TYPE from a DLL

[Scott Turchin]

I have a project in which VB will be calling a DLL.
The DLL may have a various amount of returns in an array TYPE
It returns fine with PB when PB calls the DLL, and again, it may be a VB issue but a return error about subscript out of range or something is occuring (I'm lacking information still)

ie:

mydata(1).whatever
mydata(2).whatever
Mydata(1).whatever2


Etc..

Anyway I want to return this so a VB app can call it, and maybe I am doing things right already...??

Type ProdInfo
     Value1                As Asciiz * 3
     Value2           As Asciiz * 25
     Value3                As Asciiz * 12
End Type 


Declare Function ParseEmailFile(FileSpec As Asciiz,pInfo() As ProdInfo,pInfoQty As Long) As String
'In Winmain:
Dim pInfo(1 to 20) as ProdInfo
'Again, in PB/DLL it calls the DLL and returns everything correctly...Maybe it's a question of How do you call a TYPE in VB???

Thanks!

Scott

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Scott Turchin




[This message has been edited by Scott Turchin (edited February 05, 2000).]

[Lance Edmonds]

it sounds like a vb-udt-alignment issue. did you review the faq on vb & pb udt's? see http://www.powerbasic.com/support/pb...hread.php?t=28

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lance
powerbasic support
mailto:[email protected][email protected]</a>

[Scott Turchin]

Thanks Lance,

If I can go further onto that discussion..and it appears this may not be the preferable way to do this (Not to mention I have not used VB in almost 2 years thanks to PB/DLL

It’s important to understand that Visual Basic only inserts padding if the next member item is too large to fit in the current DWORD. In the following case, all of the items fit properly, so no padding is required, and the same exact structure can be used with PowerBASIC (employing BYTE alignment):

Is this going to require me to sit and determine which one is going to be larger and whether padding is going to be required?


In the exported DLL I have the following:

Type ProdInfo
     Qty                As Asciiz * 3
     ProdName           As Asciiz * 25
     Amt                As Asciiz * 12
End Type

I suspect by what I am reading that I would have to use padding here? I would not know how to determine that ...

Confused still..but either way, I think an array will be used instead...but for general knowledge I'd be great to understand it...

Thanks Lance
Scott


[This message has been edited by Scott Turchin (edited February 06, 2000).]

[Lance Edmonds]

I'm not a "VB Guy" (nor do I have VB4 installed anymore) so I'll just give you what I think will happen, so take this with a pinch of salt:

The 1st element occupies 3 bytes, so there is a padding byte added to align the next member on a DWORD boundary. The second member occupies 25 byes, so 3 bytes of paddding are added. The last member length is a multiple of 4, so no final padding is applied.

Therefore, in PB, the structure will be 3 + 25 + 12 = 40 bytes. In VB, it is 3 + 1 + 25 + 3 + 12 = 44 bytes.

I hope this is correct!


------------------
Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>