Question

Delphi Xe.

It is given:

1.dll, in it a unit

unit DllUnit; interface

uses windows, sysutils;

Procedure GuPrcA(var p:PAnsiChar;const l:integer); StdCall;
Procedure GuPrcW(var p:PWideChar;const l:integer); StdCall;

Exports GuPrcA,GuPrcW;

implementation

procedure GuMes(s:string);
begin
MessageBox(0,pchar(s),'From dll',mb_iconinformation);
end;

Procedure GuPrcW(var p:PWideChar;const l:integer); // wide
var s:widestring;
begin
if (p=nil)or(l<1) then begin p:=nil;exit;end;
SetLength(s,trunc(l/sizeof(widechar)));Move(p^,Pointer(s)^,l);
gumes('l: '+inttostr(l)+', nl: '+inttostr(length(s))+#10+'-'+s+'-');
s:=widestring(Uppercase(s));Move(Pointer(s)^,p^,l);
end;

Procedure GuPrcA(var p:Pansichar;const l:integer); // ansi
var s:ansistring;
begin
if (p=nil)or(l<1) then begin p:=nil;exit;end;
SetLength(s,l);Move(p^,Pointer(s)^,l);
gumes('l: '+inttostr(l)+', nl: '+inttostr(length(s))+#10+'-'+s+'-');
s:=ansistring(AnsiUppercase(s));Move(Pointer(s)^,p^,l);
end;

Initialization

ReportMemoryLeaksOnShutdown:=true;

end.

2.The program, at a window memo and 2 buttons

...
implementation

{$R *.dfm}

Procedure GuPrcA(var p:PansiChar;const l:cardinal); StdCall; external 'mydll.dll' name 'GuPrcA';
Procedure GuPrcW(var p:PwideChar;const l:cardinal); StdCall; external 'mydll.dll' name 'GuPrcW';

procedure TForm1.Button6Click(Sender: TObject);
var p:pwidechar;c:cardinal;s:widestring;
begin
s:=widestring(memo1.Text);
c:=length(s)*sizeof(widechar);
p:=allocmem(c);
Move(Pointer(s)^,p^,c);
GuPrcW(p,c);
s:='';setlength(s,trunc(c/sizeof(widechar)));
Move(p^,Pointer(s)^,c);
Freemem(p,c);
memo1.Text:='='+s+'= l:'+inttostr(c);
end;

procedure TForm1.Button7Click(Sender: TObject);
var p:pansichar;c:cardinal;s:ansistring;
begin
s:=ansistring(memo1.text);
c:=length(s);
p:=allocmem(c);
Move(Pointer(s)^,p^,c);
GuPrcA(p,c);
s:='';setlength(s,c);
Move(p^,Pointer(s)^,c);
Freemem(p,c);
memo1.Text:='='+s+'= l:'+inttostr(c);
end;

Initialization

ReportMemoryLeaksOnShutdown:=true;

end.

To download an source code both it is possible here: http://www.multiupload.com/WSZKF8IGP1

By pressing buttons there is a transfer in dll lines (ansi or wide string), its display in msgbox dll, its processing there (idle time uppercase) and return to the program. The manager of memory is not used (fast – simple – sharemem). Both in a program and in dll are included ReportMemoryLeaksOnShutdown (display of events about memory losses) which both are silent, i.e. like all would work also lengths of lines too everywhere coincide.

That is necessary:

1. To look, whether there are no there errors (to check up on errors)

2. Whether it is possible to optimise or offer a way better or easier

3. Whether it is possible to address to this DLL with such procedures from VB or C++/C# ?

Thanks

Answer 1

If you do not want to use the heap manager for you transmission of data, just use WideString kind of string.

It will be (a bit) slower, but it will allow you to change the string length on every side.

And it will be true Unicode, so you won’t have any trouble about char set and such when using native Delphi UnicodeString under XE. You can use WideString in your code and the conversion to string will be done silently.

It will be all managed by Windows, so even non Delphi libraries or applications (like .Net or C++) would be able to handle it directly.