Add AsyncTask helper functions

src/core/AsyncTask.h

@@ -0,0 +1,63 @@
+/*
+ *  Copyright (C) 2017 KeePassXC Team <team@keepassxc.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 or (at your option)
+ *  version 3 of the License.
+ *
+ *  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, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef KEEPASSXC_ASYNCTASK_HPP
+#define KEEPASSXC_ASYNCTASK_HPP
+
+#include <QFuture>
+#include <QFutureWatcher>
+#include <QtConcurrent>
+
+
+/**
+ * Asynchronously run computations outside the GUI thread.
+ */
+namespace AsyncTask
+{
+
+/**
+ * Wait for the given future without blocking the event loop.
+ *
+ * @param future future to wait for
+ * @return async task result
+ */
+template<typename FunctionObject>
+typename std::result_of<FunctionObject()>::type waitForFuture(QFuture<typename std::result_of<FunctionObject()>::type> future)
+{
+    QEventLoop loop;
+    QFutureWatcher<typename std::result_of<FunctionObject()>::type> watcher;
+    QObject::connect(&watcher, SIGNAL(finished()), &loop, SLOT(quit()));
+    watcher.setFuture(future);
+    loop.exec();
+    return future.result();
+}
+
+/**
+ * Run a given task and wait for it to finish without blocking the event loop.
+ *
+ * @param task std::function object to run
+ * @return async task result
+ */
+template<typename FunctionObject>
+typename std::result_of<FunctionObject()>::type runAndWaitForFuture(FunctionObject task)
+{
+    return waitForFuture<FunctionObject>(QtConcurrent::run(task));
+}
+
+};  // namespace AsyncTask
+
+#endif //KEEPASSXC_ASYNCTASK_HPP