core/sys/stimer.c

   1 /**
   2  * \addtogroup stimer
   3  * @{
   4  */
   5
   6 /**
   7  * \file
   8  * Timer of seconds library implementation.
   9  * \author
  10  * Adam Dunkels <adam@sics.se>, Nicolas Tsiftes <nvt@sics.se>
  11  */
  12
  13 /*
  14  * Copyright (c) 2004, 2008, Swedish Institute of Computer Science.
  15  * All rights reserved.
  16  *
  17  * Redistribution and use in source and binary forms, with or without
  18  * modification, are permitted provided that the following conditions
  19  * are met:
  20  * 1. Redistributions of source code must retain the above copyright
  21  *    notice, this list of conditions and the following disclaimer.
  22  * 2. Redistributions in binary form must reproduce the above copyright
  23  *    notice, this list of conditions and the following disclaimer in the
  24  *    documentation and/or other materials provided with the distribution.
  25  * 3. Neither the name of the Institute nor the names of its contributors
  26  *    may be used to endorse or promote products derived from this software
  27  *    without specific prior written permission.
  28  *
  29  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
  30  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  31  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  32  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
  33  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  34  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  35  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  36  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  37  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  38  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  39  * SUCH DAMAGE.
  40  *
  41  * This file is part of the Contiki operating system.
  42  *
  43  * Author: Adam Dunkels <adam@sics.se>, Nicolas Tsiftes <nvt@sics.se>
  44  *
  45  * $Id: stimer.c,v 1.3 2010/03/15 15:53:57 joxe Exp $
  46  */
  47
  48 #include "contiki-conf.h"
  49 #include "sys/clock.h"
  50 #include "sys/stimer.h"
  51
  52 #define SCLOCK_GEQ(a, b)        ((unsigned long)((a) - (b)) < \
  53                                 ((unsigned long)(~((unsigned long)0)) >> 1))
  54
  55 /*---------------------------------------------------------------------------*/
  56 /**
  57  * Set a timer.
  58  *
  59  * This function is used to set a timer for a time sometime in the
  60  * future. The function stimer_expired() will evaluate to true after
  61  * the timer has expired.
  62  *
  63  * \param t A pointer to the timer
  64  * \param interval The interval before the timer expires.
  65  *
  66  */
  67 void
  68 stimer_set(struct stimer *t, unsigned long interval)
  69 {
  70   t->interval = interval;
  71   t->start = clock_seconds();
  72 }
  73 /*---------------------------------------------------------------------------*/
  74 /**
  75  * Reset the timer with the same interval.
  76  *
  77  * This function resets the timer with the same interval that was
  78  * given to the stimer_set() function. The start point of the interval
  79  * is the exact time that the timer last expired. Therefore, this
  80  * function will cause the timer to be stable over time, unlike the
  81  * stimer_restart() function.
  82  *
  83  * \param t A pointer to the timer.
  84  *
  85  * \sa stimer_restart()
  86  */
  87 void
  88 stimer_reset(struct stimer *t)
  89 {
  90   t->start += t->interval;
  91 }
  92 /*---------------------------------------------------------------------------*/
  93 /**
  94  * Restart the timer from the current point in time
  95  *
  96  * This function restarts a timer with the same interval that was
  97  * given to the stimer_set() function. The timer will start at the
  98  * current time.
  99  *
 100  * \note A periodic timer will drift if this function is used to reset
 101  * it. For preioric timers, use the stimer_reset() function instead.
 102  *
 103  * \param t A pointer to the timer.
 104  *
 105  * \sa stimer_reset()
 106  */
 107 void
 108 stimer_restart(struct stimer *t)
 109 {
 110   t->start = clock_seconds();
 111 }
 112 /*---------------------------------------------------------------------------*/
 113 /**
 114  * Check if a timer has expired.
 115  *
 116  * This function tests if a timer has expired and returns true or
 117  * false depending on its status.
 118  *
 119  * \param t A pointer to the timer
 120  *
 121  * \return Non-zero if the timer has expired, zero otherwise.
 122  *
 123  */
 124 int
 125 stimer_expired(struct stimer *t)
 126 {
 127   return SCLOCK_GEQ(clock_seconds(), t->start + t->interval);
 128 }
 129 /*---------------------------------------------------------------------------*/
 130 /**
 131  * The time until the timer expires
 132  *
 133  * This function returns the time until the timer expires.
 134  *
 135  * \param t A pointer to the timer
 136  *
 137  * \return The time until the timer expires
 138  *
 139  */
 140 unsigned long
 141 stimer_remaining(struct stimer *t)
 142 {
 143   return t->start + t->interval - clock_seconds();
 144 }
 145 /*---------------------------------------------------------------------------*/
 146 /**
 147  * The time elapsed since the timer started
 148  *
 149  * This function returns the time elapsed.
 150  *
 151  * \param t A pointer to the timer
 152  *
 153  * \return The time elapsed since the last start of the timer
 154  *
 155  */
 156 unsigned long
 157 stimer_elapsed(struct stimer *t)
 158 {
 159   return clock_seconds() - t->start;
 160 }
 161
 162 /*---------------------------------------------------------------------------*/
 163
 164 /** @} */