gp_timer.c

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