[libcalamares] Introduce networking service

- The networking service is intended to wrap up use of
   QNetworkAccessManager and others for consumption within
   Calamares, and to provide some convenience functions
   for internet access.
 - Medium term, it may also monitor network access, so that
   we can respond to changes in network availability during
   installation.

Currently very minimal and undocumented.

src/libcalamares/CMakeLists.txt

@@ -36,6 +36,9 @@ set( libSources
     locale/Lookup.cpp
     locale/TranslatableConfiguration.cpp
 
+    # Network service
+    network/Manager.cpp
+
     # Partition service
     partition/PartitionSize.cpp
 

src/libcalamares/network/Manager.cpp

@@ -0,0 +1,93 @@
+/* === This file is part of Calamares - <https://github.com/calamares> ===
+ *
+ *   Copyright 2019, Adriaan de Groot <groot@kde.org>
+ *
+ *   Calamares 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 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   Calamares 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 Calamares. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "Manager.h"
+
+#include <QEventLoop>
+#include <QNetworkAccessManager>
+#include <QNetworkReply>
+#include <QNetworkRequest>
+
+namespace CalamaresUtils
+{
+namespace Network
+{
+struct Manager::Private
+{
+    std::unique_ptr< QNetworkAccessManager > m_nam;
+    QUrl m_hasInternetUrl;
+    bool m_hasInternet;
+
+    Private();
+};
+}  // namespace Network
+}  // namespace CalamaresUtils
+CalamaresUtils::Network::Manager::Private::Private()
+    : m_nam( std::make_unique< QNetworkAccessManager >() )
+    , m_hasInternet( false )
+{
+}
+
+CalamaresUtils::Network::Manager::Manager()
+    : d( std::make_unique< Private >() )
+{
+}
+
+CalamaresUtils::Network::Manager::~Manager() {}
+
+CalamaresUtils::Network::Manager&
+CalamaresUtils::Network::Manager::instance()
+{
+    static auto* s_manager = new CalamaresUtils::Network::Manager();
+    return *s_manager;
+}
+
+bool
+CalamaresUtils::Network::Manager::hasInternet()
+{
+    return d->m_hasInternet;
+}
+
+bool
+CalamaresUtils::Network::Manager::checkHasInternet()
+{
+    bool b = false;
+    if ( d->m_hasInternetUrl.isValid() )
+    {
+        b = synchronousPing( d->m_hasInternetUrl );
+    }
+    d->m_hasInternet = b;
+    return b;
+}
+
+void
+CalamaresUtils::Network::Manager::setCheckHasInternetUrl( const QUrl& url )
+{
+    d->m_hasInternetUrl = url;
+}
+
+bool
+CalamaresUtils::Network::Manager::synchronousPing( const QUrl& url )
+{
+    QNetworkRequest req = QNetworkRequest( url );
+    QNetworkReply* reply = d->m_nam->get( req );
+    QEventLoop loop;
+    connect( reply, &QNetworkReply::finished, &loop, &QEventLoop::quit );
+    loop.exec();
+    return reply->bytesAvailable();
+}

src/libcalamares/network/Manager.h

@@ -0,0 +1,55 @@
+/* === This file is part of Calamares - <https://github.com/calamares> ===
+ *
+ *   Copyright 2019, Adriaan de Groot <groot@kde.org>
+ *
+ *   Calamares 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 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   Calamares 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 Calamares. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef LIBCALAMARES_NETWORK_MANAGER_H
+#define LIBCALAMARES_NETWORK_MANAGER_H
+
+#include "DllMacro.h"
+
+#include <QObject>
+#include <QUrl>
+
+#include <memory>
+
+namespace CalamaresUtils
+{
+namespace Network
+{
+class DLLEXPORT Manager : QObject
+{
+    Q_OBJECT
+
+    Manager();
+
+public:
+    static Manager& instance();
+    virtual ~Manager();
+
+    bool synchronousPing( const QUrl& url );
+
+    void setCheckHasInternetUrl( const QUrl& url );
+    bool checkHasInternet();
+    bool hasInternet();
+
+private:
+    struct Private;
+    std::unique_ptr< Private > d;
+};
+}  // namespace Network
+}  // namespace CalamaresUtils
+#endif  // LIBCALAMARES_NETWORK_MANAGER_H