if FileExists(FileName)  then begin
    try
        Source := FileOpen(FileName, fmShareDenyWrite); { open source file }
        if Source < 0 then begin
            ShowMessage('Failure Open File: '+ItrDataFile); exit;
        end;
        try
            try
                bytesCopied := FileRead(Source, Kyda, Skolko); { read chunk }
                if BytesCopied > 0 then { if we read anything... }
            finally
            end;
        finally
        end;
    finally
    end;   //end of try

end else begin
    Source := FileCreate(FileName);
end;

var
 F: TfileStream;
begin
 F := TfileStream.Create('файл',fmOpenRead);
  while F.Position <> F.Size do begin
   F.Read(DataStructure, sizeof(DataStructure));
 end;
 F.Free;