A little question about file streaming!

Cromfaeyr

type
  TStorage = packed record
    bt01: byte;
    sName: string [14];
    SaveDate: TDateTime;
    dwMakeIdx: DWord;
    wIndex: Word;
    wDura: Word;
    wDuraMax: Word;
    nValue: array [0..13] of Byte;
    nNone: Integer; // Reserved bytes ???
  end;

procedure TForm1.btn1Click (Sender: TObject);
var
  Stor: TStorage;
  I, nCount: Integer;
  Files: TFileStream;
begin
  Files: = TFileStream.Create (Pchar (edt1.text), fmOpenReadWrite or fmShareDenyNone);
  Files.Read (nCount, SizeOf (Integer));
  for I: = 1 to nCount do
  begin
    Files.Read (Stor, SizeOf (TStorage));
    Files.Seek (I * SizeOf (TStorage), 3);
    mmo1.Lines.Add (IntToStr (Stor.wIndex-1));
  end;
end;

The code above is why the data read when the second parameter of Seek is equal to 0, 1 or 2 is not correct. It is correct when it is equal to 3 or larger numbers. This is not only defined 0, 1 and 2 Are there three methods of operation?

njy7648

Your code is wrong. Seek is not necessary in your code, you don't have to. If you have to write, you also have to do the following:

  for I: = 1 to nCount do
  begin
    Files.Seek (I * SizeOf (TStorage), 0);
    Files.Read (Stor, SizeOf (TStorage));
    mmo1.Lines.Add (IntToStr (Stor.wIndex-1));
  end;

0 starts from the file, 1 starts from the current, and 2 starts from the end of the file.

njy7648

No, I didn't find that your loop variable starts at 1:
  for I: = 0 to nCount-1 do
  begin
    Files.Seek (I * SizeOf (TStorage), 0);
    Files.Read (Stor, SizeOf (TStorage));
    mmo1.Lines.Add (IntToStr (Stor.wIndex-1));
  end;
or:
  for I: = 1 to nCount do
  begin
    Files.Seek ((I-1) * SizeOf (TStorage), 0);
    Files.Read (Stor, SizeOf (TStorage));
    mmo1.Lines.Add (IntToStr (Stor.wIndex-1));
  end;

njy7648

Is it right when it is equal to 3 or more?
======================================================== =========================
This happened to be correct. Because your loop variable starts from 1, and your Seek and Read order is reversed. When the second parameter of the Seek function is> 2, it is automatically corrected to 0, so Seek is exactly equal to the position of the next record. Right.

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njy7648

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