1. RE: Brute Force Method Might Wrap DX Into Euphoria Library?
--- Matthew Lewis <matthewwalkerlewis at YAHOO.COM>
wrote:
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------------------------------------------------------------
>
>
> > -----Original Message-----
> > From: Mike The Spike [mailto:mtsreborn at yahoo.com]
>
> > This is how I imagined it;
> >
> > If you have the following code in C:
> > d3drm->lpVtbl->CreateDeviceFromClipper(d3drm,
> lpclip,
> > NULL, 640, 480, &lpdev)
> >
> > Wouldn't it be possible to get the address of
> d3drm,
> > and peek the value of CreateDeviceFromClipper from
> the
> > result of the subtraction of the address of d3drm
> and
> > the address of lpVtbl, added to the address of
> d3drm?
> > This is what above could could look like in Eu;
> >
> > atom CreateDeviceFromClipper
> >
> > CreateDeviceFromClipper =
> >
> peek4(d3drm_address+(lpvtbl_address-d3drm_address))
> >
> > call( CreateDeviceFromClipper )
> >
> > Would this work?
> > I think it would if all addresses remained
> constant
> > accross threads, wich is what COM is all about
> > anyways...
> >
> > Correct me if I'm wrong on this one...
> >
> > If I'm not, then expect Rebirth to go Euphoria!
>
> Nope. You haven't passed any parameters, and you
> won't be able to using
> call() alone. The reason is that the stack will be
> messed up. Check out my
> post a week ago or so. It uses a short asm routine
> that allows you to call
> by pointer. Then, it can work.
I know I know, but it's just an example, I didn't want
to show any machine code in it.
> It's really not difficult to get the address of the
> functions. All you need
> is the value of lpvtbl and the order in which the
> interface functions are
> declared. Then you can treat vtbl as an array of
> pointers (because that's
> exactly what it is). I haven't looked at any DX
> interfaces, but all
> interfaces start with IUnknown, where the first
> function (lpvtbl+0) is
> QueryInterface, then AddRef and Release.
>
> Here is how you can use COM. Link to ole32.dll
> (this is the COM automation
> server on Windows). Call OleInitialize to
> initialize OLE/COM. Call
> CoCreateInstance to initialize a class id (CLSID).
> You'll also have to
> specify an interface (IID). I simply use IUnknown,
> since every COM object
> has it. Then, you can use IUnknown::QueryInterface
> to get the lpvtbl's to
> any interface you're interested in. Just remember
> that the first parameter
> you pass has to be the pointer you got from
> CoCreateInstance (hint: it's the
> value returned in ppv--see MSDN for details). This
> is to emulate the
> implicit passing that C++ does (it's the equivalent
> of 'this', if that makes
> sense to you :). Also, remember that any string you
> pass has to be unicode
> (see WideToMultiByte / MultiByteToWide ).
>
> Remember to release any interface you've used, and
> to call OleUninitialize
> when you exit, otherwise, you may not free up
> resources properly.
>
> As I think I mentioned, I'm now able to call COM
> interfaces successfully,
> it's just a matter of wrapping the API to make it
> more friendly to use. I
> should have something meaningful to share later this
> week--most likely a way
> to use ActiveX objects with Eu.
>
> Matt Lewis
>
Mike The Spike
>
