;
; DOS "GetDiskFreeSpaceEx" INT $21/$7303 test
; (CL) Copyleft 2008-01-13 Public Domain - ABUSE at YOUR own risk !!!
; http://board.flatassembler.net/topic.php?t=8139
; Compile with FASM
; Results in .COM of 1067 bytes (sorry, not even 1 GibiByte filled  )
;
; Usage:
;
; GDFSEX drive [C] optional "C" will set Carry flag before call
; GDFSEX C:
; GDFSEX C:\ C
;
; !!! 80386 Required !!!
;
; INT $21 / $7303 "GetDiskFreeSpaceEx"
; FreeDOS,EDR-DOS - FAT32 - GET EXTENDED FREE SPACE ON DRIVE
; Call:   AX = $7303
;         DS:DX -> ASCIZ string for drive ("C:\" or "\\SERVER\Share")
;         ES:DI -> buffer for extended free space structure
;         CX = length of buffer for extended free space
; Return: CF clear if successful
;            ES:DI buffer filled
;         CF set on error
;            AX = error code
;
; 00   WORD    (ret) size of returned structure
; 02   WORD    (call) structure version (0)
;              (ret) actual structure version (0)
;
; 04   DWORD   sectors per cluster
; 08   DWORD   bytes per sector
;
; 0C   DWORD   free clusters
; 10   DWORD   total clusters
; 14   DWORD   free sectors phys
; 18   DWORD   total sectors phys
; 1C   DWORD   free clusters "alloc"
; 20   DWORD   total clusters "alloc"
;
; ToDo/Bugs:
; - Remove messy vars from code
; - Decimal > 4 GiB

format binary as "COM"
use16
org $0100

;[8086]
   push  cs
   pop   es

   mov   dx,tx1
   call  ssdxprint  ; Welcome message
   jmp   @f
;----------

tx1: db 3,'DOS "GetDiskFreeSpaceEx" INT $21/$7303 test',3
     db '(CL) 2008-01-13 Public Domain - ABUSE at YOUR own risk !!',3
     db 'Syntax: GDFSEX drive [C]',2

xdrive:  db 8  dup (0)
xbuff:   db 64 dup (0)
xcf:     db 0
xax:     db 0,0
xeax:    db 0,0,0,0

@@:   mov   ah,[$80]
      cmp   ah,3          ; !!! cmd string length + 1
      jb    qq2           ; <3, no drive, default to current, and no "C" flag

      mov   cl,7          ; Max lenght
      mov   si,$82
      mov   di,xdrive
@@:   lodsb               ; Pick
      cmp   al,32
      jbe   qq3           ; End
      stosb
      dec   cl
      jnz   @b            ; Loop until 7 chars or bad char

qq3:  lodsb               ; "C" flag ?
      cmp   al,67
      jne   qq1           ; NO
      inc   byte [xcf]    ; YES
      jmp   short qq1
;--------------------

qq2:  mov  ah,$19         ; DOS 1+ - GET CURRENT DEFAULT DRIVE
      int  $21            ; Return: AL = drive (0 = A: , 1 = B: , etc)
      add  al,65
      mov  ah,58
      mov  [xdrive],ax

qq1:  mov   dx,tx2
      call  ssdxprint
      mov   dx,xdrive
      call  ssdxprint
      mov   al,124
      call  sscharout
      call  sseol
      mov   dx,tx3
      call  ssdxprint
      mov   al,[xcf]
      add   al,48
      call  sscharout
      call  ssdeol
      jmp   @f
;-------------

tx2: db 'Checking drive: |',0
tx3: db 'Calling INT $21 with AX=$7303 and flag(C)=',0

@@:   mov   ax,$7303
      mov   cx,48
      mov   dx,xdrive
      mov   di,xbuff
      mov   bl,[xcf]
      add   bl,255
      int   $21            ; !!! HOT !!!
      mov   bl,0
      adc   bl,0
      mov   [xcf],bl
      mov   [xax],ax
      mov   al,[xbuff]
      cmp   al,49
      jae   qiq3           ; Faulty, we asked for 48 bytes only
      cmp   al,36          ; Minimum
      jae   qiq4           ; Good
qiq3: mov   byte [xbuff],0 ; Bad 

qiq4: mov   dx,tx4
      call  ssdxprint
      mov   al,[xcf]
      add   al,48
      call  sscharout      ; Flag(C)
      call  sseol
      mov   dx,tx5
      call  ssdxprint
      mov   ax,[xax]
      call  sshexd16       ; AX
      mov   dx,tx6
      call  ssdxprint
      cmp   byte [xbuff],0
      jne   @f             ; GOOD
      mov   dx,tx7
      call  ssdxprint
@@:   mov   dx,tx8
      call  ssdxprint
      jmp   @f
;-------------

tx4:  db 'Results:',3
      db 'Flag(C)=',0
tx5:  db 'AX=',0
tx6:  db 3,'Buffer ',0
tx7:  db 'NOT ',0
tx8:  db 'filled',2

@@:   cmp   byte [xcf],0
      je    @f            ; Flag(C)=0

      mov   dx,tx11
      call  ssdxprint     ; Call failed
      jmp   qq5           ; Done
;--------------

@@:   cmp   byte [xbuff],0
      jne   @f            ; GOOD, we had success

      mov   dx,tx10
      call  ssdxprint     ; Unsupported
      jmp   qq5           ; Done
;--------------

@@:   mov   dx,tx12
      call  ssdxprint     ; 9 x desc

;[80386]
      xor   ecx,ecx
@@:   mov   eax,[xbuff+ecx]
      push  ecx
      push  ax
      shr   eax,16
      call  sshexd16
      call  ssapo
      pop   ax
      call  sshex16
      mov   al,32
      call  sscharout
      pop   ecx
      add   ecx,4
      cmp   ecx,36
      jne   @b
      call  ssdeol

      mov   dx,tx9
      call  ssdxprint       ; Free

      mov   eax,[xbuff+4]   ; s/c
      mov   ebx,[xbuff+8]   ; b/s
      mul   ebx
      test  edx,edx
      jz    @f              ; Must be 0, otherwise >= 4 GiB cluster !!! 
      xor   eax,eax
@@:   mov   ebx,[xbuff+$0C] ; Free clusters
      mul   ebx             ; Now we have final result in EDX:EAX
      mov   [xeax],eax      ; Save lower 32 bits it here
      test  edx,edx
      jz    @f              ; < 4 GiB, also dec result 

      mov   ax,dx           ; Would work up to 2^48 bytes = 16 TiB
      call  sshexd16        ; Here we get full result but only in HEX, no dec 
      call  ssapo
      mov   ax,[xeax+2]
      call  sshex16
      call  ssapo
      mov   ax,[xeax]
      call  sshex16
      jmp   qq5            ; Done
;--------------

@@:   mov   ax,[xeax+2]
      call  sshexd16
      call  ssapo
      mov   ax,[xeax]
      call  sshex16
      mov   al,32
      call  sscharout
      mov   eax,[xeax]
      call  ssdec32

qq5:  call  ssdeol
      mov   ax,$4C00
      int   $21
;--------------

tx9:  db 'Free: ',0
tx10: db 'This faulty DOS/DOG seems not to support "GetDiskFreeSpaceEx" ',0
tx11: db 'Call failed, drive does not exist ',0
tx12: db 'ver...size ..sec/clus bytes/sect '
      db 'free.clust total.clus free.sects total.secs free.clust total.clus',1

; SUB Write HEXD16 | input in AX | trashes all | pritns "$" also

sshexd16:
      push  ax
      mov   al,36
      call  sscharout
      pop   ax
      ; pass

; SUB Write HEX16 | input in AX | trashes all

sshex16: mov   cl,4
qq6:     mov   dl,ah       ; DL <- AH
         shl   ax,4
         shr   dl,4
         add   dl,$30
         cmp   dl,$3A
         jb    @f          ; "b" : below unsigned | OK, a number
         add   dl,7
@@:      push  ax
         push  cx
         mov   al,dl
         call  sscharout
         pop   cx
         pop   ax
         dec   cl
         jnz   qq6
         ret
;-----------

ssapo:  mov  al,39
        jmp  short sscharout
;---------------------------

ssdeol: call sseol
; pass 

sseol: mov al,13
       call sscharout
       mov al,10
; pass 

sscharout: push  ax    ; In: AL
           push  bx
           push  dx
           cmp   al,10
           jb    @f    ; Skip crap "characters"
           mov   ah,2
           mov   dl,al
           int   $21
@@:        pop   dx
           pop   bx
           pop   ax
           ret
;-------------

ssdxprint:
         push ax   ; IN: DX ||| ASCIIZ: 0 instead of "$" !!!
         push bx   ; 0:END 1:EOL+END 2:DEOL+END 3:EOL
         push dx

         mov  bx,dx

llprlop:
         mov   al,[bx]
         cmp   al,0
         jz    qq7
         cmp   al,1
         jnz   @f
         call  sseol
         jmp   short qq7
;-----------------------
@@:      cmp   al,2
         jnz   @f
         call  ssdeol
         jmp   short qq7
;-----------------------
@@:      cmp   al,3
         jnz   @f
         call  sseol
         mov   al,0
@@:      call  sscharout
         inc   bx
         jmp   short llprlop
;---------------------------
qq7:     pop  dx
         pop  bx
         pop  ax
         ret
;-----------

; EXDEC.ASM written by MAD for use with the Assembly Tutorial Chapter 4
; Upgraded to 32 bits  In : EAX
; Converts a number in EAX to decimal format and outputs it to the screen

ssdec32:
    mov   cl,0                          ; POP counter - preset to 0
    mov   ebx,10                        ; Divisor: divide by 10
deciloop:
    xor   edx,edx                       ; High 32 bits zero.
    div   ebx                           ; Remainder in EDX, quotient in EAX
    inc   cl                            ; Increase POP counter
    push  dx                            ; And PUSH , no BYTE PUSH exists 
    test  eax,eax                       ; Is quotient zero?
    jnz   deciloop                      ; If not, get one more number

popeloop:
    pop   ax                            ; Get number
    add   al,48                         ; Add ASCII base (48="0")
    call  sscharout
    dec   cx
    jnz   popeloop
    ret
;------

;END.
    

FreeDOS

- Call fails if no slash in drive string: "C:\" works, "C:" fails. EDR-DOS doesn't have this bug.