Use a pure C function pointer to call C ++ class member functions

Starting point: I happened to see a scenario where I needed to call C ++ using C code. I didn't find a solution on google, so I recorded this requirement, today I read GECKO's NPAPI code and found a way

Principle: The static members of the class are published to the outer layer as shared, so they do not have the member function address, so it can be used to provide an opportunity for us to call the class member functions.
You can call the specific action of this pointer internally by passing the pointer of the class in the static member function.

This solves the problem that C function pointers cannot call C ++ class member functions.

The following is an instance:

# Include <iostream>

Class C;

Struct test {
Char (* a) (C *);
};

Class C {
Public:
Static char xxx (C * com_on ){
Return com_on-> _ xxx ();
}
Char _ xxx (){
Std: cout <"hei! _ Xxx called "<std: endl;
Return 'a ';
}
};

Int main (){
Test x;
C hei;
X. a = hei. xxx;
X. a (& hei );
Return 0;
}

The second method is to use the youyuan function. Do you understand the specific principle? The above code is not changed to the void * type. I think you can understand it. If you don't understand it, the following should be clear enough:

# Include <iostream>

Class C;

Struct test {
Char (* a) (void *);
};
Char xxx (void *);

Class C {
Public:
Friend char xxx (void * com_on );
Char _ xxx (){
Std: cout <"hei! _ Xxx called "<std: endl;
Return 'a ';
}
};
Char xxx (void * com_on ){
Return (C *) com_on)-> _ xxx ();
}
Int main (){
Test x;
C hei;
X. a = xxx;
X. a (& hei );
Return 0;
}

Author: "white bones of Angels"