492 lines
19 KiB
C
492 lines
19 KiB
C
/** \addtogroup lib
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* @{ */
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/**
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* \defgroup trickle-timer Trickle timers
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*
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* This library implements timers which behave in accordance with RFC 6206
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* "The Trickle Algorithm" (http://tools.ietf.org/html/rfc6206)
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*
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* Protocols wishing to use trickle timers, may use this library instead of
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* implementing the trickle algorithm internally.
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*
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* The protocol implementation will declare one (or more) variable(s) of type
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* struct ::trickle_timer and will then populate its fields by calling
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* trickle_timer_config(). trickle_timer_set() will start the timer.
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*
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* When the timer reaches time t within the current trickle interval, the
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* library will call a protocol-provided callback, which will signal to the
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* protocol that it is time to TX (see algorithm step 4 in the RFC).
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*
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* The proto does not need to check the suppression conditions. This is done by
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* the library and if TX must be suppressed, the callback won't be called at
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* all.
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*
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* The library also provides functions to be called when the protocol hears a
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* 'consistent' or 'inconsistent' message and when an 'external event' occurs
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* (in this context, those terms have the exact same meaning as in the RFC).
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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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* Trickle timer library header file.
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*
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* \author
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* George Oikonomou - <oikonomou@users.sourceforge.net>
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*/
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/*
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* Copyright (c) 2012, George Oikonomou - <oikonomou@users.sourceforge.net>
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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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*
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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 copyright holder nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* 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,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef __TRICKLE_TIMER_H__
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#define __TRICKLE_TIMER_H__
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#include "contiki-conf.h"
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#include "sys/ctimer.h"
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/*---------------------------------------------------------------------------*/
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/* Trickle Timer Library Constants */
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/*---------------------------------------------------------------------------*/
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/**
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* \name Trickle Timer Library: Constants
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* @{
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*/
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Set as value of k to disable suppression
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*/
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#define TRICKLE_TIMER_INFINITE_REDUNDANCY 0x00
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#define TRICKLE_TIMER_ERROR 0
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#define TRICKLE_TIMER_SUCCESS 1
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/**
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* \brief Use as the value of TRICKLE_TIMER_MAX_IMAX_WIDTH to enable the
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* generic 'Find max Imax' routine
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*/
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#define TRICKLE_TIMER_MAX_IMAX_GENERIC 0
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/**
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* \brief Use as the value of TRICKLE_TIMER_MAX_IMAX_WIDTH to enable the 16-bit
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* 'Find max Imax' routine
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*/
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#define TRICKLE_TIMER_MAX_IMAX_16_BIT 1
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/**
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* \brief Use as the value of TRICKLE_TIMER_MAX_IMAX_WIDTH to enable the 32-bit
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* 'Find max Imax' routine
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*/
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#define TRICKLE_TIMER_MAX_IMAX_32_BIT 2
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/**
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* \brief Constants used as values for the \e suppress param of
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* trickle_timer_cb_t
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*/
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#define TRICKLE_TIMER_TX_SUPPRESS 0
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#define TRICKLE_TIMER_TX_OK 1
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/** @} */
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Controls whether the library will try to compensate for time drifts
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* caused by getting called later than scheduled.
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*
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* 1: Enabled (default). 0: Disabled
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*
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* To override the default, define TRICKLE_TIMER_CONF_COMPENSATE_DRIFT in
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* contiki-conf.h
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*
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* Bear in mind that this controls the behaviour of the entire library (i.e.
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* all trickle timers) and not of an individual timer
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*/
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#ifdef TRICKLE_TIMER_CONF_COMPENSATE_DRIFT
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#define TRICKLE_TIMER_COMPENSATE_DRIFT TRICKLE_TIMER_CONF_COMPENSATE_DRIFT
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#else
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#define TRICKLE_TIMER_COMPENSATE_DRIFT 1
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#endif
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Turns on support for 4-byte wide, unsigned random numbers
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*
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* We need this for platforms which have a 4-byte wide clock_time_t. For those
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* platforms and if Imin << Imax is GT 0xFFFF, random_rand alone is not always
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* enough to generate a correct t in [I/2, I). Specifically, we need wide
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* randoms when I > 0x1FFFF.
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*
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* For platforms with a 2-byte wide clock_time_t, this can be defined as 0
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* to reduce code footprint and increase speed.
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*/
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#ifdef TRICKLE_TIMER_CONF_WIDE_RAND
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#define TRICKLE_TIMER_WIDE_RAND TRICKLE_TIMER_CONF_WIDE_RAND
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#else
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#define TRICKLE_TIMER_WIDE_RAND 1
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#endif
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Selects a flavor for the 'Find maximum Imax' (max_imax) function.
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*
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* When configuring a new trickle timer, the library verifies that the (Imin ,
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* Imax) pair will fit in the platform's clock_time_t boundaries. If this is
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* not the case, Imax will be adjusted down. In order to achieve this, we use
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* an internal function which is a slight variant of a standard 'Count Leading
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* Zeros'.
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*
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* This functionality is disabled when ::TRICKLE_TIMER_ERROR_CHECKING is 0
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*
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* This define helps us generate, at the pre-processing stage, the desired
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* version of this function. We start with a generic version by default. The
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* platform's contiki-conf.h can change this to use the 16- or 32-bit specific
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* flavor by defining TRICKLE_TIMER_CONF_MAX_IMAX_WIDTH.
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*
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* Depending on the toolchain, the generic variant may actually result in a
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* smaller code size. Do your own experiments.
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*
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* TRICKLE_TIMER_MAX_IMAX_GENERIC (0): Generic function which will work
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* regardless whether the platform uses a 16 or 32 bit wide clock type
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*
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* TRICKLE_TIMER_MAX_IMAX_16_BIT (1): You can select this in your
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* contiki-conf.h if your platform's clock_time_t is 16 bits wide
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*
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* TRICKLE_TIMER_MAX_IMAX_32_BIT (2): You can select this in your
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* contiki-conf.h if your platform's clock_time_t is 32 bits wide
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*/
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#ifdef TRICKLE_TIMER_CONF_MAX_IMAX_WIDTH
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#define TRICKLE_TIMER_MAX_IMAX_WIDTH TRICKLE_TIMER_CONF_MAX_IMAX_WIDTH
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#else
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#define TRICKLE_TIMER_MAX_IMAX_WIDTH TRICKLE_TIMER_MAX_IMAX_GENERIC
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#endif
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/**
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* \brief Enables/Disables error checking
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*
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* 1: Enabled (default). The library checks the validity of Imin and Imax
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* 0: Disabled. All error checking is turned off. This reduces code size.
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*/
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#ifdef TRICKLE_TIMER_CONF_ERROR_CHECKING
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#define TRICKLE_TIMER_ERROR_CHECKING TRICKLE_TIMER_CONF_ERROR_CHECKING
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#else
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#define TRICKLE_TIMER_ERROR_CHECKING 1
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#endif
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/*---------------------------------------------------------------------------*/
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/* Trickle Timer Library Macros */
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/*---------------------------------------------------------------------------*/
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/**
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* \name Trickle Timer Library: Macros
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* @{
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*/
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/**
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* \brief cross-platform method to get the maximum clock_time_t value
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*/
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#define TRICKLE_TIMER_CLOCK_MAX ((clock_time_t)~0)
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/**
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* \brief Checks if the trickle timer's suppression feature is enabled
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*
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* \param tt A pointer to a ::trickle_timer structure
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*
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* \retval non-zero Suppression is enabled
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* \retval 0 Suppression is disabled
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*/
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#define TRICKLE_TIMER_SUPPRESSION_ENABLED(tt) \
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((tt)->k != TRICKLE_TIMER_INFINITE_REDUNDANCY)
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/**
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* \brief Checks if the trickle timer's suppression feature is disabled
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*
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* \param tt A pointer to a ::trickle_timer structure
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*
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* \retval non-zero Suppression is disabled
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* \retval 0 Suppression is enabled
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*/
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#define TRICKLE_TIMER_SUPPRESSION_DISABLED(tt) \
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((tt)->k == TRICKLE_TIMER_INFINITE_REDUNDANCY)
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/**
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* \brief Determines whether the protocol must go ahead with a transmission
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*
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* \param tt A pointer to a ::trickle_timer structure
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*
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* \retval non-zero Go ahead with TX
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* \retval 0 Suppress
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*/
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#define TRICKLE_TIMER_PROTO_TX_ALLOW(tt) \
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(TRICKLE_TIMER_SUPPRESSION_DISABLED(tt) || ((tt)->c < (tt)->k))
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/**
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* \brief Determines whether the protocol must suppress a transmission
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*
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* \param tt A pointer to a ::trickle_timer structure
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*
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* \retval non-zero Suppress
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* \retval 0 Go ahead with TX
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*/
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#define TRICKLE_TIMER_PROTO_TX_SUPPRESS(tt) \
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(TRICKLE_TIMER_SUPPRESSION_ENABLED(tt) && ((tt)->c >= (tt)->k))
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/**
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* \brief Returns a timer's maximum interval size (Imin << Imax) as a number of
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* clock ticks
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*
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* \param tt A pointer to a ::trickle_timer structure
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*
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* \return Maximum trickle interval length in clock ticks
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*/
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#define TRICKLE_TIMER_INTERVAL_MAX(tt) ((tt)->i_max_abs)
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/**
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* \brief Returns the current trickle interval's end (absolute time in ticks)
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*
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* \param tt A pointer to a ::trickle_timer structure
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*
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* \return The absolute number of clock ticks when the current trickle interval
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* will expire
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*/
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#define TRICKLE_TIMER_INTERVAL_END(tt) ((tt)->i_start + (tt)->i_cur)
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/**
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* \brief Checks whether an Imin value is suitable considering the various
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* restrictions imposed by our platform's clock as well as by the library itself
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*
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* \param imin An Imin value in clock ticks
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*
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* \retval 1 The Imin value is valid
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* \retval 0 The Imin value is invalid
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*/
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#define TRICKLE_TIMER_IMIN_IS_OK(imin) \
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((imin > 1) && (i_min <= (TRICKLE_TIMER_CLOCK_MAX >> 1)))
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/**
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* \brief Checks whether an Imin value is invalid considering the various
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* restrictions imposed by our platform's clock as well as by the library itself
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*
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* \param imin An Imin value in clock ticks
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*
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* \retval 1 The Imin value is invalid
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* \retval 0 The Imin value is valid
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*/
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#define TRICKLE_TIMER_IMIN_IS_BAD(imin) \
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((imin < 2) || (i_min > (TRICKLE_TIMER_CLOCK_MAX >> 1)))
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/**
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* \brief Checks whether Imin << Imax is unsuitable considering the boundaries
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* of our platform's clock_time_t
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*
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* \param i_min Imin value
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* \param i_max Maximum number of doublings
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*
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* \retval non-zero The pair would exceed clock boundaries
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* \retval 0 The pair is suitable for the platform
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*
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* Timers scheduled far in the future can be perceived as being scheduled in
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* the past.
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* Thus, we limit Imin << Imax to be LEQ(TRICKLE_TIMER_CLOCK_MAX >> 1) + 1
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*/
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#define TRICKLE_TIMER_IPAIR_IS_BAD(i_min, i_max) \
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((TRICKLE_TIMER_CLOCK_MAX >> (i_max + 1)) < i_min - 1)
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/** @} */
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/*---------------------------------------------------------------------------*/
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/* Trickle Timer Library Data Representation */
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/*---------------------------------------------------------------------------*/
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/**
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* \name Trickle Timer Library: Data Representation
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* @{
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*/
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/**
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* \brief typedef for a callback function to be defined in the protocol's
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* implementation.
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*
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* Those callbaks are stored as a function pointer inside a ::trickle_timer
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* structure and are called by the library at time t within the current trickle
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* interval.
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*
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* Some protocols may rely on multiple trickle timers. For this reason, this
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* function's argument will be an opaque pointer, aiming to help the protocol
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* determine which timer triggered the call.
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*
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* The \e suppress argument is used so that the library can signal the protocol
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* whether it should TX or suppress
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*/
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typedef void (* trickle_timer_cb_t)(void *ptr, uint8_t suppress);
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/**
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* \struct trickle_timer
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*
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* A trickle timer.
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*
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* This structure is used for declaring a trickle timer. In order for the timer
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* to start running, the protocol must first populate the structure's fields
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* by calling trickle_timer_set(). Protocol implementations must NOT modify the
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* contents of this structure directly.
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*
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* Protocol developers must also be careful to specify the values of Imin and
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* Imax in such a way that the maximum interval size does not exceed the
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* boundaries of clock_time_t
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*/
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struct trickle_timer {
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clock_time_t i_min; /**< Imin: Clock ticks */
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clock_time_t i_cur; /**< I: Current interval in clock_ticks */
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clock_time_t i_start; /**< Start of this interval (absolute clock_time) */
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clock_time_t i_max_abs; /**< Maximum interval size in clock ticks (and not in
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number of doublings). This is a cached value of
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Imin << Imax used internally, so that we can
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have direct access to the maximum interval size
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without having to calculate it all the time */
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struct ctimer ct; /**< A \ref ctimer used internally */
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trickle_timer_cb_t cb; /**< Protocol's own callback, invoked at time t
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within the current interval */
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void *cb_arg; /**< Opaque pointer to be used as the argument of the
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protocol's callback */
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uint8_t i_max; /**< Imax: Max number of doublings */
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uint8_t k; /**< k: Redundancy Constant */
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uint8_t c; /**< c: Consistency Counter */
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};
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/** @} */
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/*---------------------------------------------------------------------------*/
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/* Trickle Timer Library Functions */
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/*---------------------------------------------------------------------------*/
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/**
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* \name Trickle Timer Library: Functions called by protocol implementations
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* @{
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*/
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/**
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* \brief Configure a trickle timer
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* \param tt A pointer to a ::trickle_timer structure
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* \param i_min The timer's Imin configuration parameter, in units of
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* clock_time_t
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* \param i_max The timer's Imax configuration parameter (maximum number of
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* doublings), specified as number of doublings
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* \param k The timer's K (redundancy constant). If the value of K
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* equals #TRICKLE_TIMER_INFINITE_REDUNDANCY, message
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* suppression will be disabled
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* \retval 0 Error (Bad argument)
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* \retval non-zero Success.
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*
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* This function is used to set the initial configuration for a trickle timer.
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* A trickle timer MUST be configured before the protocol calls
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* trickle_timer_set().
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*
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* If Imin<<Imax would exceed the platform's clock_time_t boundaries, this
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* function adjusts Imax to the maximum permitted value for the provided Imin.
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* This means that in a network with heterogenous hardware, 'we' are likely to
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* have a different Imax than 'some of them'. See RFC 6206, sec 6.3 for the
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* consequences of this situation
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*/
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uint8_t trickle_timer_config(struct trickle_timer *tt, clock_time_t i_min,
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uint8_t i_max, uint8_t k);
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/**
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* \brief Start a previously configured trickle timer
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* \param tt A pointer to a ::trickle_timer structure
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* \param proto_cb A pointer to a callback function, which will be invoked at
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* at time t within the current trickle interval
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* \param ptr An opaque pointer which will be passed as the argument to
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* proto_cb when the timer fires.
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* \retval 0 Error (tt was null or the timer was not configured properly)
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* \retval non-zero Success.
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*
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* This function is used to set a trickle timer. The protocol implementation
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* must use this function ONLY to initialise a new trickle timer and NOT to
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* reset it as a result of external events or inconsistencies.
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*
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* The protocol implementation must configure the trickle timer by calling
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* trickle_timer_config() before calling this function.
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*/
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uint8_t trickle_timer_set(struct trickle_timer *tt,
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trickle_timer_cb_t proto_cb, void *ptr);
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/**
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* \brief Stop a running trickle timer.
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* \param tt A pointer to a ::trickle_timer structure
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*
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* This function stops a running trickle timer that was previously started with
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* trickle_timer_start(). After this function has been called, the trickle
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* timer will no longer call the protocol's callback and its interval will not
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* double any more. In order to resume the trickle timer, the user application
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* must call trickle_timer_set().
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*
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* The protocol implementation must NOT use trickle_timer_stop(), _set() cycles
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* to reset a timer manually. Instead, in response to events or inconsistencies,
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* the corresponding functions must be used
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*/
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#define trickle_timer_stop(tt) ctimer_stop(&((tt)->ct))
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/**
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* \brief To be called by the protocol when it hears a consistent
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* transmission
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* \param tt A pointer to a ::trickle_timer structure
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*
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* When the trickle-based protocol hears a consistent transmission it must call
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* this function to increment trickle's consistency counter, which is later
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* used to determine whether the protocol must suppress or go ahead with its
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* own transmissions.
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*
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* As the trickle timer library implementation may change in the future to
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* perform further tasks upon reception of a consistent transmission, the
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* protocol's implementation MUST use this call to increment the consistency
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* counter instead of directly writing to the structure's field.
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*/
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void trickle_timer_consistency(struct trickle_timer *tt);
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/**
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* \brief To be called by the protocol when it hears an inconsistent
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* transmission
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* \param tt A pointer to a ::trickle_timer structure
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*
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* When the protocol hears an inconsistent transmission, it must call this
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* function to notify the library that the timer must be reset.
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*
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* Before resetting the timer, the library will perform a set of checks.
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* Therefore, it is important that the protocol calls this function instead of
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* trying to reset the timer by itself.
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*/
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void trickle_timer_inconsistency(struct trickle_timer *tt);
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/**
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* \brief To be called by the protocol when an external event occurs that
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* should trigger a timer reset
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* \param tt A pointer to a ::trickle_timer structure
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*
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* When an external event occurs that should result in a timer reset, the
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* protocol implementation must call this function to notify the library.
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*
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* Before resetting the timer, the library will perform a set of checks.
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* Therefore, it is important that the protocol calls this function instead of
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* trying to reset the timer by itself.
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*/
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#define trickle_timer_reset_event(tt) trickle_timer_inconsistency(tt)
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/** @} */
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#endif /* __TRICKLE_TIMER_H__ */
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/** @} */
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/** @} */
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