src/common/ChangeFlagRelaxed.h

/*
    Copyright (C) 2013 Christian Schoenebeck
 */

#ifndef LS_CHANGEFLAGRELAXED_H
#define LS_CHANGEFLAGRELAXED_H

#include "atomic.h"

/**
 * May be used as boolean variable to synchronize that some shared resource has
 * been changed, with relaxed memory order. It is designed for exactly 1 reading
 * thread (calling readAndReset()) and n writing threads (calling raise()).
 * Synchronization with "relaxed memory order" means here that the information
 * written by raise() calls are never lost, but it may take some time to
 * propagate to the reading thread, thus readAndReset() may not always return
 * the very latest information. So the informations might be delivered with a
 * delay.
 */
class ChangeFlagRelaxed {
public:
    ChangeFlagRelaxed() {
        newval = ATOMIC_INIT(0);
        oldval = 0;
    }
    
    inline bool readAndReset() {
        int v = atomic_read(&newval);
        bool changed = (oldval != v);
        oldval = v;
        return changed;
    }
    
    inline void raise() {
        atomic_inc(&newval);
    }
private:
    atomic_t newval;
    int      oldval;
};

#endif // LS_CHANGEFLAGRELAXED_H
1	/*
2	Copyright (C) 2013 Christian Schoenebeck
3	*/
4
5	#ifndef LS_CHANGEFLAGRELAXED_H
6	#define LS_CHANGEFLAGRELAXED_H
7
8	#include "atomic.h"
9
10	/**
11	* May be used as boolean variable to synchronize that some shared resource has
12	* been changed, with relaxed memory order. It is designed for exactly 1 reading
13	* thread (calling readAndReset()) and n writing threads (calling raise()).
14	* Synchronization with "relaxed memory order" means here that the information
15	* written by raise() calls are never lost, but it may take some time to
16	* propagate to the reading thread, thus readAndReset() may not always return
17	* the very latest information. So the informations might be delivered with a
18	* delay.
19	*/
20	class ChangeFlagRelaxed {
21	public:
22	ChangeFlagRelaxed() {
23	newval = ATOMIC_INIT(0);
24	oldval = 0;
25	}
26
27	inline bool readAndReset() {
28	int v = atomic_read(&newval);
29	bool changed = (oldval != v);
30	oldval = v;
31	return changed;
32	}
33
34	inline void raise() {
35	atomic_inc(&newval);
36	}
37	private:
38	atomic_t newval;
39	int oldval;
40	};
41
42	#endif // LS_CHANGEFLAGRELAXED_H