243 lines
7.7 KiB
C
243 lines
7.7 KiB
C
/** \addtogroup sys
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* @{ */
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/**
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* \defgroup etimer Event timers
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*
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* Event timers provides a way to generate timed events. An event
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* timer will post an event to the process that set the timer when the
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* event timer expires.
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*
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* An event timer is declared as a \c struct \c etimer and all access
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* to the event timer is made by a pointer to the declared event
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* timer.
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*
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* \sa \ref timer "Simple timer library"
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* \sa \ref clock "Clock library" (used by the timer library)
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*
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* @{
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*/
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/**
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* \file
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* Event timer header file.
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* \author
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* Adam Dunkels <adam@sics.se>
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*/
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/*
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* Copyright (c) 2004, Swedish Institute of Computer Science.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* This file is part of the Contiki operating system.
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*
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* Author: Adam Dunkels <adam@sics.se>
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*
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* $Id: etimer.h,v 1.1 2006/06/17 22:41:20 adamdunkels Exp $
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*/
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#ifndef __ETIMER_H__
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#define __ETIMER_H__
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#include "sys/timer.h"
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#include "sys/process.h"
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/**
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* A timer.
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*
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* This structure is used for declaring a timer. The timer must be set
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* with etimer_set() before it can be used.
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*
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* \hideinitializer
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*/
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struct etimer {
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struct timer timer;
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struct etimer *next;
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struct process *p;
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};
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/**
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* \name Functions called from application programs
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* @{
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*/
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/**
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* \brief Set an event timer.
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* \param et A pointer to the event timer
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* \param interval The interval before the timer expires.
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*
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* This function is used to set an event timer for a time
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* sometime in the future. When the event timer expires,
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* the event PROCESS_EVENT_TIMER will be posted to the
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* process that called the etimer_set() function.
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*
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*/
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void etimer_set(struct etimer *et, clock_time_t interval);
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/**
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* \brief Reset an event timer with the same interval as was
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* previously set.
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* \param et A pointer to the event timer.
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*
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* This function resets the event timer with the same
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* interval that was given to the event timer with the
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* etimer_set() function. The start point of the interval
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* is the exact time that the event timer last
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* expired. Therefore, this function will cause the timer
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* to be stable over time, unlike the etimer_restart()
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* function.
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*
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* \sa etimer_restart()
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*/
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void etimer_reset(struct etimer *et);
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/**
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* \brief Restart an event timer from the current point in time
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* \param et A pointer to the event timer.
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*
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* This function restarts the event timer with the same
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* interval that was given to the etimer_set()
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* function. The event timer will start at the current
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* time.
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*
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* \note A periodic timer will drift if this function is
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* used to reset it. For periodic timers, use the
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* etimer_reset() function instead.
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*
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* \sa etimer_reset()
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*/
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void etimer_restart(struct etimer *et);
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/**
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* \brief Adjust the expiration time for an event timer
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* \param et A pointer to the event timer.
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* \param td The time difference to adjust the expiration time with.
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*
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* This function is used to adjust the time the event
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* timer will expire. It can be used to synchronize
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* periodic timers without the need to restart the timer
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* or change the timer interval.
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*
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* \note This function should only be used for small
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* adjustments. For large adjustments use etimer_set()
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* instead.
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*
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* \note A periodic timer will drift unless the
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* etimer_reset() function is used.
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*
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* \sa etimer_set()
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* \sa etimer_reset()
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*/
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void etimer_adjust(struct etimer *et, int td);
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/**
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* \brief Get the expiration time for the event timer.
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* \param et A pointer to the event timer
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* \return The expiration time for the event timer.
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*
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* This function returns the expiration time for an event timer.
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*/
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clock_time_t etimer_expiration_time(struct etimer *et);
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/**
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* \brief Get the start time for the event timer.
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* \param et A pointer to the event timer
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* \return The start time for the event timer.
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*
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* This function returns the start time (when the timer
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* was last set) for an event timer.
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*/
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clock_time_t etimer_start_time(struct etimer *et);
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/**
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* \brief Check if an event timer has expired.
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* \param et A pointer to the event timer
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* \return Non-zero if the timer has expired, zero otherwise.
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*
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* This function tests if an event timer has expired and
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* returns true or false depending on its status.
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*/
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int etimer_expired(struct etimer *et);
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/**
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* \brief Stop a pending event timer.
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* \param et A pointer to the pending event timer.
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*
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* This function stops an event timer that has previously
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* been set with etimer_set() or etimer_reset(). After
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* this function has been called, the event timer will not
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* emit any event when it expires.
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*
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*/
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void etimer_stop(struct etimer *et);
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/** @} */
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/**
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* \name Functions called from timer interrupts, by the system
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* @{
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*/
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/**
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* \brief Make the event timer aware that the clock has changed
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*
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* This function is used to inform the event timer module
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* that the system clock has been updated. Typically, this
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* function would be called from the timer interrupt
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* handler when the clock has ticked.
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*/
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void etimer_request_poll(void);
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/**
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* \brief Check if there are any non-expired event timers.
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* \return True if there are active event timers, false if there are
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* no active timers.
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*
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* This function checks if there are any active event
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* timers that have not expired.
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*/
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int etimer_pending(void);
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/**
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* \brief Get next event timer expiration time.
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* \return Next expiration time of all pending event timers.
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* If there are no pending event timers this function
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* returns 0.
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*
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* This functions returns next expiration time of all
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* pending event timers.
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*/
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clock_time_t etimer_next_expiration_time(void);
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/** @} */
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PROCESS_NAME(etimer_process);
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#endif /* __ETIMER_H__ */
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/** @} */
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/** @} */
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