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+/*
+ * -------------------------------------------------------------
+ *
+ * Module: sem_wait.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"
+
+
+static void PTW32_CDECL
+ptw32_sem_wait_cleanup(void * sem)
+{
+ sem_t s = (sem_t) sem;
+
+ if (pthread_mutex_lock (&s->lock) == 0)
+ {
+ /*
+ * If sema is destroyed do nothing, otherwise:-
+ * If the sema is posted between us being cancelled and us locking
+ * the sema again above then we need to consume that post but cancel
+ * anyway. If we don't get the semaphore we indicate that we're no
+ * longer waiting.
+ */
+ if (*((sem_t *)sem) != NULL && !(WaitForSingleObject(s->sem, 0) == WAIT_OBJECT_0))
+ {
+ ++s->value;
+#ifdef NEED_SEM
+ if (s->value > 0)
+ {
+ s->leftToUnblock = 0;
+ }
+#else
+ /*
+ * Don't release the W32 sema, it doesn't need adjustment
+ * because it doesn't record the number of waiters.
+ */
+#endif /* NEED_SEM */
+ }
+ (void) pthread_mutex_unlock (&s->lock);
+ }
+}
+
+int
+sem_wait (sem_t * sem)
+ /*
+ * ------------------------------------------------------
+ * DOCPUBLIC
+ * This function waits on a semaphore.
+ *
+ * PARAMETERS
+ * sem
+ * pointer to an instance of sem_t
+ *
+ * DESCRIPTION
+ * This function waits on a 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 or until interrupted by
+ * a signal.
+ *
+ * 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;
+
+ pthread_testcancel();
+
+ 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)
+ {
+#ifdef _MSC_VER
+#pragma inline_depth(0)
+#endif
+ /* Must wait */
+ pthread_cleanup_push(ptw32_sem_wait_cleanup, (void *) s);
+ result = pthreadCancelableWait (s->sem);
+ /* Cleanup if we're canceled or on any other error */
+ pthread_cleanup_pop(result);
+#ifdef _MSC_VER
+#pragma inline_depth()
+#endif
+ }
+#ifdef NEED_SEM
+
+ if (!result && 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 /* NEED_SEM */
+
+ }
+
+ }
+
+ if (result != 0)
+ {
+ errno = result;
+ return -1;
+ }
+
+ return 0;
+
+} /* sem_wait */