protected function fillEncodingsOnce()
    {
        if ($this->filled) {
            return;
        }

        foreach ($this->loadEncodings() as $encoding) {
            $encoding = strtoupper($encoding);
            $this->encodings[] = $encoding;
            $this->encodingLookup[$encoding] = true;
        }

        $this->filled = true;
    }