nuttx/sched/clock/clock.c

/****************************************************************************
 * sched/clock/clock.c
 *
 *   Copyright (C) 2015, 2018-2019 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 <time.h>

#include <nuttx/clock.h>

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

/****************************************************************************
 * Name:  clock
 *
 * Description:
 *   The clock() function returns the implementation's best approximation to
 *   the processor time used by the process since the beginning of a
 *   implementation-defined era related only to the process invocation.
 *
 *   To determine the time in seconds, the value returned by clock() should
 *   be divided by the value of the macro CLOCKS_PER_SEC as defined in
 *   <time.h>.
 *
 *   NOTE:  The current implementation does NOT return the processor time
 *   used by the process.  NuttX currently does not keep any record of
 *   processing time.  Instead the elapsed time since power up is returned.
 *
 * Input Parameters:
 *   None
 *
 * Returned Value:
 *   The system time in units of clock ticks is returned.  If the processor
 *   time used is not available or its value cannot be represented, the
 *   function will return the value (clock_t)-1.
 *
 ****************************************************************************/

clock_t clock(void)
{
  return (clock_t)clock_systime_ticks();
}