#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <semaphore.h>
#include <sys/shm.h>
#include <sys/stat.h>

#define N_BOARD 4  // do not change
#define N_PLAYERS 10
#define N_LETTERS 6

#define IPC_KEY 0x1234
#define PLAYER_OUT 0
#define PLAYER_IN 1
#define SERVER_MOVE 0
#define PLAYER_MOVE 1
#define SEM_PLAYER(PID) (&sem[PID])     // semaphore to notify player
#define SEM_SERVER (&sem[N_PLAYERS])    // semaphore to notify server
#define SEM_ENTER  (&sem[N_PLAYERS+1])  // semaphore to enter the game

typedef struct {
  char state;          // PLAYER_OUT: no player; PLAYER_IN: player in the game
  char who;            // SERVER_MOVE: server has responded; PLAYER_MOVE: player has made new attempt
  char move[N_BOARD];  // last attempt of player or last response of server
  int attempts;        // number of attempts
} struct_player;

struct_player *players;
sem_t *sem;
int shmid, pid;

void exit_signal(int);


main() {
  // catch signal SIGINT (send by terminal when you press CTRL-C)
  signal(SIGINT, exit_signal);
  // allocate shared segment
  if ((shmid = shmget(IPC_KEY, sizeof(struct_player) * N_PLAYERS + sizeof(sem_t) * (N_PLAYERS + 2),
                      S_IRUSR | S_IWUSR)) == -1) {
    printf("shmget error!\n");
    exit(0);
  }
  // init players
  if ((players = (struct_player *) shmat(shmid, NULL, 0)) == (void *) -1) {
    printf("shmat error!\n");
    exit(0);
  }
  // init semaphores
  sem = (sem_t *) ((void *) players + sizeof(struct_player) * N_PLAYERS);
  // try to enter in the game
  ...
  // main loop
  ...
  return 0;
}

void exit_signal(int sig) {
  // free shared segment
  shmdt(players);
  exit(0);
}