nuttx/sched/sem_getvalue.c

/************************************************************
 * sem_getvalue.c
 *
 *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
 *
 * 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 Gregory Nutt 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 <sys/types.h>
#include <semaphore.h>
#include "sem_internal.h"

/************************************************************
 * Compilation Switches
 ************************************************************/

/************************************************************
 * Definitions
 ************************************************************/

/************************************************************
 * Private Type Declarations
 ************************************************************/

/************************************************************
 * Global Variables
 ************************************************************/

/************************************************************
 * Private Variables
 ************************************************************/

/************************************************************
 * Private Functions
 ************************************************************/

/************************************************************
 * Public Functions
 ************************************************************/

/************************************************************
 * Function:  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
 *
 * Return Value:
 *   0 (OK), or -1 (ERROR) if unsuccessful
 *
 * Assumptions:
 *
 ************************************************************/

int sem_getvalue(sem_t *sem, int *sval)
{
  int ret = ERROR;

  if (sem && sval)
    {
      *sval = sem->semcount;
      ret = OK;
    }

  return ret;
}