{$I-}
program zdisk;
uses dos,crt,strnglib;
label
  finish;
const
  debug   = false;
  bufsize = 32768;
  smblk   = 512;
  titleline = 2;
  blkszline = 3;
  statsline = 4;
  msgline   = 5;
  finishline= 10;
  version   = '3.1';
type
  strng80 = string[80];
var
  buffer    : array[1..bufsize] of byte;
  file0,
  file1     : file;
  blktitle  : string[20];
  fname     : strng80;
  status    : byte;

  function checkio(errmsg : strng80) : boolean;
  var
    iores : integer;
  begin { checkio }
    iores := ioresult;
    if iores <> 0
      then begin
        writeln('IO Err # ',iores,'. ',errmsg);
        checkio := true;
      end
      else begin
        if debug
          then begin
            writeln(errmsg,' -- OK.');
          end;
        checkio := false;
      end;
  end; { checkio }

  function zerofile(var outfile : file; fn : strng80; bufsizeused : word)
    : boolean;
  var
    can,
    done          : boolean;
    blockno       : longint;
    blockswritten : integer;
    ch            : char;
    signature     : strng80;
    i             : integer;
  begin { zerofile }
      gotoxy(1,blkszline);
      clreol;
      writeln('Writing in blocks of ',bufsizeused,' bytes to file ',fn);
      gotoxy(1,statsline);
      clreol;
      write(blktitle);
      zerofile := false; { not cancelled by operator }
      { Create buffer to write to disk }
      signature := 'ZDisk '+ version + ' was here.';
      fillchar(buffer,sizeof(buffer),0);
      for i := 1 to length(signature) do
        buffer[i] := ord(signature[i]);
      { open temporary output file }
      assign(outfile,fn);
      if checkio('assigning '+fn+' to temporary output file.')
        then begin
          zerofile := true;
          exit;
        end;
      rewrite(outfile,bufsizeused);
      if checkio('opening '+fn+'.')
        then begin
          zerofile := true;
          exit;
        end;
      done := false;
      blockno := 0;
      ch := 'N'; { indicate no operator cancel }
      repeat
        blockwrite(outfile,buffer,1,blockswritten);
        blockno := blockno + blockswritten;
        if keypressed
          then begin
            { get rid of key which caused interruption }
            ch := readkey;
            if ch = #0
              then ch := readkey;
            gotoxy(1,msgline);
            clreol;
            write('Cancel ZDisk ? ');
            ch := upcase(readkey);
            write(ch);
            gotoxy(1,msgline);
            clreol;
            done := ch = 'Y';
            if done
              then write('ZDisk cancelled by operator.')
              else begin
                write('Press any key to cancel.');
                ch := 'N';
              end;
            zerofile := done;
          end
          else done := blockswritten = 0;
        gotoxy(1+length(blktitle),statsline);
        write(blockno:7);
      until (done);
      close(outfile);
  end; { zerofile }

begin { zdisk }
  if ParamCount > 0
    then begin
      fname := upcas(trim(Paramstr(1)));
      if fname[1] in ['A'..'Z']
        then fname := fname + ':\$Z$E$R$0.TMP'
        else begin
          writeln('ZDisk Version ',version,
            ' Error -- Illegal Drive Parameter.');
          halt(3);
        end;
    end
    else fname := FExpand('\$Z$E$R$0.TMP');

  blktitle := 'Block No.: ';
  status := 0; { Normal Termination }
  clrscr;
  gotoxy(1,titleline);
  writeln('ZDisk ',version,
          ' -- Overwrite unused sectors with binary zeroes.');
  gotoxy(1,msgline);
  clreol;
  writeln('Press any key to cancel');
  if zerofile(file0,fname,bufsize)
    then begin
      status := 1;
      goto finish;
    end;
  fname[length(fname)-4] := '1';
  if zerofile(file1,fname,smblk)
    then status := 2;
finish:
  gotoxy(1,finishline);
  clreol;
  erase(file0);
  erase(file1);
  halt(status);
end. { zdisk }