' ===========================================================================
'                   Source code: PowerBASIC for DOS
'
'           Author: Egbert Zijlema (e.zylema@castel.nl)
' Copyright status: Public Domain
'
' Runs SCANDISK.EXE every month to test your hard disk's integrity.

' How to install:
' 1. Compile it in line with the power of your CPU
' 2. Copy DISKSCAN.EXE to a path-directory (e.g. C:\DOS or C:\)
' 3. Add the following command to your AUTOEXEC.BAT file: diskscan

' What it does:
' On every startup DISKSCAN will check when it has been accessed for the
' last time. When this was (more than) 30 days ago, it will propose you
' to run DOS' SCANDISK (ENTER = yes, Esc = no). DISKSCAN modifies its
' own date stamp (to-day's date = DATE$) for a next 30-days period.

' Related article at: http://www.basicguru.com/zijlema/
' ===========================================================================

$INCLUDE "STAMPINC.TXT"

FUNCTION MySelf AS STRING

  ' This function returns name and location (= full pathname) of the
  ' active executable file. (Note: in the IDE this is PB.EXE, so compile
  ' it before running it). For the sake of a clear explanation I wrote
  ' this function in plain BASIC. An ASM-version (faster!) can be
  ' obtained from Thomas Gohel's Website at:
  '          "www.snafu.de/~pbsound/english/index.html" .

  ' DOS saves the program's environment in the environment block. The
  ' memory location of this block is stored in the Program Segment
  ' Prefix (or PSP). Let's find this first:

  REG 1, &H6200                           ' service in AX-register
  CALL INTERRUPT &H21
  PSP = REG(2)                            ' result in BX-register

  ' The segment address of the environment block itself is stored in
  ' offset 2D hex (high) and 2C hex (low) of the PSP

  DEF SEG = PSP                           ' load PSP
  blok = PEEK(&H2D) * 256 + PEEK(&H2C)    ' retrieve block segment address
  DEF SEG = blok                          ' now load block segment

  ' The environment block has 2 parts. The first contains information
  ' set by CONFIG.SYS/AUTOEXEC.BAT. We don't need that here.
  ' Fortunately the 2 'halfs' of the block are separated by
  ' 4 bytes, the first 2 being zero. So we simply skip the first
  ' half by reading it until we find 2 zero bytes on a row.
  ' Note: 1 INTEGER has a length of 2 bytes. So, we use PEEKI.

  offset = 0                              ' first offset of the segment
  DO
    INCR offset                           ' next offset
  LOOP UNTIL PEEKI(offset) = 0            ' 2 zeros on a row

  INCR offset, 4                          ' skip 4 separating bytes
  DO
    temp$ = temp$ + CHR$(PEEK(offset))    ' character reading
    INCR offset
  LOOP UNTIL PEEK(offset) = 0             ' until end of ASCIIZ-string
  DEF SEG                                 ' restore default segment
  FUNCTION = temp$
END FUNCTION

FUNCTION GetKey AS INTEGER
  DO
  LOOP UNTIL INSTAT
  FUNCTION = CVI(INKEY$ + CHR$(0))
END FUNCTION

' MAIN
  FileName$ = MySelf                          ' pathname of running file
  MakeStampsAvailable FileName$
  dStamp?? = REG(4)                           ' date stamp
  IF DateToStamp(DATE$) - dStamp?? => 32 THEN ' accessed it (more than)
                                              '    1 month ago?
    AttachStamps FileName$, _
                 TimeToStamp(TIME$), _
                 DateToStamp(DATE$)           ' then modify stamp ....

    ' .... and propose to run SCANDISK:

    COLOR 7, 0
    CLS
    LOCATE 2, 2
    PRINT "It's a month (or more) ago that the integrity of your"
    LOCATE 3, 2
    PRINT "computer's hard disk has been tested by SCANDISK"
    LOCATE 5, 2
    PRINT "Press         to run SCANDISK"
    LOCATE 6, 2
    PRINT "Press       to skip this monthly procedure"
    COLOR 15
    LOCATE 5, 8 : PRINT "[ENTER]"
    LOCATE 6, 8 : PRINT "[ESC]"
    COLOR 7
    DO
      KeyIn = GetKey
      SELECT CASE KeyIn
        CASE 27 : EXIT LOOP                   ' Esc pressed, don't run
        CASE 13 : EXECUTE "scandisk"          ' doit

        ' note:
        ' when your (older) DOS-version does not support SCANDISK
        ' then modify the above line as: EXECUTE "chkdsk /f"

      END SELECT
    LOOP
  END IF
END