using System;
using System.Threading;
 
namespace Recetas.CSharp.Cap04.R0410
{
    public sealed class UsoSincronizacionSemaphore
    {
        // Representa una instancia de Semaphore:
        private static Semaphore semaforo;
 
        // Intervalo de orden de la salida:
        private static int _intervalo;
 
        public static void Main()
        {
            Console.Title = "Uso Sincronización Semáforo";
            Console.WriteLine ();
 
            // Crea una instancia de Semaphore>
            semaforo = new Semaphore(0, 3);
 
            // Crea hasta 5 threads:
            for (int i = 1; i <= 5; ++i)
            {
                Thread t = new 
                    Thread(new ParameterizedThreadStart (Tarea));
 
                t.Start (i);
            }
 
            // Suspensión por 0.5 segundos para dejar que todos los 
            // threads entren en el semáforo:
            Thread.Sleep (500);
 
            // Completa el semáforo (atención de todos los threads):
            Console.WriteLine ("Invocación de semaforo.Release(3).");
            semaforo.Release(3);
 
            Console.WriteLine ("\n`Main` ha finalizado.\n");
        }
 
        private static void Tarea(object numero)
        {
            // Cada thread solicita el paso al objeto Semaphore:
            Console.WriteLine ("El thread `{0}` se ha iniciado y espera en el semáforo.", 
                numero
            );
            semaforo.WaitOne ();
 
            // Suma una cantidad de tiempo al intervalo anterior:
            int intervalo = Interlocked.Add (ref _intervalo, 100);
 
            Console.WriteLine ("El thread `{0}` acaba de entrar al semáforo.", 
                numero
            );
 
            // Simula la ejecución de una tarea larga:
            Thread.Sleep (1000 + intervalo);
 
            Console.WriteLine ("El thread `{0}` libera el semáforo.", numero );
            Console.WriteLine ("Contador de threads en el semáforo: {0}", 
                semaforo.Release()
            );
        }
    }
}

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