DrvQElPtr
#include <Files.h>
typedef struct { Size Offset Description
struct QElem * qLink; 4 0 Address of next queue element (0=last)
short qType; 2 4 0=dQDrvSz is drive size, 1=very
large
short dQDrive; 2 6 Drive number
short dQRefNum; 2 8 Driver reference number
short dQFSID; 2 10 File-system identifier (0=native,
else=other)
short dQDrvSz; 2 12 Blocks on disk (total bytes or
low-word)
short dQDrvSz2; 2 14 Hi word of disk block count (if
qType=1)
typedef DrvQEl *DrvQElPtr;
Notes: The meaning of the qType field has been corrupted. If HFS is present, then
this field indicates how to calculate the size of the drive. It is one of:
0 The drive contains dQDrvSz blocks (probably 512-bytes each)
1 The drive contains dQDrvSz +( dQDrvSz * 0x10000 ) blocks
3 MFS is probably present and dQDrvSz is the total blocks
Preceding this structure in memory is a 4-byte set of flags, defined as
follows:
Offset Description
-4 (bit 7 set) = disk is locked ( write-protected)
-3 0 no disk in drive
1 or 2 disk is in drive
8 non-ejectable disk
FCh...FFh disk was ejected within last 1.5 seconds
48h non-ejectable disk, but driver expects a call (?)
-2 (used internally during system startup)
-1 (bit 7 clear) drive supports only single-sided media
See GetDrvQHdr for an example of how to access these prefix bytes and how to calculate the true size of the drive.
The global variable DrvQHdr contains the queue header which begins the
chain of drive queue elements. Or call GetDrvQHdr to obtain that address. dQDrvSz2 is only used if qType is 1. In this case, dQDrvSz2 contains the
high-order word of the size, and dQDrvSz contains the low-order word.