Qt Reference Documentation

# main.cpp Example File

network/download/main.cpp

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     #include <QCoreApplication>
     #include <QFile>
     #include <QFileInfo>
     #include <QList>
     #include <QNetworkAccessManager>
     #include <QNetworkRequest>
     #include <QNetworkReply>
     #include <QStringList>
     #include <QTimer>
     #include <QUrl>

     #include <stdio.h>

     class DownloadManager: public QObject
     {
         Q_OBJECT
         QNetworkAccessManager manager;
         QList<QNetworkReply *> currentDownloads;

     public:
         DownloadManager();
         void doDownload(const QUrl &url);
         QString saveFileName(const QUrl &url);
         bool saveToDisk(const QString &filename, QIODevice *data);

     public slots:
         void execute();
         void downloadFinished(QNetworkReply *reply);
     };

     DownloadManager::DownloadManager()
     {
         connect(&manager, SIGNAL(finished(QNetworkReply*)),
                 SLOT(downloadFinished(QNetworkReply*)));
     }

     void DownloadManager::doDownload(const QUrl &url)
     {
         QNetworkRequest request(url);
         QNetworkReply *reply = manager.get(request);

         currentDownloads.append(reply);
     }

     QString DownloadManager::saveFileName(const QUrl &url)
     {
         QString path = url.path();
         QString basename = QFileInfo(path).fileName();

         if (basename.isEmpty())
             basename = "download";

         if (QFile::exists(basename)) {
             // already exists, don't overwrite
             int i = 0;
             basename += '.';
             while (QFile::exists(basename + QString::number(i)))
                 ++i;

             basename += QString::number(i);
         }

         return basename;
     }

     bool DownloadManager::saveToDisk(const QString &filename, QIODevice *data)
     {
         QFile file(filename);
         if (!file.open(QIODevice::WriteOnly)) {
             fprintf(stderr, "Could not open %s for writing: %s\n",
                     qPrintable(filename),
                     qPrintable(file.errorString()));
             return false;
         }

         file.write(data->readAll());
         file.close();

         return true;
     }

     void DownloadManager::execute()
     {
         QStringList args = QCoreApplication::instance()->arguments();
         args.takeFirst();           // skip the first argument, which is the program's name
         if (args.isEmpty()) {
             printf("Qt Download example - downloads all URLs in parallel\n"
                    "Usage: download url1 [url2... urlN]\n"
                    "\n"
                    "Downloads the URLs passed in the command-line to the local directory\n"
                    "If the target file already exists, a .0, .1, .2, etc. is appended to\n"
                    "differentiate.\n");
             QCoreApplication::instance()->quit();
             return;
         }

         foreach (QString arg, args) {
             QUrl url = QUrl::fromEncoded(arg.toLocal8Bit());
             doDownload(url);
         }
     }

     void DownloadManager::downloadFinished(QNetworkReply *reply)
     {
         QUrl url = reply->url();
         if (reply->error()) {
             fprintf(stderr, "Download of %s failed: %s\n",
                     url.toEncoded().constData(),
                     qPrintable(reply->errorString()));
         } else {
             QString filename = saveFileName(url);
             if (saveToDisk(filename, reply))
                 printf("Download of %s succeeded (saved to %s)\n",
                        url.toEncoded().constData(), qPrintable(filename));
         }

         currentDownloads.removeAll(reply);
         reply->deleteLater();

         if (currentDownloads.isEmpty())
             // all downloads finished
             QCoreApplication::instance()->quit();
     }

     int main(int argc, char **argv)
     {
         QCoreApplication app(argc, argv);

         DownloadManager manager;
         QTimer::singleShot(0, &manager, SLOT(execute()));

         app.exec();
     }

     #include "main.moc"