os3/stage1/screen.c

#include "../os3_common/datatypes.h"
#include "../os3_common/packing.h"
#include "include/screen.h"

int x = 0;
int y = 0;

void write_character(char c, os_u8 color) {
	os_u16* vram = (os_u16*) 0xB8000;
	os_u16* cursor_pos = vram + ((y * 80) + x);
	*cursor_pos = c | (color << 8);
}

void screen_write(const char* str, int max_len, os_u8 color) {
	int i = 0;
	do {
		char c = *str;
		if (c == 0) {
			return;
		}

		if (c == '\n') {
			if (y == 24) {
				screen_clear();
			}
			y = (y + 1) % 25;
			x = 0;
			str++;
			continue;
		}

		write_character(c, color);
		x++;
		if (x >= 80) {
			if (y == 24) {
				screen_clear();
			}
			y = (y + 1) % 25;
			x = 0;
		}
		str++;
		i++;
	} while(i < max_len || max_len == 0);
}

void screen_write_string(const char* str, int length) {
	screen_write(str, length, 0x0A);
}

void screen_write_error(const char* str, int length) {
	screen_write(str, length, 0x0C);
}

void screen_clear() {
	os_u16* ptr = (os_u16*) 0xB8000;
	for (int y = 0; y < 25; y++) {
		for (int x  = 0; x < 80; x++) {
			*ptr = 0;
			ptr++;
		}
	}
	x = 0;
	y = 0;
}

void screen_write_number_impl(os_u32 number, os_u8 color) {
	char buffer[32];
	char buffer_2[32];

	os_s32 i = 1;
	while(i < 32) {
		if (i > 1 && number == 0) {
			break;
		}

		buffer[i] = ((char)(number % 10)) + '0';
		i++;
		number /= 10;
	}
	i--;
	buffer[0] = '\0';
	char* buffer_2_ptr = buffer_2;
	while(i >= 0) {
		*buffer_2_ptr = buffer[i];
		buffer_2_ptr++;
		i--;
	}

	screen_write(buffer_2, 0, color);
}

void screen_write_number(os_u32 number) {
	screen_write_number_impl(number, 0x0A);
}

void screen_write_number_error(os_u32 number) {
	screen_write_number_impl(number, 0x0C);
}

void screen_set_pos(int nx, int ny) {
	x = nx;
	y = ny;
}