#include <semaphore.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <sys/shm.h>
#include <unistd.h>
#include <iostream>
#include <cstring>
#include <fstream>
#include <stdio.h>
#include <fcntl.h>

using namespace std;

#define MEMORY_ONE "/shm_one"
#define SEMAPHORE_ONE "/sem_one"
#define SIZE 4096

int main() {

	int mc_fd;
	char * ptr;

	// Open SHARED MEMORY
	mc_fd = shm_open(MEMORY_ONE, O_RDWR, 0666);
	if(mc_fd == -1) {
		cerr << "Fallimento nell'apertura della memoria condivisa" << endl;
		exit(-1);
	}

	// Map SHARED MEMORY
	ptr = (char *) mmap(NULL, SIZE, PROT_WRITE, MAP_SHARED, mc_fd, 0);
	if(ptr == MAP_FAILED) {
		cerr << "Fallimento nella mappatura" << endl;
		exit(-1);
	}

	// Open SEMAPHORE
	sem_t * sem_id = sem_open(SEMAPHORE_ONE, 0);

	cout << "WEBCAM avviata..." << endl;
	// -----------------------------------------------------------------
	sem_wait(sem_id);
	cout << "Start -> SEZIONE CRITICA!" << endl;

	const char * message[] = {
		"Hello",
		"Shared",
		"Memory!"
	};
	ftruncate(mc_fd, sizeof(message));
	for (int i = 0; i < strlen(* message); i++) {
		sprintf(ptr, "%s ", message[i]);
		ptr += strlen(message[i]);
	}

	sem_post(sem_id);
	cout << "Stop  -> SEZIONE CRITICA!" << endl;
	// -----------------------------------------------------------------
	cout << "WEBCAM disattivata..." << endl;

	return 0;
}