SHM ConcurrentCounter

Fast concurrent counter for 2 threads:

struct ConcurrentCounter {

private: // shm data

    unsigned long mCounter_byFirstThread;
    char CPU_CACHE_GUARD[PAD_SIZE];
    unsigned long mCounter_bySecondThread;

public: // interface for first thread

    inline void increment_byFirstThread() { mCounter_byFirstThread++; }
    inline void decrement_byFirstThread() { mCounter_byFirstThread--; }

public: // interface for second thread

    inline void increment_bySecondThread() { mCounter_bySecondThread++; }
    inline void decrement_bySecondThread() { mCounter_bySecondThread--; }

public: // concurrent interface

    inline unsigned long getCounter_safe() {
        return (mCounter_byFirstThread + mCounter_bySecondThread);
    }

public: // init interface

    void initCounter_unsafe(unsigned long aValue = 0) {
        mCounter_byFirstThread = 0;
        mCounter_bySecondThread = 0;
        if (0 == aValue) return;
        mCounter_byFirstThread = aValue / 2;
        mCounter_bySecondThread = aValue - mCounter_byFirstThread;
    }

} __attribute__((__packed__));

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