etimer.c

Go to the documentation of this file.

/*
 * 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>
 *
 */

/**
 * \addtogroup etimer
 * @{
 */

/**
 * \file
 * Event timer library implementation.
 * \author
 * Adam Dunkels <adam@sics.se>
 */

#include "contiki-conf.h"

#include "sys/etimer.h"
#include "sys/process.h"

static struct etimer *timerlist;
static clock_time_t next_expiration;

PROCESS(etimer_process, "Event timer");
/*---------------------------------------------------------------------------*/
static void
update_time(void)
{
  clock_time_t tdist;
  clock_time_t now;
  struct etimer *t;

  if (timerlist == NULL) {
    next_expiration = 0;
  } else {
    now = clock_time();
    t = timerlist;
    /* Must calculate distance to next time into account due to wraps */
    tdist = t->timer.start + t->timer.interval - now;
    for(t = t->next; t != NULL; t = t->next) {
      if(t->timer.start + t->timer.interval - now < tdist) {
        tdist = t->timer.start + t->timer.interval - now;
      }
    }
    next_expiration = now + tdist;
  }
}
/*---------------------------------------------------------------------------*/
PROCESS_THREAD(etimer_process, ev, data)
{
  struct etimer *t, *u;
        
  PROCESS_BEGIN();

  timerlist = NULL;
  
  while(1) {
    PROCESS_YIELD();

    if(ev == PROCESS_EVENT_EXITED) {
      struct process *p = data;

      while(timerlist != NULL && timerlist->p == p) {
        timerlist = timerlist->next;
      }

      if(timerlist != NULL) {
        t = timerlist;
        while(t->next != NULL) {
          if(t->next->p == p) {
            t->next = t->next->next;
          } else
            t = t->next;
        }
      }
      continue;
    } else if(ev != PROCESS_EVENT_POLL) {
      continue;
    }

  again:
    
    u = NULL;
    
    for(t = timerlist; t != NULL; t = t->next) {
      if(timer_expired(&t->timer)) {
        if(process_post(t->p, PROCESS_EVENT_TIMER, t) == PROCESS_ERR_OK) {
          
          /* Reset the process ID of the event timer, to signal that the
             etimer has expired. This is later checked in the
             etimer_expired() function. */
          t->p = PROCESS_NONE;
          if(u != NULL) {
            u->next = t->next;
          } else {
            timerlist = t->next;
          }
          t->next = NULL;
          update_time();
          goto again;
        } else {
          etimer_request_poll();
        }
      }
      u = t;
    }
    
  }
  
  PROCESS_END();
}
/*---------------------------------------------------------------------------*/
void
etimer_request_poll(void)
{
  process_poll(&etimer_process);
}
/*---------------------------------------------------------------------------*/
static void
add_timer(struct etimer *timer)
{
  struct etimer *t;

  etimer_request_poll();

  if(timer->p != PROCESS_NONE) {
    for(t = timerlist; t != NULL; t = t->next) {
      if(t == timer) {
        /* Timer already on list, bail out. */
        timer->p = PROCESS_CURRENT();
        update_time();
        return;
      }
    }
  }

  /* Timer not on list. */
  timer->p = PROCESS_CURRENT();
  timer->next = timerlist;
  timerlist = timer;

  update_time();
}
/*---------------------------------------------------------------------------*/
void
etimer_set(struct etimer *et, clock_time_t interval)
{
  timer_set(&et->timer, interval);
  add_timer(et);
}
/*---------------------------------------------------------------------------*/
void
etimer_reset(struct etimer *et)
{
  timer_reset(&et->timer);
  add_timer(et);
}
/*---------------------------------------------------------------------------*/
void
etimer_restart(struct etimer *et)
{
  timer_restart(&et->timer);
  add_timer(et);
}
/*---------------------------------------------------------------------------*/
void
etimer_adjust(struct etimer *et, int timediff)
{
  et->timer.start += timediff;
  update_time();
}
/*---------------------------------------------------------------------------*/
int
etimer_expired(struct etimer *et)
{
  return et->p == PROCESS_NONE;
}
/*---------------------------------------------------------------------------*/
clock_time_t
etimer_expiration_time(struct etimer *et)
{
  return et->timer.start + et->timer.interval;
}
/*---------------------------------------------------------------------------*/
clock_time_t
etimer_start_time(struct etimer *et)
{
  return et->timer.start;
}
/*---------------------------------------------------------------------------*/
int
etimer_pending(void)
{
  return timerlist != NULL;
}
/*---------------------------------------------------------------------------*/
clock_time_t
etimer_next_expiration_time(void)
{
  return etimer_pending() ? next_expiration : 0;
}
/*---------------------------------------------------------------------------*/
void
etimer_stop(struct etimer *et)
{
  struct etimer *t;

  /* First check if et is the first event timer on the list. */
  if(et == timerlist) {
    timerlist = timerlist->next;
    update_time();
  } else {
    /* Else walk through the list and try to find the item before the
       et timer. */
    for(t = timerlist; t != NULL && t->next != et; t = t->next);

    if(t != NULL) {
      /* We've found the item before the event timer that we are about
         to remove. We point the items next pointer to the event after
         the removed item. */
      t->next = et->next;

      update_time();
    }
  }

  /* Remove the next pointer from the item to be removed. */
  et->next = NULL;
  /* Set the timer as expired */
  et->p = PROCESS_NONE;
}
/*---------------------------------------------------------------------------*/
/** @} */