Getting Garbage Values while reading struct data from a binary file

Question

Hi guys in my previous question, I was able to get the data of a struct to be loaded on a file, but now the issue is I\'m getting garbage value while retrieving it.

Answer 1

Formatted input requires delimiters so it knows when to stop reading for a particular value. Even though you're opening the file in binary mode what you're writing is in essence a text file with no delimiters so you can't read it back.

If you must have a binary file then this is the way to read/write one using your structure:

#include 
#include 
#include 
#include 
#include 

const char* SettingsFilePath = "settings.bin";

struct Setting
{
    int SettingID;
    int SettingINTValue;
    double SettingDOUBLEValue;
    char SettingCHARValue;
    std::string SettingSTRINGValue;
    std::string SettingName;

    Setting()
        : SettingID(0)
        , SettingINTValue(0)
        , SettingDOUBLEValue(0)
        , SettingCHARValue(0)
    {
    }

    void Write(std::fstream& out)
    {
        out.write(reinterpret_cast(&SettingID), sizeof(SettingID));

        out.write(reinterpret_cast(&SettingINTValue), sizeof(SettingINTValue));

        out.write(reinterpret_cast(&SettingDOUBLEValue), sizeof(SettingDOUBLEValue));

        out.write(reinterpret_cast(&SettingCHARValue), sizeof(SettingCHARValue));

        size_t str_size = SettingSTRINGValue.size();
        out.write(reinterpret_cast(&str_size), sizeof(str_size));
        out.write(SettingSTRINGValue.c_str(), SettingSTRINGValue.size());

        str_size = SettingName.size();
        out.write(reinterpret_cast(&str_size), sizeof(str_size));
        out.write(SettingName.c_str(), SettingName.size());
    }

    void Read(std::fstream& in)
    {
        in.read(reinterpret_cast(&SettingID), sizeof(SettingID));

        in.read(reinterpret_cast(&SettingINTValue), sizeof(SettingINTValue));

        in.read(reinterpret_cast(&SettingDOUBLEValue), sizeof(SettingDOUBLEValue));

        in.read(reinterpret_cast(&SettingCHARValue), sizeof(SettingCHARValue));

        size_t str_size;
        std::vector str_data;

        in.read(reinterpret_cast(&str_size), sizeof(str_size));
        str_data.resize(str_size);
        in.read(&str_data[0], str_size);
        SettingSTRINGValue.assign(str_data.begin(), str_data.end());

        in.read(reinterpret_cast(&str_size), sizeof(str_size));
        str_data.resize(str_size);
        in.read(&str_data[0], str_size);
        SettingName.assign(str_data.begin(), str_data.end());
    }

    void Print(const std::string& title)
    {
        std::cout << title << "\n";
        std::cout << std::string(title.size(), '-') << "\n";

        const size_t w = 22;
        std::cout << std::setw(w) << std::right << "SettingID : " << SettingID << "\n";
        std::cout << std::setw(w) << std::right << "SettingINTValue : " << SettingINTValue << "\n";
        std::cout << std::setw(w) << std::right << "SettingDOUBLEValue : " << SettingDOUBLEValue << "\n";
        std::cout << std::setw(w) << std::right << "SettingCHARValue : " << SettingCHARValue << "\n";
        std::cout << std::setw(w) << std::right << "SettingSTRINGValue : " << SettingSTRINGValue << "\n";
        std::cout << std::setw(w) << std::right << "SettingName : " << SettingName << "\n";

        std::cout << "\n";
    }
};

int main()
{
    {
        Setting s;
        s.Print("Default before Write");

        s.SettingID = 1;
        s.SettingINTValue = 2;
        s.SettingDOUBLEValue = 3.5;
        s.SettingCHARValue = 'Z';
        s.SettingSTRINGValue = "Blah Blah";
        s.SettingName = "Some Settings";

        std::fstream f(SettingsFilePath, std::ios::out | std::ios::binary);
        s.Write(f);

        s.Print("Values written to file");
    }

    {
        Setting s;
        s.Print("Default before read");

        std::fstream f(SettingsFilePath, std::ios::in | std::ios::binary);
        s.Read(f);
        s.Print("Values after read");
    }

    return EXIT_SUCCESS;
}