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From: Kai_Henningsen@ms.maus.de (Kai Henningsen)
Newsgroups: comp.lang.pascal
Subject: Re: how can I readout my FAT?
Message-ID: <14186@ms.maus.de>
Date: 27 Apr 91 11:52:00 GMT
Distribution: world,comp
Organization: Maus Mailbox Netz - UUCP-Gateway Bremen
Lines: 164


Stefan Focke focke @ gmdzi.gmd.de schrieb am 22.04.1991, 08:33

SF>Hello,
SF>
SF>it is not too hard to do that:
SF>
SF>- Read the boot-sektor to find out where your directory and FAT is
SF>- From the directory you get the first cluster of your file
SF>- Than you have to follow the FAT to find all clusters of your file
SF>- You have to find out if you have a 12-bit or a 16-Bit FAT (DOS 4.x)
SF>  I do not know where you can find this information. Who can help?

Well, looks like it's time to post a program I wrote. The purpose is to set the
date of every directory on a disk to that of the youngest file within. Be
warned that, while the program runs without a problem on *my* harddisk (DOS 4),
I do not make any claims that the same will be true elsewhere - the risk is
yours, completely; I wrote this only for myself. You better make a backup
first!!

Also, the code is for TP 6.0, I use the inline assembler. As for comments, well
... Pascal is supposed to be selfdocumenting, no? But ask me if you don't
understand something ...

So, first a support unit   ...

unit DosAbsUt;
interface
uses Dos;
type
  BootRec = record
              jmp: array[1..3] of byte;
              OEM: array[1..8] of char;
              bps: word;
              spc: byte;
              res: word;
              nFAT: byte;
              RootSz: word;
              Size: word;
              Media: byte;
              spFAT: word;
              spt: word;
              nHeads: word;
              res40: longint;
              Size40: longint;
              Phys: byte;
              nix: byte;
              Sig: byte; { $29 }
              ID: longint;
              Volume: array [1..11] of char;
              nix2: array[1..8] of char;
            end;
function AbsRead(Drive: byte; nSecs: word; Start: longint; var Buffer): word;
function AbsWrite(Drive: byte; nSecs: word; Start: longint; var Buffer): word;
function SecSize(Drive: byte): word;
procedure ResetDisk;
implementation
var
  r: registers;
  Dos4Abs : record
              First: longint;
              Count: word;
              Buf: pointer;
            end;
function AbsRead(Drive: byte; nSecs: word; Start: longint; var Buffer): word;
begin
  if lo(dosversion)<4 then begin
    asm {[f-]}
      mov        al, [Drive];
      mov        cx, [nSecs];
      mov        dx, word ptr [Start];
      push        ds;
      lds        bx, [Buffer];
      int        $25;
      jc        @Err;
      xor        ax, ax;
@Err:
      popf;
      pop        ds;
      mov        [@Result], ax
    end {[f+]};
  end
  else begin
    with Dos4Abs do begin
      First:=Start;
      Count:=nSecs;
      Buf:=@Buffer;
    end;
    asm {[f-]}
      mov        al, [Drive];
      mov        cx, -1;
      push        ds;
      mov        bx, seg Dos4Abs;
      mov        ds, bx;
      mov        bx, offset Dos4Abs;
      int        $25;
      jc        @Err;
      xor        ax, ax;
@Err:
      popf;
      pop        ds;
      mov        [@Result], ax
    end {[f+]};
  end;
end;
function AbsWrite(Drive: byte; nSecs: word; Start: longint; var Buffer): word;
begin
  if lo(dosversion)<4 then begin
    asm {[f-]}
      mov        al, [Drive];
      mov        cx, [nSecs];
      mov        dx, word ptr [Start];
      push        ds;
      lds        bx, [Buffer];
      int        $26;
      jc        @Err;
      xor        ax, ax;
@Err:
      popf;
      pop        ds;
      mov        [@Result], ax
    end {[f+]};
  end
  else begin
    with Dos4Abs do begin
      First:=Start;
      Count:=nSecs;
      Buf:=@Buffer;
    end;
    asm {[f-]}
      mov        al, [Drive];
      mov        cx, -1;
      push        ds;
      mov        bx, seg Dos4Abs;
      mov        ds, bx;
      mov        bx, offset Dos4Abs;
      int        $26;
      jc        @Err;
      xor        ax, ax;
@Err:
      popf;
      pop        ds;
      mov        [@Result], ax
    end {[f+]};
  end;
end;
function SecSize(Drive: byte): word;
begin
  with r do begin
    ah:=$1c;
    dl:=drive+1;
    msdos(r);
    secsize:=cx;
  end;
end;
procedure ResetDisk;
begin
  r.ah:=$0d;
  msdos(r);
end;

end.

MfG Kai