protected static function getLockData()
    {
        if ( null === static::$lockData )
        {
            $data = Json::decode(
                file_get_contents( static::LOCK_FILE ),
                Json::TYPE_ARRAY
            );

            if ( empty( $data ) )
            {
                static::$lockData = array();
            }
            else
            {
                static::$lockData = (array) $data;
            }
        }

        return static::$lockData;
    }