49         if (readings.empty())  in update()
56         return function->calculate(readings, timestamp);  in update()
61         readings.emplace_back(timestamp, reading);  in update()
65         return function->calculate(readings, timestamp);  in update()
71         auto it = readings.begin();  in cleanup()
72         for (auto kt = std::next(readings.rbegin()); kt != readings.rend();  in cleanup()
83         readings.erase(readings.begin(), it);  in cleanup()
87             readings.front().first =  in cleanup()
88                 std::max(readings.front().first, timestamp - duration.t);  in cleanup()
93     std::vector<ReadingItem> readings;  member in metrics::DataInterval
106         if (readings.empty())  in update()
111         return function->calculateForStartupInterval(readings, timestamp);  in update()
116         readings.emplace_back(timestamp, reading);  in update()
117         return function->calculateForStartupInterval(readings, timestamp);  in update()
122     std::vector<ReadingItem> readings;  member in metrics::DataStartup