Hi Marc,

> > I'm not an expert on writing UDFs at all... but:
> > > i created this function:
> > >
> > > function MixStr(Str:PChar):PChar;
> >
> > What's the declaration you're using? cdecl?
> >
> > > var
> > > i, j : Integer;
> > > c1 : Char;
> > > begin
> > > if (Str = nil) then
> > > result := nil
> > > else
> > > begin
> > > for i:=Length(Str) downto 1 do
> >
> > What does Length(Str) return?
> for allo, that return 4... it's ok

I've been testing it with other values - it works OK. It
seems Delphi is converting it to it's native string type.

> What is the length of
> > a PChar in Delphi? According to the Help:
> > function Length(S): Integer;
> > S is a string- or array-valued expression.
> >
> > > begin
> > > j:=Random(i)+1;
> > > c1:=Str[i];
> > > Str[i]:=Str[j];
> > > Str[j]:=c1;
> > > end;
> > > result := Str;
> > > end;
> > > end;
> > >
> > > under firebirdi declared:
> > >
> > > Declare external function f_MixStr cstring(64)
> > > returns cstring(64) free_it
> > > entry_point 'MixStr' module_name 'brudflib2.dll';
> >
> > As you're not grabbing any memory, should you use
> > FREE_IT?
> >
> have remove it...
>
>
> function MixStr(Str:PChar):PChar;cdecl; export;
> var
> i, j : Integer;
> c1 : Char;
> begin
> if (Str = nil) then
> result := nil
> else
> begin
> for i:=Length(Str) downto 1 do
> begin
> j:=Random(i)+1;
> c1:=Str[i];
> Str[i]:=Str[j];
> Str[j]:=c1;
> end;
> result := Str;
> end;
> end;
>
> drop external function f_MixStr;
> Declare external function f_MixStr cstring(64)
> returns cstring(64)
> entry_point 'MixStr' module_name 'brudflib2.dll';
>
> select f_MixStr('allo') from rdb$database;
>
>
> sometime that return a, sometime al, sometime la, sometime lla, sometime
> llao...
> return not all letter

Well, I've been testing your routine in plain delphi:

procedure TForm1.Button1Click(Sender: TObject);
var
i, j : Integer;
c1 : Char;
str: PChar;
begin
GetMem(str, Length('test_string'));
StrPCopy(str, 'test_string');

<insert rest here>

But it returns all sorts of strings, but never with all characters.

What should your routine do? IMO, it's syntax may be alright,
but the routine itself isn't.

With regards,

Martijn Tonies
Database Workbench - developer tool for InterBase, Firebird, MySQL & MS SQL
Server.
Upscene Productions
http://www.upscene.com