+/*
+ Copyright (C) 2018 Carl Hetherington <cth@carlh.net>
+
+ This file is part of DCP-o-matic.
+
+ DCP-o-matic 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.
+
+ DCP-o-matic 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 DCP-o-matic. If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+/** @file src/lib/checker.h
+ * @brief Checker class.
+ */
+
+#ifndef DCPOMATIC_CHECKER_H
+#define DCPOMATIC_CHECKER_H
+
+#include "signaller.h"
+#include <boost/signals2.hpp>
+
+/** Parent for classes which check some condition every so often and signal
+ * when the state of the condition changes.
+ */
+class Checker : public Signaller, public boost::noncopyable
+{
+public:
+ virtual ~Checker ();
+
+ void run ();
+
+ bool ok () const;
+
+ /** Emitted when the state of our condition changes */
+ boost::signals2::signal<void (void)> StateChanged;
+
+protected:
+
+ Checker (int period);
+
+ /** @return true if the condition is `ok', otherwise false */
+ virtual bool check () const = 0;
+
+private:
+
+ void thread ();
+
+ boost::thread* _thread;
+ mutable boost::mutex _mutex;
+ bool _terminate;
+ bool _ok;
+ /** check period in seconds */
+ int _period;
+};
+
+#endif