RateLimiter.cpp

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// ======================================================================
// \title  RateLimiter.cpp
// \author vwong
// \brief  cpp file for a rate limiter utility class
//
// \copyright
// Copyright (C) 2009-2020 California Institute of Technology.
// ALL RIGHTS RESERVED. United States Government Sponsorship
// acknowledged.
// ======================================================================

#include <Utils/RateLimiter.hpp>

namespace Utils {

RateLimiter ::RateLimiter(U32 counterCycle, U32 timeCycle) : m_counterCycle(counterCycle), m_timeCycle(timeCycle) {
    this->reset();
}

RateLimiter ::RateLimiter() : m_counterCycle(0), m_timeCycle(0) {
    this->reset();
}

void RateLimiter ::setCounterCycle(U32 counterCycle) {
    this->m_counterCycle = counterCycle;
}

void RateLimiter ::setTimeCycle(U32 timeCycle) {
    this->m_timeCycle = timeCycle;
}

void RateLimiter ::reset() {
    this->resetCounter();
    this->resetTime();
}

void RateLimiter ::resetCounter() {
    this->m_counter = 0;
}

void RateLimiter ::resetTime() {
    this->m_time = Fw::Time();
    this->m_timeAtNegativeInfinity = true;
}

void RateLimiter ::setCounter(U32 counter) {
    this->m_counter = counter;
}

void RateLimiter ::setTime(Fw::Time time) {
    this->m_time = time;
    this->m_timeAtNegativeInfinity = false;
}

bool RateLimiter ::trigger(Fw::Time time) {
    // NB: this implements a 4-bit decision, logically equivalent to this pseudo-code
    //
    // A = HAS_COUNTER, B = HAS_TIME, C = COUNTER_TRIGGER, D = TIME_TRIGGER
    //
    // if (!A && !B) => true
    // if (A && B) => C || D
    // if (A) => C
    // if (B) => D
    // false
    //
    if (this->m_counterCycle == 0 && this->m_timeCycle == 0) {
        return true;
    }

    // evaluate trigger criteria
    bool shouldTrigger = false;
    if (this->m_counterCycle > 0) {
        shouldTrigger = shouldTrigger || this->shouldCounterTrigger();
    }
    if (this->m_timeCycle > 0) {
        shouldTrigger = shouldTrigger || this->shouldTimeTrigger(time);
    }

    // update states
    if (this->m_counterCycle > 0) {
        this->updateCounter(shouldTrigger);
    }
    if (this->m_timeCycle > 0) {
        this->updateTime(shouldTrigger, time);
    }

    return shouldTrigger;
}

bool RateLimiter ::trigger() {
    FW_ASSERT(this->m_timeCycle == 0);
    return trigger(Fw::Time::zero());
}

bool RateLimiter ::shouldCounterTrigger() {
    FW_ASSERT(this->m_counterCycle > 0);

    // trigger at 0
    bool shouldTrigger = (this->m_counter == 0);

    return shouldTrigger;
}

bool RateLimiter ::shouldTimeTrigger(Fw::Time time) {
    FW_ASSERT(this->m_timeCycle > 0);

    // trigger at prev trigger time + time cycle seconds OR when time is at negative infinity
    Fw::Time timeCycle = Fw::Time(this->m_timeCycle, 0);
    Fw::Time nextTrigger = Fw::Time::add(this->m_time, timeCycle);
    bool shouldTrigger = (time >= nextTrigger) || this->m_timeAtNegativeInfinity;

    return shouldTrigger;
}

void RateLimiter ::updateCounter(bool triggered) {
    FW_ASSERT(this->m_counterCycle > 0);

    if (triggered) {
        // triggered, set to next state
        this->m_counter = 1;

    } else {
        // otherwise, just increment and maybe wrap
        if (++this->m_counter >= this->m_counterCycle) {
            this->m_counter = 0;
        }
    }
}

void RateLimiter ::updateTime(bool triggered, Fw::Time time) {
    FW_ASSERT(this->m_timeCycle > 0);

    if (triggered) {
        // mark time of trigger
        this->m_time = time;
    }
    this->m_timeAtNegativeInfinity = false;
}

}  // end namespace Utils