System.Text.InternalDecoderBestFitFallbackBuffer.TryBestFit C# (CSharp) Method

        private char TryBestFit(byte[] bytesCheck)
        {
            // Need to figure out our best fit character, low is beginning of array, high is 1 AFTER end of array
            int lowBound = 0;
            int highBound = _oFallback.arrayBestFit.Length;
            int index;
            char cCheck;

            // Check trivial case first (no best fit)
            if (highBound == 0)
                return '\0';

            // If our array is too small or too big we can't check
            if (bytesCheck.Length == 0 || bytesCheck.Length > 2)
                return '\0';

            if (bytesCheck.Length == 1)
                cCheck = unchecked((char)bytesCheck[0]);
            else
                cCheck = unchecked((char)((bytesCheck[0] << 8) + bytesCheck[1]));

            // Check trivial out of range case
            if (cCheck < _oFallback.arrayBestFit[0] || cCheck > _oFallback.arrayBestFit[highBound - 2])
                return '\0';

            // Binary search the array
            int iDiff;
            while ((iDiff = (highBound - lowBound)) > 6)
            {
                // Look in the middle, which is complicated by the fact that we have 2 #s for each pair,
                // so we don't want index to be odd because it must be word aligned.
                // Also note that index can never == highBound (because diff is rounded down)
                index = ((iDiff / 2) + lowBound) & 0xFFFE;

                char cTest = _oFallback.arrayBestFit[index];
                if (cTest == cCheck)
                {
                    // We found it
                    Debug.Assert(index + 1 < _oFallback.arrayBestFit.Length,
                        "[InternalDecoderBestFitFallbackBuffer.TryBestFit]Expected replacement character at end of array");
                    return _oFallback.arrayBestFit[index + 1];
                }
                else if (cTest < cCheck)
                {
                    // We weren't high enough
                    lowBound = index;
                }
                else
                {
                    // We weren't low enough
                    highBound = index;
                }
            }

            for (index = lowBound; index < highBound; index += 2)
            {
                if (_oFallback.arrayBestFit[index] == cCheck)
                {
                    // We found it
                    Debug.Assert(index + 1 < _oFallback.arrayBestFit.Length,
                        "[InternalDecoderBestFitFallbackBuffer.TryBestFit]Expected replacement character at end of array");
                    return _oFallback.arrayBestFit[index + 1];
                }
            }

            // Char wasn't in our table
            return '\0';
        }