/* * ------------------------------------------------------------- * * 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" #include <stdio.h> int sem_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. * * ------------------------------------------------------ */ { #ifdef NEED_SEM /* * not yet implemented! */ errno = ENOTSUP; return -1; #else /* NEED_SEM */ 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++; result = EAGAIN; } (void) pthread_mutex_unlock (&s->lock); } if (result != 0) { errno = result; return -1; } return 0; #endif /* NEED_SEM */ } /* sem_trywait */