/* Copyright (C) 2000,02 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Written by Gaël Le Mignot <kilobug@hurdfr.org>

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

/*
 *	POSIX Threads Extension: Semaphores			<semaphore.c>
 */

#include <semaphore.h>
#include <stdlib.h>

/* Initialize the semaphore and set the initial value - as in LinuxThreads
   pshared must be zero right now. */
int 
sem_init (sem_t *sem, int pshared, unsigned int value)
{
  if (pshared)
    return -1;
  
  sem = malloc (sizeof (*sem));
  if (sem == NULL)
    return -1;
  
  sem->count = value;
  pthread_cond_init (&sem->lock, NULL);
  pthread_mutex_init (&sem->count_lock, NULL);
  return 0;
}


/* Destroys the semaphore */
int 
sem_destroy (sem_t *sem)
{
  pthread_mutex_destroy (&sem->count_lock);
  pthread_cond_destroy (&sem->lock);
  free (sem);
  return 0;
}

/* Wait until the count is > 0, and then decrease it  */
int 
sem_wait (sem_t *sem)
{
  pthread_mutex_lock (&sem->count_lock);
  while (1)
    {
      if (sem->count)
	{
	  sem->count--;
	  pthread_mutex_unlock (&sem->count_lock);
	  return 0;
	}
      pthread_cond_wait (&sem->lock, &sem->count_lock);
    }
  pthread_mutex_unlock (&sem->count_lock);
}

/* Non-blocking variant of sem_wait. Returns -1 if count == 0. */
int 
sem_trywait (sem_t *sem)
{
  int res = -1;
  
  pthread_mutex_lock (&sem->count_lock);
  if (sem->count)
    {
      res = 0;
      sem->count--;
    }
  pthread_mutex_unlock (&sem->count_lock);
  
  return res;
}

/* Increments the count */
int 
sem_post (sem_t *sem)
{
  pthread_mutex_lock (&sem->count_lock);
  sem->count++;
  pthread_cond_signal (&sem->lock);
  pthread_mutex_unlock (&sem->count_lock);
  return 0;
}

/* Return the value of the semaphore */
int 
sem_getvalue (sem_t *sem, int *sval)
{
  pthread_mutex_lock (&sem->count_lock);
  *sval = sem->count;
  pthread_mutex_unlock (&sem->count_lock);
  return 0;
}