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A specific Question dealing with Classes in .dlls with the articles.

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I don''t understand some things in C++, such as function pointers. I''ve been researching the .dll class thing for a few days, and I understand almost everything, except for a line or two.
extern "C"
{
	HRESULT createRendererInterface(rendererInterface **pInterface);
	typedef HRESULT (*CREATERENDERERINTERFACE)(rendererInterface **pInterface);

	HRESULT destroyRendererInterface(rendererInterface **pInterface);
	typedef HRESULT (*DESTROYRENDERERINTERFACE)(rendererInterface **pInterface);
} 
I don''t really understand the typedef thing, and how it is used in the examples in the GameDev.net article. Could anyone give me a quick explanation about how they would be used?

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the typedef is just defining a type that can point to actual functions.

For example this:

typedef int i32;

would create a type that when used would point to an integer (technically speaking)

but this

typedef int (*pfn)(void);

would create a type that pointed to a function so that if you had a function like:

int myfunction()
{
//
}

you could do something like

pfn avar = myfunction;

and then calling ''avar'' with ''('' and '')'' would actually call teh function it points to.

avar(); // same as calling myfunction();

The typedef that''s in your question is based around the same concept of function pointers, but its a little more complicated syntax. if you did

CREATERENDERERINTERFACE avar;

then avar would have to point to a function that returns an HRESULT and takes a pointer to a pointer to a renderInterface

avar = // some function with above signature

renderInterface* pInterface;

avar( &pInterface );

would call the function that avar points to. This is basically used to initialize the interface to the dll.

Try this, it might help you out a bit more. It''s a plugin manager implementation.


:::: [ Triple Buffer ] ::::

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