#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* mutex;
	sem_t* vuoto;
	sem_t* pieno; 
	int* out; 
	float value;

	mutex=sem_open("mutex", 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);	
	
	fd = shm_open("mymem",  O_EXCL |O_RDWR, S_IRUSR | S_IWUSR);	/* mi collego alla memoria condivisa */
	buffer = mmap(NULL ,size,PROT_READ | PROT_WRITE, MAP_SHARED ,fd, 0);

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

	while(1) {
		sem_wait(pieno); 
		sem_wait(mutex);

		value = buffer[*out]; /* leggo il buffer */
		*out = (*out + 1) % BUF_SIZE;	

		sem_post(mutex);
		sem_post(vuoto);
		printf ("\tho letto %f\n", value);
	}
}