protected function unescapeControlCharacters($string)
    {
        $unescapedString = $string;

        foreach ($this->controlCharactersEscapingMap as $escapedCharValue => $charValue) {
            // only unescape characters that don't contain the escaped escape character for now
            $unescapedString = preg_replace("/(?<!_x005F)($escapedCharValue)/", $charValue, $unescapedString);
        }

        return $this->unescapeEscapeCharacter($unescapedString);
    }