/* * ------------------------------------------------------------- * * Module: sem_trywait.c * * Purpose: *	Semaphores aren't actually part of the PThreads standard. *	They are defined by the POSIX Standard: * *		POSIX 1003.1b-1993	(POSIX.1b) * * ------------------------------------------------------------- * * -------------------------------------------------------------------------- * *      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., *      59 Temple Place - Suite 330, Boston, MA 02111-1307, USA */#include "pthread.h"#include "semaphore.h"#include "implement.h"intsem_trywait (sem_t * sem)     /*      * ------------------------------------------------------      * DOCPUBLIC      *      This function tries to wait on a semaphore.      *      * PARAMETERS      *      sem      *              pointer to an instance of sem_t      *      * DESCRIPTION      *      This function tries to wait on a semaphore. If the      *      semaphore value is greater than zero, it decreases      *      its value by one. If the semaphore value is zero, then      *      this function returns immediately with the error EAGAIN      *      * RESULTS      *              0               successfully decreased semaphore,      *              -1              failed, error in errno      * ERRNO      *              EAGAIN          the semaphore was already locked,      *              EINVAL          'sem' is not a valid semaphore,      *              ENOTSUP         sem_trywait is 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)    {      if (s->value > 0)	{	  s->value--;	}      else	{	  result = EAGAIN;	}      (void) pthread_mutex_unlock (&s->lock);    }  if (result != 0)    {      errno = result;      return -1;    }  return 0;}				/* sem_trywait */