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POC++/CLI class wrapper for c library - callbacks
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copied!<p>I am wrapping a C library using C++/CLI. The C library was designed to be used from an unmanaged C++ class. This means that the library functions accept a C++ object pointer and then provide that pointer back in callbacks. This enables the callback code to redirect requests to an appropriate event function in the calling C++ object.</p> <p>The actual functions are quite involved, so I have simplified the problem space to just a few basic items:</p> <pre><code>// C library function signature void CLibFunc(CLIBCALLBACK *callback, void *caller); // C callback signature // Second parameter is meant to point to the calling C++ object typedef int (__stdcall CLIBCALLBACK) (int param1, void *caller); // C callback implementation int CallBackImpl(int param1, void* caller) { // Need to call the ManagedCaller's EventFunction from here // ??? } // C++/CLI caller class public ref class ManagedCaller { public: void CallerFunction(void) { // Call the C library function // Need to pass some kind of this class pointer that refers to this object CLibFunc(CallBackImpl, ????); } void EventFunction(param1) { } } </code></pre> <p>Now the C library functions need to be called from a managed C++ class. Under C++/CLI, the garbage collector moves objects around in memory, so passing a simple fixed pointer to the class does not work anymore. I can solve the problem by pinning the object, but that is not recommended because it leads to memory fragmentation. It seems that another option would be to use auto_gcroot pointers, but I am fairly new to managed C++ an I am not sure how to make this work.</p> <p>Does anyone know how to make this work? What kind of pointer should be passed to the C function? How should the callback implementation redirect to the calling object's event function?</p>

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