avt.DynamicFlashRotator.Net.RegCore.Cryptography.BigInteger.Jacobi C# (CSharp) Method

        public static int Jacobi(BigInteger a, BigInteger b)
        {
            // Jacobi defined only for odd integers
            if ((b.data[0] & 0x1) == 0)
                throw (new ArgumentException("Jacobi defined only for odd integers."));

            if (a >= b) a %= b;
            if (a.dataLength == 1 && a.data[0] == 0) return 0;  // a == 0
            if (a.dataLength == 1 && a.data[0] == 1) return 1;  // a == 1

            if (a < 0) {
                if ((((b - 1).data[0]) & 0x2) == 0)       //if( (((b-1) >> 1).data[0] & 0x1) == 0)
                    return Jacobi(-a, b);
                else
                    return -Jacobi(-a, b);
            }

            int e = 0;
            for (int index = 0; index < a.dataLength; index++) {
                uint mask = 0x01;

                for (int i = 0; i < 32; i++) {
                    if ((a.data[index] & mask) != 0) {
                        index = a.dataLength;      // to break the outer loop
                        break;
                    }
                    mask <<= 1;
                    e++;
                }
            }

            BigInteger a1 = a >> e;

            int s = 1;
            if ((e & 0x1) != 0 && ((b.data[0] & 0x7) == 3 || (b.data[0] & 0x7) == 5))
                s = -1;

            if ((b.data[0] & 0x3) == 3 && (a1.data[0] & 0x3) == 3)
                s = -s;

            if (a1.dataLength == 1 && a1.data[0] == 1)
                return s;
            else
                return (s * Jacobi(b % a1, a1));
        }