/***********************************************************************\
   exemple_semaphores
 
   Programme d'exemple du livre "Developpement systeme en C sous Linux"
   
   (c) 2000,2005 - Christophe Blaess
 
\***********************************************************************/

	#include <stdio.h>
	#include <stdlib.h>
	#include <pthread.h>
	#include <semaphore.h>
	#include <unistd.h>

	sem_t	semaphore;

	static void *	routine_thread (void * numero_thread);
	static int      aleatoire      (int maximum);

	int
main (void)
{
	int        i;
	pthread_t  thread;

	sem_init(& semaphore, 0, 3);
	for (i = 0; i < 10; i ++)
		pthread_create(& thread, NULL, routine_thread, (void *) i);
	sleep(1);
	pthread_exit(NULL);
}

	void *
routine_thread (void * numero_thread)
{
	int    i;
	for (i = 0; i < 2; i ++) {
		sem_wait(& semaphore);
		fprintf(stdout, "Thread %d dans portion critique\n",
				 (int) numero_thread);
		sleep(aleatoire(4));
		
		fprintf(stdout, "Thread %d sort de la portion critique\n",
				 (int) numero_thread);
		sem_post(& semaphore);
		sleep(aleatoire(4));
	}
	return NULL;
}		


	static int
aleatoire (int maximum)
{
	double d;
	d = (double) maximum * rand();
	d = d / (RAND_MAX + 1.0);
	return ((int) d);
}