public function generate_single_key_prefix() {
        if ($this->keyprefixsingle === null) {
            $this->keyprefixsingle = $this->mode.'/'.$this->component.'/'.$this->area;
            $this->keyprefixsingle .= '/'.$this->get_cache_identifier();
            $identifiers = $this->get_identifiers();
            if ($identifiers) {
                foreach ($identifiers as $key => $value) {
                    $this->keyprefixsingle .= '/'.$key.'='.$value;
                }
            }
            $this->keyprefixsingle = md5($this->keyprefixsingle);
        }
        return $this->keyprefixsingle;
    }