os-tutorial/monitor.c at master · MgaMPKAy/os-tutorial · GitHub

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#include "monitor.h"

u16int *video_memory = (u16int *)0xB8000;
u8int cursor_x = 0;
u8int cursor_y = 0;

static void move_cursor()
{
	u16int cursorLocation = cursor_y * cursor_x;
	outb(0x3D4, 14);
	outb(0x3D5,cursorLocation >> 8);
	outb(0x3D4, 15);
	outb(0x3D5, cursorLocation);
}

static void scroll()
{
	u8int attributeByte = (0 << 4) | (15 & 0x0F);
	u16int blank = 0x20;

	if (cursor_y >= 5) {
		int i;
		for (i = 0*80; i < 24 * 80; i++) {
			video_memory[i] = video_memory[i+80];
		}

		for (i = 24 * 80; i < 25 * 80; i++) {
			video_memory[i] = blank;
		}

		cursor_y = 24;
	}
}

void monitor_put(char c)
{
	u8int backColor = 0;
	u8int foreColor = 15;

	u8int attributeByte = (backColor << 4) | (foreColor & 0x0F);

	u16int attribute = attributeByte << 8;

	u16int *location;

	if (c == 0x08 && cursor_x) {
		cursor_x--;
	} else if (c == '\r') {
		cursor_x = 0;
	} else if (c == '\n') {
		cursor_y++;
	} else if (c >= ' ') {
		location = video_memory + (cursor_y * 80 + cursor_x);
		*location = c | attribute;
		cursor_x++;
	}

	if (cursor_x >= 80) {
		cursor_x = 0;
		cursor_y++;
	}

	scroll();
	move_cursor();
}

void monitor_clear()
{
	u8int attributeByte = (0 << 4) | (15 & 0x0F);
	u16int blank = 0x20 | (attributeByte << 8);

	int i;
	for (i = 0; i < 80 * 25; i++) {
		video_memory[i] = blank;
	}

	cursor_x = 0;
	cursor_y = 0;
	move_cursor();
}

void monitor_write(char *c)
{
	int i = 0;
	while (c[i]) {
		monitor_put(c[i++]);
	}
}