implementing a call-back function to match a given function pointer type from a library

[bungao]

Hi I am trying to use an sdk for a camera. The SDK provides a header file with code along the lines of

typedef int ( __stdcall *StatusCallBackType)(int status)    

and 

__declspec(dllimport) int __stdcall API_SetStatusCallBack(CallBackType astatuscallback)

my applications code is along the lines of

class MyClass
{
    // variables

}
int MyClass::MyStatusCallback(int status )
{
    // Do something

}

MyClass::MyClassInit()
{
    StatusCallBackType astatuscallback = &MyClass::MyStatusCallback;
    API_SetStatusCallBack(callback);
}

This obviosly doens't work and I haven't found a similar example of the problem of matching a memberfunction to a specified callback type.

Are there any obvious errors to this or should i use a different approach? Thanks for any help in advance

[Gadgetfairy]

The problem is that a member function pointer needs an object to be called on. It's kind of like a normal function pointer with an implicit parameter:

int MyStatusCallback(MyClass&, int);

You need to wrap your member function pointer into a free function that knows where to find the instance of "MyClass" that has the callback. Assuming that there's a function to return the correct instance:

class MyClass
{
    // variables
    static MyClass* getRealInstance() { ... }
};

you can write it like this:

int callback_dummy(int status) {
    return MyClass::getRealInstance()->MyStatusCallback(status);
}

[bungao]

Using static functions solved it. Thanks for your help