mul2: function()

in src/ecp.js [1220:1319]
90 lines of code
4 McCabe index (conditional complexity)

        mul2: function(e, Q, f) {
            var te = new ctx.BIG(),
                tf = new ctx.BIG(),
                mt = new ctx.BIG(),
                S = new ECP(),
                T = new ECP(),
                C = new ECP(),
                W = [],
                w = [],
                i, s, ns, nb,
                a, b;

            te.copy(e);
            tf.copy(f);

            // precompute table
            W[1] = new ECP();
            W[1].copy(this);
            W[1].sub(Q);
            W[2] = new ECP();
            W[2].copy(this);
            W[2].add(Q);
            S.copy(Q);
            S.dbl();
            W[0] = new ECP();
            W[0].copy(W[1]);
            W[0].sub(S);
            W[3] = new ECP();
            W[3].copy(W[2]);
            W[3].add(S);
            T.copy(this);
            T.dbl();
            W[5] = new ECP();
            W[5].copy(W[1]);
            W[5].add(T);
            W[6] = new ECP();
            W[6].copy(W[2]);
            W[6].add(T);
            W[4] = new ECP();
            W[4].copy(W[5]);
            W[4].sub(S);
            W[7] = new ECP();
            W[7].copy(W[6]);
            W[7].add(S);

            // if multiplier is odd, add 2, else add 1 to multiplier, and add 2P or P to correction

            s = te.parity();
            te.inc(1);
            te.norm();
            ns = te.parity();
            mt.copy(te);
            mt.inc(1);
            mt.norm();
            te.cmove(mt, s);
            T.cmove(this, ns);
            C.copy(T);

            s = tf.parity();
            tf.inc(1);
            tf.norm();
            ns = tf.parity();
            mt.copy(tf);
            mt.inc(1);
            mt.norm();
            tf.cmove(mt, s);
            S.cmove(Q, ns);
            C.add(S);

            mt.copy(te);
            mt.add(tf);
            mt.norm();
            nb = 1 + Math.floor((mt.nbits() + 1) / 2);

            // convert exponent to signed 2-bit window
            for (i = 0; i < nb; i++) {
                a = (te.lastbits(3) - 4);
                te.dec(a);
                te.norm();
                te.fshr(2);
                b = (tf.lastbits(3) - 4);
                tf.dec(b);
                tf.norm();
                tf.fshr(2);
                w[i] = (4 * a + b);
            }
            w[nb] = (4 * te.lastbits(3) + tf.lastbits(3));
            S.copy(W[Math.floor((w[nb] - 1) / 2)]);

            for (i = nb - 1; i >= 0; i--) {
                T.select(W, w[i]);
                S.dbl();
                S.dbl();
                S.add(T);
            }
            S.sub(C); /* apply correction */
            S.affine();

            return S;
        }