Subject: CD-ROM device name

85. *****
 Q: How do I get the character device name of the (first) CD-ROM?

 A: First the code for a quick and dirty method to find the
character device name
  function MSCDEXFN : string;
  var s : string;
      f : text;
      i : byte;
      fmSave : byte;
  begin
    mscdexfn := '';                  { To indicate not found }
    fmSave := FileMode;              { Store the original file mode }
    FileMode := 0;                   { Also if read-only }
    Assign (f, 'c:\autoexec.bat');   { Browse the AUTOEXEC.BAT }
    {$I-} Reset (f); {$I+}
    if IOResult <> 0 then exit;      { AUTOEXEC.BAT not found }
    while not eof(f) do begin        { Line by line }
      readln (f, s);
      for i := 1 to Length(s) do s[i] := Upcase(s[i]);
      if Pos('MSCDEX', s) > 0 then begin      { Is this the line }
        if Pos ('REM', s) = 1 then continue;  { Skip rem lines }
        Close (f);
        FileMode := fmSave;          { Restore the original mode }
        i := Pos('/D:', s);          { Look for the switch }
        if i = 0 then exit;          { Nah! }
        i := i + 3;                  { Where the name should start }
        if i > Length(s) then exit;  { Nothing there! }
        s := Copy (s, i, 255);       { Rest of the line after /D: }
        mscdexfn := s;
        i := Pos (' ', s);
        if i = 0 then exit;
        mscdexfn := Copy (s, 1, i-1);
        exit;                        { Don't close twice }
      end; {if}
    end; {while}
    Close (f);
    FileMode := fmSave;              { Restore the original mode }
  end; (* mscdexfn *)

 A2: There is more general and orthodox solution to finding the
character device name for the (first)m CD-ROM. This was kindly
provided to me by Chris Rankin (rankin@shfax1.shef.ac.uk).
  uses Dos;
  function GetCDROMDevice : string;
  const driver_name_len = 8;
  type
    sig     = array[1..6] of char;
    siglet  = array[1..4] of char;
    signum  = array[1..2] of char;
    drvname = array[1..driver_name_len] of char;
    driverstr = string[driver_name_len];
  type
    PCDROMDriver = ^TCDROMDriver;
    TCDROMDriver = record
                     NextDriver:         PCDROMDriver;
                     DeviceAttr:         word;
                     StrategyEntryPoint: word;
                     INTEntryPoint:      word;
                     DeviceName:         drvname;
                     Reserved:           word;
                     DriveLetter:        byte;
                     Units:              byte;
                   case byte of
                     0: (SigLetters:     siglet;
                         SigNumbers:     signum);
                     1: (Signature:      sig)
                   end;
    TDriveEntry = record
                    SubUnit: byte;
                    Driver:  PCDROMDriver
                  end;
  var
    DeviceList: array[1..26] of TDriveEntry;
    Regs:       registers;
    Name:       driverstr;
  begin
    with Regs do
      begin
        ax := $1500;
        bx := 0;
        intr($2f,Regs);      (* Ask for number of CD-ROM drives. *)
        if bx = 0 then       (* If none, then exit.              *)
          begin
            Name[0] := #0;
            GetCDROMDevice := Name;
            exit
          end;
        ax := $1501;           (* Put information about each CD-ROM *)
        es := seg(DeviceList); (*  into DeviceList[].               *)
        bx := ofs(DeviceList);
        intr($2f,Regs)
      end;  (* Below: Name of first CD-ROM driver *)
    Name := DeviceList[1].Driver^.DeviceName;
    while Name[length(Name)] = ' ' do  (* Strip off trailing blanks.. *)
      dec(Name[0]);
    GetCDROMDevice := Name
  end;
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