forked from Archive/PX4-Autopilot
109 lines
4.2 KiB
C
109 lines
4.2 KiB
C
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/****************************************************************************
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* lib/semaphore/sem_getvalue.c
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*
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* Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <semaphore.h>
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#include <errno.h>
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/****************************************************************************
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* Definitions
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****************************************************************************/
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/****************************************************************************
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* Private Type Declarations
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****************************************************************************/
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/****************************************************************************
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* Global Variables
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****************************************************************************/
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/****************************************************************************
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* Private Variables
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****************************************************************************/
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Function: sem_getvalue
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*
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* Description:
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* This function updates the location referenced by 'sval' argument to
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* have the value of the semaphore referenced by 'sem' without effecting
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* the state of the semaphore. The updated value represents the actual
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* semaphore value that occurred at some unspecified time during the call,
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* but may not reflect the actual value of the semaphore when it is
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* returned to the calling task.
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*
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* If 'sem' is locked, the value return by sem_getvalue() will either be
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* zero or a negative number whose absolute value represents the number
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* of tasks waiting for the semaphore.
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*
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* Parameters:
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* sem - Semaphore descriptor
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* sval - Buffer by which the value is returned
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*
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* Return Value:
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* 0 (OK), or -1 (ERROR) if unsuccessful
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*
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* Assumptions:
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*
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****************************************************************************/
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int sem_getvalue(FAR sem_t *sem, FAR int *sval)
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{
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if (sem && sval)
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{
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*sval = sem->semcount;
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return OK;
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}
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else
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{
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set_errno(EINVAL);
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return ERROR;
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}
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}
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