System.Xml.XmlUTF8TextReader.ReadTextAndWatchForInvalidCharacters C# (CSharp) Méthode

        private int ReadTextAndWatchForInvalidCharacters(byte[] buffer, int offset, int offsetMax)
        {
            byte[] charType = XmlUTF8TextReader.s_charType;
            int textOffset = offset;

            while (offset < offsetMax && ((charType[buffer[offset]] & CharType.Text) != 0 || buffer[offset] == 0xEF))
            {
                if (buffer[offset] != 0xEF)
                {
                    offset++;
                }
                else
                {
                    // Ensure that we have three bytes (buffer[offset], buffer[offset + 1], buffer[offset + 2])  
                    // available for IsNextCharacterNonFFFE to check. 
                    if (offset + 2 < offsetMax)
                    {
                        if (IsNextCharacterNonFFFE(buffer, offset))
                        {
                            // if first byte is 0xEF, UTF8 mandates a 3-byte character representation of this Unicode code point
                            offset += 3;
                        }
                        else
                        {
                            XmlExceptionHelper.ThrowXmlException(this, new XmlException(SR.Format(SR.XmlInvalidFFFE)));
                        }
                    }
                    else
                    {
                        if (BufferReader.Offset < offset)
                        {
                            // We have read some characters already
                            // Let the outer ReadText advance the bufferReader and return text node to caller
                            break;
                        }
                        else
                        {
                            // Get enough bytes for us to process next character, then go back to top of while loop
                            int dummy;
                            BufferReader.GetBuffer(3, out dummy);
                        }
                    }
                }
            }
            return offset - textOffset;
        }