source: bootcd/isolinux/syslinux-6.03/dos/__udivmoddi4.c

#include <stdint.h>

uint64_t __udivmoddi4(uint64_t num, uint64_t den, uint64_t * rem_p)
{
    uint64_t quot = 0, qbit = 1;

    if (den == 0) {
        asm volatile ("int $0");
        return 0;               /* If trap returns... */
    }

    /* Left-justify denominator and count shift */
    while ((int64_t) den >= 0) {
        den <<= 1;
        qbit <<= 1;
    }

    while (qbit) {
        if (den <= num) {
            num -= den;
            quot += qbit;
        }
        den >>= 1;
        qbit >>= 1;
    }

    if (rem_p)
        *rem_p = num;

    return quot;
}