src/core/common/trickle_timer.hpp

/*
 *  Copyright (c) 2016, The OpenThread Authors.
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 *     derived from this software without specific prior written permission.
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 */

/**
 * @file
 *   This file includes definitions for the trickle timer logic.
 */

#ifndef TRICKLE_TIMER_HPP_
#define TRICKLE_TIMER_HPP_

#include "common/context.hpp"
#include "common/timer.hpp"

namespace ot {

/**
 * @addtogroup core-timer-trickle
 *
 * @brief
 *   This module includes definitions for the trickle timer logic.
 *
 * @{
 *
 */

/**
 * This class implements a trickle timer.
 *
 */
class TrickleTimer: public Timer
{
public:

    /**
     * Represents the modes of operation for the TrickleTimer
     */
    typedef enum Mode
    {
        kModeNormal     = 0,  ///< Runs the normal trickle logic.
        kModePlainTimer = 1,  ///< Runs a normal timer between Imin and Imax.
        kModeMPL        = 2,  ///< Runs the trickle logic modified for MPL.
    } Mode;

    /**
     * This function pointer is called when the timer expires.
     *
     * @param[in]  aTimer  A reference to the expired timer.
     *
     * @retval TRUE   If the trickle timer should continue running.
     * @retval FALSE  If the trickle timer should stop running.
     */
    typedef bool (*Handler)(TrickleTimer &aTimer);

    /**
     * This constructor creates a trickle timer instance.
     *
     * @param[in]  aScheduler               A reference to the timer scheduler.
     * @param[in]  aRedundancyConstant      The redundancy constant for the timer, k.
     * @param[in]  aTransmitHandler         A pointer to a function that is called when transmission should occur.
     * @param[in]  aIntervalExpiredHandler  An optional pointer to a function that is called when the interval expires.
     * @param[in]  aContext                 A pointer to arbitrary context information.
     *
     */
    TrickleTimer(TimerScheduler &aScheduler,
#ifdef ENABLE_TRICKLE_TIMER_SUPPRESSION_SUPPORT
                 uint32_t aRedundancyConstant,
#endif
                 Handler aTransmitHandler, Handler aIntervalExpiredHandler, void *aContext);

    /**
     * This method indicates whether or not the trickle timer instance is running.
     *
     * @retval TRUE   If the trickle timer is running.
     * @retval FALSE  If the trickle timer is not running.
     */
    bool IsRunning(void) const;

    /**
     * This method start the trickle timer.
     *
     * @param[in]  aIntervalMin  The minimum interval for the timer, Imin.
     * @param[in]  aIntervalMax  The maximum interval for the timer, Imax.
     * @param[in]  aMode         The operating mode for the timer.
     *
     */
    void Start(uint32_t aIntervalMin, uint32_t aIntervalMax, Mode aMode);

    /**
     * This method start the trickle timer.
     *
     * @param[in]  aStartTime    The start time.
     * @param[in]  aIntervalMin  The minimum interval for the timer, Imin.
     * @param[in]  aIntervalMax  The maximum interval for the timer, Imax.
     * @param[in]  aMode         The operating mode for the timer.
     *
     */
    void StartAt(uint32_t aStartTime, uint32_t aIntervalMin, uint32_t aIntervalMax, Mode aMode);

    /**
     * This method stops the trickle timer.
     *
     */
    void Stop(void);

#ifdef ENABLE_TRICKLE_TIMER_SUPPRESSION_SUPPORT
    /**
     * This method indicates to the trickle timer a 'consistent' state.
     *
     */
    void IndicateConsistent(void);
#endif

    /**
     * This method indicates to the trickle timer an 'inconsistent' state.
     *
     */
    void IndicateInconsistent(void);

private:
    bool TransmitFired(void) { return mTransmitHandler(*this); }
    bool IntervalExpiredFired(void) { return mIntervalExpiredHandler ? mIntervalExpiredHandler(*this) : true; }

    void StartNewInterval(void);

    static void HandleTimerFired(Timer &aTimer);
    void HandleTimerFired(void);

    // Shadow base class method to ensure it is hidden.
    void StartAt(void) { }

    typedef enum Phase
    {
        ///< Indicates we are currently not running
        kPhaseDormant    = 1,
        ///< Indicates that when the timer expires, it should evaluate for transmit callbacks
        kPhaseTransmit   = 2,
        ///< Indicates that when the timer expires, it should process interval expiration callbacks
        kPhaseInterval   = 3,
    } Phase;

#ifdef ENABLE_TRICKLE_TIMER_SUPPRESSION_SUPPORT
    // Redundancy constant
    const uint32_t k;

    // A counter, keeping track of the number of "consistent" transmissions received
    uint32_t c;
#endif

    // Minimum interval size
    uint32_t Imin;
    // Maximum interval size
    uint32_t Imax;
    // The mode of operation
    Mode mMode;

    // The current interval size (in milliseconds)
    uint32_t I;
    // The time (in milliseconds) into the interval at which we should transmit
    uint32_t t;

    // The current trickle phase for the timer
    Phase mPhase;

    // Callback variables
    Handler mTransmitHandler;
    Handler mIntervalExpiredHandler;
};

/**
 * @}
 *
 */

}  // namespace ot

#endif  // TRICKLE_TIMER_HPP_