#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/mman.h>
#define BUF_SIZE 5 
#define SHARED_MEM_SIZE (BUF_SIZE+2)*sizeof(int) 

int main (void)
{ 	
	int pid, i, j, value; 
	int* shared_memory; 
	int *in; 
	int *out; 
	int *buffer;
 
	shared_memory=mmap(0,SHARED_MEM_SIZE,PROT_READ|PROT_WRITE,MAP_ANONYMOUS|MAP_SHARED,-1,0);
	buffer = (int*) shared_memory; 
	in = (int*) shared_memory + BUF_SIZE*sizeof(int);
	out = (int*) shared_memory + (BUF_SIZE+1)*sizeof(int);	*in = *out = 0; 
	pid = fork();
	if (pid == 0)	{ /* consumatore*/
		for (i = 0; i < 20; i++)  { 	
			while (*in == *out) ; 	
		    		value = buffer[*out]; /* leggo il buffer */
				*out = (*out + 1) % BUF_SIZE;	
		 		printf ("\tleggo buf[%d] == %d\n", *out, value);
		   	}
		}
	else
	{ 	/* produttore */
		for (j = 0; j < 20; j++)   { 	
			while ((*in + 1) % BUF_SIZE == *out);	
			buffer[*in] = j;  /* scrivo il buffer */
			*in = (*in + 1) % BUF_SIZE;  
			printf ("ho scritto  %d  in buf[%d]\n", j, *in);
		}
		wait (pid);
	}
	exit (0);
}