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Thread: Newbie question... accessing 2D arrays passed from VB

  1. Jun 7th, 2002, 10:04 AM #1
    Jotaf98
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    Newbie question... accessing 2D arrays passed from VB

    Hi all. I tried to make a DLL that needs to access some 2D arrays passed from VB (some of them are DX textures, others are simple 2D arrays [lookup tables]). Of course it didn't work
    Can someone here please explain it to me? The way I did it was like this: *(PointerToFirstElement + Y * Width + X)
    Code:
    Temp = Me.GetIQ()
'Error 9: Overflow
'DON'T PANIC! :eek:

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  2. Jun 7th, 2002, 10:53 AM #2
    CornedBee
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    I think VB arrays are sorted the other way round.
    So VB
    arr(x, y)
    would be C
    arr[y * width + x];

    How do you have the function declared in VB, how in C, how do you call it?
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  3. Jun 7th, 2002, 01:12 PM #3
    parksie
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    Search the forum for SAFEARRAY - I think this one's been asked before.
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  4. Jun 8th, 2002, 05:14 PM #4
    Jotaf98
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    Huh... thanks, both of you... but... cornedbee that's exactly how I'm doing it (look at my code ) ... and parksie, I know about the SAFEARRAY type and that's why I'm passing a pointer to the raw data (item(0,0)).

    Come on, it's not a hard question. I thought that anyone here could answer that. All I need is working code to access an array... obviously the one I'm using doesn't work

    Btw is this legal in C++? arr[y * width + x]
    Code:
    Temp = Me.GetIQ()
'Error 9: Overflow
'DON'T PANIC! :eek:

    To learn how to use realistic effects in your games like fire, rain, snow and magic effects, read my article on particles systems here.


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  6. Jun 8th, 2002, 06:52 PM #5
    parksie
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    You can give whatever index into it you want, so that expression will be perfectly valid.

    I have no idea what format VB tries to pass them as. You might be best off using ByVal ptr As Long in the Declare for the function, and then VarPtr(myarray(0)) as the argument when you call it.
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  7. Jun 8th, 2002, 07:58 PM #6
    Jotaf98
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    Heh thanks
    Well I used ByRef in the declaration... so I'm not using VarPtr... if it doesn't work I'll try that.

    Btw I found the thread you were talking about... but I don't have the time to check it out now... well... I'll tell ya something later ok?
    Code:
    Temp = Me.GetIQ()
'Error 9: Overflow
'DON'T PANIC! :eek:

    To learn how to use realistic effects in your games like fire, rain, snow and magic effects, read my article on particles systems here.


    Jotaf's Theories!
    "Cats land on their feet. Toast lands peanut butter side down. A cat with toast strapped to its back will hover above the ground in a state of quantum indecision."
    Reply With Quote Reply With Quote
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