aureooms/js-integer-big-endian

import assert from 'assert';

/**
 * Divides a big endian number by a single limb number and returns only the
 * remainder.
 *
 * Only works with limbs of size at most sqrt( 2^53 ).
 *
 * @param {Number} r The radix of D.
 * @param {Number} d The divisor >= 1.
 * @param {Array} D The dividend (NOT modified).
 * @param {Number} Di Left of D.
 * @param {Number} Dj Right of D.
 * @returns {Number} The remainder D % d.
 */
export default function _mod_limb(r, d, D, Di, Dj) {
    assert(r >= 2);
    assert(d >= 1 && d <= r - 1);
    assert(Di >= 0 && Dj <= D.length);

    let R = 0;

    while (Di < Dj) {
        R *= r;
        R += D[Di];
        R %= d;
        ++Di;
    }

    return R;
}