Qt Reference Documentation

# downloadmanager.cpp Example File

network/downloadmanager/downloadmanager.cpp

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     ** This file is part of the examples of the Qt Toolkit.
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     #include "downloadmanager.h"

     #include <QFileInfo>
     #include <QNetworkRequest>
     #include <QNetworkReply>
     #include <QString>
     #include <QStringList>
     #include <QTimer>
     #include <stdio.h>

     DownloadManager::DownloadManager(QObject *parent)
         : QObject(parent), downloadedCount(0), totalCount(0)
     {
     }

     void DownloadManager::append(const QStringList &urlList)
     {
         foreach (QString url, urlList)
             append(QUrl::fromEncoded(url.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()));
         } else {
             printf("Succeeded.\n");
             ++downloadedCount;
         }

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

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