timer.c

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00001 /**
00002  * \addtogroup timer
00003  * @{
00004  */
00005 
00006 /**
00007  * \file
00008  * Timer library implementation.
00009  * \author
00010  * Adam Dunkels <adam@sics.se>
00011  */
00012 
00013 /*
00014  * Copyright (c) 2004, Swedish Institute of Computer Science.
00015  * All rights reserved.
00016  *
00017  * Redistribution and use in source and binary forms, with or without
00018  * modification, are permitted provided that the following conditions
00019  * are met:
00020  * 1. Redistributions of source code must retain the above copyright
00021  *    notice, this list of conditions and the following disclaimer.
00022  * 2. Redistributions in binary form must reproduce the above copyright
00023  *    notice, this list of conditions and the following disclaimer in the
00024  *    documentation and/or other materials provided with the distribution.
00025  * 3. Neither the name of the Institute nor the names of its contributors
00026  *    may be used to endorse or promote products derived from this software
00027  *    without specific prior written permission.
00028  *
00029  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
00030  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
00031  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
00032  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
00033  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
00034  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
00035  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
00036  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
00037  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
00038  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
00039  * SUCH DAMAGE.
00040  *
00041  * This file is part of the Contiki operating system.
00042  *
00043  * Author: Adam Dunkels <adam@sics.se>
00044  *
00045  * $Id: timer.c,v 1.8 2010/06/21 19:07:24 joxe Exp $
00046  */
00047 
00048 #include "contiki-conf.h"
00049 #include "sys/clock.h"
00050 #include "sys/timer.h"
00051 
00052 /*---------------------------------------------------------------------------*/
00053 /**
00054  * Set a timer.
00055  *
00056  * This function is used to set a timer for a time sometime in the
00057  * future. The function timer_expired() will evaluate to true after
00058  * the timer has expired.
00059  *
00060  * \param t A pointer to the timer
00061  * \param interval The interval before the timer expires.
00062  *
00063  */
00064 void
00065 timer_set(struct timer *t, clock_time_t interval)
00066 {
00067   t->interval = interval;
00068   t->start = clock_time();
00069 }
00070 /*---------------------------------------------------------------------------*/
00071 /**
00072  * Reset the timer with the same interval.
00073  *
00074  * This function resets the timer with the same interval that was
00075  * given to the timer_set() function. The start point of the interval
00076  * is the exact time that the timer last expired. Therefore, this
00077  * function will cause the timer to be stable over time, unlike the
00078  * timer_restart() function.
00079  *
00080  * \param t A pointer to the timer.
00081  *
00082  * \sa timer_restart()
00083  */
00084 void
00085 timer_reset(struct timer *t)
00086 {
00087   t->start += t->interval;
00088 }
00089 /*---------------------------------------------------------------------------*/
00090 /**
00091  * Restart the timer from the current point in time
00092  *
00093  * This function restarts a timer with the same interval that was
00094  * given to the timer_set() function. The timer will start at the
00095  * current time.
00096  *
00097  * \note A periodic timer will drift if this function is used to reset
00098  * it. For preioric timers, use the timer_reset() function instead.
00099  *
00100  * \param t A pointer to the timer.
00101  *
00102  * \sa timer_reset()
00103  */
00104 void
00105 timer_restart(struct timer *t)
00106 {
00107   t->start = clock_time();
00108 }
00109 /*---------------------------------------------------------------------------*/
00110 /**
00111  * Check if a timer has expired.
00112  *
00113  * This function tests if a timer has expired and returns true or
00114  * false depending on its status.
00115  *
00116  * \param t A pointer to the timer
00117  *
00118  * \return Non-zero if the timer has expired, zero otherwise.
00119  *
00120  */
00121 int
00122 timer_expired(struct timer *t)
00123 {
00124   /* Note: Can not return diff >= t->interval so we add 1 to diff and return
00125      t->interval < diff - required to avoid an internal error in mspgcc. */
00126   clock_time_t diff = (clock_time() - t->start) + 1;
00127   return t->interval < diff;
00128 
00129 }
00130 /*---------------------------------------------------------------------------*/
00131 /**
00132  * The time until the timer expires
00133  *
00134  * This function returns the time until the timer expires.
00135  *
00136  * \param t A pointer to the timer
00137  *
00138  * \return The time until the timer expires
00139  *
00140  */
00141 clock_time_t
00142 timer_remaining(struct timer *t)
00143 {
00144   return t->start + t->interval - clock_time();
00145 }
00146 /*---------------------------------------------------------------------------*/
00147 
00148 /** @} */

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