tokenbucket.h

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// Copyright (c) The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#ifndef BITCOIN_UTIL_TOKENBUCKET_H
#define BITCOIN_UTIL_TOKENBUCKET_H
 
#include <util/time.h>
 
namespace util {

template <typename Clock>
class TokenBucket
{
public:
    using clock = Clock;
    using time_point = typename Clock::time_point;
    using duration = typename Clock::duration;
 
    const double m_rate{1};     
    const double m_cap{0};      

    TokenBucket(double rate, double value, double cap) : m_rate{rate}, m_cap{cap}, m_value{std::min(value, cap)} {}

    void increment(const time_point& now)
    {
        if (now > m_last_updated) {
            if (m_value < m_cap && m_last_updated > MIN_TIME) {
                double inc = m_rate * std::chrono::duration_cast<SecondsDouble>(now - m_last_updated).count();
                m_value = std::min(m_cap, m_value + inc);
            }
        }
        m_last_updated = now;
    }

    bool decrement(double n = 1.0, double floor = 0.0)
    {
        m_value -= n;
        return (m_value > floor);
    }

    double value() const { return m_value; }
 
private:
    static constexpr time_point MIN_TIME{time_point::min()};
    time_point m_last_updated{MIN_TIME};
    double m_value{0};
};
 
} // namespace util
 
#endif // BITCOIN_UTIL_TOKENBUCKET_H