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/*
* -------------------------------------------------------------
*
* Module: sem_getvalue.c
*
* Purpose:
* Semaphores aren't actually part of PThreads.
* They are defined by the POSIX Standard:
*
* POSIX 1003.1-2001
*
* -------------------------------------------------------------
*
* Pthreads-win32 - POSIX Threads Library for Win32
* Copyright(C) 1998 John E. Bossom
* Copyright(C) 1999,2002 Pthreads-win32 contributors
*
* Contact Email: rpj@ise.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"
int
sem_getvalue(sem_t * sem, int * sval)
/*
* ------------------------------------------------------
* DOCPUBLIC
* This function stores the current count value of the
* semaphore.
* RESULTS
*
* Return value
*
* 0 sval has been set.
* -1 failed, error in errno
*
* in global errno
*
* EINVAL 'sem' is not a valid semaphore,
* ENOSYS this function is not supported,
*
*
* PARAMETERS
*
* sem pointer to an instance of sem_t
*
* sval pointer to int.
*
* DESCRIPTION
* This function stores the current count value of the semaphore
* pointed to by sem in the int pointed to by sval.
*/
{
int result = 0;
if ( sem == NULL || *sem == NULL || sval == NULL )
{
result = EINVAL;
}
else
{
#ifdef NEED_SEM
result = ENOSYS;
#else
long value = *sval;
/* From "Win32 System Programming - Second Edition"
* by Johnson M Hart, chapter 9, page 256 :
*
* "The release count must be greater than zero, but if it
* would cause the semaphore count to exceed the maximum,
* the call will fail, returning FALSE, and the count will
* remain unchanged. Releasing a semaphore with a large count
* is a method used to obtain the current count atomically
* (of course, another thread might change the value immediately)."
*/
if ( ! ReleaseSemaphore( (*sem)->sem, _POSIX_SEM_VALUE_MAX + 1, &value) )
{
*sval = value;
}
else
{
/* This should NEVER occur. */
result = ENOSYS;
}
#endif
}
if ( result != 0 )
{
errno = result;
return -1;
}
return 0;
} /* sem_getvalue */
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