Esempio n. 1
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        // ---------------------------------------------------------------------
        //
        // Private methods
        //
        // ---------------------------------------------------------------------

        #region Private Methods

        /// <summary>
        /// Advances a reading position by one character code
        /// and reads the next availbale character from a stream.
        /// This character becomes available as NextCharacter property.
        /// </summary>
        /// <remarks>
        /// Throws InvalidOperationException if attempted to be called on EndOfStream
        /// condition.
        /// </remarks>
        private void GetNextCharacter()
        {
            if (_nextCharacterCode == -1)
            {
                throw new InvalidOperationException("GetNextCharacter method called at the end of a stream");
            }

            _previousCharacter = _nextCharacter;

            _nextCharacter     = _lookAheadCharacter;
            _nextCharacterCode = _lookAheadCharacterCode;
            // next character not an entity as of now
            _isNextCharacterEntity = false;

            this.ReadLookAheadCharacter();

            if (_nextCharacter == '&')
            {
                if (_lookAheadCharacter == '#')
                {
                    // numeric entity - parse digits - &#DDDDD;
                    int entityCode;
                    entityCode = 0;
                    this.ReadLookAheadCharacter();

                    // largest numeric entity is 7 characters
                    for (int i = 0; i < 7 && Char.IsDigit(_lookAheadCharacter); i++)
                    {
                        entityCode = 10 * entityCode + (_lookAheadCharacterCode - (int)'0');
                        this.ReadLookAheadCharacter();
                    }
                    if (_lookAheadCharacter == ';')
                    {
                        // correct format - advance
                        this.ReadLookAheadCharacter();
                        _nextCharacterCode = entityCode;

                        // if this is out of range it will set the character to '?'
                        _nextCharacter = (char)_nextCharacterCode;

                        // as far as we are concerned, this is an entity
                        _isNextCharacterEntity = true;
                    }
                    else
                    {
                        // not an entity, set next character to the current lookahread character
                        // we would have eaten up some digits
                        _nextCharacter     = _lookAheadCharacter;
                        _nextCharacterCode = _lookAheadCharacterCode;
                        this.ReadLookAheadCharacter();
                        _isNextCharacterEntity = false;
                    }
                }
                else if (Char.IsLetter(_lookAheadCharacter))
                {
                    // entity is written as a string
                    string entity = "";

                    // maximum length of string entities is 10 characters
                    for (int i = 0; i < 10 && (Char.IsLetter(_lookAheadCharacter) || Char.IsDigit(_lookAheadCharacter)); i++)
                    {
                        entity += _lookAheadCharacter;
                        this.ReadLookAheadCharacter();
                    }
                    if (_lookAheadCharacter == ';')
                    {
                        // advance
                        this.ReadLookAheadCharacter();

                        if (HtmlSchema.IsEntity(entity))
                        {
                            _nextCharacter         = HtmlSchema.EntityCharacterValue(entity);
                            _nextCharacterCode     = (int)_nextCharacter;
                            _isNextCharacterEntity = true;
                        }
                        else
                        {
                            // just skip the whole thing - invalid entity
                            // move on to the next character
                            _nextCharacter     = _lookAheadCharacter;
                            _nextCharacterCode = _lookAheadCharacterCode;
                            this.ReadLookAheadCharacter();

                            // not an entity
                            _isNextCharacterEntity = false;
                        }
                    }
                    else
                    {
                        // skip whatever we read after the ampersand
                        // set next character and move on
                        _nextCharacter = _lookAheadCharacter;
                        this.ReadLookAheadCharacter();
                        _isNextCharacterEntity = false;
                    }
                }
            }
        }