Strange behavior of move with strings
- by Umair Ahmed
I am testing some enhanced string related functions with which I am trying to use move as a way to copy strings around for faster, more efficient use without delving into pointers.
While testing a function for making a delimited string from a TStringList, I encountered a strange issue. The compiler referenced the bytes contained through the index when it was empty and when a string was added to it through move, index referenced the characters contained.
Here is a small downsized barebone code sample:-
unit UI;
interface
uses
System.SysUtils, System.Types, System.UITypes, System.Rtti, System.Classes,
System.Variants, FMX.Types, FMX.Controls, FMX.Forms, FMX.Dialogs, FMX.Layouts,
FMX.Memo;
type
TForm1 = class(TForm)
Results: TMemo;
procedure FormCreate(Sender: TObject);
end;
var
Form1: TForm1;
implementation
{$R *.fmx}
function StringListToDelimitedString
( const AStringList: TStringList; const ADelimiter: String ): String;
var
Str : String;
Temp1 : NativeInt;
Temp2 : NativeInt;
DelimiterSize : Byte;
begin
Result := ' ';
Temp1 := 0;
DelimiterSize := Length ( ADelimiter ) * 2;
for Str in AStringList do
Temp1 := Temp1 + Length ( Str );
SetLength ( Result, Temp1 );
Temp1 := 1;
for Str in AStringList do
begin
Temp2 := Length ( Str ) * 2;
// Here Index references bytes in Result
Move ( Str [1], Result [Temp1], Temp2 );
// From here the index seems to address characters instead of bytes in Result
Temp1 := Temp1 + Temp2;
Move ( ADelimiter [1], Result [Temp1], DelimiterSize );
Temp1 := Temp1 + DelimiterSize;
end;
end;
procedure TForm1.FormCreate(Sender: TObject);
var
StrList : TStringList;
Str : String;
begin
// Test 1 : StringListToDelimitedString
StrList := TStringList.Create;
Str := '';
StrList.Add ( 'Hello1' );
StrList.Add ( 'Hello2' );
StrList.Add ( 'Hello3' );
StrList.Add ( 'Hello4' );
Str := StringListToDelimitedString ( StrList, ';' );
Results.Lines.Add ( Str );
StrList.Free;
end;
end.
Please devise a solution and if possible, some explanation. Alternatives are welcome too.
