omos-tcnj2024/sys/video.c

#include <types.h>
#include <video.h>

void
vga_write(s8 *sequence, s16 size, s8 flags)
{
	if (size > VGA_TEXT_SIZE) {
		s16 using_size = size - VGA_TEXT_SIZE;

		for (s16 i = 0; i <= VGA_TEXT_SIZE; i++) {
			vga_vidmem[i * 2] = sequence[using_size + i];
			vga_vidmem[i * 2 + 1] = flags; 
		}

		unused = VGA_SIZE;
		return;
	}

	if (size * 2 + unused > VGA_SIZE) {
		s16 needed_space = size * 2;

		for (s16 i = 0; i <= (unused = VGA_SIZE - needed_space); i++) {
			vga_vidmem[i] = vga_vidmem[needed_space + i];
		}
	}

	for (s16 i = 0; i < size; i++) {
		vga_vidmem[unused++] = sequence[i];
		vga_vidmem[unused++] = flags;
	}
}

void
vga_clearscreen(void)
{
	unused = 0;
    for (s16 i = 0; i <= VGA_SIZE; i++) {
        vga_vidmem[i] = 0;
    }
}