invmodp: function()

in src/big.js [931:992]
57 lines of code
11 McCabe index (conditional complexity)

        invmodp: function(p) {
            var u = new BIG(0),
                v = new BIG(0),
                x1 = new BIG(1),
                x2 = new BIG(0),
                t = new BIG(0),
                one = new BIG(1);

            this.mod(p);
            u.copy(this);
            v.copy(p);

            while (BIG.comp(u, one) !== 0 && BIG.comp(v, one) !== 0) {
                while (u.parity() === 0) {
                    u.fshr(1);
                    if (x1.parity() !== 0) {
                        x1.add(p);
                        x1.norm();
                    }
                    x1.fshr(1);
                }

                while (v.parity() === 0) {
                    v.fshr(1);
                    if (x2.parity() !== 0) {
                        x2.add(p);
                        x2.norm();
                    }
                    x2.fshr(1);
                }

                if (BIG.comp(u, v) >= 0) {
                    u.sub(v);
                    u.norm();
                    if (BIG.comp(x1, x2) >= 0) {
                        x1.sub(x2);
                    } else {
                        t.copy(p);
                        t.sub(x2);
                        x1.add(t);
                    }
                    x1.norm();
                } else {
                    v.sub(u);
                    v.norm();
                    if (BIG.comp(x2, x1) >= 0) {
                        x2.sub(x1);
                    } else {
                        t.copy(p);
                        t.sub(x1);
                        x2.add(t);
                    }
                    x2.norm();
                }
            }

            if (BIG.comp(u, one) === 0) {
                this.copy(x1);
            } else {
                this.copy(x2);
            }
        },