////  TimeWeightedAvg.h//  libraries/shared/src////  Created by Yixin Wang on 7/29/2014//  Copyright 2013 High Fidelity, Inc.////  Distributed under the Apache License, Version 2.0.//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html// #ifndef hifi_TimeWeightedAvg_h#define hifi_TimeWeightedAvg_h #include "SharedUtil.h" template <typename T>class TimeWeightedAvg { public:     TimeWeightedAvg()        : _firstSampleTime(0),        _lastSample(),        _lastSampleTime(0),        _weightedSampleSumExcludingLastSample(0.0)    {}     void reset() {        _firstSampleTime = 0;        _lastSampleTime = 0;        _weightedSampleSumExcludingLastSample = 0.0;    }     void  updateWithSample(T sample) {        quint64 now = usecTimestampNow();         if (_firstSampleTime == 0) {            _firstSampleTime = now;        } else {            _weightedSampleSumExcludingLastSample = getWeightedSampleSum(now);        }         _lastSample = sample;        _lastSampleTime = now;    }     double getAverage() const {        if (_firstSampleTime == 0) {            return 0.0;        }        quint64 now = usecTimestampNow();        quint64 elapsed = now - _firstSampleTime;        return getWeightedSampleSum(now) / (double)elapsed;    }     quint64 getElapsedUsecs() const {        if (_firstSampleTime == 0) {            return 0;        }        return usecTimestampNow() - _firstSampleTime;    } private:    // if no sample has been collected yet, the return value is undefined    double getWeightedSampleSum(quint64 now) const {        quint64 lastSampleLasted = now - _lastSampleTime;        return _weightedSampleSumExcludingLastSample + (double)_lastSample * (double)lastSampleLasted;    } private:    quint64 _firstSampleTime;     T _lastSample;    quint64 _lastSampleTime;        double _weightedSampleSumExcludingLastSample;}; #endif // hifi_TimeWeightedAvg_h