How to get values via ByRef parameter of a DLL Function

[RAMESHBABU]

Hi All,

The following code working Ok in VB.

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Public Declare Function GetDeviceTime Lib "DeviceLib" (ByVal nHandleIndex As Long, ByRef nTotalCount As Long, ByRef pnDateTime As Date) As Long
 

To call the same function in our FWH, I wrote the code as under:

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DLL32 Function GetDeviceTime(nHandleIndex AS LONG, nTotalCount AS LONG, pnDateTime AS STRING) AS LONG PASCAL LIB hLib
 

and

When I called as under:

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#include "fivewin.ch"

FUNCTION main()

LOCAL nTotalCount  := 0
LOCAL pnDateTime := SPACE(19)     // 9999-99-99 99:99:99

GetDeviceTime(nHandleIndex, @nTotalCount @pnDateTime)
?nTotalCount, pnDateTime

RETURN nil
 

I am not getting the Referenced date type variable populated with correct value and getting some junk characters.

Not only Date type, even (LONG) type of referenced parameters are not returning correct values but
returning only the Initial values originally assigned to them at the the time of their declaration.

Can anybody help me please.

Thanks,

- Ramesh Babu P

[Enrico Maria Giordano]

Try

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@nTotalCount AS PTR

EMG

[RAMESHBABU]

Hello Mr.Enrico,

Thanks for your attention.

I tried your suggestion with no result.

Regards,

- Ramesh Babu P

[Enrico Maria Giordano]

What value are you passing as nHandleIndex?

EMG

[RAMESHBABU]

Hi Enrico,

>>What value are you passing as nHandleIndex?

I have a 3rd party DLL and as per the documentation I am calling a function as under:

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hLib := LoadLib32("fka.dll")
nHandleIndex := ConnectUSB(1, 123456)

IF nHandleIndex = 1 //RUN_SUCESS
   MsgInfo("The Device is connected.")
ELSE
   MsgInfo("Sorry. The Device is not connected.")
   RETURN nil
ENDIF
 

Expect the ByVal all other functions mentioned in the documentation of the DLL is working fine.

I am currently having problems only with the parameters passed by reference in functions
provided in the DLL. They are not returning the actual values other than the initial values
assigned at their declaration.

Regards,

- Ramesh Babu P

[RAMESHBABU]

Mr.Enrico,

As usually you have helped this time also from a big problem.
Your solution worked very well.

I did not put '@' before DLL FUNCTION variables earlier. Thats the
reason, I have come this forum for solution.

But I still have problem with the DataTime String variable. I am
getting some binary characters junk. The DLL Provider's DateTime format is
yyyy-mm-dd hh:mm:ss.

But when I am calling the value by reference I am not getting proper values.
What is the correct data type I should use with AS orgument while calling
the DLL FUNCTION to get the correct value.

All Numeric values are properly shown with 'AS PTR'

Can you please suggest a way out to this also.

Regards,

- Ramesh Babu P

[Enrico Maria Giordano]

Try

Code: Select all  Expand view

DLL32 Function GetDeviceTime(nHandleIndex AS LONG, @nTotalCount AS PTR, @pnDateTime AS LPSTR) AS LONG PASCAL LIB hLib

EMG