Error getting value in PointerByReference with JNA and Delphi DLL

Question

I need to develop a Java program with a Delphi DLL, but a problem is:

I mapped in JNA as follows:

- Delphi function:

function send_command (const command : byte; var size : byte; var data : pbyte) : integer; stdcall external 'comunication.dll';

- Java function:

public int send_command(byte command, ByteByReference size, PointerByReference data);

The function returned 1 (Success result) but I can´t get the value in data variable.

How can I get the value in data ?

In Delphi Test Program, the function is called as follows:

const
    cmdREAD_STATUS = $17;

procedure TForm1.ReadStatus1Click(Sender: TObject);
var
    Data,
    p    : pbyte;
    tam  : byte;
    i,
    result: integer;
    saux : string;
begin
    getmem (Data, 40);
    tam:= 0;
    result:= send_comand (cmdREAD_STATUS, tam, Data);
    if result= 1 then
      begin
        memo1.Lines.add ('Command OK');
        i:= 0;
        sAux:= '';
        p:= Data;
        while (i < Tam) do
          begin
            sAux:= sAux + inttohex (p^, 2)+' ';
            if length (sAux) > 59 then
              begin
                memo1.Lines.add (SAux);
                sAux:= '';
              end;
            inc (p);
            inc (i);
          end;
        if sAux <> '' then
          memo1.Lines.add (SAux);
      end
    else
      memo1.Lines.add ('Result: '+inttostr(result)+' in command execution');
    freemem (Data);
end;

what do you mean by "can´t get the value in data variable"? — CristiFati
This DLL speaks with an equipment and this function return a array of bytes, in Delphi returns as the example of test software. — Rafael Guerra
@DavidHeffernan, changing the variables ? byte to BYTE and pbyte to PBYTE ? — Rafael Guerra
What code is not working exactly? The Delphi code that populates data, or the Java code that tried to read from data? You need to be more specific. — Remy Lebeau

David Heffernan David Heffernan · Accepted Answer · 2015-07-21T17:47:01

Do it using the Memory class.

Memory memory = new Memory(40);
PointerByReference data = new PointerByReference();
data.setValue(memory);
// call the function now
byte[] bytes = new byte[40];
memory.read(0, bytes, 0, 40);

Bear in mind that I don't know Java at all and so there may well be syntax errors in the above. But I'm confident that the basic approach is sound.

Error getting value in PointerByReference with JNA and Delphi DLL

1 Answers