arithmetic-operations-for/integers-modulo-n-big-endian

import {
    _alloc as n_alloc,
    _zeros as n_zeros,
    _copy as n_copy,
    _idivmod as n_idivmod,
    _trim_positive as n_trim_positive,
    _cmp_n as n_cmp_n,
} from '@arithmetic-operations-for/naturals-big-endian';

import modR from './modR.js';

export default function modN(r, N, x) {
    const k = N.length;
    const xj = x.length;
    const xi = n_trim_positive(x, 0, xj);
    const xn = xj - xi;
    if (xn > k || (xn === k && n_cmp_n(x, xi, xj, N, 0) >= 0)) {
        const xmodN = n_alloc(xn); // TODO Use UintXArray ?
        n_copy(x, xi, xj, xmodN, 0);
        const _ = n_zeros(xn); // TODO use _imod once implemented
        n_idivmod(r, xmodN, 0, xn, N, 0, k, _, 0, xn);
        return modR(k, xmodN);
    }

    const xmodN = n_zeros(k); // TODO Use UintXArray ?
    n_copy(x, xi, xj, xmodN, k - xn);
    return xmodN;
}