OleVariant and String assignments in Delphi 5 - string

Question

I have a Delphi 5 legacy application and there's a part in which a "string" value is been assigned to an "OleVariant" variable. Something like this:
var
X: OleVariant;
S: string;
Begin
S:= ‘This string should contain 200 characters as per design’;
X:= S;
End;
If the length of “S” is greater than 128, then the value of “X” gets truncated and it only holds a maximum of 128 characters.
Is there a way to overcome this?
I believe there is a way, because if I create my own demo application from scratch (in the same PC, with the same Delphi 5), it allows me to pass longer string values and no truncating is done.
Maybe it is something about the project settings or compiler directives. I have played around with this idea, but I have no workaround yet.
Any help is appreciated. Thanks.
Demo:
procedure TForm1.Button1Click(Sender: TObject);
var
X: OleVariant;
S: string;
begin
//in the Edit I pass a string of 240 chars, let's say;
S:= Edit1.Text;
X:= S;
ShowMessage(IntToStr(Length(X)) + ' : ' + IntToStr(Length(S)));
//this showmessage shows "128 : 240"
end;

Answer 1

Try this OleVariantToString and StringToOleVariant functions at http://www.foxbase.ru/delphi/vzaimnye-preobrazovaniya-olevariant-i-string.htm
They work perfectly for me.
uses Classes, Variants;
function OleVariantToString(const Value: OleVariant): string;
var ss: TStringStream;
Size: integer;
Data: PByteArray;
begin
Result:='';
if Length(Value) = 0 then Exit;
ss:=TStringStream.Create;
try
Size := VarArrayHighBound (Value, 1) - VarArrayLowBound(Value, 1) + 1;
Data := VarArrayLock(Value);
try
ss.Position := 0;
ss.WriteBuffer(Data^, Size);
ss.Position := 0;
Result:=ss.DataString;
finally
VarArrayUnlock(Value);
end;
finally
ss.Free;
end;
end;
function StringToOleVariant(const Value: string): OleVariant;
var Data: PByteArray;
ss: TStringStream;
begin
Result:=null;
if Value='' then Exit;
ss:=TStringStream.Create(Value);
try
Result := VarArrayCreate ([0, ss.Size - 1], varByte);
Data := VarArrayLock(Result);
try
ss.Position := 0;
ss.ReadBuffer(Data^, ss.Size);
finally
VarArrayUnlock(Result);
end;
finally
ss.Free;
end;
end;

Answer 2

One explanation is that OleVariant holds the entire string but that you are looking at the debugger tooltip. In older Delphi versions the debugger tooltip truncates at 128 characters for strings held in a variant. Note that the debugger tooltip for a plain string does not truncate at this length. Try showing the variant in a dialog box and you will see that the entire string is present.
I checked this out on Delphi 6 and there was no truncation with your code (other than the debugger tooltip). Andreas did likewise on Delphi 4 and Rodrigo did so with Delphi 5. I cannot imagine that it could really be the case that strings in a Delphi 5 OleVariant are truncated at 128 characters.
If you really are seeing what you are report then I can think of the following explanations:
Your code is erroneously truncating the string, but you have not yet found the code that does this. Only you can debug that.
You have a local bug private to your Delphi installation. Are you by any chance compiling your own RTL?

Answer 3

I made this work. Summary: instead of filling an “OleVariant” with a “string”; I filled a “Variant” and then typecasted that “Variant” to “OleVariant”. Take a look at the code below so that you can get the idea.
procedure TForm1.Button1Click(Sender: TObject);
var
//X: OleVariant;
X: Variant;
S: string;
begin
//Let's say in the Edit1 I pass a string of 240 chars,
S:= Edit1.Text;
X:= S;
//ShowMessage(IntToStr(Length(X)) + ' : ' + IntToStr(Length(S)));
ShowMessage(IntToStr(Length(OleVariant(X))) + ' : ' + IntToStr(Length(S)));
//This ShowMessage shows "128 : 240"
end;
Honestly, I don’t know for sure why this makes a difference, but it does. It works ok now.
Thanks a lot for your help folks!