How to write Binary data to a file in a windows store app using c++

Question

Hey I'm having trouble with file IO. I am using some standard file pointer stuff but i keep getting this error: Unhandled exception at 0x58CBC465 (msvcr120_app.dll) in ChemicalWar.exe: An invalid parameter was passed to a function that considers invalid parameters fatal.

Now from what I gathered I think it has something to do with not having permission to write to default location but I am unsure how to change the location.

here is the code I wrote so far that is giving me trouble:

FILE* ofile;
NametoBinary(_filename);
fopen_s(&ofile, (char*)folder->ToString(), "wb");
fwrite(&animhead, sizeof(Afhead), 1, ofile);
fwrite(binbuff.data(), sizeof(unsigned char), binbuff.size(), ofile);
fclose(ofile);

it breaks on the first fwrite call. Any help would be great. Thanks in advance.

Answer 1

So I figured out the solution so I will post it in case anyone else needs to know.

FILE* ofile = nullptr;
NametoBinary(_filename);
auto folder = Windows::Storage::ApplicationData::Current->RoamingFolder;
std::wstring ws(folder->Path->Data());
std::string full(ws.begin(), ws.end());
full += "\\";
full += _filename;
fopen_s(&ofile, full.c_str(), "wb");
if (nullptr == ofile) return false;
fwrite(&animhead, sizeof(Afhead), 1, ofile);

So the new windows apps have there own FileI0 system. This solution will save a file in a folder in the appdata folder.