Thread notifier class for synchronization between threads. More...

#include <pithreadnotifier.h>

Public Member Functions
void	wait ()
	Start waiting, return if other thread call notify().
bool	waitFor (PISystemTime timeout)
	Start waiting no longer than "timeout", return true if other thread call notify(), false if timeout expired.
void	notify ()
	Notify one waiting thread, which waiting on wait() function.

Detailed Description

Thread notifier class for synchronization between threads.

Class for simple notify and wait in different threads.

Each notify() stores one pending wake-up. A later wait() or waitFor() consumes one stored notification; with multiple waiters the resume order is unspecified.

Synopsis

This class used as event mechanism between threads. One thread wait for some event, and another send this event, unblocking first thread. It is useful to syncronize some actions in several threads.

Usage

PIThreadNotifier notifier;
PITimeMeasurer time;
 
class Worker: public PIThread {
    PIOBJECT_SUBCLASS(Worker, PIThread)
public:
    Worker(const PIString & n) {
        setName(n);
    }
    void run() override {
        piCoutObj << (int)time.elapsed_m() << "wait ...";
        notifier.wait();
        piCoutObj << (int)time.elapsed_m() << "done";
    };
};
 
 
int main(int argc, char * argv[]) {
    PIVector<Worker*> workers;
 
    // create 2 threads
    for (auto n: {"first ", "second"})
        workers << new Worker(n);
 
    // start them
    for (auto * w: workers)
        w->startOnce();
 
    piMSleep(500);
    notifier.notify(); // notify one of them after 500 ms
    piMSleep(500);
    notifier.notify(); // notify one of them after 1000 ms
 
    for (auto * w: workers)
        w->waitForFinish();
}
 
// [Worker "first "] 0 wait ...
// [Worker "second"] 0 wait ...
// [Worker "second"] 500 done
// [Worker "first "] 1000 done

Member Function Documentation

◆ wait()

void PIThreadNotifier::wait ( )

Start waiting, return if other thread call notify().

If notify() has been called before, then returns immediately.
If notify() has been called "n" times, then returns immediately "n" times, but only if wait in one thread.
If many threads waiting, then if notify() has been called "n" times, all threads total returns "n" times in undefined sequence.

◆ notify()

void PIThreadNotifier::notify ( )

Notify one waiting thread, which waiting on wait() function.