/*
 * Semaphore.java
 * From: Silberschatz, Galvin, Gagne: AOS, FIgure 7.41
 *
 *
 */

public class Semaphore
{
    private int value;


    // Object creation
    public Semaphore()
    {
	value = 0;
    };

    // Object creation with initial value
    public Semaphore(int v)
    {
	value = v;
    };

    // Wait on the semaphore
    public synchronized void P()
    {
	while(value <= 0)
	    {
		try
		    {
			wait();
		    }
		catch(InterruptedException e){}
	    };
	value--;
    };

    // Wait on the semaphore (alternative method)
    public synchronized void Wait()
    {
	P();
    };

    // Release the semaphore
    public synchronized void V()
    {
	//System.out.println("V()\n");
	++value;
	notify();
    };

    // Release the semaphore (alternative method)
    public synchronized void Signal()
    {
	V();
    };
    
};