Help passing UDT Array from VB to PBDLL

[Gregery D Engle]

Here is the VB Code I have:

Public Declare Function PerVac Lib "VacPer.dll" Alias "PERVAC" (Employee() As EmployeeStruct) As Long

Type PeriodStruct
    Jan As Long
    Feb As Long
    Mar As Long
    Apr As Long
    May As Long
    Jun As Long
    Jul As Long
    Aug As Long
    Sep As Long
    Oct As Long
    Nov As Long
    Dec As Long
End Type

Type EmployeeStruct
     SSN As String * 9
     PersonalEarned As PeriodStruct
     PersonalUsed As PeriodStruct
     VacationEarned As PeriodStruct
     VacationUsed As PeriodStruct
End Type

..

sub TEST()
     Dim Employee(1 To 3000) As EmployeeStruct
     Employee(1).SSN = "123456789"
     a& = PerVac(Employee())
     Debug.Print Employee(1).SSN
     Debug.Print Employee(2).SSN
end sub

Example PB Code

#compile dll "C:\winnt\system32\vacper.dll"

#INCLUDE "C:\PBDLL60\Samples\Vb32\VBAPI32.INC" 
TYPE PeriodStruct DWORD
    Jan AS LONG
    Feb AS LONG
    Mar AS LONG
    Apr AS LONG
    May AS LONG
    Jun AS LONG
    Jul AS LONG
    Aug AS LONG
    Sep AS LONG
    Oct AS LONG
    Nov AS LONG
    Dec AS LONG
END TYPE

TYPE EmployeeStruct DWORD
     SSN AS STRING * 9
     PersonalEarned AS PeriodStruct
     PersonalUsed AS PeriodStruct
     VacationEarned AS PeriodStruct
     VacationUsed AS PeriodStruct
END TYPE

FUNCTION PerVac(Info AS DWORD) EXPORT AS LONG
    msgbox "Start"
    LOCAL l  AS LONG
    LOCAL u  AS LONG
    LOCAL vb AS DWORD
    l  = vbArrayLBound(Info, 1)
    u  = vbArrayUBound(Info, 1)
    vb = vbArrayFirstElem(Info)

    DIM Employee(1 TO u) AS EmployeeStruct AT vb

    MSGBOX "lBound: " & STR$(l)
    MSGBOX "ubound: " & STR$(u)
    MSGBOX "First Elem: " & STR$(vb)
    MSGBOX Employee(1).SSN                                
end function

When running this code, I get the following message Boxes:

"Powerbasic - Start"
"lbound: 1"
"ubound: 3000"

with the message box "First Element:" I get a crazy number which makes no sense
when I do a messagebox Employee(1).SSN I get a random number

Any ideas?

Thanks


------------------
-Greg

[Tom Hanlin]

I think that when you define the parameter as Employee() on the VB end, you're
telling VB to pass something like an array handle in VB's format, rather than
the actual data. Try defining the parameter "ByVal pEmployee As Long" on the VB
end, and pass VarPtr(Employee(LBound(Employee))) to the routine. That should
allow your PowerBASIC routine to properly map the VB data to the PB array.


------------------
Tom Hanlin
PowerBASIC Staff

[Gregery D Engle]

Tom,

I tried what your suggested and I did infact pass the address
of the array but as soon as I tried to access it within PB
it crashes. Any more ideas?

------------------
-Greg

[Michael Mattias]

I think you need DWORD alignment on EmployeeStruc.

That STRING * 9 is probably throwing it off.

MCM

[Gregery D Engle]

Michael,

Maybe I'm missing something but I think I already have DWORD
alignment on EmployeeStruct

------------------
-Greg

[Gregery D Engle]

Ok, I thought about what Micheal said, and I already did have
DWORD alignment but I thought I would change the:

SSN as string * 9 to
SSN as long


After doing that, everything worked fine. What would cause this?

------------------
-Greg

[Joseph W Murphy]

VB does not use DWORD alignment. It uses natural alignment. I would put in a filler type of 1 or 3 bytes after SSN. Or better yet place SSN at the end of the type.

Added later: By the way, what version of VB are you using?
VB3, VB4/16 use byte alignment
VB4/32, VB5 use 'natural' alignment (I have never used VB6)

Joe


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[This message has been edited by Joseph W Murphy (edited June 30, 2001).]

[Gregery D Engle]

Moving SSN at the end of the type as STRING * 9 doesn't change
anything. I still get GPF's. But it looks like I will just
leave the SSN as a LONG. a lot more stable in performance.

Thanks for everyone's help.

------------------
-Greg

[Doug McDonald]

Hi, If your just writing a fast (meaning time to write code
not exacution speed) application for your own use and have
lots of extra ram (structure size) a quick and dirty
trick is to write the VB structure to a ram drive and reading it
from PD/DLL. Reading and writing to a file is byte by byte
(if openend for bianry) so there's no need to pad
or depad the structure in PB or VB. If your writing a new app
then line up your structure's but if it's an older app
and you need a quick fix till you have time to rewrite the code
then this works and is pretty fast since its all in ram. I wish
VB (Mircosoft) would be like PB and let you set the boundry of
the structure's but till they do we're stuck with the stupid way
VB works. The FAQ in this fourm explains all the VB/PB UDT stuff
very well.

Doug

------------------

[Gregery D Engle]

D. McDonald,

This application will be installed on 7 or 10 different users.
Setting up a RAMDRIVE would not be an option. If I remember
correctly don't you have to put that in the CONFIG.SYS?

Anyways, I am using DAO for most of the work in VB but there
are some things that are SO slow in VB and that is what PB is for.
I'm making a PB DLL with SQLTools to do the directy work and
returning a UDT Array of all Employee's and there vacation and
personal balance's. PB takes about 2 seconds to complete this
for all employees. Visual Basic took about 2 second PER employee.


------------------
-Greg