Reading Byte Array From Delphi Pointer In C#

Question

I have asked question before. Call Delphi Function From C#

I have added two methods like this.

C#

public interface IStringFunctions
{
  [MethodImplAttribute(MethodImplOptions.PreserveSig)]
  void SetValueAsByteArray(IntPtr DataPointer, int DataLength);

  [MethodImplAttribute(MethodImplOptions.PreserveSig)]
  IntPtr GetValueAsByteArray(out int DataLength);
}
if (instance != null)
{
  // Sending Pointer of Byte Array  To Delphi Function. 
  byte[] inputBytes = new byte[3];
  inputBytes[0] = 65;
  inputBytes[1] = 66;
  inputBytes[2] = 67;

  IntPtr unmanagedPointer = Marshal.AllocHGlobal(inputBytes.Length);
  Marshal.Copy(inputBytes, 0, unmanagedPointer, inputBytes.Length);
  instance.SetValueAsByteArray(unmanagedPointer, inputBytes.Length);


  // Getting Byte Array from Pointer 
  int dataLength = 0;
  IntPtr outPtr = instance.GetValueAsByteArray(out dataLength);
  byte[] outBytes = new byte[dataLength];
  Marshal.Copy(outPtr, outBytes, 0, dataLength);
  string resultStr = System.Text.Encoding.UTF8.GetString(outBytes);             
}

Delphi DLL

 TStringFunctions = class(TInterfacedObject, IStringFunctions)
  private 
    FValueAsByteArray: TByteArray;
  public
    procedure SetValueAsByteArray(DataPointer:Pointer;DataLength:Integer); stdcall;
    function GetValueAsByteArray(out DataLength:Integer): Pointer; stdcall;
  end;

procedure TStringFunctions.SetValueAsByteArray(DataPointer:Pointer;DataLength:Integer); stdcall; export;
var
  Source: Pointer;
  SourceSize: Integer;
  Destination: TByteArray;
begin
  Source := DataPointer;
  SourceSize := DataLength;
  SetLength(Destination, SourceSize);
  Move(Source^, Destination[0], SourceSize);

  FValueAsByteArray := Destination;

  ShowMessage(TEncoding.UTF8.GetString(TBytes(Destination)));
  ShowMessage(IntToStr(Length(Destination)));
  ShowMessage('DataLength:'+IntToStr(DataLength));
end;

function TStringFunctions.GetValueAsByteArray(out DataLength:Integer): Pointer; stdcall; export;
begin
  DataLength := Length(FValueAsByteArray);

  ShowMessage(TEncoding.UTF8.GetString(TBytes(FValueAsByteArray)));
  ShowMessage(IntToStr(Length(FValueAsByteArray)));

  Result := Addr(FValueAsByteArray);
end;

SetValueAsByteArray worked.

But GetValueAsByteArray method incorrect pointer and bytes.

How to read correct pointer of FValueAsByteArray and bytes[] in c# ?

What's my fault ?

Answer 1

Result := Addr(FValueAsByteArray);

That's the address of the pointer to the array. You want to return the address of the array:

Result := Pointer(FValueAsByteArray);

If I were you I'd avoid allocating unmanaged memory and let the marshaller marshal byte arrays.

I already told you about the futility of export. It's frustrating to repeat myself.