Hello,

The class below is one way to implement a class that can read IP address from user’s input in C++;

Can convert to string or/and enumerate in range:

#include <iostream>
#include <string>
#include <vector>
#include <sstream>
#include <array>

using namespace std;
class ipv4
{
    std::array<unsigned char, 4> data;

public:
    constexpr ipv4() : data{{0}} {}
    constexpr ipv4(unsigned char const a, unsigned char const b,
                   unsigned char const c, unsigned char const d) : data{{a, b, c, d}} {}
    explicit constexpr ipv4(unsigned long a) : data{{static_cast<unsigned char>((a >> 24) & 0xFF),
                                                     static_cast<unsigned char>((a >> 16) & 0xFF),
                                                     static_cast<unsigned char>((a >> 8) & 0xFF),
                                                     static_cast<unsigned char>(a & 0xFF)}} {}
    ipv4(ipv4 const &other) noexcept : data(other.data) {}
    ipv4 &operator=(ipv4 const &other) noexcept
    {
        data = other.data;
        return *this;
    }
    std::string to_string() const
    {
        std::stringstream sstr;
        sstr << *this;
        return sstr.str();
    }
    constexpr unsigned long to_ulong() const noexcept
    {
        return (static_cast<unsigned long>(data[0]) << 24) |
               (static_cast<unsigned long>(data[1]) << 16) |
               (static_cast<unsigned long>(data[2]) << 8) |
               static_cast<unsigned long>(data[3]);
    }
    friend std::ostream &operator<<(std::ostream &os, const ipv4 &a)
    {
        os << static_cast<int>(a.data[0]) << '.'
           << static_cast<int>(a.data[1]) << '.'
           << static_cast<int>(a.data[2]) << '.'
           << static_cast<int>(a.data[3]);
        return os;
    }
    friend std::istream &operator>>(std::istream &is, ipv4 &a)
    {
        char d1, d2, d3;
        int b1, b2, b3, b4;
        is >> b1 >> d1 >> b2 >> d2 >> b3 >> d3 >> b4;
        if (d1 == '.' && d2 == '.' && d3 == '.')
            a = ipv4(b1, b2, b3, b4);
        else
            is.setstate(std::ios_base::failbit);
        return is;
    }

    ipv4 &operator++()
    {
        *this = ipv4(1 + to_ulong());
        return *this;
    }
    ipv4 &operator++(int)
    {
        ipv4 result(*this);
        ++(*this);
        return *this;
    }
    friend bool operator==(ipv4 const &a1, ipv4 const &a2) noexcept
    {
        return a1.data == a2.data;
    }
    friend bool operator!=(ipv4 const &a1, ipv4 const &a2) noexcept { return !(a1 == a2); }
    friend bool operator<(ipv4 const &a1, ipv4 const &a2) noexcept
    {
        return a1.to_ulong() < a2.to_ulong();
    }
    friend bool operator>(ipv4 const &a1, ipv4 const &a2) noexcept { return a2 < a1; }
    friend bool operator<=(ipv4 const &a1, ipv4 const &a2) noexcept { return !(a1 > a2); }
    friend bool operator>=(ipv4 const &a1, ipv4 const &a2) noexcept { return !(a1 < a2); }

    ipv4 &operator+(int i)
    {
        //cout << "adding" << i << endl;
        *this = ipv4(i + to_ulong());
        return *this;
    }
};

int main()
{

    ipv4 address(168, 192, 0, 1);
    std::cout << address << std::endl;
    ipv4 ip;
    std::cout << ip << std::endl;
    std::cin >> ip;

    string test_ip = ip.to_string();

    if (!std::cin.fail())
        std::cout << ip << std::endl;

    cout << "IP: " << test_ip << endl;
    cout << "Next IP: " << ip++ << endl;
    cout << "Next 5th IP: " << ip + 5 << endl;
    return 0;
}

Hope this helps and good luck.

— Saeed 🙂

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