public function bufferFullVariable()
    {
        if (!$this->bufferFullVariableIndex) {
            $this->bufferFullVariableIndex = $this->nextIndex++;
            $this->variables[] = new Variable('', '', [
                'status' => new StatusMessage(
                    true,
                    StatusMessage::REFERENCE_VARIABLE_VALUE,
                    new FormatMessage(
                        self::BUFFER_FULL_MESSAGE
                    )
                )
            ]);
        }
        return new Variable('', '', [
            'varTableIndex' => $this->bufferFullVariableIndex
        ]);
    }