How to pass data from a Delphi pascal DLL class to a LabView data cluster?

Question

Hi all,
I have the following problem:
I'm using a dll written in Delphi Pascal to transfer data to LabView using the "Call Library Function Node".
My Delphi dll contains this class:
  TFlash=class
    Fi:TFileInfo;
    constructor Create;
    procedure LoadFi(Filedir_and_nametring);
  end;
 TFileInfo=record
    Idx:smallint; 
    IdxLstSpl:array[0..4] of longint;
    Ms:word;
    Sp:array[0..4]of word;
  end;
I've created the TFileInfo record datastructure into a LabView cluster to have the "same" variable.
My plan was to call a Deplhi DLL function with the "Call Library Function Node" and to pass the address of the TFileInfo record, so the data would be passed to the LabView Cluster.
When I make a simple delphi dll function like this, it works because I only pass an small integer to Labview (without reference to the data structure):
var  Data:TFlash; 
function GetNrOfRows(FilePath: string):integer;stdcall; 
begin
  Data:=TFlash.Create;
  Data.LoadFi(FilePath); //this function gets the number of rows out of the selected file.
  Result := Data.Fi.Idx;
end;
When I try to use this procedure instead of the function above, to pass the address of the whole complex data structure of "Data" (TFileInfo), I'm unable to get the information of "Data" into my Labview cluster:
procedure LoadFileInfo(FilePath: string; DataPointer: Pointer);stdcall; 
begin
  Data:=TFlash.Create;
  Data.LoadFi(FilePath);
  DataPointer:=@Data;
end;
Call Library Function Node settings:
- stdcall (WINAPI)
- Run in UI Thread
- Function prototype: void LoadFileInfo(PStr FilePath, void *DataPointer);
      * DataPointer --> Type: 'Adapt to Type' and Data format: 'Pointers to Handles'.
      * FilePath --> Type: 'string', string format: 'pascal string pointer'
I'm struggeling with this problem for almost a week now and I can't really find a solution on the forum or google.
I've also read the following posts:
http://forums.ni.com/ni/board/message?board.id=170&message.id=229930&requireLogin=False
http://forums.ni.com/ni/board/message?board.id=170&message.id=77947&requireLogin=False
http://forums.ni.com/ni/board/message?board.id=170&message.id=51245&requireLogin=False
(or did I miss something in these posts?)
Hope my explanation is clear.
Thx
Solved!
Go to Solution.

Answer 1

Ok, I'm one step further:
Because it works when passing an integer from the dll to Labview,
I tried a simple vi containing a cluster with an small integer (16 bit signed Integer) in it and passing the pointer to that cluster:
same settings:
Call Library Function Node settings:
- stdcall (WINAPI)
- Run in UI Thread
- Function prototype: void LoadFileInfo(PStr FilePath, void *DataPointer);
      * DataPointer --> Type: 'Adapt to Type' and Data format: 'Pointers to Handles'. (and the cluster wired to the output of the Call Library Function Node)
      * FilePath --> Type: 'string', string format: 'pascal string pointer'
Changed the Delphi function to:
procedure LoadFileInfo(FilePath: string; DataPointer: Pinteger);stdcall; 
begin
  Data:=TFlash.Create;
  Data.LoadFi(FilePath);  --> this function fills in the data in Data.Fi
  DataPointer^:=Data.Fi.Idx; --> write the smallint on the address given by Labview
end;
When I call my DLL this way, the expected value appears in smallint indicator in de cluster on the front panel.
When I'm passing a pointer from the TFileInfo Type:
Delphi:
var  Data:TFlash;
type  PtrTFileInfo = ^TFileinfo;
procedure LoadFileInfo(FilePath: string; DataPointer: PtrTFileInfo);stdcall; 
begin
  Data:=TFlash.Create;
  Data.LoadFi(Copy(FilePath,2,length(FilePath)-1));
  DataPointer^:=Data.Fi;
end;
During debugging in my Delphi environment: when I get out of this function and pass this to Labview, an error occurs: access violation at 0x004E7125: read of address failed 0x00002A24. Process stopped.
Is it actually possible to access data with 2 applications? Delphi--> common stack <--Labview