def count_special_chars(self, char, prev_char):
        """Update parenthesis counters"""
        if char == '(':
            self.parenthesis_count += 1
        elif char == ')':
            self.parenthesis_count -= 1
            if self.parenthesis_count < 0:
                raise RMarkdownOptionParsingError(
                    'Option line "{}" has too many '
                    'closing parentheses'.format(self.line))
        elif char == '{':
            self.curly_bracket_count += 1
        elif char == '}':
            self.curly_bracket_count -= 1
            if self.curly_bracket_count < 0:
                raise RMarkdownOptionParsingError(
                    'Option line "{}" has too many '
                    'closing curly brackets'.format(self.line))
        elif char == '[':
            self.square_bracket_count += 1
        elif char == ']':
            self.square_bracket_count -= 1
            if self.square_bracket_count < 0:
                raise RMarkdownOptionParsingError(
                    'Option line "{}" has too many '
                    'closing square brackets'.format(self.line))
        elif char == "'" and prev_char != '\\':
            self.in_single_quote = not self.in_single_quote
        elif char == '"' and prev_char != '\\':
            self.in_double_quote = not self.in_double_quote
Update parenthesis counters