fileIOAdvExample

#include <iostream>
#include <fstream>

const int maxNameLen{ 50 };
struct Player
{
    int id;
    char* name;
    int rank;
};

void writePlayersFile(Player* playersArr, int playersSize, int append = 0)
{
    std::ofstream outf;
    outf.open("file.dat", std::ios::binary | (append ? std::ios::app : 0));
    for (int i{ 0 }; i < playersSize; ++i)
    {
        outf.write((char*)&playersArr[i].id, sizeof(int));
        size_t nameLen = strlen(playersArr[i].name) + 1;
        outf.write(playersArr[i].name, nameLen);
        if (nameLen < maxNameLen) { outf.seekp(maxNameLen - nameLen, std::ios::cur); };
        outf.write((char*)&playersArr[i].rank, sizeof(int));
    }
    outf.close();
}
void readPlayersFile(Player* playersArr, int playersSize)
{
    std::ifstream inf;
    inf.open("file.dat", std::ios::binary);
    const int bufSzie{ 100 };
    char buf[bufSzie];
    for (int i{ 0 }; i < playersSize; ++i)
    {
        inf.read((char*)&playersArr[i].id, sizeof(int));
        for (int i{ 0 }; inf.read(buf + i, 1), buf[i] and i < bufSzie; ++i);
        int nameLen = strlen(buf) + 1;
        playersArr[i].name = new char[nameLen];
        strcpy_s(playersArr[i].name, nameLen, buf);
        if (nameLen < maxNameLen) { inf.seekg(maxNameLen - nameLen, std::ios::cur); };
        inf.read((char*)&playersArr[i].rank, sizeof(int));
    }
    inf.close();
}

int changePlayersFileById(int searchId, const char* name)
{
    std::fstream file;
    file.open("file.dat", std::ios::in | std::ios::out | std::ios::binary);

    int id{ 0 };
    int nameLen{ 0 };
    for (int i{ 0 }; i < 3; ++i)
    {

        file.read((char*)&id, sizeof(id));
        if (id == searchId)
        {
            nameLen = strlen(name) + 1;
            file.seekp((int)file.tellg(), std::ios::beg);
            file.write(name, nameLen);
            file.close();
            return 0;
        }
        file.seekg(maxNameLen + sizeof(int), std::ios::cur);
    }
    file.close();
    return 1;
}
void printPlayersArr(Player* playersArr, int playersSize)
{
    for (int i{ 0 }; i < playersSize; ++i)
    {
        std::cout << playersArr[i].id << ' ' << playersArr[i].name << ' ' << playersArr[i].rank << '\n';
    }
}

int main()
{

    Player players[3]{ {2607, new char[sizeof("MadMax")]{"MadMax"}, 39},{2802, new char[sizeof("Batman")]{"Batman"}, 25},{2902, new char[sizeof("Joker")]{"Joker"}, 15} };
    writePlayersFile(players, 3);
    for (int i{ 0 }; i < 3; ++i) { delete[] players[i].name; };

    Player readPlayers[3]{};
    readPlayersFile(readPlayers, 3);
    printPlayersArr(readPlayers, 3);
    for (int i{ 0 }; i < 3; ++i) { delete[] readPlayers[i].name; };

    changePlayersFileById(2802, "BATMAN FOREVER YOUNG!");
    changePlayersFileById(2902, "Joker Rockker :]");
    readPlayersFile(readPlayers, 3);
    printPlayersArr(readPlayers, 3);
    for (int i{ 0 }; i < 3; ++i) { delete[] readPlayers[i].name; };
}