BaseNcoding.BaseN.GetBits64 C# (CSharp) Метод

        private static ulong GetBits64(byte[] data, int bitPos, int bitsCount)
        {
            ulong result = 0;

            int currentBytePos = bitPos / 8;
            int currentBitInBytePos = bitPos % 8;
            int xLength = Math.Min(bitsCount, 8 - currentBitInBytePos);
            if (xLength != 0)
            {
                result = ((ulong)data[currentBytePos] << 56 + currentBitInBytePos) >> 64 - xLength << bitsCount - xLength;

                currentBytePos += (currentBitInBytePos + xLength) / 8;
                currentBitInBytePos = (currentBitInBytePos + xLength) % 8;

                int x2Length = bitsCount - xLength;
                if (x2Length > 8)
                    x2Length = 8;

                while (x2Length > 0)
                {
                    xLength += x2Length;
                    result |= (ulong)data[currentBytePos] >> 8 - x2Length << bitsCount - xLength;

                    currentBytePos += (currentBitInBytePos + x2Length) / 8;
                    currentBitInBytePos = (currentBitInBytePos + x2Length) % 8;

                    x2Length = bitsCount - xLength;
                    if (x2Length > 8)
                        x2Length = 8;
                }
            }

            return result;
        }