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#include "kernel.h"

int strlen(string str);
void dec2bin(dword decimal, int prefix);
void drawdesktop(byte ch, char fore, char back);
void drawwindow(string title, int xpos, int ypos, int width, int height, char fore, char back);


void kernel(void) // kernel entry point
{
	drawdesktop(177, COLOR_WHITE, COLOR_BLUE);
	drawwindow(" Simple OS Example - by Napalm ", 4, 4, 72, 16, COLOR_LTWHITE, COLOR_BLUE);
	putsnocr("Welcome to this example! ");
        /* I put another putsnocr line here but it didnt show up only "Welcome to this example" showed  */
	hidecursor();
	
	dword value = 0xDEADBEEF;
	while(1){
		// display value in decimal
		gotoxy(6, 9);
		dword decimal = value;
		char base[10];
		int i = 0;
		while(decimal > 0){
			base[i++] = '0' + (decimal % 10);
			decimal /= 10;
		}
		while(i-- > 0) putch(base[i]);
		
		// display value in hex	
		gotoxy(6, 10);
		putsnocr("0x");
		for(int i = 28; i > -1; i -= 4){
			byte nibble = ((value >> i) & 0x0F);
			if(nibble < 10) putch('0' + nibble);
			else putch('A' + (nibble - 10));
		}
		
		// display value in binary
		gotoxy(6, 11);
		dec2bin(value, 32);
		value++;
	}
}

int strlen(string str) // simple string length
{
	string end = str;
	while(*end++);
	return (end - str);
}

void drawdesktop(byte ch, char fore, char back)
{
	// clear screen with foreground and background
	// and also with desired character
	settextcolor(fore, back);
	cls(ch);
}

// decimal to binary
void dec2bin(dword decimal, int prefix)
{
	dword j = 0;
	for(int i = prefix; i >= 0; --i, j = ((decimal & (1 << i)) >> i))
		if(prefix || j) prefix = putch('0' + j);
}

void drawwindow(string title, int xpos, int ypos, int width, int height, char fore, char back)
{
	int xextent = (xpos + width - 1), yextent = (ypos + height - 1);
	// draw window
	for(int y = ypos; y <= yextent; y++){
		settextcolor(fore, back);
		gotoxy(xpos, y);
		if(y == ypos){ // draw top caption bar
			settextcolor(COLOR_LTYELLOW, COLOR_RED);
			for(int x = xpos; x <= xextent; x++){
				if(x == xpos) putch(213);
				else if(x == xextent) putch(254);
				else putch(205);
			}
			gotoxy(xpos + ((width - strlen(title)) / 2), y);
			putsnocr(title);
		}else if(y < yextent){ // draw middle lines
			for(int x = xpos; x <= xextent; x++){
				if(x == xpos || x == xextent) putch(179);
				else putch(' ');
			}
		}else{ // draw bottom edge
			for(int x = xpos; x <= xextent; x++){
				if(x == xpos) putch(192);
				else if(x == xextent) putch(217);
				else putch(196);
			}
		}
	}
	// draw vertical shadow
	for(int y = ypos; y <= yextent; y++){
		gotoxy(xextent + 1, y + 1);
		settextcolor(COLOR_WHITE, COLOR_BLACK);
		putch(177);
	}
	// draw horizontal shadow
	for(int x = xpos; x <= xextent; x++){
		gotoxy(x + 1, yextent + 1);
		settextcolor(COLOR_WHITE, COLOR_BLACK);
		putch(177);
	}
	// position cursor inside window
	gotoxy(xpos + 2, ypos + 2);
	settextcolor(fore, back);
}