ECP2.mapit = function()

in src/ecp2.js [829:911]
69 lines of code
8 McCabe index (conditional complexity)

    ECP2.mapit = function(h) {
        var fa = new ctx.BIG(0),
            fb = new ctx.BIG(0),
            q, x, one, Q, T, K, X, xQ, x2Q;

        q = new ctx.BIG(0);
        q.rcopy(ctx.ROM_FIELD.Modulus);
        x = ctx.BIG.fromBytes(h);
        one = new ctx.BIG(1);
        x.mod(q);

        for (;;) {
            X = new ctx.FP2(one, x);
            Q = new ECP2();
            Q.setx(X);
            if (!Q.is_infinity()) {
                break;
            }
            x.inc(1);
            x.norm();
        }
        /* Fast Hashing to G2 - Fuentes-Castaneda, Knapp and Rodriguez-Henriquez */
        fa.rcopy(ctx.ROM_FIELD.Fra);
        fb.rcopy(ctx.ROM_FIELD.Frb);
        X = new ctx.FP2(fa, fb);
        if (ctx.ECP.SEXTIC_TWIST == ctx.ECP.M_TYPE) {
            X.inverse();
            X.norm();
        }

        x = new ctx.BIG(0);
        x.rcopy(ctx.ROM_CURVE.CURVE_Bnx);

        if (ctx.ECP.CURVE_PAIRING_TYPE == ctx.ECP.BN) {
            T = new ECP2();
            T.copy(Q);
            T = T.mul(x);
            if (ctx.ECP.SIGN_OF_X == ctx.ECP.NEGATIVEX) {
                T.neg();
            }
            K = new ECP2();
            K.copy(T);
            K.dbl();
            K.add(T); //K.affine();

            K.frob(X);
            Q.frob(X);
            Q.frob(X);
            Q.frob(X);
            Q.add(T);
            Q.add(K);
            T.frob(X);
            T.frob(X);
            Q.add(T);
        }

        if (ctx.ECP.CURVE_PAIRING_TYPE == ctx.ECP.BLS) {

            xQ = Q.mul(x);
            x2Q = xQ.mul(x);

            if (ctx.ECP.SIGN_OF_X == ctx.ECP.NEGATIVEX) {
                xQ.neg();
            }

            x2Q.sub(xQ);
            x2Q.sub(Q);

            xQ.sub(Q);
            xQ.frob(X);

            Q.dbl();
            Q.frob(X);
            Q.frob(X);

            Q.add(x2Q);
            Q.add(xQ);
        }

        Q.affine();

        return Q;
    };