aureooms/js-integer-little-endian

/**
 * /!\ BLOCK MULTIPLICATION RESULT MUST HOLD IN THE JAVASCRIPT NUMBER TYPE (DOUBLE i.e. 53 bits)
 *
 * big endian 1 block multiplication
 *
 */

export function bmul53_t ( r ) {

    /**
     * Multiply two blocks, result is put in a 1 or 2 blocks big endian array.
     * aj - ai <= 1, bj - bi <= 1, cj - ci <= 2
     *
     *
     * @param {array} a first operand
     * @param {int} ai a left
     * @param {int} aj a right
     * @param {array} b second operand
     * @param {int} bi b left
     * @param {int} bj b right
     * @param {array} c result, must be 0 initialized
     * @param {int} ci c left
     * @param {int} cj c right
     */

    var mul = function(a, ai, aj, b, bi, bj, c, ci, cj){

        var v;

        // EMPTY CASE
        if (aj <= ai || bj <= bi || cj <= ci) return;

        v = a[ai] * b[bi];
        c[cj-1] = v % r;

        if (cj > ci + 1) {
            c[cj-2] = (v - c[cj-1]) / r;
        }

    };

    return mul;

}


/**
 * /!\ BLOCK MULTIPLICATION RESULT MUST HOLD IN THE JAVASCRIPT NUMBER TYPE (DOUBLE i.e. 53 bits)
 *
 * little endian 1 block multiplication
 *
 */

export function lmul53_t (r){

    /**
     * Multiply two blocks, result is put in a 1 or 2 blocks little endian array.
     * aj - ai <= 1, bj - bi <= 1, cj - ci <= 2
     *
     *
     * @param {array} a first operand
     * @param {int} ai a left
     * @param {int} aj a right
     * @param {array} b second operand
     * @param {int} bi b left
     * @param {int} bj b right
     * @param {array} c result, must be 0 initialized
     * @param {int} ci c left
     * @param {int} cj c right
     */

    var mul = function(a, ai, aj, b, bi, bj, c, ci, cj){

        var v;

        // EMPTY CASE
        if (aj <= ai || bj <= bi || cj <= ci) return;

        v = a[ai] * b[bi];
        c[ci] = v % r;

        if (cj > ci + 1) {
            c[ci+1] = (v - c[ci]) / r;
        }

    };

    return mul;

}