Class log_printf_t

less_slow.cpp:6385–6420

}

struct log_printf_t {
    std::size_t operator()(                    //
        char *buffer, std::size_t buffer_size, //
        std::source_location const &location, int code, std::string_view message) const noexcept {
        // On MSVC, the `high_resolution_clock` is the `steady_clock`, which won't work with `to_time_t`.
        // `std::chrono::high_resolution_clock` is usually just an alias to either `system_clock` or
        // `steady_clock`. There is debate on whether using it is a good idea at all.
        // https://en.cppreference.com/w/cpp/chrono/high_resolution_clock
#if defined(_MSC_VER) || defined(__APPLE__)
        auto now = std::chrono::system_clock::now();
#else
        auto now = std::chrono::high_resolution_clock::now();
#endif
        auto time_since_epoch = now.time_since_epoch();

        // Extract seconds and milliseconds
        auto seconds = std::chrono::duration_cast<std::chrono::seconds>(time_since_epoch);
        auto milliseconds = std::chrono::duration_cast<std::chrono::milliseconds>(time_since_epoch) - seconds;

        // Format as ISO 8601: YYYY-MM-DDTHH:MM:SS.mmm
        auto time_t_now = std::chrono::system_clock::to_time_t(now);
        auto tm = std::gmtime(&time_t_now); // UTC only, no local timezone dependency

        int count_bytes = std::snprintf( //
            buffer, buffer_size,
            "%04d-%02d-%02dT%02d:%02d:%02d.%03dZ | "                                     // time format
            "%s:%d <%03d> "                                                              // location and code format
            "\"%.*s\"\n",                                                                // message format
            tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday,                             // date
            tm->tm_hour, tm->tm_min, tm->tm_sec, static_cast<int>(milliseconds.count()), // time
            location.file_name(), location.line(), code,                                 // location and code
            static_cast<int>(message.size()), message.data()                             // message of known length
        );
        return static_cast<std::size_t>(count_bytes);
    }
};

BENCHMARK(logging<log_printf_t>)->Name("log_printf")->MinTime(2);