Lidgren.Network.NetBigInteger.Square C# (CSharp) Method

        private static int[] Square(
			int[] w,
			int[] x)
        {
            // Note: this method allows w to be only (2 * x.Length - 1) words if result will fit
            //			if (w.Length != 2 * x.Length)
            //				throw new ArgumentException("no I don't think so...");

            ulong u1, u2, c;

            int wBase = w.Length - 1;

            for (int i = x.Length - 1; i != 0; i--)
            {
                ulong v = (ulong)(uint)x[i];

                u1 = v * v;
                u2 = u1 >> 32;
                u1 = (uint)u1;

                u1 += (ulong)(uint)w[wBase];

                w[wBase] = (int)(uint)u1;
                c = u2 + (u1 >> 32);

                for (int j = i - 1; j >= 0; j--)
                {
                    --wBase;
                    u1 = v * (ulong)(uint)x[j];
                    u2 = u1 >> 31; // multiply by 2!
                    u1 = (uint)(u1 << 1); // multiply by 2!
                    u1 += c + (ulong)(uint)w[wBase];

                    w[wBase] = (int)(uint)u1;
                    c = u2 + (u1 >> 32);
                }

                c += (ulong)(uint)w[--wBase];
                w[wBase] = (int)(uint)c;

                if (--wBase >= 0)
                {
                    w[wBase] = (int)(uint)(c >> 32);
                }
                else
                {
                    Debug.Assert((uint)(c >> 32) == 0);
                }
                wBase += i;
            }

            u1 = (ulong)(uint)x[0];
            u1 = u1 * u1;
            u2 = u1 >> 32;
            u1 = u1 & IMASK;

            u1 += (ulong)(uint)w[wBase];

            w[wBase] = (int)(uint)u1;
            if (--wBase >= 0)
            {
                w[wBase] = (int)(uint)(u2 + (u1 >> 32) + (ulong)(uint)w[wBase]);
            }
            else
            {
                Debug.Assert((uint)(u2 + (u1 >> 32)) == 0);
            }

            return w;
        }