public function process_cdata($cdata) {
        global $CFG;
        if ($cdata === '$@NULL@$') {  // Some cases we know we can skip complete processing
            return null;
        } else if ($cdata === '') {
            return '';
        } else if (is_numeric($cdata)) {
            return $cdata;
        } else if (strlen($cdata) < 32) { // Impossible to have one link in 32cc
            return $cdata;                // (http://10.0.0.1/file.php/1/1.jpg, http://10.0.0.1/mod/url/view.php?id=)
        } else if (strpos($cdata, '$@FILEPHP@$') === false) { // No $@FILEPHP@$, nothing to convert
            return $cdata;
        }

        if ($CFG->slasharguments) {
            $slash = '/';
            $forcedownload = '?forcedownload=1';
        } else {
            $slash = '%2F';
            $forcedownload = '&amp;forcedownload=1';
        }

        // We have to remove trailing slashes, otherwise file URLs will be restored with an extra slash.
        $basefileurl = rtrim(moodle_url::make_legacyfile_url($this->courseid, null)->out(true), $slash);
        // Decode file.php calls
        $search = array ("$@FILEPHP@$");
        $replace = array($basefileurl);
        $result = str_replace($search, $replace, $cdata);

        // Now $@SLASH@$ and $@FORCEDOWNLOAD@$ MDL-18799
        $search = array('$@SLASH@$', '$@FORCEDOWNLOAD@$');
        $replace = array($slash, $forcedownload);

        return str_replace($search, $replace, $result);
    }