why crashes the find function if a file is writeprotected ?

[cdkiller]

hello,

i have a little question.
why crashes these find in file function when a file is writeprotected ?
i will not change datas i will oly search in it.

can someone give me the changes which i must do that the function will read writeprotected files ?

thansks...

Delphi-Quellcode:

function FindInFile(const FileName   : string;
                    SearchWord : string; MatchCase : Boolean) : Integer;
var
  fs     : TFileStream;
  Buffer : array [1..10000] of Char;
  Size   : Integer;
  idx    : Integer;
  i      : Integer;
begin
  Result := -1;
  idx := 1;
  if not MatchCase then
   SearchWord := UpperCase(SearchWord);
  fs := TFileStream.Create(FileName, fmopenreadwrite or fmsharedenynone);
  try
    Repeat
      Application.ProcessMessages;
      Size := (Fs.Size - Fs.Position);
      if Size > 10000 then Size := 10000;
      Fs.ReadBuffer(Buffer, Size);
      if not MatchCase then
      begin
        for i := 1 to Size do
          Buffer[i] := Uppercase(Buffer)[i];
      end;
      for i := 1 to Size do
      begin
        if (Buffer[i] = SearchWord[idx]) then
          Inc(idx)
        else
          idx := 1;
        if (idx = Length(SearchWord)+1) then
        begin
          Result := (fs.Position - Size) + i - idx + 1;
          Exit;
        end;
      end;
    until fs.Position >= fs.Size;
  finally
   fs.Free;
  end;
end;