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#### BP compatibility: Dos

The following listing contains the interface of the Dos unit.

This is a portable implementation of most routines from BP's `Dos` unit. A few routines that are Dos - or even IA32 real mode - specific, are only available if `__BP_UNPORTABLE_ROUTINES__` is defined, BP Incompatibilities.

The same functionality and much more is available in the Run Time System, Run Time System. In some cases, the RTS routines have the same interface as the routines in this unit (e.g. `GetEnv`, `FSplit`, `FExpand`, `FSearch`), in other cases, they have different names and/or easier and less limiting interfaces (e.g. `ReadDir` etc. vs. `FindFirst` etc.), and are often more efficient.

Therefore, using this unit is not recommended in newly written programs.

    { Portable BP compatible Dos unit

      This unit supports most of the routines and declarations of BP's
      Dos unit.

      Notes:

      - The procedures Keep, GetIntVec, SetIntVec are not supported
        since they make only sense for Dos real-mode programs (and GPC
        compiled programs do not run in real-mode, even on IA32 under
        Dos). The procedures Intr and MsDos are only supported under
        DJGPP if __BP_UNPORTABLE_ROUTINES__ is defined (with the
        -D__BP_UNPORTABLE_ROUTINES__ option). A few other routines are
        also only supported with this define, but on all platforms (but
        they are crude hacks, that's why they are not supported without
        this define).

      - The internal structure of file variables (FileRec and TextRec)
        is different in GPC. However, as far as TFDDs are concerned,
        there are other ways to achieve the same in GPC, see the GPC
        unit.

      Copyright (C) 1998-2003 Free Software Foundation, Inc.

      Authors: Frank Heckenbach <frank@pascal.gnu.de>
               Prof. Abimbola A. Olowofoyeku <African_Chief@bigfoot.com>

      This file is part of GNU Pascal.

      GNU Pascal is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published
      by the Free Software Foundation; either version 2, or (at your
      option) any later version.

      GNU Pascal is distributed in the hope that it will be useful, but
      WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
      General Public License for more details.

      You should have received a copy of the GNU General Public License
      along with GNU Pascal; see the file COPYING. If not, write to the
      Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
      02111-1307, USA.

      As a special exception, if you link this file with files compiled
      with a GNU compiler to produce an executable, this does not cause
      the resulting executable to be covered by the GNU General Public
      License. This exception does not however invalidate any other
      reasons why the executable file might be covered by the GNU
      General Public License. }

    {$gnu-pascal,I-}
    {$if __GPC_RELEASE__ < 20030412}
    {$error This unit requires GPC release 20030412 or newer.}
    {$endif}

    module Dos;

    { GPC and this unit use AnyFile for different meanings. Export
      renaming helps us to avoid a conflict here. If you use both units,
      the meaning of the latter one will be effective, but you always
      get the built-in meaning by using GPC_AnyFile. }
    export Dos = all (DosAnyFile => AnyFile, FSearch, FExpand, FSplit,
      GetEnv);

    import GPC; System;

    type
      GPC_AnyFile = AnyFile;
      Byte8 = Cardinal attribute (Size = 8);
      Word16 = Cardinal attribute (Size = 16);
      Word32 = Cardinal attribute (Size = 32);
      TDosAttr = Word;

    const
      { File attribute constants }
      ReadOnly   = $01;
      Hidden     = $02;  { set for dot files except '.' and '..' }
      SysFile    = $04;  { not supported }
      VolumeID   = $08;  { not supported }
      Directory  = $10;
      Archive    = $20;  { means: not executable }
      DosAnyFile = $3f;

      { Flag bit masks -- only used by the unportable Dos routines }
      FCarry     = 1;
      FParity    = 4;
      FAuxiliary = $10;
      FZero      = $40;
      FSign      = $80;
      FOverflow  = $800;

      { DosError codes }
      DosError_FileNotFound = 2;
      DosError_PathNotFound = 3;
      DosError_AccessDenied = 5;
      DosError_InvalidMem   = 9;
      DosErorr_InvalidEnv   = 10;
      DosError_NoMoreFiles  = 18;
      DosError_IOError      = 29;
      DosError_ReadFault    = 30;

    type
      { String types. Not used in this unit, but declared for
        compatibility. }
      ComStr  = String [127];  { Command line string }
      PathStr = String [79];   { File pathname string }
      DirStr  = String [67];   { Drive and directory string }
      NameStr = String [8];    { File name string }
      ExtStr  = String [4];    { File extension string }

      TextBuf = array [0 .. 127] of Char;

      { Search record used by FindFirst and FindNext }
      SearchRecFill = packed array [1 .. 21] of Byte8;
      SearchRec = record
        Fill: SearchRecFill;
        Attr: Byte8;
        Time,
        Size: LongInt;
        Name: {$ifdef __BP_TYPE_SIZES__}
              String [12]
              {$else}
              TString
              {$endif}
      end;

      { Date and time record used by PackTime and UnpackTime }
      DateTime = record
        Year, Month, Day, Hour, Min, Sec: Word
      end;

      { 8086 CPU registers -- only used by the unportable Dos routines }
      Registers = record
      case Boolean of
        False: (ax, bx, cx, dx, bp, si, di, ds, es, Flags: Word16);
        True : (al, ah, bl, bh, cl, ch, dl, dh: Byte8)
      end;

    var
      { Error status variable }
      DosError: Integer = 0;

    procedure GetDate (var Year, Month, Day, DayOfWeek: Word); attribute
      (name = '_p_GetDate');
    procedure GetTime (var Hour, Minute, Second, Sec100: Word);
      attribute (name = '_p_GetTime');
    procedure GetCBreak (var BreakOn: Boolean); attribute (name
      = '_p_GetCBreak');
    procedure SetCBreak (BreakOn: Boolean); attribute (name
      = '_p_SetCBreak');
    { GetVerify and SetVerify are dummies except for DJGPP (in the
      assumption that any real OS knows by itself when and how to verify
      its disks). }
    procedure GetVerify (var VerifyOn: Boolean); attribute (name
      = '_p_GetVerify');
    procedure SetVerify (VerifyOn: Boolean); attribute (name
      = '_p_SetVerify');
    function  DiskFree (Drive: Byte): LongInt; attribute (name
      = '_p_DiskFree');
    function  DiskSize (Drive: Byte): LongInt; attribute (name
      = '_p_DiskSize');
    procedure GetFAttr (var f: GPC_AnyFile; var Attr: TDosAttr);
      attribute (name = '_p_GetFAttr');
    procedure SetFAttr (var f: GPC_AnyFile; Attr: TDosAttr); attribute
      (name = '_p_SetFAttr');
    procedure GetFTime (var f: GPC_AnyFile; var MTime: LongInt);
      attribute (name = '_p_GetFTime');
    procedure SetFTime (var f: GPC_AnyFile; MTime: LongInt); attribute
      (name = '_p_SetFTime');

    { FindFirst and FindNext are quite inefficient since they emulate
      all the brain-dead Dos stuff. If at all possible, the standard
      routines OpenDir, ReadDir and CloseDir (in the GPC unit) should be
      used instead. }
    procedure FindFirst (const Path: String; Attr: TDosAttr; var SR:
      SearchRec); attribute (name = '_p_FindFirst');
    procedure FindNext  (var SR: SearchRec); attribute (name
      = '_p_FindNext');

    procedure FindClose (var SR: SearchRec); attribute (name
      = '_p_FindClose');
    procedure UnpackTime (p: LongInt; var t: DateTime); attribute (name
      = '_p_UnpackTime');
    procedure PackTime (const t: DateTime; var p: LongInt); attribute
      (name = '_p_PackTime');
    function  EnvCount: Integer;
    function  EnvStr (EnvIndex: Integer): TString;
    procedure SwapVectors;
    { Exec executes a process via Execute, so RestoreTerminal is called
      with the argument True before and False after executing the
      process. }
    procedure Exec (const Path, Params: String);
    function  DosExitCode: Word;

    { Unportable Dos-only routines and declarations }

    {$ifdef __BP_UNPORTABLE_ROUTINES__}
    {$ifdef __GO32__}
    { These are unportable Dos-only declarations and routines, since
      interrupts are Dos and CPU specific (and have no place in a
      high-level program, anyway). }
    procedure Intr (IntNo: Byte; var Regs: Registers); attribute (name
      = '_p_Intr');
    procedure MsDos (var Regs: Registers); attribute (name
      = '_p_MsDos');
    {$endif}

    { Though probably all non-Dos systems have versions numbers as well,
      returning them here would usually not do what is expected, e.g.
      testing if certain Dos features are present by comparing the
      version number. Therefore, this routine always returns 7 (i.e.,
      version 7.0) on non-Dos systems, in the assumption that any real
      OS has at least the features of Dos 7. }
    function  DosVersion: Word; attribute (name = '_p_DosVersion');

    { Changing the system date and time is a system administration task,
      not allowed to a normal process. On non-Dos systems, these
      routines emulate the changed date/time, but only for GetTime and
      GetDate (not the RTS date/time routines), and only for this
      process, not for child processes or even the parent process or
      system-wide. }
    procedure SetDate (Year, Month, Day: Word); attribute (name
      = '_p_SetDate');
    procedure SetTime (Hour, Minute, Second, Sec100: Word); attribute
      (name = '_p_SetTime');
    {$endif}