C++, cooperating FILE* and std streams

Question

I need to use an existing C library in a C++ project. My problem is the C existing library uses FILE* as streams, is there a standard compliant way to use FILE* streams to put or to get from C++ streams?

I tried seeking FILE* in the C++11 standard, but it appears only if few examples.

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EDIT, example.
We have a function which write in a FILE*:
fputs(char const*, FILE*)

We have an output C++ stream:
auto strm = std::cout;

Can I, in a standard compliant way, to use fputs to write to strm?

You can also think a similar input example with a C function that reads from a FILE* and a input C++ stream.

Answer 1

Check this answer ,

https://stackoverflow.com/a/5253726/1807864

#include <cstdio>
#include <iostream>
#include <fstream>
#include <string>

using namespace std;

int main()
{
ofstream ofs("test.txt");
ofs << "Writing to a basic_ofstream object..." << endl;
ofs.close();

int posix_handle = ::_fileno(::fopen("test.txt", "r"));

ifstream ifs(::_fdopen(posix_handle, "r")); // 1

string line;
getline(ifs, line);
ifs.close();
cout << "line: " << line << endl;
return 0;
}

Answer 2

The C++ standard, with very few exceptions says that C functionality is all included. Certainly all the stadnard C FILE * functionality is supported [obviously subject to general support for FILE * on the platform - an embedded system that doesn't have a 'files' (eg there is no storage) in general will hardly have much useful support for FILE * - nor will C++ style fstream work].

So, as long as you don't try to mix reading/writing to the same file from both C++ fstream and C FILE * at the same time, it should work just fine. You will need to close the file between C++ and C access, however.

Answer 3

As far as I understand, doing so is non-portable and non-standard . Whether it works in practice or not is another question. I would create wrapper classes around your legacy code, or use FILE* streams directly like in C - they are not that bad. :)