protected function parseCapability($str, $trusted=false)
    {
        $str = preg_replace('/^\* CAPABILITY /i', '', $str);

        $this->capability = explode(' ', strtoupper($str));

        if (!empty($this->prefs['disabled_caps'])) {
            $this->capability = array_diff($this->capability, $this->prefs['disabled_caps']);
        }

        if (!isset($this->prefs['literal+']) && in_array('LITERAL+', $this->capability)) {
            $this->prefs['literal+'] = true;
        }

        if ($trusted) {
            $this->capability_readed = true;
        }
    }