mbr_asm/vga.c

#include "vga.h"

void clearScreen(uint bgColor)
{
	volatile short *vga = (short *)VGA_ADDR;
	long int colorAttr  = bgColor << 12;
	for (int i = 0; i < VGA_WIDTH * VGA_HEIGHT; i++) {
		vga[i] = colorAttr;
	}
}

void printInt(int integer, uint color, uint bgColor, int startX, int startY)
{
	char num[sizeof(int) *
		 3]; // int max is 2^(sizeof(int)*8) which is (2^3)^(sizeof(int)*8/3) =
		     // 8^(sizeof(int)*8/3) ~ 10^(sizeof(int)*8/3)
	int x = startX;
	int i = 0, k = 0;
	if (integer < 0) {
		printChar('-', color, bgColor, x++, startY);
	}
	while (integer != 0) {
		int digit = integer % 10;
		num[i++]  = (digit > 0) ? digit : -digit;
		integer   = integer / 10;
	}
	for (k = i - 1; k >= 0; k--) {
		printChar(num[k] + '0', color, bgColor, x++, startY);
	}
}

void printChar(const char str, uint color, uint bgColor, int startX, int startY)
{
	volatile short *vga       = (short *)VGA_ADDR;
	long int colorAttr        = (bgColor << 4 | (color & 0x0f)) << 8;
	vga[80 * startY + startX] = colorAttr | str;
}

void printString(const char *str, uint color, uint bgColor, int startX, int startY)
{
	volatile short *vga = (short *)VGA_ADDR;
	int i               = 0;
	long int colorAttr  = (bgColor << 4 | (color & 0x0f)) << 8;
	while (*str) {
		vga[80 * startY + startX + i] = colorAttr | *str;
		str++;
		i++;
	}
}