text: /****************************************************************************
   * sched/clock/clock_time2ticks.c
   *
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.  The
   * ASF licenses this file to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance with the
   * License.  You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
   * License for the specific language governing permissions and limitations
   * under the License.
   *
   ****************************************************************************/
  
  /****************************************************************************
   * Included Files
   ****************************************************************************/
  
  #include <nuttx/config.h>
  
  #include <stdint.h>
  #include <time.h>
  
  #include "clock/clock.h"
  
  /****************************************************************************
   * Public Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Name: clock_time2ticks
   *
   * Description:
   *   Convert a timespec delay to system timer ticks.  This function is
   *   suitable for calculating relative time delays and does not depend on
   *   the other clock_* logic.
   *
   * Input Parameters:
   *   reltime - Convert this relative time to system clock ticks.
   *   ticks - Return the converted number of ticks here.
   *
   * Returned Value:
   *   Always returns OK
   *
   * Assumptions:
   *
   ****************************************************************************/
  
  int clock_time2ticks(FAR const struct timespec *reltime,
                       FAR sclock_t *ticks)
  {
  #ifdef CONFIG_HAVE_LONG_LONG
    int64_t relnsec;
  
    /* Convert the relative time into nanoseconds.  The range of the int64_t
     * is sufficiently large that there is no real need for range checking.
     */
  
    relnsec = (int64_t)reltime->tv_sec * NSEC_PER_SEC +
              (int64_t)reltime->tv_nsec;
  
    /* Convert nanoseconds to clock ticks, rounding up to the smallest integer
     * that is greater than or equal to the exact number of tick.
     */
  
    *ticks = (sclock_t)((relnsec + NSEC_PER_TICK - 1) / NSEC_PER_TICK);
    return OK;
  #else
    int32_t relusec;
  
    /* This function uses an int32_t to only the relative time in microseconds.
     * that means that the maximum supported relative time is 2,147,487.647
     * seconds
     */
  
  #if 0 // overkill
    DEBUGASSERT(reltime->tv_sec  <  2147487 ||
                reltime->tv_sec  == 2147487 &&
                reltime->tv_nsec <= 647 * NSEC_PER_MSEC);
  #endif
  
    /* Convert the relative time into microseconds, rounding up to the smallest
     * value that is greater than or equal to the exact number of microseconds.
     */
  
    relusec = reltime->tv_sec * USEC_PER_SEC +
              (reltime->tv_nsec + NSEC_PER_USEC - 1) / NSEC_PER_USEC;
  
    /* Convert microseconds to clock ticks, rounding up to the smallest integer
     * that is greater than or equal to the exact number of tick.
     */
  
    *ticks = (sclock_t)((relusec + USEC_PER_TICK - 1) / USEC_PER_TICK);
    return OK;
  #endif
  }
  