System.Data.SqlTypes.SqlDecimal.MultByULong C# (CSharp) Method

        private void MultByULong(uint uiMultiplier)
        {
            int iDataMax = _bLen; // How many UI4s currently in *this

            ulong dwlAccum = 0;       // accumulated sum
            ulong dwlNextAccum = 0;   // accumulation past dwlAccum
            int iData;              // which UI4 in *This we are on.

            uint[] rguiData = new uint[4] { _data1, _data2, _data3, _data4 };

            for (iData = 0; iData < iDataMax; iData++)
            {
                Debug.Assert(dwlAccum < s_ulInt32Base);

                ulong ulTemp = rguiData[iData];
                dwlNextAccum = ulTemp * uiMultiplier;
                dwlAccum += dwlNextAccum;
                if (dwlAccum < dwlNextAccum)        // Overflow of int64 add
                    dwlNextAccum = s_ulInt32Base;   // how much to add to dwlAccum after div x_dwlBaseUI4
                else
                    dwlNextAccum = 0;
                rguiData[iData] = (uint)dwlAccum;           // equivalent to mod x_dwlBaseUI4
                dwlAccum = (dwlAccum >> 32) + dwlNextAccum; // equivalent to div x_dwlBaseUI4
            }

            // If any carry,
            if (dwlAccum != 0)
            {
                // Either overflowed
                Debug.Assert(dwlAccum < s_ulInt32Base, "dwlAccum < x_dwlBaseUI4", "Integer overflow");
                if (iDataMax == s_cNumeMax)
                    throw new OverflowException(SQLResource.s_arithOverflowMessage);

                // Or extend length by one uint
                rguiData[iDataMax] = (uint)dwlAccum;
                _bLen++;
            }

            if (FGt10_38(rguiData))
                throw new OverflowException(SQLResource.s_arithOverflowMessage);

            StoreFromWorkingArray(rguiData);
        }

        private static SqlDecimal Round(SqlDecimal n, int lPosition, bool fTruncate)
        {
            if (n.IsNull)
                return SqlDecimal.Null;

            if (lPosition >= 0)
            {
                //If round to the right of decimal number
                lPosition = Math.Min(s_NUMERIC_MAX_PRECISION, lPosition);
                if (lPosition >= n.m_bScale)
                    return n;   //No need to round
            }
            else
            {
                //If round to the left of the decimal point
                lPosition = Math.Max(-s_NUMERIC_MAX_PRECISION, lPosition);

                //Return +0.00 if truncation of integer part
                if (lPosition < n.m_bScale - n.m_bPrec)
                {
                    n.SetToZero();
                    return n;
                }
            }

            uint ulRem = 0;                                         // Remainder: the highest significant digit to be truncated
            int lAdjust = Math.Abs(lPosition - (int)n.m_bScale);    // Precision adjustment
            uint ulLastDivBase = 1;                                 //

            //Compute the integral part of the numeric
            while (lAdjust > 0)
            {
                if (lAdjust >= 9)
                {
                    ulRem = n.DivByULong(s_rgulShiftBase[8]);
                    ulLastDivBase = s_rgulShiftBase[8];
                    lAdjust -= 9;
                }
                else
                {
                    ulRem = n.DivByULong(s_rgulShiftBase[lAdjust - 1]);
                    ulLastDivBase = s_rgulShiftBase[lAdjust - 1];
                    lAdjust = 0;
                }
            }

            // The rounding only depends on the first digit after the rounding position
            if (ulLastDivBase > 1)
            {
                ulRem /= (ulLastDivBase / 10);
            }

            //If result is zero, return
            if (n.FZero() && (fTruncate || ulRem < 5))
            {
                n.SetPositive();
                n.AssertValid();
                return n;
            }

            // Adjust by adding 1 if remainder is larger than 5
            if (ulRem >= 5 && !fTruncate)
                n.AddULong(1);

            // Convert back to original scale
            lAdjust = Math.Abs(lPosition - n.m_bScale);

            while (lAdjust-- > 0)
            {
                n.MultByULong(s_ulBase10);
            }

            n.AssertValid();
            return n;
        }