Move DownloadHandlerImpl class to its own file

This also resolves lupdate warning.

src/base/net/private/downloadhandlerimpl.h

@@ -0,0 +1,67 @@
+/*
+ * Bittorrent Client using Qt and libtorrent.
+ * Copyright (C) 2015, 2018  Vladimir Golovnev <glassez@yandex.ru>
+ * Copyright (C) 2006  Christophe Dumez <chris@qbittorrent.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ *
+ * In addition, as a special exception, the copyright holders give permission to
+ * link this program with the OpenSSL project's "OpenSSL" library (or with
+ * modified versions of it that use the same license as the "OpenSSL" library),
+ * and distribute the linked executables. You must obey the GNU General Public
+ * License in all respects for all of the code used other than "OpenSSL".  If you
+ * modify file(s), you may extend this exception to your version of the file(s),
+ * but you are not obligated to do so. If you do not wish to do so, delete this
+ * exception statement from your version.
+ */
+
+#pragma once
+
+#include <QNetworkReply>
+
+#include "base/net/downloadmanager.h"
+
+class QObject;
+class QUrl;
+
+class DownloadHandlerImpl : public Net::DownloadHandler
+{
+    Q_OBJECT
+    Q_DISABLE_COPY(DownloadHandlerImpl)
+
+public:
+    explicit DownloadHandlerImpl(const Net::DownloadRequest &downloadRequest, QObject *parent);
+    ~DownloadHandlerImpl() override;
+
+    void cancel() override;
+
+    QString url() const;
+    const Net::DownloadRequest downloadRequest() const;
+
+    void assignNetworkReply(QNetworkReply *reply);
+
+private:
+    void processFinishedDownload();
+    void checkDownloadSize(qint64 bytesReceived, qint64 bytesTotal);
+    void handleRedirection(const QUrl &newUrl);
+    void setError(const QString &error);
+    void finish();
+
+    static QString errorCodeToString(QNetworkReply::NetworkError status);
+
+    QNetworkReply *m_reply = nullptr;
+    const Net::DownloadRequest m_downloadRequest;
+    Net::DownloadResult m_result;
+};