }
}
// funkcija koju izvrsava nit 1
void a() {
  for (int i = 0; i < 3; ++i) printf("U a() %d\n",i);
  
  asm mov ax, 7
  
  dispatch(2);
 
  asm mov i, ax
  
  printf(" u a() ax = %d\n",i);

  for (i = 0; i < 3; ++i) printf("U a() %d\n",i);

  dispatch(2);
}
// funkcija koju izvrsava nit 2
void b() {
  for (int i = 0; i < 3; ++i) printf("U b() %d\n",i);

  asm mov ax, 2

  dispatch(1);

  for (i = 0; i < 3; ++i) printf("U b() %d\n",i);
 
  dispatch(0);
}
void createThread (PCB * newPCB, void (*body)()) {
  unsigned* st = new unsigned[1024];
  
  unsigned newPC = FP_OFF(body);
  st[1023] = newPC; // upisuje se rec - int
  
  // pocetni kontekst 
  //(proizvoljne vrednosti)
  // st[1023-1018] = {PC,BP,AX…DX}   
  newPCB->sp = FP_OFF(st+1018);
  newPCB->stack = st;
}

void delete_all() {
  delete [] p[1]->stack;
  delete [] p[2]->stack;
  delete p[0];
  delete p[1];
  delete p[2];
}
int main() {
  p[1] = new PCB();
  createThread(p[1], a);
  printf("napravio a\n");

  p[2] = new PCB();
  createThread(p[2], b);
  printf("napravio b\n");

  p[0] = new PCB();
  running = p[0];
  dispatch(1);
  
  printf("Kraj.\n");
  delete_all();
  return 0;
}