/*
 * Copyright (c) 1995, 1996 Gunther Schadow.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#ifndef SEMAPHOR_H_
#define SEMAPHOR_H_

/*
 * Interface to the sysv semaphore facility for the simple case of one
 * binary semaphore. Essentially provides the V(mutex) and P(mutex)
 * operations.
 */

#include <stdlib.h>

#ifdef sun
#include <sys/types.h>
#include <sys/ipc.h>
#endif

#include <sys/sem.h>

#ifdef sun
  extern int semget(key_t key, int nsems, int semflg);
  extern int semctl(int semid, int semnum, int cmd, union semun arg);
  extern int semop(int semid, struct sembuf *sops, int nsops);
#endif

struct semaphor_s {
  int id;
  struct sembuf buf;
};

typedef struct semaphor_s *semaphor;

#ifdef __GNUC__
static __inline__
semaphor SEM_ALLOC(int flag)
{
  semaphor mutex = (semaphor)malloc(sizeof(struct semaphor_s));
  if(mutex == NULL) return NULL;

  mutex->id = semget(IPC_PRIVATE, 1, IPC_CREAT|0600);
  if(mutex->id == FAIL) return NULL;

  mutex->buf.sem_num = 0;
  mutex->buf.sem_flg = flag;

  if(semctl(mutex->id, 0, SETVAL, 1) == FAIL) return NULL;
  return mutex;
}

static __inline__
result SEM_FREE(semaphor mutex)
{
  if(mutex != NULL)
    {
      result res = semctl(mutex->id, 0, IPC_RMID, 0);
      free(mutex);
      return res;
    }
  else
    return SUCCESS;
}

static __inline__
result SEM_OP(semaphor mutex, short op)
{
  mutex->buf.sem_op = op;
  return semop(mutex->id, &mutex->buf, 1);
}
#else /* ! __GNUC__ */
  semaphor _sem_alloc(int flag);
  result   _sem_free(semaphor mutex);
  result   _sem_op(semaphor mutex, short op);

# define SEM_ALLOC _sem_alloc
# define SEM_FREE  _sem_free
# define SEM_OP    _sem_op
#endif

#define SEM_MODE(mutex, mode) ((mutex)->buf.sem_flg=mode)

#define SEMOP_P -1
#define SEMOP_V +1

#define PROBEREN(mutex) SEM_OP(mutex, SEMOP_P)
#define VERHOGEN(mutex) SEM_OP(mutex, SEMOP_V)

#endif /* SEMAPHOR_H_ */