#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/mman.h>
#include <sys/stat.h>        /* mnemonici in mode */
#include <fcntl.h>           /* mnemonici in oflag */
#include <semaphore.h>

#define BUF_SIZE 5

int main (void)
{ 	
	int fd, i, pid, size=(BUF_SIZE+2)*sizeof(float); 
	float* buffer;
	sem_t* mutex2; 
	sem_t* vuoto; 
	sem_t* pieno; 
	int* in; 
	int* out; 
	float value, elto=0;
	
	mutex2=sem_open("/mutex2", O_CREAT, S_IRUSR | S_IWUSR, 1);	/* creo i semafori */
	vuoto=sem_open("/vuoto", O_CREAT, S_IRUSR | S_IWUSR, BUF_SIZE);
	pieno=sem_open("/pieno", O_CREAT, S_IRUSR | S_IWUSR, 0);	
	
	shm_unlink("mymem2");
	fd = shm_open("mymem2",  O_CREAT | O_EXCL |O_RDWR, S_IRUSR | S_IWUSR);	/* creo la shmem */
 	ftruncate(fd,size);
 	buffer = mmap(NULL ,size,PROT_READ | PROT_WRITE, MAP_SHARED ,fd, 0);

	in = (int*) (buffer + BUF_SIZE*sizeof(float));
	out = (int*) (buffer + (BUF_SIZE+1)*sizeof(float));

 	*in = *out = 0; 

	for(i=0;i<100;i++) {
		sem_wait(vuoto); 
		sem_wait(mutex2);
			usleep(500000); /*aspetta 1/2 secondo */
			value=elto++;
			buffer[*in] = value;  /* scrivo il buffer */
			*in = (*in + 1) % BUF_SIZE;  
		sem_post(mutex2);
		sem_post(pieno);
		printf ("ho scritto  %f  \n", value);
	}
	shm_unlink("mymem2");
}