SPP_TP34_exo1

package ex1;

public class MySemaphore implements SemaphoreInterface {

    private int slots;
    private int waitingThreads;


    public MySemaphore() {
        this.slots = 0;
        this.waitingThreads = 0;
    }

    @Override
    public synchronized void up() {

        slots++;
        int waiting = waitingThreads;
        if(waiting > 0) {
            waitingThreads--;
        }
        notify(); // Notifying thread to wake up
    }

    @Override
    public synchronized void down() {

        int s = slots;
        while (s == 0) {
            try {
                waitingThreads++;
                wait(); // Blocking current thread
                } catch (InterruptedException exception) {
                    exception.printStackTrace();
                }
                s = slots;
            }
            slots--;
    }

    @Override
    public synchronized int releaseAll() {

        int tmp = waitingThreads;
        int waiting = waitingThreads;

        while(waiting > 0) {
            notify();
            waiting--;
        }

        waitingThreads = 0;
        slots += tmp;

        return tmp;
    }

}