#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>


static int start_semvalue(int sem_num)
{

    return( semget((key_t)sem_num, 1, 0666 | IPC_CREAT)); 

}

static int set_semvalue(int sem_id,int semVal)
{
    union semun{
       int val;
       struct semid_ds *buf;
       ushort *array;
    }sem_union;

    sem_union.val = semVal;
    if (semctl(sem_id, 0, SETVAL, sem_union) == -1) return(0);
    return(1);
}

static void del_semvalue(int sem_id)
{
    union semun{
       int val;
       struct semid_ds *buf;
       ushort *array;
    }sem_union;
    
    if (semctl(sem_id, 0, IPC_RMID, sem_union) == -1)
        fprintf(stderr, "Failed to delete semaphore\n");
}

static int semaphore_p(int sem_id)
{
    struct sembuf sem_b;
    
    sem_b.sem_num = 0;
    sem_b.sem_op = -1; /* P() */
    sem_b.sem_flg = SEM_UNDO;
    if (semop(sem_id, &sem_b, 1) == -1) {
        fprintf(stderr, "semaphore_p failed\n");
        return(0);
    }
    return(1);
}

static int semaphore_v(int sem_id)
{
    struct sembuf sem_b;
    
    sem_b.sem_num = 0;
    sem_b.sem_op = 1; /* V() */
    sem_b.sem_flg = SEM_UNDO;
    if (semop(sem_id, &sem_b, 1) == -1) {
        fprintf(stderr, "semaphore_v failed\n");
        return(0);
    }
    return(1);
}