#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)*sizeof(int) + 2*sizeof(int*)
//syncro-5.c
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*sizeof(int) + sizeof(int*));	*in = *out = 0; 
	
	if ((pid = fork()) == 0) /* consumatore*/
		for (i = 0; i < 10; i++)  { 	
			while (*in == *out) ; 	
		    	value = buffer[*out]; /* leggo il buffer */
			*out = (*out + 1) % BUF_SIZE;	
		 	printf ("\tleggo1 buf[%d] == %d\n", *out, value);
		   }
	 
	if ((pid = fork()) == 0) /* consumatore*/
		   for (i = 0; i < 10; i++)  { 	
			while (*in == *out) ; 	
		    	value = buffer[*out]; /* leggo il buffer */
			*out = (*out + 1) % BUF_SIZE;	
		 	printf ("\t\tleggo2 buf[%d] == %d\n", *out, value);
		   }

	
	/* produttore */
	for (j = 0; j < 10; 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);
	} 



	return(0);
}