Qt 5.11 | Qt Network | Network Download Manager Example | downloadmanager.cpp Example File

Qt 5.11.3 Reference Documentation

# downloadmanager.cpp Example File

downloadmanager/downloadmanager.cpp

      /****************************************************************************
      **
      ** Copyright (C) 2017 The Qt Company Ltd.
      ** Contact: https://www.qt.io/licensing/
      **
      ** This file is part of the examples of the Qt Toolkit.
      **
      ** $QT_BEGIN_LICENSE:BSD$
      ** Commercial License Usage
      ** Licensees holding valid commercial Qt licenses may use this file in
      ** accordance with the commercial license agreement provided with the
      ** Software or, alternatively, in accordance with the terms contained in
      ** a written agreement between you and The Qt Company. For licensing terms
      ** and conditions see https://www.qt.io/terms-conditions. For further
      ** information use the contact form at https://www.qt.io/contact-us.
      **
      ** BSD License Usage
      ** Alternatively, you may use this file under the terms of the BSD license
      ** as follows:
      **
      ** "Redistribution and use in source and binary forms, with or without
      ** modification, are permitted provided that the following conditions are
      ** met:
      **   * Redistributions of source code must retain the above copyright
      **     notice, this list of conditions and the following disclaimer.
      **   * Redistributions in binary form must reproduce the above copyright
      **     notice, this list of conditions and the following disclaimer in
      **     the documentation and/or other materials provided with the
      **     distribution.
      **   * Neither the name of The Qt Company Ltd nor the names of its
      **     contributors may be used to endorse or promote products derived
      **     from this software without specific prior written permission.
      **
      **
      ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
      ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
      ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
      ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
      ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
      ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
      ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
      ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
      ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
      ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
      ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
      **
      ** $QT_END_LICENSE$
      **
      ****************************************************************************/

      #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';
      }