aureooms/js-integer-big-endian

import assert from 'assert';

/**
 * Adds single limb to a big endian array.
 * Wraps on overflow.
 *
 * Input:
 *   - |A| >= 1.
 *
 * @param {Number} r base (radix)
 * @param {Number} x limb to add
 * @param {Array} a first operand
 * @param {Number} ai a left
 * @param {Number} aj a right
 */

export default function _iadd_limb(r, x, a, ai, aj) {
    assert(r >= 2);
    assert(x >= 0 && x <= r - 1);
    assert(ai >= 0 && aj <= a.length);
    assert(aj - ai >= 1);

    let T = a[--aj] + x;
    a[aj] = T % r;

    while (T >= r && --aj >= ai) {
        T = a[aj] + 1;
        a[aj] = T % r;
    }
}