qint64 get_size()
{   
    QString link = url->text();
    std::cout<<qPrintable(link)<<std::endl;
    QNetworkAccessManager manager;
    QEventLoop loop;
    QNetworkReply *reply = manager.head(QNetworkRequest(link));
    QObject::connect(reply,SIGNAL(finished()), &loop, SLOT(quit()), Qt::DirectConnection);
    loop.exec();
    QVariant var = reply->header(QNetworkRequest::ContentLengthHeader);
    delete reply;
    qint64 size = var.toLongLong();
    std::cout<<size<<std::endl;
    return size;
}