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a timer of seconds

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nvt-se 2008-10-02 10:17:48 +00:00
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147
core/sys/stimer.c Normal file
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/**
* \addtogroup stimer
* @{
*/
/**
* \file
* Timer of seconds library implementation.
* \author
* Adam Dunkels <adam@sics.se>, Nicolas Tsiftes <nvt@sics.se>
*/
/*
* Copyright (c) 2004, 2008, Swedish Institute of Computer Science.
* All rights reserved.
*
* 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 of the Institute 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 INSTITUTE 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 INSTITUTE 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.
*
* This file is part of the Contiki operating system.
*
* Author: Adam Dunkels <adam@sics.se>, Nicolas Tsiftes <nvt@sics.se>
*
* $Id: stimer.c,v 1.1 2008/10/02 10:17:48 nvt-se Exp $
*/
#include "contiki-conf.h"
#include "sys/clock.h"
#include "sys/stimer.h"
#define SCLOCK_LT(a, b) ((unsigned long)((a) - (b)) < \
((unsigned long)(~((unsigned long)0)) >> 1))
/*---------------------------------------------------------------------------*/
/**
* Set a timer.
*
* This function is used to set a timer for a time sometime in the
* future. The function stimer_expired() will evaluate to true after
* the timer has expired.
*
* \param t A pointer to the timer
* \param interval The interval before the timer expires.
*
*/
void
stimer_set(struct stimer *t, unsigned long interval)
{
t->interval = interval;
t->start = clock_seconds();
}
/*---------------------------------------------------------------------------*/
/**
* Reset the timer with the same interval.
*
* This function resets the timer with the same interval that was
* given to the stimer_set() function. The start point of the interval
* is the exact time that the timer last expired. Therefore, this
* function will cause the timer to be stable over time, unlike the
* stimer_restart() function.
*
* \param t A pointer to the timer.
*
* \sa stimer_restart()
*/
void
stimer_reset(struct stimer *t)
{
t->start += t->interval;
}
/*---------------------------------------------------------------------------*/
/**
* Restart the timer from the current point in time
*
* This function restarts a timer with the same interval that was
* given to the stimer_set() function. The timer will start at the
* current time.
*
* \note A periodic timer will drift if this function is used to reset
* it. For preioric timers, use the stimer_reset() function instead.
*
* \param t A pointer to the timer.
*
* \sa stimer_reset()
*/
void
stimer_restart(struct stimer *t)
{
t->start = clock_seconds();
}
/*---------------------------------------------------------------------------*/
/**
* Check if a timer has expired.
*
* This function tests if a timer has expired and returns true or
* false depending on its status.
*
* \param t A pointer to the timer
*
* \return Non-zero if the timer has expired, zero otherwise.
*
*/
int
stimer_expired(struct stimer *t)
{
return SCLOCK_LT(clock_seconds(), t->start + t->interval);
}
/*---------------------------------------------------------------------------*/
/**
* The time until the timer expires
*
* This function returns the time until the timer expires.
*
* \param t A pointer to the timer
*
* \return The time until the timer expires
*
*/
unsigned long
stimer_remaining(struct stimer *t)
{
return t->start + t->interval - clock_seconds();
}
/*---------------------------------------------------------------------------*/
/** @} */

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core/sys/stimer.h Normal file
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/** \addtogroup sys
* @{ */
/**
* \defgroup timer Seconds timer library
*
* The stimer library provides functions for setting, resetting and
* restarting timers, and for checking if a timer has expired. An
* application must "manually" check if its timers have expired; this
* is not done automatically.
*
* A timer is declared as a \c struct \c stimer and all access to the
* timer is made by a pointer to the declared timer.
*
* \note The stimer library is not able to post events when a timer
* expires. The \ref etimer "Event timers" should be used for this
* purpose.
*
* \note The stimer library uses the \ref clock "Clock library" to
* measure time. Intervals should be specified in the seconds.
*
* \sa \ref etimer "Event timers"
*
* @{
*/
/**
* \file
* Second timer library header file.
* \author
* Adam Dunkels <adam@sics.se>, Nicolas Tsiftes <nvt@sics.se>
*/
/*
* Copyright (c) 2004, 2008, Swedish Institute of Computer Science.
* All rights reserved.
*
* 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 of the Institute 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 INSTITUTE 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 INSTITUTE 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.
*
* This file is part of the Contiki operating system.
*
* Author: Adam Dunkels <adam@sics.se>, Nicolas Tsiftes <nvt@sics.se>
*
* $Id: stimer.h,v 1.1 2008/10/02 10:17:48 nvt-se Exp $
*/
#ifndef __STIMER_H__
#define __STIMER_H__
#include "sys/clock.h"
typedef unsigned long clock_second_t;
/**
* A timer.
*
* This structure is used for declaring a timer. The timer must be set
* with stimer_set() before it can be used.
*
* \hideinitializer
*/
struct stimer {
clock_second_t start;
clock_second_t interval;
};
void stimer_set(struct stimer *t, clock_second_t interval);
void stimer_reset(struct stimer *t);
void stimer_restart(struct stimer *t);
int stimer_expired(struct stimer *t);
clock_second_t stimer_remaining(struct stimer *t);
#endif /* __STIMER_H__ */
/** @} */
/** @} */