downloadmanager.cpp Example File

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 #include "downloadmanager.h"

 #include <QTextStream>

 #include <cstdio>

 using namespace std;

 DownloadManager::DownloadManager(QObject *parent)
     : QObject(parent)
 {
 }

 void DownloadManager::append(const QStringList &urls)
 {
     for (const QString &urlAsString : urls)
         append(QUrl::fromEncoded(urlAsString.toLocal8Bit()));

     if (downloadQueue.isEmpty())
         QTimer::singleShot(0, this, SIGNAL(finished()));
 }

 void DownloadManager::append(const QUrl &url)
 {
     if (downloadQueue.isEmpty())
         QTimer::singleShot(0, this, SLOT(startNextDownload()));

     downloadQueue.enqueue(url);
     ++totalCount;
 }

 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;
 }

 void DownloadManager::startNextDownload()
 {
     if (downloadQueue.isEmpty()) {
         printf("%d/%d files downloaded successfully\n", downloadedCount, totalCount);
         emit finished();
         return;
     }

     QUrl url = downloadQueue.dequeue();

     QString filename = saveFileName(url);
     output.setFileName(filename);
     if (!output.open(QIODevice::WriteOnly)) {
         fprintf(stderr, "Problem opening save file '%s' for download '%s': %s\n",
                 qPrintable(filename), url.toEncoded().constData(),
                 qPrintable(output.errorString()));

         startNextDownload();
         return;                 // skip this download
     }

     QNetworkRequest request(url);
     currentDownload = manager.get(request);
     connect(currentDownload, SIGNAL(downloadProgress(qint64,qint64)),
             SLOT(downloadProgress(qint64,qint64)));
     connect(currentDownload, SIGNAL(finished()),
             SLOT(downloadFinished()));
     connect(currentDownload, SIGNAL(readyRead()),
             SLOT(downloadReadyRead()));

     // prepare the output
     printf("Downloading %s...\n", url.toEncoded().constData());
     downloadTime.start();
 }

 void DownloadManager::downloadProgress(qint64 bytesReceived, qint64 bytesTotal)
 {
     progressBar.setStatus(bytesReceived, bytesTotal);

     // calculate the download speed
     double speed = bytesReceived * 1000.0 / downloadTime.elapsed();
     QString unit;
     if (speed < 1024) {
         unit = "bytes/sec";
     } else if (speed < 1024*1024) {
         speed /= 1024;
         unit = "kB/s";
     } else {
         speed /= 1024*1024;
         unit = "MB/s";
     }

     progressBar.setMessage(QString::fromLatin1("%1 %2")
                            .arg(speed, 3, 'f', 1).arg(unit));
     progressBar.update();
 }

 void DownloadManager::downloadFinished()
 {
     progressBar.clear();
     output.close();

     if (currentDownload->error()) {
         // download failed
         fprintf(stderr, "Failed: %s\n", qPrintable(currentDownload->errorString()));
         output.remove();
     } else {
         // let's check if it was actually a redirect
         if (isHttpRedirect()) {
             reportRedirect();
             output.remove();
         } else {
             printf("Succeeded.\n");
             ++downloadedCount;
         }
     }

     currentDownload->deleteLater();
     startNextDownload();
 }

 void DownloadManager::downloadReadyRead()
 {
     output.write(currentDownload->readAll());
 }

 bool DownloadManager::isHttpRedirect() const
 {
     int statusCode = currentDownload->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
     return statusCode == 301 || statusCode == 302 || statusCode == 303
            || statusCode == 305 || statusCode == 307 || statusCode == 308;
 }

 void DownloadManager::reportRedirect()
 {
     int statusCode = currentDownload->attribute(QNetworkRequest::HttpStatusCodeAttribute).toInt();
     QUrl requestUrl = currentDownload->request().url();
     QTextStream(stderr) << "Request: " << requestUrl.toDisplayString()
                         << " was redirected with code: " << statusCode
                         << '\n';

     QVariant target = currentDownload->attribute(QNetworkRequest::RedirectionTargetAttribute);
     if (!target.isValid())
         return;
     QUrl redirectUrl = target.toUrl();
     if (redirectUrl.isRelative())
         redirectUrl = requestUrl.resolved(redirectUrl);
     QTextStream(stderr) << "Redirected to: " << redirectUrl.toDisplayString()
                         << '\n';
 }