stock.c

/* Code from tuto http://franckh.developpez.com/tutoriels/posix/pthreads/ please do not copy check link for more infos */
/* I'm not the author of this code I just followed a very good tutorial from Franck Hecht on pthread */

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

#define psleep(sec) sleep((sec))

#define INITIAL_STOCK	20
#define	NB_CLIENTS		5

typedef struct
{
	int stock;

	pthread_t	thread_store;
	pthread_t	thread_clients[NB_CLIENTS];

	pthread_mutex_t mutex_stock;
	pthread_cond_t cond_stock;
	pthread_cond_t cond_clients;
}
store_t;

static store_t store =
{
	.stock = INITIAL_STOCK,
	.mutex_stock = PTHREAD_MUTEX_INITIALIZER,
	.cond_stock = PTHREAD_COND_INITIALIZER,
	.cond_clients = PTHREAD_COND_INITIALIZER,
};

static	int get_random(int max)
{
	double val;

	val = (double) max * rand();
	val = val / (RAND_MAX + 1.0);
	return ((int) val);
}

/* store thread */
static void *fn_store (void *p_data)
{
	while (1)
	{
		/* debut de la zone protegee */
		pthread_mutex_lock(&store.mutex_stock);
		pthread_cond_wait(&store.cond_stock, &store.mutex_stock);

		store.stock = INITIAL_STOCK;
		printf("Remplissage du stock de %d articles !\n", store.stock);

		/* fin de la zone protege */
		pthread_cond_signal(&store.cond_clients);
		pthread_mutex_unlock(&store.mutex_stock);
	}
	return NULL;
}

/* clients thread */
static void *fn_clients(void *p_data)
{
	int nb = (int)p_data;

	while (1)
	{
		int val = get_random(6);
		psleep(get_random(3));
		pthread_mutex_lock(&store.mutex_stock);
		if (val > store.stock)
		{
			pthread_cond_signal(&store.cond_stock);
			pthread_cond_wait(&store.cond_clients, &store.mutex_stock);
		}
		store.stock = store.stock - val;
		printf("Client %d prend %d du stock, reste, %d en stock!\n",
				nb, val, store.stock);
		pthread_mutex_unlock(&store.mutex_stock);
	}
	return NULL;
}

int main (void)
{
	int i = 0;
	int ret = 0;

	/* create store thread */
	printf("Creation du thread magasin!\n");
	ret = pthread_create(&store.thread_store, NULL, fn_store, NULL);
	if (!ret)
	{
		printf("Creation des threads clients !\n");
		for (i = 0; i < NB_CLIENTS; i++)
		{
			ret = pthread_create(&store.thread_clients[i], NULL, fn_clients, (void *)i);
			if (ret)
				fprintf(stderr, "%s", strerror(ret));
		}
	}
	else
		fprintf(stderr, "%s", strerror(ret));
	/* wait for thread to finish */
	i = 0;
	for (i = 0; i < NB_CLIENTS; i++)
		pthread_join(store.thread_clients[i], NULL);
	pthread_join(store.thread_store, NULL);

	return (EXIT_SUCCESS);

}