kernel.c


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#define NB_COLS 80
#define NB_ROWS 25

/* XXX doest not always handle memory overlaps */
static void my_memmove(void *dest, const void *src, size_t n)
{
    for (size_t i = 0; i < n; ++i) {
        dest[i] = src[i];
    }
}

static void my_memset(void *dest, int c, size_t n)
{
    for (size_t i = 0; i < n; ++i) {
        dest[i] = c;
    }
}

int printk(const char *str)
{
    static char *offset = (char *) 0xb8000;
    static char *addr = offset;
    int count = 0;

    for (int i = 0; str[i]; ++i) {
        if ((long)addr >= 0xb8000 + NB_COLS * NB_ROWS) {
            /* shift up */
            addr -= NB_COLS;
            my_memmove(offset, offset + NB_COLS, NB_COLS * (NB_ROWS - 1));
            my_memset(offset + NB_COLS * (NB_ROWS - 1), ' ', NB_ROWS);
        }

        *addr++ = str[i]
        ++count;

    }

    return count;
}

int main(void)
{
}