Computer Select (Limited Edition)/Computer Select.iso/pcmag/v10n15/pcmfat.pas

Pascal/Delphi Source File | 1991-08-25 | 5.7 KB | 173 lines

PROGRAM pcmfat;
{*******************************************************************************
*                                                                              *
*              PCMFAT 1.1 Copyright (c) 1991 Barry Simon                       *
*                        all rights reserved                                   *
*                                                                              *
*          First Published in PC Magazine, September 10, 1991                  *
*                                                                              *
*  Requires Turbo Pascal 6.0 to compile (because of use of inline assembler)   *
*                                                                              *
*******************************************************************************}
  {$A-}
  {the directive $A- needed StartCluster to line up}
USES DOS, common;

VAR
  dta : RECORD
          rawdrive : Byte;
          unused : ARRAY[0..25] OF Byte; {standard DTA starts at 0}
          StartCluster : Word;    {to work require $A- directive!}
          FSize : LongInt;
        END;
  FCluster : LongInt;
  infcb : ARRAY[0..36] OF Byte;
  regs : registers;
  s : STRING;
  fname : STRING[8];
  fext : STRING[3];
  i, j : Byte;
  NumFATSec, FirstFATSec, InMemSec, CurrentSec, NumCluster : Word;
  CurrentCluster, PriorCluster, RecSec, RecOff : Word;
  RecShift : Boolean;             {determines if first byte is offset in 3 nibble fat}
  separator : Char;
  NumFrag : Byte;

  PROCEDURE SyntaxError;
  BEGIN
    WriteLn('  Proper syntax is:');
    WriteLn('      PCMFAT <filename>');
    WriteLn('  where <filename> is in the default drive and directory.');
    Halt;
  END;

  FUNCTION GetRec : Word;
  BEGIN
    IF Use3NibbleFAT THEN BEGIN
      IF RecShift THEN
        GetRec := (Word(Sector[RecOff]) DIV 16)+16*Word(Sector[RecOff+1])
      ELSE
        GetRec := Word(Sector[RecOff])+256*(Word(Sector[RecOff+1]) MOD 16);
    END ELSE
      GetRec := Word(Sector[RecOff])+256*Word(Sector[RecOff+1]);
  END;

  PROCEDURE GetLoc;
  BEGIN
    IF Use3NibbleFAT THEN BEGIN
      RecSec := 3*(CurrentCluster DIV 1024)+FirstFATSec;
      IF RecSec > NumFATSec THEN BEGIN
        WriteLn;
        WriteLn('FAT error.  Please run chkdsk **without** /f. Program Halted.');
        Halt;
      END;
      RecOff := ((3*(CurrentCluster MOD 1024)) DIV 2);
      IF ((RecOff MOD 3) = 0) THEN RecShift := False ELSE RecShift := True;
    END ELSE BEGIN
      RecSec := Hi(CurrentCluster)+FirstFATSec;
      IF RecSec > NumFATSec THEN BEGIN
        WriteLn;
        WriteLn('FAT error.  Please run chkdsk **without** /f. Program Halted.');
        Halt;
      END;
      RecOff := 2*Lo(CurrentCluster);
    END;
  END;

  PROCEDURE GetSector;
  BEGIN
    CurrentSec := RecSec;
    IF NOT(CurrentSec = InMemSec) THEN BEGIN
      ReadSector(CurrentSec);
      InMemSec := CurrentSec;
    END;
  END;

BEGIN
  WriteLn('PC Magazine''s FAT Reader');
  WriteLn('  copyright, Barrry Simon 1991');
  IF ParamCount = 0 THEN SyntaxError;
  s := ParamStr(1);
  IF (pos('\', s)+pos(':', s)) > 0 THEN SyntaxError;
  i := pos('.', s);
  IF i = 0 THEN BEGIN
    s := s+'.';
    i := Length(s);
  END;
  IF i > 9 THEN SyntaxError;
  fname := Copy(s, 1, i-1);
  Delete(s, 1, i);
  IF Length(s) > 3 THEN SyntaxError;
  fext := s;
  FOR j := 1 TO Length(fname) DO fname[j] := Upcase(fname[j]);
  FOR j := 1 TO Length(fext) DO fext[j] := Upcase(fext[j]);
  s := fname+'.'+fext;
  FOR j := 1 TO (8-Length(fname)) DO fname := fname+' ';
  FOR j := 1 TO (3-Length(fext)) DO fext := fext+' ';
  FOR i := 1 TO 8 DO infcb[i] := Ord(fname[i]);
  FOR i := 9 TO 11 DO infcb[i] := Ord(fext[i-8]);
  infcb[0] := 0;                  {default drive}
  WITH regs DO BEGIN
    ah := $1A;                    {set DTA}
    ds := Seg(dta);
    dx := Ofs(dta);
    msdos(regs);
    ah := $11;
    dx := Ofs(infcb);
    ds := Seg(infcb);
    msdos(regs);
    IF al <> 0 THEN BEGIN
      WriteLn('  ', s, ' not found');
      SyntaxError;
    END;
  END;
  DriveNum := dta.rawdrive-1;     {int 25 and service 11 differ on A=0 or 1, etc}
  ReadSector(0);
  IF (BootSector.BytesPerSector <> 512) THEN BEGIN
    WriteLn('  The sector size isn''t 512 bytes; program halted.');
    Halt;
  END;
  FCluster := ((dta.FSize-1) DIV (512*BootSector.SectorsPerCluster))+1;
  WriteLn('  The file ', s, ' has ', FCluster, ' clusters');
  WriteLn('   Starting Cluster is ',
          HexWord(dta.StartCluster), ' Hex (= ', dta.StartCluster, ' decimal)');
     {For display purposes, limit to files with no more than 256 clusters -
       that's 512K on a typical hard disk}
  IF (FCluster > 256) THEN BEGIN
    WriteLn('   This program will only report detailed allotment');
    WriteLn('       for files with fewer than 256 clusters.  Program halted.');
    Halt;
  END;
  FirstFATSec := BootSector.SectorsBeforeData;
  NumFATSec := BootSector.NumSecPerFAT;
  asm
    mov ah, $1B
    push ds
    Int $21
    pop ds
    mov NumCluster, dx
  END;
  Use3NibbleFAT := (NumCluster < 4097);
    {Should read Partition table for totally accurate call}
  CurrentCluster := dta.StartCluster;
  InMemSec := 0;
  NumFrag := 1;
  Writeln ('   The files occupies clusters (* indicates fragments):' );
  Write (' ' , HexWord(CurrentCluster));
  for i := 2 to FCluster do begin
  GetLoc;
  GetSector;
  PriorCluster := CurrentCluster;
  CurrentCluster := GetRec;
  If (CurrentCluster = (PriorCluster + 1)) then separator := ' ' else begin
  separator := '*';
  inc (NumFrag);
  end;
  Write (separator,HexWord (CurrentCluster));
  end;
  Writeln;
  Writeln;
  Writeln ('The file has ',NumFrag ,' fragments.');
end.