mac地址转换

#pragma once
template <class T>
class single_instance {
public:
    static inline T instance() { 
        static T obj;
        return obj;
    }
private:
    single_instance() = default;
    virtual ~single_instance() = default;
};

#pragma once
#include <stdio.h>
#include "single_instance.hpp"
class net_utility {
public:
    void get_mac_str(unsigned long mac_val, std::string &mac_str) {
        static const char *convert_format = "%02x:%02x:%02x:%02x:%02x:%02x";
        char buf[24] = "";
        snprintf(buf, sizeof(buf), convert_format, (mac_val >> 40) & 0xff,
                                                           (mac_val >> 32) & 0xff,
                                                           (mac_val >> 24) & 0xff,
                                                           (mac_val >> 16) & 0xff,
                                                           (mac_val >> 8) & 0xff,
                                                           mac_val & 0xff);
        mac_str = buf;
    }
};

#define  G_NET_UTILITY single_instance<net_utility>::instance()

#include "net_utility.hpp"
#include <iostream>
int main() {
    std::string mac_str;
    G_NET_UTILITY.get_mac_str(1, mac_str);
    std::cout << mac_str << std::endl;
    
    return 0;
}