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

#define SEM_MODE 0666

void P (int semid)
{
	struct sembuf sbuf;

	sbuf.sem_num = 0;
	sbuf.sem_op = -1;
	sbuf.sem_flg = 0;
	if (semop (semid, &sbuf, 1) < 0)
		perror ("semop P"), exit(1);
	return;
}

void V (int semid)
{
	struct sembuf sbuf;

	sbuf.sem_num = 0;
	sbuf.sem_op = 1;
	sbuf.sem_flg = 0;
	if (semop (semid, &sbuf, 1) < 0)
		perror ("semop V"), exit(1);
	return;
}

// Send in unique number for semid, return value is a unique system semid.
void Init (int* semid, int value)
{
	int new_semid=0;
	
	union {
		int val;
		struct semid_ds *buf;
		u_short *array;
	} arg;
	
	//if ((new_semid = semget(new_semid,1,IPC_CREAT | SEM_MODE))<0)
	if ((new_semid = semget(IPC_PRIVATE,1,IPC_CREAT | SEM_MODE))<0)
    	{
		perror ("semget IPC_CREAT"), exit(1);
    	}
	printf("INIT: Mutex id created: %d\n", new_semid);	

	arg.val = value;
	if (semctl (new_semid, 0, SETVAL, arg) < 0)
		perror ("semctl SETVAL"), exit(1);
		
	*semid = new_semid;
	return;
}

void Remove (int semid)
{
	if (semctl (semid, 0, IPC_RMID) < 0)
		perror ("semctl SETVAL"), exit(1);		
	return;
}

void Print (int semid)
{
	int val;
	
	if ((val = semctl (semid, 0, GETVAL)) < 0)
		perror ("semctl GETVAL"), exit(1);
	printf ("Semaphore %d's value = %d\n", semid, val);
	return;
}