/** \addtogroup lib
|
* @{ */
|
|
/**
|
* \defgroup trickle-timer Trickle timers
|
*
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* This library implements timers which behave in accordance with RFC 6206
|
* "The Trickle Algorithm" (http://tools.ietf.org/html/rfc6206)
|
*
|
* Protocols wishing to use trickle timers, may use this library instead of
|
* implementing the trickle algorithm internally.
|
*
|
* The protocol implementation will declare one (or more) variable(s) of type
|
* struct ::trickle_timer and will then populate its fields by calling
|
* trickle_timer_config(). trickle_timer_set() will start the timer.
|
*
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* When the timer reaches time t within the current trickle interval, the
|
* library will call a protocol-provided callback, which will signal to the
|
* protocol that it is time to TX (see algorithm step 4 in the RFC).
|
*
|
* The proto does not need to check the suppression conditions. This is done by
|
* the library and if TX must be suppressed, the callback won't be called at
|
* all.
|
*
|
* The library also provides functions to be called when the protocol hears a
|
* 'consistent' or 'inconsistent' message and when an 'external event' occurs
|
* (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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* \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>
|
*/
|
|
/*
|
* 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
|
* 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
|
* notice, this list of conditions and the following disclaimer.
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* 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.
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* 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.
|
*/
|
#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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/*---------------------------------------------------------------------------*/
|
/**
|
* \name Trickle Timer Library: Constants
|
* @{
|
*/
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/*---------------------------------------------------------------------------*/
|
/**
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* \brief Set as value of k to disable suppression
|
*/
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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
|
|
/**
|
* \brief Use as the value of TRICKLE_TIMER_MAX_IMAX_WIDTH to enable the
|
* generic 'Find max Imax' routine
|
*/
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#define TRICKLE_TIMER_MAX_IMAX_GENERIC 0
|
/**
|
* \brief Use as the value of TRICKLE_TIMER_MAX_IMAX_WIDTH to enable the 16-bit
|
* 'Find max Imax' routine
|
*/
|
#define TRICKLE_TIMER_MAX_IMAX_16_BIT 1
|
/**
|
* \brief Use as the value of TRICKLE_TIMER_MAX_IMAX_WIDTH to enable the 32-bit
|
* 'Find max Imax' routine
|
*/
|
#define TRICKLE_TIMER_MAX_IMAX_32_BIT 2
|
|
/**
|
* \brief Constants used as values for the \e suppress param of
|
* trickle_timer_cb_t
|
*/
|
#define TRICKLE_TIMER_TX_SUPPRESS 0
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#define TRICKLE_TIMER_TX_OK 1
|
|
/**
|
* \brief A trickle timer is considered 'stopped' when
|
* i_cur == TRICKLE_TIMER_IS_STOPPED.
|
*
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* trickle_timer_stop() must be used to correctly disable a trickle timer.
|
* Do NOT set the value of i_cur to 0 directly, as this will fail to stop the
|
* timer.
|
*/
|
#define TRICKLE_TIMER_IS_STOPPED 0
|
/** @} */
|
/*---------------------------------------------------------------------------*/
|
/**
|
* \brief Controls whether the library will try to compensate for time drifts
|
* caused by getting called later than scheduled.
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*
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* 1: Enabled (default). 0: Disabled
|
*
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* To override the default, define TRICKLE_TIMER_CONF_COMPENSATE_DRIFT in
|
* contiki-conf.h
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*
|
* Bear in mind that this controls the behaviour of the entire library (i.e.
|
* all trickle timers) and not of an individual timer
|
*/
|
#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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* \brief Turns on support for 4-byte wide, unsigned random numbers
|
*
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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
|
* 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
|
* to reduce code footprint and increase speed.
|
*/
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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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* \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 ,
|
* Imax) pair will fit in the platform's clock_time_t boundaries. If this is
|
* not the case, Imax will be adjusted down. In order to achieve this, we use
|
* an internal function which is a slight variant of a standard 'Count Leading
|
* Zeros'.
|
*
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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
|
* version of this function. We start with a generic version by default. The
|
* platform's contiki-conf.h can change this to use the 16- or 32-bit specific
|
* flavor by defining TRICKLE_TIMER_CONF_MAX_IMAX_WIDTH.
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*
|
* Depending on the toolchain, the generic variant may actually result in a
|
* smaller code size. Do your own experiments.
|
*
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* TRICKLE_TIMER_MAX_IMAX_GENERIC (0): Generic function which will work
|
* regardless whether the platform uses a 16 or 32 bit wide clock type
|
*
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* TRICKLE_TIMER_MAX_IMAX_16_BIT (1): You can select this in your
|
* contiki-conf.h if your platform's clock_time_t is 16 bits wide
|
*
|
* TRICKLE_TIMER_MAX_IMAX_32_BIT (2): You can select this in your
|
* contiki-conf.h if your platform's clock_time_t is 32 bits wide
|
*/
|
#ifdef TRICKLE_TIMER_CONF_MAX_IMAX_WIDTH
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#define TRICKLE_TIMER_MAX_IMAX_WIDTH TRICKLE_TIMER_CONF_MAX_IMAX_WIDTH
|
#else
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#define TRICKLE_TIMER_MAX_IMAX_WIDTH TRICKLE_TIMER_MAX_IMAX_GENERIC
|
#endif
|
|
/**
|
* \brief Enables/Disables error checking
|
*
|
* 1: Enabled (default). The library checks the validity of Imin and Imax
|
* 0: Disabled. All error checking is turned off. This reduces code size.
|
*/
|
#ifdef TRICKLE_TIMER_CONF_ERROR_CHECKING
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#define TRICKLE_TIMER_ERROR_CHECKING TRICKLE_TIMER_CONF_ERROR_CHECKING
|
#else
|
#define TRICKLE_TIMER_ERROR_CHECKING 1
|
#endif
|
/*---------------------------------------------------------------------------*/
|
/* Trickle Timer Library Macros */
|
/*---------------------------------------------------------------------------*/
|
/**
|
* \name Trickle Timer Library: Macros
|
* @{
|
*/
|
/**
|
* \brief cross-platform method to get the maximum clock_time_t value
|
*/
|
#define TRICKLE_TIMER_CLOCK_MAX ((clock_time_t)~0)
|
|
|
/**
|
* \brief Checks if the trickle timer's suppression feature is enabled
|
*
|
* \param tt A pointer to a ::trickle_timer structure
|
*
|
* \retval non-zero Suppression is enabled
|
* \retval 0 Suppression is disabled
|
*/
|
#define TRICKLE_TIMER_SUPPRESSION_ENABLED(tt) \
|
((tt)->k != TRICKLE_TIMER_INFINITE_REDUNDANCY)
|
|
/**
|
* \brief Checks if the trickle timer's suppression feature is disabled
|
*
|
* \param tt A pointer to a ::trickle_timer structure
|
*
|
* \retval non-zero Suppression is disabled
|
* \retval 0 Suppression is enabled
|
*/
|
#define TRICKLE_TIMER_SUPPRESSION_DISABLED(tt) \
|
((tt)->k == TRICKLE_TIMER_INFINITE_REDUNDANCY)
|
|
/**
|
* \brief Determines whether the protocol must go ahead with a transmission
|
*
|
* \param tt A pointer to a ::trickle_timer structure
|
*
|
* \retval non-zero Go ahead with TX
|
* \retval 0 Suppress
|
*/
|
#define TRICKLE_TIMER_PROTO_TX_ALLOW(tt) \
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(TRICKLE_TIMER_SUPPRESSION_DISABLED(tt) || ((tt)->c < (tt)->k))
|
|
/**
|
* \brief Determines whether the protocol must suppress a transmission
|
*
|
* \param tt A pointer to a ::trickle_timer structure
|
*
|
* \retval non-zero Suppress
|
* \retval 0 Go ahead with TX
|
*/
|
#define TRICKLE_TIMER_PROTO_TX_SUPPRESS(tt) \
|
(TRICKLE_TIMER_SUPPRESSION_ENABLED(tt) && ((tt)->c >= (tt)->k))
|
|
/**
|
* \brief Returns a timer's maximum interval size (Imin << Imax) as a number of
|
* clock ticks
|
*
|
* \param tt A pointer to a ::trickle_timer structure
|
*
|
* \return Maximum trickle interval length in clock ticks
|
*/
|
#define TRICKLE_TIMER_INTERVAL_MAX(tt) ((tt)->i_max_abs)
|
|
/**
|
* \brief Returns the current trickle interval's end (absolute time in ticks)
|
*
|
* \param tt A pointer to a ::trickle_timer structure
|
*
|
* \return The absolute number of clock ticks when the current trickle interval
|
* will expire
|
*/
|
#define TRICKLE_TIMER_INTERVAL_END(tt) ((tt)->i_start + (tt)->i_cur)
|
|
/**
|
* \brief Checks whether an Imin value is suitable considering the various
|
* restrictions imposed by our platform's clock as well as by the library itself
|
*
|
* \param imin An Imin value in clock ticks
|
*
|
* \retval 1 The Imin value is valid
|
* \retval 0 The Imin value is invalid
|
*/
|
#define TRICKLE_TIMER_IMIN_IS_OK(imin) \
|
((imin > 1) && (i_min <= (TRICKLE_TIMER_CLOCK_MAX >> 1)))
|
|
/**
|
* \brief Checks whether an Imin value is invalid considering the various
|
* restrictions imposed by our platform's clock as well as by the library itself
|
*
|
* \param imin An Imin value in clock ticks
|
*
|
* \retval 1 The Imin value is invalid
|
* \retval 0 The Imin value is valid
|
*/
|
#define TRICKLE_TIMER_IMIN_IS_BAD(imin) \
|
((imin < 2) || (i_min > (TRICKLE_TIMER_CLOCK_MAX >> 1)))
|
|
/**
|
* \brief Checks whether Imin << Imax is unsuitable considering the boundaries
|
* of our platform's clock_time_t
|
*
|
* \param i_min Imin value
|
* \param i_max Maximum number of doublings
|
*
|
* \retval non-zero The pair would exceed clock boundaries
|
* \retval 0 The pair is suitable for the platform
|
*
|
* Timers scheduled far in the future can be perceived as being scheduled in
|
* the past.
|
* Thus, we limit Imin << Imax to be LEQ(TRICKLE_TIMER_CLOCK_MAX >> 1) + 1
|
*/
|
#define TRICKLE_TIMER_IPAIR_IS_BAD(i_min, i_max) \
|
((TRICKLE_TIMER_CLOCK_MAX >> (i_max + 1)) < i_min - 1)
|
/** @} */
|
/*---------------------------------------------------------------------------*/
|
/* Trickle Timer Library Data Representation */
|
/*---------------------------------------------------------------------------*/
|
/**
|
* \name Trickle Timer Library: Data Representation
|
* @{
|
*/
|
|
/**
|
* \brief typedef for a callback function to be defined in the protocol's
|
* implementation.
|
*
|
* Those callbaks are stored as a function pointer inside a ::trickle_timer
|
* structure and are called by the library at time t within the current trickle
|
* interval.
|
*
|
* Some protocols may rely on multiple trickle timers. For this reason, this
|
* function's argument will be an opaque pointer, aiming to help the protocol
|
* determine which timer triggered the call.
|
*
|
* The \e suppress argument is used so that the library can signal the protocol
|
* whether it should TX or suppress
|
*/
|
typedef void (* trickle_timer_cb_t)(void *ptr, uint8_t suppress);
|
|
/**
|
* \struct trickle_timer
|
*
|
* A trickle timer.
|
*
|
* This structure is used for declaring a trickle timer. In order for the timer
|
* to start running, the protocol must first populate the structure's fields
|
* by calling trickle_timer_set(). Protocol implementations must NOT modify the
|
* contents of this structure directly.
|
*
|
* Protocol developers must also be careful to specify the values of Imin and
|
* Imax in such a way that the maximum interval size does not exceed the
|
* boundaries of clock_time_t
|
*/
|
struct trickle_timer {
|
clock_time_t i_min; /**< Imin: Clock ticks */
|
clock_time_t i_cur; /**< I: Current interval in clock_ticks */
|
clock_time_t i_start; /**< Start of this interval (absolute clock_time) */
|
clock_time_t i_max_abs; /**< Maximum interval size in clock ticks (and not in
|
number of doublings). This is a cached value of
|
Imin << Imax used internally, so that we can
|
have direct access to the maximum interval size
|
without having to calculate it all the time */
|
struct ctimer ct; /**< A \ref ctimer used internally */
|
trickle_timer_cb_t cb; /**< Protocol's own callback, invoked at time t
|
within the current interval */
|
void *cb_arg; /**< Opaque pointer to be used as the argument of the
|
protocol's callback */
|
uint8_t i_max; /**< Imax: Max number of doublings */
|
uint8_t k; /**< k: Redundancy Constant */
|
uint8_t c; /**< c: Consistency Counter */
|
};
|
/** @} */
|
/*---------------------------------------------------------------------------*/
|
/* Trickle Timer Library Functions */
|
/*---------------------------------------------------------------------------*/
|
/**
|
* \name Trickle Timer Library: Functions called by protocol implementations
|
* @{
|
*/
|
|
/**
|
* \brief Configure a trickle timer
|
* \param tt A pointer to a ::trickle_timer structure
|
* \param i_min The timer's Imin configuration parameter, in units of
|
* clock_time_t
|
* \param i_max The timer's Imax configuration parameter (maximum number of
|
* doublings), specified as number of doublings
|
* \param k The timer's K (redundancy constant). If the value of K
|
* equals #TRICKLE_TIMER_INFINITE_REDUNDANCY, message
|
* suppression will be disabled
|
* \retval 0 Error (Bad argument)
|
* \retval non-zero Success.
|
*
|
* This function is used to set the initial configuration for a trickle timer.
|
* A trickle timer MUST be configured before the protocol calls
|
* trickle_timer_set().
|
*
|
* If Imin<<Imax would exceed the platform's clock_time_t boundaries, this
|
* function adjusts Imax to the maximum permitted value for the provided Imin.
|
* This means that in a network with heterogenous hardware, 'we' are likely to
|
* have a different Imax than 'some of them'. See RFC 6206, sec 6.3 for the
|
* consequences of this situation
|
*/
|
uint8_t trickle_timer_config(struct trickle_timer *tt, clock_time_t i_min,
|
uint8_t i_max, uint8_t k);
|
|
/**
|
* \brief Start a previously configured trickle timer
|
* \param tt A pointer to a ::trickle_timer structure
|
* \param proto_cb A pointer to a callback function, which will be invoked at
|
* at time t within the current trickle interval
|
* \param ptr An opaque pointer which will be passed as the argument to
|
* proto_cb when the timer fires.
|
* \retval 0 Error (tt was null or the timer was not configured properly)
|
* \retval non-zero Success.
|
*
|
* This function is used to set a trickle timer. The protocol implementation
|
* must use this function ONLY to initialise a new trickle timer and NOT to
|
* reset it as a result of external events or inconsistencies.
|
*
|
* The protocol implementation must configure the trickle timer by calling
|
* trickle_timer_config() before calling this function.
|
*/
|
uint8_t trickle_timer_set(struct trickle_timer *tt,
|
trickle_timer_cb_t proto_cb, void *ptr);
|
|
/**
|
* \brief Stop a running trickle timer.
|
* \param tt A pointer to a ::trickle_timer structure
|
*
|
* This function stops a running trickle timer that was previously started with
|
* trickle_timer_start(). After this function has been called, the trickle
|
* timer will no longer call the protocol's callback and its interval will not
|
* double any more. In order to resume the trickle timer, the user application
|
* must call trickle_timer_set().
|
*
|
* The protocol implementation must NOT use trickle_timer_stop(), _set() cycles
|
* to reset a timer manually. Instead, in response to events or inconsistencies,
|
* the corresponding functions must be used
|
*/
|
#define trickle_timer_stop(tt) do { \
|
ctimer_stop(&((tt)->ct)); \
|
(tt)->i_cur = TRICKLE_TIMER_IS_STOPPED; \
|
} while(0)
|
|
/**
|
* \brief To be called by the protocol when it hears a consistent
|
* transmission
|
* \param tt A pointer to a ::trickle_timer structure
|
*
|
* When the trickle-based protocol hears a consistent transmission it must call
|
* this function to increment trickle's consistency counter, which is later
|
* used to determine whether the protocol must suppress or go ahead with its
|
* own transmissions.
|
*
|
* As the trickle timer library implementation may change in the future to
|
* perform further tasks upon reception of a consistent transmission, the
|
* protocol's implementation MUST use this call to increment the consistency
|
* counter instead of directly writing to the structure's field.
|
*/
|
void trickle_timer_consistency(struct trickle_timer *tt);
|
|
/**
|
* \brief To be called by the protocol when it hears an inconsistent
|
* transmission
|
* \param tt A pointer to a ::trickle_timer structure
|
*
|
* When the protocol hears an inconsistent transmission, it must call this
|
* function to notify the library that the timer must be reset.
|
*
|
* Before resetting the timer, the library will perform a set of checks.
|
* Therefore, it is important that the protocol calls this function instead of
|
* trying to reset the timer by itself.
|
*/
|
void trickle_timer_inconsistency(struct trickle_timer *tt);
|
|
/**
|
* \brief To be called by the protocol when an external event occurs that
|
* should trigger a timer reset
|
* \param tt A pointer to a ::trickle_timer structure
|
*
|
* When an external event occurs that should result in a timer reset, the
|
* protocol implementation must call this function to notify the library.
|
*
|
* Before resetting the timer, the library will perform a set of checks.
|
* Therefore, it is important that the protocol calls this function instead of
|
* trying to reset the timer by itself.
|
*/
|
#define trickle_timer_reset_event(tt) trickle_timer_inconsistency(tt)
|
|
/**
|
* \brief To be called in order to determine whether a trickle timer is
|
* running
|
* \param tt A pointer to a ::trickle_timer structure
|
* \retval 0 The timer is stopped
|
* \retval non-zero The timer is running
|
*
|
*/
|
#define trickle_timer_is_running(tt) ((tt)->i_cur != TRICKLE_TIMER_IS_STOPPED)
|
|
/** @} */
|
|
#endif /* __TRICKLE_TIMER_H__ */
|
/** @} */
|
/** @} */
|
