contiki/core/sys/etimer.h

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/** \addtogroup sys
* @{ */
/**
* \defgroup etimer Event timers
*
* Event timers provides a way to generate timed events. An event
* timer will post an event to the process that set the timer when the
* event timer expires.
*
* An event timer is declared as a \c struct \c etimer and all access
* to the event timer is made by a pointer to the declared event
* timer.
*
* \sa \ref timer "Simple timer library"
* \sa \ref clock "Clock library" (used by the timer library)
*
* @{
*/
/**
* \file
* Event timer header file.
* \author
* Adam Dunkels <adam@sics.se>
*/
/*
* Copyright (c) 2004, 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>
*
*/
#ifndef ETIMER_H_
#define ETIMER_H_
#include "sys/timer.h"
#include "sys/process.h"
/**
* A timer.
*
* This structure is used for declaring a timer. The timer must be set
* with etimer_set() before it can be used.
*
* \hideinitializer
*/
struct etimer {
struct timer timer;
struct etimer *next;
struct process *p;
};
/**
* \name Functions called from application programs
* @{
*/
/**
* \brief Set an event timer.
* \param et A pointer to the event timer
* \param interval The interval before the timer expires.
*
* This function is used to set an event timer for a time
* sometime in the future. When the event timer expires,
* the event PROCESS_EVENT_TIMER will be posted to the
* process that called the etimer_set() function.
*
*/
CCIF void etimer_set(struct etimer *et, clock_time_t interval);
/**
* \brief Reset an event timer with the same interval as was
* previously set.
* \param et A pointer to the event timer.
*
* This function resets the event timer with the same
* interval that was given to the event timer with the
* etimer_set() function. The start point of the interval
* is the exact time that the event timer last
* expired. Therefore, this function will cause the timer
* to be stable over time, unlike the etimer_restart()
* function.
*
* \sa etimer_restart()
*/
CCIF void etimer_reset(struct etimer *et);
/**
* \brief Restart an event timer from the current point in time
* \param et A pointer to the event timer.
*
* This function restarts the event timer with the same
* interval that was given to the etimer_set()
* function. The event timer will start at the current
* time.
*
* \note A periodic timer will drift if this function is
* used to reset it. For periodic timers, use the
* etimer_reset() function instead.
*
* \sa etimer_reset()
*/
void etimer_restart(struct etimer *et);
/**
* \brief Adjust the expiration time for an event timer
* \param et A pointer to the event timer.
* \param td The time difference to adjust the expiration time with.
*
* This function is used to adjust the time the event
* timer will expire. It can be used to synchronize
* periodic timers without the need to restart the timer
* or change the timer interval.
*
* \note This function should only be used for small
* adjustments. For large adjustments use etimer_set()
* instead.
*
* \note A periodic timer will drift unless the
* etimer_reset() function is used.
*
* \sa etimer_set()
* \sa etimer_reset()
*/
void etimer_adjust(struct etimer *et, int td);
/**
* \brief Get the expiration time for the event timer.
* \param et A pointer to the event timer
* \return The expiration time for the event timer.
*
* This function returns the expiration time for an event timer.
*/
clock_time_t etimer_expiration_time(struct etimer *et);
/**
* \brief Get the start time for the event timer.
* \param et A pointer to the event timer
* \return The start time for the event timer.
*
* This function returns the start time (when the timer
* was last set) for an event timer.
*/
clock_time_t etimer_start_time(struct etimer *et);
/**
* \brief Check if an event timer has expired.
* \param et A pointer to the event timer
* \return Non-zero if the timer has expired, zero otherwise.
*
* This function tests if an event timer has expired and
* returns true or false depending on its status.
*/
CCIF int etimer_expired(struct etimer *et);
/**
* \brief Stop a pending event timer.
* \param et A pointer to the pending event timer.
*
* This function stops an event timer that has previously
* been set with etimer_set() or etimer_reset(). After
* this function has been called, the event timer will not
* emit any event when it expires.
*
*/
void etimer_stop(struct etimer *et);
/** @} */
/**
* \name Functions called from timer interrupts, by the system
* @{
*/
/**
* \brief Make the event timer aware that the clock has changed
*
* This function is used to inform the event timer module
* that the system clock has been updated. Typically, this
* function would be called from the timer interrupt
* handler when the clock has ticked.
*/
void etimer_request_poll(void);
/**
* \brief Check if there are any non-expired event timers.
* \return True if there are active event timers, false if there are
* no active timers.
*
* This function checks if there are any active event
* timers that have not expired.
*/
int etimer_pending(void);
/**
* \brief Get next event timer expiration time.
* \return Next expiration time of all pending event timers.
* If there are no pending event timers this function
* returns 0.
*
* This functions returns next expiration time of all
* pending event timers.
*/
clock_time_t etimer_next_expiration_time(void);
/** @} */
PROCESS_NAME(etimer_process);
#endif /* ETIMER_H_ */
/** @} */
/** @} */