Run-Time Error for reading a binary file in C++ for a struct

Question

I have been trying to read data from a binary file in C++, but I'm getting run time error, Program has stopped working!

I have used the similar code before and it is still working. I am getting an error while executing the constructor of the class SettingsClass [Maybe because of the read function, because after removing it, everything just ran great.]

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

class SettingsClass {
  public:
    void ResetSettings() {
       fstream SettingFile;                                  
       Setting defaultsetting[NoOfSettings];

       for(int i=1;i<=NoOfSettings;i++) {
         defaultsetting[i-1].SettingID = i;
         defaultsetting[i-1].SettingINTValue = 0;
         defaultsetting[i-1].SettingDOUBLEValue = 0.0;
         defaultsetting[i-1].SettingCHARValue = '#';
         defaultsetting[i-1].SettingSTRINGValue = "null";
         switch(i) {
           default:
             defaultsetting[i-1].SettingName = "Compression Levels";
             defaultsetting[i-1].SettingSTRINGValue = "Normal";
             defaultsetting[i-1].SettingINTValue = 1;
             break;
         }
         cout<<i<<". "<<defaultsetting[i-1].SettingName<<"\n\t "<<defaultsetting[i-1].SettingINTValue<<"\n\t "<<defaultsetting[i-1].SettingDOUBLEValue<<"\n\t "<<defaultsetting[i-1].SettingCHARValue<<"\n\t "<<defaultsetting[i-1].SettingSTRINGValue<<"\n\t ";
         cout<<"\n";
       }

       SettingFile.open(SettingsFilePath,ios::binary|ios::out);
       if(SettingFile.is_open()){
         SettingFile.write(reinterpret_cast<char const *>(&defaultsetting),sizeof(defaultsetting));
       } else {
         cout<<"Error!";
       }
       SettingFile.close();                                   
    }

    SettingsClass() {
        fstream SettingFile;
        SettingFile.open(SettingsFilePath,ios::binary|ios::in);
        if(SettingFile.is_open()) {
          Setting TempSettings[NoOfSettings]; 
          SettingFile.read((char*)&TempSettings,sizeof(TempSettings)); 
        } else {
          cout<<"Error...";
        }
        SettingFile.close();
    }
} Settings;

You can't read and write std::string to a file like that and expect it to work. You need to serialize properly. — Retired Ninja
– Retired Ninja, Commented Oct 21, 2013 at 18:04

pippin1289 · Accepted Answer · 2013-10-21 18:09:23Z

1

You should go read and learn more about file streams and the associated input and output operators << and >>. You cannot simply input characters into an array like this line of code:

SettingFile.read((char*)&TempSettings,sizeof(TempSettings));

The array is not of char and yet you cast it as such. Instead you should loop over the available input and fill in the array, e.g.:

for(size_t i = 0; i<NoSetting; ++i) {
  SettingFile >> TempSettings[i];
}

Of course you should overload the appropriate input operator:

istream& operator>>(istream& _is, Setting& _s) {
  //read all variables of setting, i.e.:
  //_is >> _s.var1;
  //_is >> _s.var2;
  //etc.
}

You likely have the same error for your output. You should overload:

ostream& operator<<(ostream& _os, const Setting& _s) {
  //output all variables of Setting, e.g.:
  //_os << _s.var1;
}

Do something like this instead of filestream write:

for(size_t i = 0; i<NoSetting; ++i) {
  SettingsFile << defaultSetting[i];
}

answered Oct 21, 2013 at 18:09

pippin1289

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6 Comments

Darius967 Over a year ago

Dude, I did the exact same thing as you said - First overload and then use it, but it helped to get rid of the run-time error, but still I got no data in my file!?

pippin1289 Over a year ago

You should start a new question for the data not showing up in the file. But there are many examples of this online, make sure you follow it to the letter. Also try a smaller program practicing with ostream and istream. This will give you more experience to be able to implement them in a larger project.

Darius967 Over a year ago

Oh, sorry, it's working fine, I just used the wrong operator! Thanks Anyways.

Darius967 Over a year ago

Hey, but there is a problem with that retrieving data part, I'm getting garbage values! Please help me out.

pippin1289 Over a year ago

Again I recommend a separate question now, as it is slightly different. And remember to post a minimal example of what doesn't work.

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