TokenBucket.hpp

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

#ifndef TokenBucket_HPP
#define TokenBucket_HPP

#include <Fw/FPrimeBasicTypes.hpp>
#include <Fw/Time/Time.hpp>

#define MAX_TOKEN_BUCKET_TOKENS 1000

namespace Utils {

class TokenBucket {
  public:
    // Full constructor
    //
    // replenishInterval is in microseconds
    //
    TokenBucket(U32 replenishInterval, U32 maxTokens, U32 replenishRate, U32 startTokens, Fw::Time startTime);

    // replenishRate=1, startTokens=maxTokens, startTime=0
    TokenBucket(U32 replenishInterval, U32 maxTokens);

  public:
    // Adjust settings at runtime
    void setMaxTokens(U32 maxTokens);
    void setReplenishInterval(U32 replenishInterval);
    void setReplenishRate(U32 replenishRate);

    U32 getMaxTokens() const;
    U32 getReplenishInterval() const;
    U32 getReplenishRate() const;
    U32 getTokens() const;

    // Manual replenish
    void replenish();

    // Main point of entry
    //
    // Evaluates time since last trigger to determine number of tokens to
    // replenish. If time moved backwards, always returns false.
    //
    // If number of tokens is not zero, consumes one and returns true.
    // Otherwise, returns false.
    //
    bool trigger(const Fw::Time time);

  private:
    // parameters
    U32 m_replenishInterval;
    U32 m_maxTokens;
    U32 m_replenishRate;

    // state
    U32 m_tokens;
    Fw::Time m_time;
};

}  // end namespace Utils

#endif