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

        private char TryBestFit(char cUnknown)
        {
            // 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;

            // 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 we want to be on word boundaries.
                // Also note that index can never == highBound (because diff is rounded down)
                index = ((iDiff / 2) + lowBound) & 0xFFFE;

                char cTest = _oFallback.arrayBestFit[index];
                if (cTest == cUnknown)
                {
                    // We found it
                    Debug.Assert(index + 1 < _oFallback.arrayBestFit.Length,
                        "[InternalEncoderBestFitFallbackBuffer.TryBestFit]Expected replacement character at end of array");
                    return _oFallback.arrayBestFit[index + 1];
                }
                else if (cTest < cUnknown)
                {
                    // 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] == cUnknown)
                {
                    // We found it
                    Debug.Assert(index + 1 < _oFallback.arrayBestFit.Length,
                        "[InternalEncoderBestFitFallbackBuffer.TryBestFit]Expected replacement character at end of array");
                    return _oFallback.arrayBestFit[index + 1];
                }
            }

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