//  v1_zad8.cpp
//  prevodjenje iz komandne linije: bcc -ms -Ic:\bc31\include -Lc:\bc31\lib v1_zad8.cpp

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

struct cnt_buf {  // pomeraj
	unsigned sp;  // +0
	unsigned ax;  // +2
	unsigned bx;  // +4
	unsigned cx;  // +6
	unsigned dx;  // +8
	unsigned pc;  // +10
	unsigned bp;  // +12
};

struct PCB {
	cnt_buf* context;
	unsigned* stack;
};

unsigned _setjmp(cnt_buf *b){
	asm { 
		push bx
		mov bx, [bp+4]		// BX = b 
		mov bx[2], ax		// ax polje
		pop WORD PTR [bx+4]	// bx
		mov bx[6], cx		// cx
		mov bx[8], dx		// dx
		mov ax, bp[0]		// AX = old_bp
		mov bx[12], ax		// bp
		mov ax, bp[2]		// AX = pc_ret
		mov bx[10], ax		// pc
		mov [bx], sp			// running->sp=SP
		//skida se sa steka b, PC, BP
		add WORD PTR[bx], 6 
	}
	return 0;
}
void _longjmp(cnt_buf *b, unsigned i){
	asm {
		mov ax, [bp+6]			// AX = i
		mov bx, [bp+4]			// BX = b;
		mov sp, [bx]			// restauriramo stek
		push bx					// Vracamo b,
		push WORD PTR bx[10]	// pc,
		push WORD PTR bx[12]	// i bp na stek.
		mov bp, sp				// BP <= SP
	//	mov ax, bx[2]			// ne radi se restauracija ax, jer ce to biti povratna vrednost!!!
		push WORD PTR bx[4]		// cuvamo bx polje na steku
		mov cx, bx[6]			// restauracija CX
		mov dx, bx[8]			// restauracija DX
		pop bx					// restauracija BX
	}
}
void createThread(PCB *newPCB, void (*body)()) {
	newPCB->stack = new unsigned[1024];
	newPCB->context = new cnt_buf;

	newPCB->context->pc = FP_OFF(body);
	newPCB->context->sp = FP_OFF(newPCB->stack+1024);
}


PCB *p[3];
PCB* running; 

int nextThread;

//makro
#define dispatch(x) { \
	nextThread = x; \
	_dispatch(); \
}

void _dispatch(){
	if (_setjmp(running->context) == 0) {
		
		running = p[nextThread];
		_longjmp(running->context,1);
	} else {
		return;
	}
}

// funkcija koju izvrsava nit 1
void a() {
	int i;
	for (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 delete_all() {
	delete [] p[1]->stack;
	delete [] p[2]->stack;
	delete [] p[1]->context;
	delete [] p[2]->context;
	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;
}