Category : C++ Source Code
Archive   : VCCRT2.ZIP
Filename : DISKFREE.ASM

page ,132
title getdiskfree - contains the _dos_getdiskfree() function
;***
;diskfree.asm - contains _dos_getdiskfree()
;
; Copyright (c) 1987-1992, Microsoft Corporation. All rights reserved.
;
;Purpose:
; This module contains the _dos_getdiskfree() function.
;
;*******************************************************************************

include version.inc
.xlist
include cmacros.inc
include msdos.inc
include errno.inc
.list

diskfree_t struc
total_clusters dw ?
avail_clusters dw ?
sectors_cluster dw ?
bytes_sector dw ?
diskfree_t ends

extrn __dosreturn:near

sBegin data
externW errno
sEnd

sBegin code

assumes cs,code
assumes ds,data

page
;***
;int _dos_getdiskfree(drive, p_diskspace) - return free space on disk drive
;
;Purpose:
; The function "_dos_getdiskfree" allows the user to determine
; the number of available clusters on a given disk drive, as well
; as the total number of clusters, the cluster size (in sectors)
; and the sector size (in bytes).
;
;Entry:
; unsigned drive; drive to be described (0=default, 1=A:, 2=B:,...)
; struct diskfree_t {
; unsigned total_clusters;
; unsigned avail_clusters;
; unsigned sectors_per_clusters;
; unsigned bytes_per_sector;
; } *p_diskspace; address of structure to store information
;
;Exit:
; AX = 0 if successful
; else AX = -1 and errno = EINVAL if the "drive" parameter was invalid
;
;Uses:
;
;Exceptions:
;
;*******************************************************************************

cProc _dos_getdiskfree,,<>

parmB _drive ; drive to be described
parmDP _p_diskspace ; address of structure to store information

cBegin
mov dl,(_drive)
callos getdskspc ; get free space on the specified drive
cmp ax,-1
jne drive_okay ; AX == -1 means error
;
; Bad Drive - return AX=-1 after setting errno=EINVAL
;
mov [errno],EINVAL
jmp short done ; AX = -1
;
; Valid Drive -- store information
;
drive_okay:
push si ; preserve register
if sizeD
push ds ; preserve register
lds si,(_p_diskspace)
else
mov si,(_p_diskspace)
endif
mov [si.sectors_cluster],ax
mov [si.avail_clusters],bx
mov [si.bytes_sector],cx
mov [si.total_clusters],dx
if sizeD
pop ds ; restore register
endif
pop si ; restore register
xor ax,ax ; return 0 for success
done:

ifdef _WINDOWS
cEnd
else
pop bp
ret
cEnd
endif


sEnd

end