kernel hexdump

#define COLS 16

static void hexdump(const char *buf, size_t length)
{
    bool star = false;
    size_t i, j;

    for (i = 0; i < length; i += COLS, buf += COLS) {
        if (i && !memcmp(buf, buf - COLS, COLS)) {
            if (!star)
                printk(KERN_CONT "*\n");
            star = true;
            continue;
        }
        star = false;
        printk("%px  ", buf + i);
        for (j = 0; j < COLS; j++) {
            printk(KERN_CONT "%02hhx ", buf[j]);
            if ((j & (COLS / 2 - 1)) == COLS / 2 - 1)
                printk(KERN_CONT " ");
        }
        printk(KERN_CONT "|");
        for (j = 0; j < COLS; j++) {
            int c = buf[j];
            printk(KERN_CONT "%c", c >= ' ' && c <= '~' ? c : '.');
        }
        printk(KERN_CONT "|\n");
    }
}