pfales@ttrde.UUCP (Peter Fales) (01/09/89)
Someone was asking how to find out how much space is available on
a drive, when that drive has been JOINed to another directory. At least
one solution has been posted, but I think the following method is much
simpler, even though it also depends on an undocumented DOS function.
(This is function is documented in Ralf Brown's interrupt list, an
excellent reference, which has been posted to the net).
------------------------------ cut here -------------------------------------
/****************************************************************************
FUNCTION: DiskFreeSpace
PURPOSE: Returns number of free bytes on selected disk. Argument
is a path to a file or directory on the selected disk. If the
file is actually on a JOINed drive, the amount of free space
on the joined drive will be returned.
****************************************************************************/
#include <dos.h>
long
DiskFreeSpace(char *path)
{
union REGS r;
struct SREGS s;
char buffer[80];
/* Use the undocumented DOS function 0x60 to map a relative path to a fully
qualified path name. Then use the first character of that pathname to
determine the drive to which that path belongs. The key thing here is
that it works even if the path is on another drive that has been JOINed */
r.x.ax = 0x6000;
r.x.si = (unsigned)path; /* ds:si is input path */
segread(&s);
r.x.di = (unsigned)buffer; /* es:di is output path */
s.es = s.ds;
intdosx(&r,&r,&s);
/* The first character of the returned path is the drive name, so we
use function 0x36 to read the free space */
r.x.ax = 0x3600;
r.x.dx = buffer[0]-'A'+1;
intdos(&r,&r);
/* Returns: Sectors/cluster in ax
Bytes/sector in cx
Available clusters in bx
*/
return((long)r.x.bx * r.x.cx * r.x.ax);
}
--
Peter Fales AT&T, Room 2F-217
200 Park Plaza
UUCP: ...att!ttrde!pfales Naperville, IL 60566
Domain: pfales@ttrde.att.com work: (312) 416-5357 Ralf.Brown@B.GP.CS.CMU.EDU (01/10/89)
In article <812@ttrde.UUCP>, pfales@ttrde.UUCP (Peter Fales) writes: }/* Use the undocumented DOS function 0x60 to map a relative path to a fully }qualified path name. Then use the first character of that pathname to }determine the drive to which that path belongs. The key thing here is }that it works even if the path is on another drive that has been JOINed */ I also tried it on a SUBSTed path, and that worked the same way. Just a drive letter did strange things, though (looks like the DOS function doesn't put anything into the result buffer). INT 21 - DOS 3+ internal - RESOLVE PATH STRING TO FULLY QUALIFIED PATH STRING AH = 60h DS:SI -> ASCIZ relative path string ES:DI -> 67???-byte buffer for ASCIZ fully qualified name Return: buffer filled with qualified name of form D:\PATH may return error code, unknown. Note: if path string is on a JOINed drive, the returned name is the one that would be needed if the drive were not JOINed; similarly for a SUBSTed drive letter. Because of this, it is possible to get a qualified name that is not legal with the current combination of SUBSTs and JOINs -- UUCP: {ucbvax,harvard}!cs.cmu.edu!ralf -=-=-=- Voice: (412) 268-3053 (school) ARPA: ralf@cs.cmu.edu BIT: ralf%cs.cmu.edu@CMUCCVMA FIDO: Ralf Brown 1:129/31 Disclaimer? I claimed something? You cannot achieve the impossible without attempting the absurd.