obs-studio/deps/w32-pthreads/ptw32_semwait.c

/*
 * ptw32_semwait.c
 *
 * Description:
 * This translation unit implements mutual exclusion (mutex) primitives.
 *
 * --------------------------------------------------------------------------
 *
 *      Pthreads-win32 - POSIX Threads Library for Win32
 *      Copyright(C) 1998 John E. Bossom
 *      Copyright(C) 1999,2005 Pthreads-win32 contributors
 * 
 *      Contact Email: rpj@callisto.canberra.edu.au
 * 
 *      The current list of contributors is contained
 *      in the file CONTRIBUTORS included with the source
 *      code distribution. The list can also be seen at the
 *      following World Wide Web location:
 *      http://sources.redhat.com/pthreads-win32/contributors.html
 * 
 *      This library is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU Lesser General Public
 *      License as published by the Free Software Foundation; either
 *      version 2 of the License, or (at your option) any later version.
 * 
 *      This 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
 *      Lesser General Public License for more details.
 * 
 *      You should have received a copy of the GNU Lesser General Public
 *      License along with this library in the file COPYING.LIB;
 *      if not, write to the Free Software Foundation, Inc.,
 *      51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
 */

#if !defined(_UWIN)
/*#   include <process.h> */
#endif
#include "pthread.h"
#include "implement.h"


int
ptw32_semwait (sem_t * sem)
     /*
      * ------------------------------------------------------
      * DESCRIPTION
      *      This function waits on a POSIX semaphore. If the
      *      semaphore value is greater than zero, it decreases
      *      its value by one. If the semaphore value is zero, then
      *      the calling thread (or process) is blocked until it can
      *      successfully decrease the value.
      *
      *      Unlike sem_wait(), this routine is non-cancelable.
      *
      * RESULTS
      *              0               successfully decreased semaphore,
      *              -1              failed, error in errno.
      * ERRNO
      *              EINVAL          'sem' is not a valid semaphore,
      *              ENOSYS          semaphores are not supported,
      *              EINTR           the function was interrupted by a signal,
      *              EDEADLK         a deadlock condition was detected.
      *
      * ------------------------------------------------------
      */
{
  int result = 0;
  sem_t s = *sem;

  if (s == NULL)
    {
      result = EINVAL;
    }
  else
    {
      if ((result = pthread_mutex_lock (&s->lock)) == 0)
        {
          int v;

	  /* See sem_destroy.c
	   */
	  if (*sem == NULL)
	    {
	      (void) pthread_mutex_unlock (&s->lock);
	      errno = EINVAL;
	      return -1;
	    }

          v = --s->value;
          (void) pthread_mutex_unlock (&s->lock);

          if (v < 0)
            {
              /* Must wait */
              if (WaitForSingleObject (s->sem, INFINITE) == WAIT_OBJECT_0)
		{
#if defined(NEED_SEM)
		  if (pthread_mutex_lock (&s->lock) == 0)
		    {
        	      if (*sem == NULL)
        	        {
        	          (void) pthread_mutex_unlock (&s->lock);
        	          errno = EINVAL;
        	          return -1;
        	        }

		      if (s->leftToUnblock > 0)
			{
			  --s->leftToUnblock;
			  SetEvent(s->sem);
			}
		      (void) pthread_mutex_unlock (&s->lock);
		    }
#endif
		  return 0;
		}
            }
          else
	    {
	      return 0;
	    }
        }
    }

  if (result != 0)
    {
      errno = result;
      return -1;
    }

  return 0;

}				/* ptw32_semwait */