text: /*
   * Copyright (c) 2012, George Oikonomou - <oikonomou@users.sourceforge.net>
   * 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 copyright holder 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 COPYRIGHT HOLDERS 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
   * COPYRIGHT HOLDER 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.
   */
  
  /**
   * \file
   *   Trickle timer library implementation.
   * \author
   *   George Oikonomou - <oikonomou@users.sourceforge.net>
   */
  
  /**
   * \addtogroup trickle-timer
   * @{
   */
  
  #include <net/buf.h>
  
  #include "contiki-conf.h"
  #include "trickle-timer.h"
  #include "sys/ctimer.h"
  #include "sys/cc.h"
  #include "lib/random.h"
  /*---------------------------------------------------------------------------*/
  #ifdef CONFIG_NETWORK_IP_STACK_DEBUG_TRICKLE
  #define DEBUG 1
  #endif
  #include "contiki/ip/uip-debug.h"
  
  /*---------------------------------------------------------------------------*/
  /**
   * \brief Wide randoms for platforms using a 4-byte wide clock
   * (see ::TRICKLE_TIMER_WIDE_RAND)
   */
  #if TRICKLE_TIMER_WIDE_RAND
  #define tt_rand() wide_rand()
  #else
  #define tt_rand() random_rand()
  #endif
  /*---------------------------------------------------------------------------*/
  /* Declarations of variables of local interest */
  /*---------------------------------------------------------------------------*/
  static struct trickle_timer *loctt;   /* Pointer to a struct for local use */
  static clock_time_t loc_clock; /* A local, general-purpose placeholder */
  
  static void fire(struct net_buf *buf, void *ptr);
  static void double_interval(struct net_buf *buf, void *ptr);
  /*---------------------------------------------------------------------------*/
  /* Local utilities and functions to be used as ctimer callbacks */
  /*---------------------------------------------------------------------------*/
  #if TRICKLE_TIMER_WIDE_RAND
  /* Returns a 4-byte wide, unsigned random number */
  static uint32_t
  wide_rand(void)
  {
    return ((uint32_t)random_rand() << 16 | random_rand());
  }
  #endif
  /*---------------------------------------------------------------------------*/
  /*
   * Returns the maximum sane Imax value for a given Imin
   *
   * This function is a variant of a fairly standard 'Count Leading Zeros'. It
   * has three flavours. The most suitable one for a specific platform can be
   * configured by changing the value of TRICKLE_TIMER_CONF_MAX_IMAX_WIDTH
   * in the platform's contiki-conf.h
   */
  #if TRICKLE_TIMER_ERROR_CHECKING
  static uint8_t
  max_imax(clock_time_t value)
  {
    uint8_t zeros = 0;
  #if (TRICKLE_TIMER_MAX_IMAX_WIDTH==TRICKLE_TIMER_MAX_IMAX_GENERIC)
    uint8_t i;
    clock_time_t mask = 0xFFFF;
  
    value--;
  
    for(i = sizeof(clock_time_t) << 2; i > 0; i >>= 1) {
      if((value & (mask <<= i)) == 0) {
        zeros += i;
        value <<= i;
      }
    }
  
  #elif (TRICKLE_TIMER_MAX_IMAX_WIDTH==TRICKLE_TIMER_MAX_IMAX_16_BIT)
    if((value & 0xFF00) == 0) {
      zeros += 8;
      value <<= 8;
    }
    if((value & 0xF000) == 0) {
      zeros += 4;
      value <<= 4;
    }
    if((value & 0xC000) == 0) {
      zeros += 2;
      value <<= 2;
    }
    if((value & 0x8000) == 0) {
      zeros++;
    }
  #elif (TRICKLE_TIMER_MAX_IMAX_WIDTH==TRICKLE_TIMER_MAX_IMAX_32_BIT)
    if((value & 0xFFFF0000) == 0) {
      zeros += 16;
      value <<= 16;
    }
    if((value & 0xFF000000) == 0) {
      zeros += 8;
      value <<= 8;
    }
    if((value & 0xF0000000) == 0) {
      zeros += 4;
      value <<= 4;
    }
    if((value & 0xC0000000) == 0) {
      zeros += 2;
      value <<= 2;
    }
    if((value & 0x80000000) == 0) {
      zeros += 1;
    }
  #endif
  
    return zeros - 1; /* Always non-negative due to the range of 'value' */
  }
  #endif /* TRICKLE_TIMER_ERROR_CHECKING */
  /*---------------------------------------------------------------------------*/
  /* Returns a random time point t in [I/2 , I) */
  static clock_time_t
  get_t(clock_time_t i_cur)
  {
    i_cur >>= 1;
  
    PRINTF("trickle_timer get t: [%lu, %lu)\n", (unsigned long)i_cur,
           (unsigned long)(i_cur << 1));
  
    return i_cur + (tt_rand() % i_cur);
  }
  /*---------------------------------------------------------------------------*/
  static void
  schedule_for_end(struct trickle_timer *tt)
  {
    /* Reset our ctimer, schedule interval_end to run at time I */
    clock_time_t now = clock_time();
  
    loc_clock = TRICKLE_TIMER_INTERVAL_END(tt) - now;
  
    PRINTF("trickle_timer sched for end: at %lu, end in %ld\n",
           (unsigned long)clock_time(), (signed long)loc_clock);
  
    /* Interval's end will happen in loc_clock ticks. Make sure this isn't in
     * the past... */
    if(loc_clock > (TRICKLE_TIMER_CLOCK_MAX >> 1)) {
      loc_clock = 0; /* Interval ended in the past, schedule for in 0 */
      PRINTF("trickle_timer doubling: Was in the past. Compensating\n");
    }
  
    ctimer_set(NULL, &tt->ct, loc_clock, double_interval, tt);
  }
  /*---------------------------------------------------------------------------*/
  /* This is used as a ctimer callback, thus its argument must be void *. ptr is
   * a pointer to the struct trickle_timer that fired */
  static void
  double_interval(struct net_buf *buf, void *ptr)
  {
    clock_time_t last_end;
  
    /* 'cast' ptr to a struct trickle_timer */
    loctt = (struct trickle_timer *)ptr;
  
    loctt->c = 0;
  
    PRINTF("trickle_timer doubling: at %lu, (was for %lu), ",
           (unsigned long)clock_time(),
           (unsigned long)TRICKLE_TIMER_INTERVAL_END(loctt));
  
    /* Remember the previous interval's end (absolute time), before we double */
    last_end = TRICKLE_TIMER_INTERVAL_END(loctt);
  
    /* Double the interval if we have to */
    if(loctt->i_cur <= TRICKLE_TIMER_INTERVAL_MAX(loctt) >> 1) {
      /* If I <= Imax/2, we double */
      loctt->i_cur <<= 1;
      PRINTF("I << 1 = %lu\n", (unsigned long)loctt->i_cur);
    } else {
      /* We may have I > Imax/2 but I <> Imax, in which case we set to Imax
       * This will happen when I didn't start as Imin (before the first reset) */
      loctt->i_cur = TRICKLE_TIMER_INTERVAL_MAX(loctt);
      PRINTF("I = Imax = %lu\n", (unsigned long)loctt->i_cur);
    }
  
    /* Random t in [I/2, I) */
    loc_clock = get_t(loctt->i_cur);
  
    PRINTF("trickle_timer doubling: t=%lu\n", (unsigned long)loc_clock);
  
  #if TRICKLE_TIMER_COMPENSATE_DRIFT
    /* Schedule for t ticks after the previous interval's end, not after now. If
     * that is in the past, schedule in 0 */
    loc_clock = (last_end + loc_clock) - clock_time();
    PRINTF("trickle_timer doubling: at %lu, in %ld ticks\n",
           (unsigned long)clock_time(), (signed long)loc_clock);
    if(loc_clock > (TRICKLE_TIMER_CLOCK_MAX >> 1)) {
      /* Oops, that's in the past */
      loc_clock = 0;
      PRINTF("trickle_timer doubling: Was in the past. Compensating\n");
    }
    ctimer_set(NULL, &loctt->ct, loc_clock, fire, loctt);
  
    /* Store the actual interval start (absolute time), we need it later.
     * We pretend that it started at the same time when the last one ended */
    loctt->i_start = last_end;
  #else
    /* Assumed that the previous interval's end is 'now' and schedule in t ticks
     * after 'now', ignoring potential offsets */
    ctimer_set(NULL, &loctt->ct, loc_clock, fire, loctt);
    /* Store the actual interval start (absolute time), we need it later */
    loctt->i_start = loctt->ct.etimer.timer.start;
  #endif
  
    PRINTF("trickle_timer doubling: Last end %lu, new end %lu, for %lu, I=%lu\n",
           (unsigned long)last_end,
           (unsigned long)TRICKLE_TIMER_INTERVAL_END(loctt),
           (unsigned long)(loctt->ct.etimer.timer.start +
                           loctt->ct.etimer.timer.interval),
           (unsigned long)(loctt->i_cur));
  }
  /*---------------------------------------------------------------------------*/
  /* Called by the ctimer module at time t within the current interval. ptr is
   * a pointer to the struct trickle_timer of interest */
  static void
  fire(struct net_buf *buf, void *ptr)
  {
    /* 'cast' c to a struct trickle_timer */
    loctt = (struct trickle_timer *)ptr;
  
    PRINTF("trickle_timer fire: at %lu (was for %lu)\n",
           (unsigned long)clock_time(),
           (unsigned long)(loctt->ct.etimer.timer.start +
                           loctt->ct.etimer.timer.interval));
  
    if(loctt->cb) {
      /*
       * Call the protocol's TX callback, with the suppression status as an
       * argument.
       */
      PRINTF("trickle_timer fire: Suppression Status %u (%u < %u)\n",
             TRICKLE_TIMER_PROTO_TX_ALLOW(loctt), loctt->c, loctt->k);
      loctt->cb(loctt->cb_arg, TRICKLE_TIMER_PROTO_TX_ALLOW(loctt));
    }
  
    if(trickle_timer_is_running(loctt)) {
      schedule_for_end(loctt);
    }
  }
  /*---------------------------------------------------------------------------*/
  /* New trickle interval, either due to a newly set trickle timer or due to an
   * inconsistency. Schedule 'fire' to be called in t ticks. */
  static void
  new_interval(struct trickle_timer *tt)
  {
    tt->c = 0;
  
    /* Random t in [I/2, I) */
    loc_clock = get_t(tt->i_cur);
  
    ctimer_set(NULL, &tt->ct, loc_clock, fire, tt);
  
    /* Store the actual interval start (absolute time), we need it later */
    tt->i_start = tt->ct.etimer.timer.start;
    PRINTF("trickle_timer new interval: at %lu, ends %lu, ",
           (unsigned long)clock_time(),
           (unsigned long)TRICKLE_TIMER_INTERVAL_END(tt));
    PRINTF("t=%lu, I=%lu\n", (unsigned long)loc_clock, (unsigned long)tt->i_cur);
  }
  /*---------------------------------------------------------------------------*/
  /* Functions to be called by the protocol implementation */
  /*---------------------------------------------------------------------------*/
  void
  trickle_timer_consistency(struct trickle_timer *tt)
  {
    if(tt->c < 0xFF) {
      tt->c++;
    }
    PRINTF("trickle_timer consistency: c=%u\n", tt->c);
  }
  /*---------------------------------------------------------------------------*/
  void
  trickle_timer_inconsistency(struct trickle_timer *tt)
  {
    /* "If I is equal to Imin when Trickle hears an "inconsistent" transmission,
     * Trickle does nothing." */
    if(tt->i_cur != tt->i_min) {
      PRINTF("trickle_timer inconsistency\n");
      tt->i_cur = tt->i_min;
  
      new_interval(tt);
    }
  }
  /*---------------------------------------------------------------------------*/
  uint8_t
  trickle_timer_config(struct trickle_timer *tt, clock_time_t i_min,
                       uint8_t i_max, uint8_t k)
  {
  #if TRICKLE_TIMER_ERROR_CHECKING
    /*
     * Although in theory Imin=1 is a valid value, it would break get_t() and
     * doesn't make sense anyway. Thus Valid Imin values are in the range:
     * 1 < Imin <= (TRICKLE_TIMER_CLOCK_MAX >> 1) + 1
     */
    if(TRICKLE_TIMER_IMIN_IS_BAD(i_min)) {
      PRINTF("trickle_timer config: Bad Imin value\n");
      return TRICKLE_TIMER_ERROR;
    }
  
    if(tt == NULL || i_max == 0 || k == 0) {
      PRINTF("trickle_timer config: Bad arguments\n");
      return TRICKLE_TIMER_ERROR;
    }
  
    /*
     * If clock_time_t is not wide enough to store Imin << Imax, we adjust Imax
     *
     * This means that 'we' are likely to have a different Imax than 'them'
     * See RFC 6206, sec 6.3 for the consequences of this situation
     */
    if(TRICKLE_TIMER_IPAIR_IS_BAD(i_min, i_max)) {
      PRINTF("trickle_timer config: %lu << %u would exceed clock boundaries. ",
             (unsigned long)i_min, i_max);
  
      /* For this Imin, get the maximum sane Imax */
      i_max = max_imax(i_min);
      PRINTF("trickle_timer config: Using Imax=%u\n", i_max);
    }
  #endif
  
    tt->i_min = i_min;
    tt->i_max = i_max;
    tt->i_max_abs = i_min << i_max;
    tt->k = k;
  
    PRINTF("trickle_timer config: Imin=%lu, Imax=%u, k=%u\n",
           (unsigned long)tt->i_min, tt->i_max, tt->k);
  
    return TRICKLE_TIMER_SUCCESS;
  }
  /*---------------------------------------------------------------------------*/
  uint8_t
  trickle_timer_set(struct trickle_timer *tt, trickle_timer_cb_t proto_cb,
                    void *ptr)
  {
  #if TRICKLE_TIMER_ERROR_CHECKING
    /* Sanity checks */
    if(tt == NULL || proto_cb == NULL) {
      PRINTF("trickle_timer set: Bad arguments\n");
      return TRICKLE_TIMER_ERROR;
    }
  #endif
  
    tt->cb = proto_cb;
    tt->cb_arg = ptr;
  
    /* Random I in [Imin , Imax] */
    tt->i_cur = tt->i_min +
      (tt_rand() % (TRICKLE_TIMER_INTERVAL_MAX(tt) - tt->i_min + 1));
  
    PRINTF("trickle_timer set: I=%lu in [%lu , %lu]\n", (unsigned long)tt->i_cur,
           (unsigned long)tt->i_min,
           (unsigned long)TRICKLE_TIMER_INTERVAL_MAX(tt));
  
    new_interval(tt);
  
    PRINTF("trickle_timer set: at %lu, ends %lu, t=%lu in [%lu , %lu)\n",
           (unsigned long)tt->i_start,
           (unsigned long)TRICKLE_TIMER_INTERVAL_END(tt),
           (unsigned long)tt->ct.etimer.timer.interval,
           (unsigned long)tt->i_cur >> 1, (unsigned long)tt->i_cur);
  
    return TRICKLE_TIMER_SUCCESS;
  }
  /*---------------------------------------------------------------------------*/
  /** @} */
  