ditto-os/fb.c

#include "kmain.h"
#include "fb.h"

void fb_write_cell(unsigned int i, char c, unsigned char fg, unsigned char bg) {
    char *fb = (char *) 0x000B8000;
    fb[i] = c;
    fb[i + 1] = ((fg & 0x0F) << 4) | (bg & 0x0F);
}

void fb_move_cursor(unsigned short pos)
{
    outb(FB_COMMAND_PORT, FB_HIGH_BYTE_COMMAND);
    outb(FB_DATA_PORT, ((pos >> 8) & 0x00FF));
    outb(FB_COMMAND_PORT, FB_LOW_BYTE_COMMAND);
    outb(FB_DATA_PORT, pos & 0x00FF);
}

int fb_write(char *buf, unsigned int len) {
    for(int i = 0; i <= (int)len; i++) {
        fb_write_cell((int)(i * 2), buf[i], 0, 15);
        fb_move_cursor(i);
    }
    return 0;
}