#include </usr/sys/sys/types.h>
#include </usr/sys/sys/ipc.h>
#include </usr/sys/sys/sem.h>
#include "pv.h"


initsem(semkey)
key_t semkey;
{
	int status = 0, semid;

	if((semid = semget(semkey, 1,
		SEMPERM|IPC_CREAT|IPC_EXCL))==-1)
		if(errno == EEXIST)
			semid = semget(semkey,1,0);
	else
		status = semctl(semid,0,SETVAL,1);

	if(semid == -1 || status == -1)
		{
		perror("initsem failed");
		return(-1);
		}
	else
		{
		printf("calling v(%d) for pid=any\n",semid);
		v(semid);
		return semid;
		}
}

p(semid)
int semid;
{
	struct sembuf p_buf;

	p_buf.sem_num = 0;
	p_buf.sem_op = -1;
	p_buf.sem_flg = SEM_UNDO;

	if(semop(semid, &p_buf, 1) == -1)
		{
		perror("p(semid) failed");
		exit(1);
		}
	else
		return(0);
}

v(semid)
int semid;
{
	struct sembuf v_buf;

	v_buf.sem_num = 0;
	v_buf.sem_op = 1;
	v_buf.sem_flg = SEM_UNDO;
	
	if(semop(semid, &v_buf, 1) == -1)
		{
		perror("v(semid) failed");
		exit(1);
		}
	else
		return(0);
}