windowed_counter.h

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#pragma once
 
#include <cstdint>
#include <type_traits>
 
namespace stats
{
template <typename T> class WindowedCounter
{
    static_assert(std::is_unsigned_v<T>, "wrap-safe deltas need unsigned arithmetic");
 
public:
    T sample(T total)
    {
        const T delta = static_cast<T>(total - prev_);
        prev_ = total;
        return delta;
    }
 
private:
    T prev_ = 0;
};
 
template <typename T> constexpr T window_avg(T sum, T count) { return count ? static_cast<T>(sum / count) : T{0}; }
 
constexpr unsigned window_percent(uint64_t part, uint64_t whole)
{
    return whole ? static_cast<unsigned>(part * 100 / whole) : 0u;
}
} // namespace stats