System.Data.ExpressionParser.Scan C# (CSharp) Method

        internal Tokens Scan()
        {
            char ch;
            char[] text = _text;

            _token = Tokens.None;

            while (true)
            {
            loop:
                _start = _pos;
                _op = Operators.Noop;
                ch = text[_pos++];
                switch (ch)
                {
                    case (char)0:
                        _token = Tokens.EOS;
                        goto end_loop;

                    case ' ':
                    case '\t':
                    case '\n':
                    case '\r':
                        ScanWhite();
                        goto loop;

                    case '(':
                        _token = Tokens.LeftParen;
                        goto end_loop;

                    case ')':
                        _token = Tokens.RightParen;
                        goto end_loop;

                    case '#':
                        ScanDate();
                        CheckToken(Tokens.Date);
                        goto end_loop;

                    case '\'':
                        ScanString('\'');
                        CheckToken(Tokens.StringConst);
                        goto end_loop;

                    case '=':
                        _token = Tokens.BinaryOp;
                        _op = Operators.EqualTo;
                        goto end_loop;

                    case '>':
                        _token = Tokens.BinaryOp;
                        ScanWhite();
                        if (text[_pos] == '=')
                        {
                            _pos++;
                            _op = Operators.GreaterOrEqual;
                        }
                        else
                            _op = Operators.GreaterThen;
                        goto end_loop;
                    case '<':
                        _token = Tokens.BinaryOp;
                        ScanWhite();
                        if (text[_pos] == '=')
                        {
                            _pos++;
                            _op = Operators.LessOrEqual;
                        }
                        else if (text[_pos] == '>')
                        {
                            _pos++;
                            _op = Operators.NotEqual;
                        }
                        else
                            _op = Operators.LessThen;
                        goto end_loop;

                    case '+':
                        _token = Tokens.BinaryOp;
                        _op = Operators.Plus;
                        goto end_loop;

                    case '-':
                        _token = Tokens.BinaryOp;
                        _op = Operators.Minus;
                        goto end_loop;

                    case '*':
                        _token = Tokens.BinaryOp;
                        _op = Operators.Multiply;
                        goto end_loop;

                    case '/':
                        _token = Tokens.BinaryOp;
                        _op = Operators.Divide;
                        goto end_loop;

                    case '%':
                        _token = Tokens.BinaryOp;
                        _op = Operators.Modulo;
                        goto end_loop;

                    /* Beginning of bitwise operators */
                    case '&':
                        _token = Tokens.BinaryOp;
                        _op = Operators.BitwiseAnd;
                        goto end_loop;

                    case '|':
                        _token = Tokens.BinaryOp;
                        _op = Operators.BitwiseOr;
                        goto end_loop;
                    case '^':
                        _token = Tokens.BinaryOp;
                        _op = Operators.BitwiseXor;
                        goto end_loop;
                    case '~':
                        _token = Tokens.BinaryOp;
                        _op = Operators.BitwiseNot;
                        goto end_loop;

                    /* we have bracketed identifier */
                    case '[':
                        // BUG: special case
                        ScanName(']', _escape, "]\\");
                        CheckToken(Tokens.Name);
                        goto end_loop;

                    case '`':
                        ScanName('`', '`', "`");
                        CheckToken(Tokens.Name);
                        goto end_loop;

                    default:
                        /* Check for list separator */

                        if (ch == _listSeparator)
                        {
                            _token = Tokens.ListSeparator;
                            goto end_loop;
                        }

                        if (ch == '.')
                        {
                            if (_prevOperand == Empty)
                            {
                                ScanNumeric();
                            }
                            else
                            {
                                _token = Tokens.Dot;
                            }
                            goto end_loop;
                        }

                        /* Check for binary constant */
                        if (ch == '0' && (text[_pos] == 'x' || text[_pos] == 'X'))
                        {
                            ScanBinaryConstant();
                            _token = Tokens.BinaryConst;
                            goto end_loop;
                        }

                        /* Check for number: digit is always good; . or - only if osNil. */
                        if (IsDigit(ch))
                        {
                            ScanNumeric();
                            goto end_loop;
                        }

                        /* Check for reserved word */
                        ScanReserved();
                        if (_token != Tokens.None)
                        {
                            goto end_loop;
                        }

                        /* Alpha means identifier */

                        if (IsAlphaNumeric(ch))
                        {
                            ScanName();
                            if (_token != Tokens.None)
                            {
                                CheckToken(Tokens.Name);
                                goto end_loop;
                            }
                        }

                        /* Don't understand that banter at all. */
                        _token = Tokens.Unknown;
                        throw ExprException.UnknownToken(new string(text, _start, _pos - _start), _start + 1);
                }
            }
        end_loop:
            return _token;
        }