private function pop($valueToPrevLevel)
    {
        $this->state = array_pop($this->stateStack);

        if ($this->state !== self::STATE_ROOT) {
            $this->value = array_pop($this->valueStack);
            $this->value []= $valueToPrevLevel;
        } else {
            // we have final result
            $this->decoded = $valueToPrevLevel;
        }
    }