nuttx/libc/semaphore/sem_getvalue.c

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/****************************************************************************
* libc/semaphore/sem_getvalue.c
*
* Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <semaphore.h>
#include <errno.h>
#include <nuttx/semaphore.h>
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: nxsem_getvalue
*
* Description:
* This function updates the location referenced by 'sval' argument to
* have the value of the semaphore referenced by 'sem' without effecting
* the state of the semaphore. The updated value represents the actual
* semaphore value that occurred at some unspecified time during the call,
* but may not reflect the actual value of the semaphore when it is
* returned to the calling task.
*
* If 'sem' is locked, the value return by nxsem_getvalue() will either be
* zero or a negative number whose absolute value represents the number
* of tasks waiting for the semaphore.
*
* Parameters:
* sem - Semaphore descriptor
* sval - Buffer by which the value is returned
*
* Returned Value:
* This is an internal OS interface and should not be used by applications.
* It follows the NuttX internal error return policy: Zero (OK) is
* returned on success. A negated errno value is returned on failure.
*
****************************************************************************/
int nxsem_getvalue(FAR sem_t *sem, FAR int *sval)
{
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if (sem != NULL && sval != NULL)
{
*sval = sem->semcount;
return OK;
}
return -EINVAL;
}
/****************************************************************************
* Name: sem_getvalue
*
* Description:
* This function updates the location referenced by 'sval' argument to
* have the value of the semaphore referenced by 'sem' without effecting
* the state of the semaphore. The updated value represents the actual
* semaphore value that occurred at some unspecified time during the call,
* but may not reflect the actual value of the semaphore when it is
* returned to the calling task.
*
* If 'sem' is locked, the value return by sem_getvalue() will either be
* zero or a negative number whose absolute value represents the number
* of tasks waiting for the semaphore.
*
* Parameters:
* sem - Semaphore descriptor
* sval - Buffer by which the value is returned
*
* This returns zero (OK) if successful. Otherwise, -1 (ERROR) is
* returned and the errno value is set appropriately.
*
****************************************************************************/
int sem_getvalue(FAR sem_t *sem, FAR int *sval)
{
int ret;
ret = nxsem_getvalue(sem, sval);
if (ret < 0)
{
set_errno(-ret);
ret = ERROR;
}
return ret;
}