How to implement binary128 in C?

  128-bit, c++, floating-point

I started to try and implement new data types, specifically floating-point values, using C. I came up with this sort of way on implementing binary128 using longer_int which I haven’t fully understood.

The way how I started was to implement it via copying the code and modifying it. However, the code is C++, and C doesn’t support OOP, so what I have to do is to try and translate the code.

I can’t find the C version for longer_int because this question I once owned (the same account but now deleted) is now deleted and I can’t view the links.

With the help of these C++ files, how can I implement binary128 using C?

And just so this question won’t get closed, I want to know how to translate the OOP format in longer_int.h.

class longer_int {
    char num_str[];
    longer_int(const int &num);
    longer_int(const char &num[]);
    longer_int(const longer_int &num);

// Sample code from it, now translated to C, but still OOP

Source: Windows Questions C++