[fpc-devel] Re: TBits problem

[Andrea Mauri]

>
>
> If you send a minimal test-case and actual results you might have a
> better chance at getting a reply...



Below a sample test project.
I create a TBits (b1) and then I set 16 bits as 1. Then I create 2 TBits 
(b2 and b3) with size 164, I use .OrBits to OR b1 with b2 and b3. I 
expect that b2 and b3 will result in a TBits with size 164 but with only 
first 16 bits as 1. What I got is different. A lot of bits between 
bits[16] and bits[163] are set to 1.
You can easily check it using the following test project.
Tested on windows fpc 2.6.2.


program Project1;

{$mode objfpc}{$H+}

uses
   {$IFDEF UNIX}{$IFDEF UseCThreads}
   cthreads,
   {$ENDIF}{$ENDIF}
   Classes, SysUtils, CustApp
   { you can add units after this };

type

   { TMyApplication }

   TMyApplication = class(TCustomApplication)
   protected
     procedure DoRun; override;
   public
     constructor Create(TheOwner: TComponent); override;
     destructor Destroy; override;
     procedure WriteHelp; virtual;
     function bitstostring(b: TBits): string;
   end;

{ TMyApplication }

procedure TMyApplication.DoRun;
var
   ErrorMsg: String;
   i, bsize1, bsize2: integer;
   b1, b2, b3: TBits;
   s1, s2, s3: string;
begin
   // quick check parameters
   ErrorMsg:=CheckOptions('h','help');
   if ErrorMsg<>'' then begin
     ShowException(Exception.Create(ErrorMsg));
     Terminate;
     Exit;
   end;

   // parse parameters
   if HasOption('h','help') then begin
     WriteHelp;
     Terminate;
     Exit;
   end;

   { add your program here }
   bsize1:= 16;
   bsize2:= 164;
   b1:= TBits.Create;
   b2:= TBits.Create(bsize2);
   b3:= TBits.Create(bsize2);
   for i:= 0 to bsize1 - 1 do
     b1[i]:= True;

   b2.OrBits(b1);
   b3.OrBits(b1);
   for i:= b1.Size to bsize2 - 1 do
     b3[i]:= False;
   if not b2.Equals(b3) then
   begin
     writeln(bitstostring(b1));
     writeln(bitstostring(b2));
     writeln(bitstostring(b3));
   end;
   b1.Free;
   b2.Free;
   b3.Free;
   // stop program loop
   Terminate;
end;

constructor TMyApplication.Create(TheOwner: TComponent);
begin
   inherited Create(TheOwner);
   StopOnException:=True;
end;

destructor TMyApplication.Destroy;
begin
   inherited Destroy;
end;

procedure TMyApplication.WriteHelp;
begin
   { add your help code here }
   writeln('Usage: ',ExeName,' -h');
end;

function TMyApplication.bitstostring(b: TBits): string;
var
   i: integer;
   bs: string;
begin
   bs:= '';
   for i:= 0 to b.Size - 1 do
     if b[i] then
       bs:= bs + '1'
     else
       bs:= bs + '0';
   Result:= bs;
end;

var
   Application: TMyApplication;
begin
   Application:=TMyApplication.Create(nil);
   Application.Title:='My Application';
   Application.Run;
   Application.Free;
end.