protected function slowScan()
    {
        if ($this->haveSlowResults) {
            return;
        }

        // copy trie object add CopyInto() method
        $excl = $this->dirsExcluded;
        $notIncl = $this->dirsNotIncluded;

        for ($i = 0, $_i = count($excl); $i < $_i; $i++) {
            if (!$this->couldHoldIncluded($excl[$i])) {
                $this->scandir($this->basedir . $excl[$i], $excl[$i] . DIRECTORY_SEPARATOR, false);
            }
        }

        for ($i = 0, $_i = count($notIncl); $i < $_i; $i++) {
            if (!$this->couldHoldIncluded($notIncl[$i])) {
                $this->scandir($this->basedir . $notIncl[$i], $notIncl[$i] . DIRECTORY_SEPARATOR, false);
            }
        }

        $this->haveSlowResults = true;
    }