C++ file handle - c++

Question

I am trying to implement a file handle class similar to the one in Bjarne Stroustrup's FAQ page. (Scroll to "Why doesn't C++ provide a 'finally' construct".) Unlike his example, however, I want to use C++ file streams instead of a FILE*.
Right now, I am considering creating a FileHandleBase class, or something similarly named, and two derived classes—one for input files and one for output files. Below is the implementation I wrote as a proof-of-concept; keep in mind that it is very simple and unfinished.
class FileHandle {
public:
FileHandle(const char* fn, ios_base::openmode mode = ios_base::in | ios_base::out) {
file.open(fn, mode);
// Check to make sure file is open
}
FileHandle(const string &fn, ios_base::openmode mode = ios_base::in | ios_base::out) {
file.open(fn, mode);
// Check to make sure file is open
}
~FileHandle() {
file.close();
}
private:
fstream file;
};
I would like to know if this is a viable way of making a file handle, that is, whether my inheritance idea is good. I also want to know the best way to deal with the ios_base::openmode parameter because the C++ reference page for std::ifstream says this:
Note that even though ifstream is an input stream, its internal filebuf object may be set to also support output operations.
In what cases would an ifstream be used for output operations, and, similarly, when would an of stream be used for input operations; and should I restrict the options for the ios_base::openmode parameter for my file handle class(es)? That way my input file handle would only handle input operations, and the output version would only handle output operations.

Answer 1

In what cases would an ifstream be used for output operations, and, similarly, when would an ofstream be used for input operations
You would open an output file stream with an std::ios_base::in openmode and vice-versa for an input file stream if you would still like to perform those associated operations using the internal std::filebuf object, which is accessible by stream->rdbuf(). Note that the streams std::ofstream and std::ifstream will still be able to perform output and input respectively even if they are opened with opposite openmodes.
int main() {
std::ofstream stream("test.txt");
stream << "Hello" << std::flush;
stream.close();
stream.open("test.txt", std::ios_base::in);
char buffer[SIZE] = {};
stream.rdbuf()->sgetn(buffer, SIZE);
std::cout << buffer << std::endl;
}