downloadmanager.cpp Example File

  /****************************************************************************
  **
  ** 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';
  }