Source code of Windows XP (NT5)
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/* demgset.c - Drive related SVC hanlers.
*
* demSetDefaultDrive
* demGetBootDrive
* demGetDriveFreeSpace
* demGetDrives
* demGSetMediaID
* demQueryDate
* demQueryTime
* demSetDate
* demSetTime
* demSetDTALocation
* demGSetMediaID
* demGetDPB
* Modification History:
*
* Sudeepb 02-Apr-1991 Created
*
*/
#include "dem.h"
#include "demmsg.h"
#include <softpc.h>
#include <mvdm.h>
#include <winbase.h>
#include "demdasd.h"
#define BOOTDRIVE_PATH "Software\\Microsoft\\Windows\\CurrentVersion\\Setup"
#define BOOTDRIVE_VALUE "BootDir"
#define SUCCESS 0
#define NODISK 1
#define FAILURE 2
BYTE demGetDpbI(BYTE Drive, DPB UNALIGNED *pDpb);
UCHAR PhysicalDriveTypes[26]={0};
extern PDOSSF pSFTHead;
USHORT nDrives = 0;
CHAR IsAPresent = TRUE;
CHAR IsBPresent = TRUE;
/* demSetDefaultDrive - Set the default drive
*
*
* Entry -
* Client (DS:SI) Current Directory on that drive
* Client (dl) Zero based DriveNum
*
* Exit - SUCCESS
* Client (CY) = 0
* Current Drive Set
*
* FAILURE
* Client (CY) = 1
* Current Drive Not Set
*
* Notes:
* The DOS keeps a current directory for each of the drives,
* However winnt keeps only one current Drive, Directory per
* process, and it is cmd.exe which associates a current
* directory for each of the drive.
*/
VOID demSetDefaultDrive (VOID)
{
LPSTR lpPath;
lpPath = (LPSTR)GetVDMAddr (getDS(),getSI());
// only in sp4
#ifdef NOVELL_NETWARE_SETERRORMODE
//
// For removable drives check for media\volume info to avoid triggering
// hard errors when no media is present. There exists win32 code
// (e.g novell netware redir vdd) which is known to clobber our error
// mode setting.
//
// 16-Jul-1997 Jonle
//
{
UCHAR DriveType;
CHAR DriveNum;
DriveNum = (CHAR)getDL();
DriveType = demGetPhysicalDriveType(DriveNum);
if (DriveType == DRIVE_REMOVABLE || DriveType == DRIVE_CDROM) {
VOLINFO VolInfo;
//
// if No Media in drive, the drive is still valid,
// but the win32 curdir is still the old one.
//
if (!GetMediaId(DriveNum, &VolInfo)) {
if (GetLastError() == ERROR_INVALID_DRIVE) {
setCF(1);
}
else {
setCF(0);
}
return;
}
}
}
#endif
if (!SetCurrentDirectoryOem(lpPath) && GetLastError() == ERROR_INVALID_DRIVE) {
//
// Only return error if drive was invalid, the DOS doesn't check
// for curdir when changing drives. Note that a number of old dos
// apps will walk all of the drives, and do setdefaultdrive,
// to determine the valid drives letters. The SetCurrentDirectoryOem
// causes ntio to touch the drive and verify that the dir exists.
// This is a significant performance problem for removable media
// and network drives, but we have no choice since locking the
// current dir for this drive is mandatory for winnt.
//
setCF(1);
}
else {
setCF(0);
}
return;
}
/* demGetBootDrive - Get the boot drive
*
*
* Entry - None
*
* Exit - CLIENT (AL) has 1 base boot drive (i.e. C=3)
*
* We try to read the registry value that indicates the real boot drive. This
* should be the location of autoexec.bat, etc. If we can't find the key,
* or if the value indicates some drive letter that is not a fixed drive,
* then we use a fallback plan of just saying drive C.
*
*/
VOID demGetBootDrive (VOID)
{
#if defined(NEC_98) // NTBUG #98466
CHAR szBootDir[MAX_PATH];
BYTE Drive = 1; // default it to 'A:'
UINT retCode;
retCode = GetSystemDirectory(szBootDir,MAX_PATH);
if (retCode == 0 || retCode > MAX_PATH){
// error: can't get path
goto DefaultBootDrive;
}
szBootDir[2] = '\\';
szBootDir[3] = '\0';
#else // !NEC_98
HKEY hKey;
DWORD retCode;
DWORD dwType, cbData = MAX_PATH;
CHAR szBootDir[MAX_PATH];
BYTE Drive = 3; // default it to 'C:'
retCode = RegOpenKeyEx (HKEY_LOCAL_MACHINE,
BOOTDRIVE_PATH,
0,
KEY_EXECUTE, // Requesting read access.
&hKey);
if (retCode) {
// error: can't find section
goto DefaultBootDrive;
}
retCode = RegQueryValueEx(hKey,
BOOTDRIVE_VALUE,
NULL,
&dwType,
szBootDir,
&cbData);
RegCloseKey(hKey);
if (retCode) {
// error: can't find key
goto DefaultBootDrive;
}
#endif // NEC_98
if (GetDriveType(szBootDir) != DRIVE_FIXED) {
// error: drive is not a valid boot drive
goto DefaultBootDrive;
}
Drive = (BYTE)(tolower(szBootDir[0])-'a')+1;
DefaultBootDrive:
setAL(Drive);
return;
}
/* demGetDriveFreeSpace - Get free Space on the drive
*
*
* Entry - Client (AL) Drive in question
* 0 - A: etc.
*
* Exit -
* SUCCESS
* Client (CY) = 0
* Client (AL) = FAT ID byte
* Client (BX) = Number of free allocation units
* Client (CX) = Sector size
* Client (DX) = Total Number of allocation units on disk
* Client (SI) = Sectors per allocation unit
*
* FAILURE
* Client (CY) = 1
* Client (AX) = Error code
*/
VOID demGetDriveFreeSpace (VOID)
{
WORD SectorsPerCluster;
WORD BytesPerSector;
WORD FreeClusters;
WORD TotalClusters;
BYTE Drive;
PBDS pbds;
Drive = getAL();
if (demGetDiskFreeSpace(Drive,
&BytesPerSector,
&SectorsPerCluster,
&TotalClusters,
&FreeClusters) == FALSE)
{
demClientError(INVALID_HANDLE_VALUE, (CHAR)(getAL() + 'A'));
return;
}
if (pbds = demGetBDS(Drive)) {
// if the device is a floppy, reload its bpb
if (!(pbds->Flags & NON_REMOVABLE) && !demGetBPB(pbds))
pbds->bpb.MediaID = 0xF8;
setAL(pbds->bpb.MediaID);
}
else
setAL(0);
setBX(FreeClusters);
setCX(BytesPerSector);
setDX(TotalClusters);
setSI(SectorsPerCluster);
setCF(0);
return;
}
//
// retrieves drive type for physical drives
// substd, redir drives are returned as unknown
// uses same DriveType definitions as win32 GetDriveTypeW
//
UCHAR
demGetPhysicalDriveType(
UCHAR DriveNum)
{
return DriveNum < 26 ? PhysicalDriveTypes[DriveNum] : DRIVE_UNKNOWN;
}
//
// worker function for DemGetDrives
//
UCHAR
DosDeviceDriveTypeToPhysicalDriveType(
UCHAR DeviceDriveType
)
{
switch (DeviceDriveType) {
case DOSDEVICE_DRIVE_REMOVABLE:
return DRIVE_REMOVABLE;
case DOSDEVICE_DRIVE_FIXED:
return DRIVE_FIXED;
case DOSDEVICE_DRIVE_CDROM:
return DRIVE_CDROM;
case DOSDEVICE_DRIVE_RAMDISK:
return DRIVE_RAMDISK;
}
//case DOSDEVICE_DRIVE_REMOTE:
//case DOSDEVICE_DRIVE_UNKNOWN:
//default:
return DRIVE_UNKNOWN;
}
/* demGetDrives - Get number of logical drives in the system
* called by ntdos from msinit to get numio
* initializes the physical drive list, which consists
* of drive types for true physical drives. subst
* and redir drives are classed as DRIVE_UNKNOWN.
*
* Entry - None
*
* Exit -
* SUCCESS
* Client (CY) = 0
* Client (AL) = number of drives
*
* FAILURE
* None
*/
VOID demGetDrives (VOID)
{
NTSTATUS Status;
UCHAR DriveNum;
UCHAR DriveType;
BOOL bCounting;
PROCESS_DEVICEMAP_INFORMATION ProcessDeviceMapInfo;
Status = NtQueryInformationProcess( NtCurrentProcess(),
ProcessDeviceMap,
&ProcessDeviceMapInfo.Query,
sizeof(ProcessDeviceMapInfo.Query),
NULL
);
if (!NT_SUCCESS(Status)) {
RtlZeroMemory( &ProcessDeviceMapInfo, sizeof(ProcessDeviceMapInfo));
}
//
// A and B are special cases.
// if A doesn't exist means b also doesn't exist
//
PhysicalDriveTypes[0] = DosDeviceDriveTypeToPhysicalDriveType(
ProcessDeviceMapInfo.Query.DriveType[0]
);
if (PhysicalDriveTypes[0] == DRIVE_UNKNOWN) {
IsAPresent = FALSE;
IsBPresent = FALSE;
}
PhysicalDriveTypes[1] = DosDeviceDriveTypeToPhysicalDriveType(
ProcessDeviceMapInfo.Query.DriveType[1]
);
if (PhysicalDriveTypes[1] == DRIVE_UNKNOWN) {
IsBPresent = FALSE;
}
DriveNum = 2;
nDrives = 2;
bCounting = TRUE;
do {
PhysicalDriveTypes[DriveNum] = DosDeviceDriveTypeToPhysicalDriveType(
ProcessDeviceMapInfo.Query.DriveType[DriveNum]
);
if (bCounting) {
if (PhysicalDriveTypes[DriveNum] == DRIVE_REMOVABLE ||
PhysicalDriveTypes[DriveNum] == DRIVE_FIXED ||
PhysicalDriveTypes[DriveNum] == DRIVE_CDROM ||
PhysicalDriveTypes[DriveNum] == DRIVE_RAMDISK )
{
nDrives++;
}
else {
bCounting = FALSE;
}
}
} while (++DriveNum < 26);
setAX(nDrives);
setCF(0);
return;
}
/* demQueryDate - Get The Date
*
*
* Entry - None
*
* Exit -
* SUCCESS
* Client (DH) - month
* Client (DL) - Day
* Client (CX) - Year
* Client (AL) - WeekDay
*
* FAILURE
* Never
*/
VOID demQueryDate (VOID)
{
SYSTEMTIME TimeDate;
GetLocalTime(&TimeDate);
setDH((UCHAR)TimeDate.wMonth);
setDL((UCHAR)TimeDate.wDay);
setCX(TimeDate.wYear);
setAL((UCHAR)TimeDate.wDayOfWeek);
return;
}
/* demQueryTime - Get The Time
*
*
* Entry - None
*
* Exit -
* SUCCESS
* Client (CH) - hour
* Client (CL) - minutes
* Client (DH) - seconds
* Client (DL) - hundredth of seconds
*
* FAILURE
* Never
*/
VOID demQueryTime (VOID)
{
SYSTEMTIME TimeDate;
GetLocalTime(&TimeDate);
setCH((UCHAR)TimeDate.wHour);
setCL((UCHAR)TimeDate.wMinute);
setDH((UCHAR)TimeDate.wSecond);
setDL((UCHAR)(TimeDate.wMilliseconds/10));
return;
}
/* demSetDate - Set The Date
*
*
* Entry - Client (CX) - Year
* Client (DH) - month
* Client (DL) - Day
*
* Exit - SUCCESS
* Client (AL) - 00
*
*
* FAILURE
* Client (AL) - ff
*/
VOID demSetDate (VOID)
{
SYSTEMTIME TimeDate;
GetLocalTime(&TimeDate);
TimeDate.wYear = (WORD)getCX();
TimeDate.wMonth = (WORD)getDH();
TimeDate.wDay = (WORD)getDL();
if(SetLocalTime(&TimeDate) || GetLastError() == ERROR_PRIVILEGE_NOT_HELD)
setAL(0);
else
setAL(0xff);
}
/* demSetTime - Set The Time
*
*
* Entry - Client (CH) - hour
* Client (CL) - minutes
* Client (DH) - seconds
* Client (DL) - hundredth of seconds
*
* Exit - None
*
*/
VOID demSetTime (VOID)
{
SYSTEMTIME TimeDate;
GetLocalTime(&TimeDate);
TimeDate.wHour = (WORD)getCH();
TimeDate.wMinute = (WORD)getCL();
TimeDate.wSecond = (WORD)getDH();
TimeDate.wMilliseconds = (WORD)getDL()*10;
if (SetLocalTime(&TimeDate) || GetLastError() == ERROR_PRIVILEGE_NOT_HELD)
setAL(0);
else
setAL(0xff);
}
/* demSetDTALocation - Set The address of variable where Disk Transfer Address
* is stored in NTDOS.
*
*
* Entry - Client (DS:AX) - DTA variable Address
* Client (DS:DX) - CurrentPDB address
*
* Exit - None
*
*/
VOID demSetDTALocation (VOID)
{
PDOSWOWDATA pDosWowData;
pulDTALocation = (PULONG) GetVDMAddr(getDS(),getAX());
pusCurrentPDB = (PUSHORT) GetVDMAddr(getDS(),getDX());
pExtendedError = (PDEMEXTERR) GetVDMAddr(getDS(),getCX());
pDosWowData = (PDOSWOWDATA) GetVDMAddr(getDS(),getSI());
pSFTHead = (PDOSSF) GetVDMAddr(getDS(),(WORD)pDosWowData->lpSftAddr);
return;
}
/* demGSetMediaID - Get or set volume serial and volume label
*
* Entry - Client (BL) - Drive Number (0=A;1=B..etc)
* Client (AL) - Get or Set (0=Get;1=Set)
* Client (DS:DX) - Buffer to return information
* (see VOLINFO in dosdef.h)
*
* Exit - SUCCESS
* Client (CF) - 0
*
* FAILURE
* Client (CF) - 1
* Client (AX) - Error code
*
* NOTES:
* Currently There is no way for us to set Volume info.
*/
VOID demGSetMediaID (VOID)
{
CHAR Drive;
PVOLINFO pVolInfo;
// Set Volume info is not currently supported
if(getAL() != 0){
setCF(1);
return;
}
pVolInfo = (PVOLINFO) GetVDMAddr (getDS(),getDX());
Drive = (CHAR)getBL();
if (!GetMediaId(Drive, pVolInfo)) {
demClientError(INVALID_HANDLE_VALUE, (CHAR)(Drive + 'A'));
return;
}
setCF(0);
return;
}
//
// GetMediaId
//
//
BOOL
GetMediaId(
CHAR DriveNum,
PVOLINFO pVolInfo
)
{
CHAR RootPathName[] = "?:\\";
CHAR achVolumeName[NT_VOLUME_NAME_SIZE];
CHAR achFileSystemType[MAX_PATH];
DWORD adwVolumeSerial[2],i;
// Form Root path
RootPathName[0] = DriveNum + 'A';
// Call the supreme source of information
if(!GetVolumeInformationOem( RootPathName,
achVolumeName,
NT_VOLUME_NAME_SIZE,
adwVolumeSerial,
NULL,
NULL,
achFileSystemType,
MAX_PATH) )
{
return FALSE;
}
// Fill in user buffer. Remember to convert the null characters
// to spaces in different strings.
STOREDWORD(pVolInfo->ulSerialNumber,adwVolumeSerial[0]);
strncpy(pVolInfo->VolumeID,achVolumeName,DOS_VOLUME_NAME_SIZE);
for(i=0;i<DOS_VOLUME_NAME_SIZE;i++) {
if (pVolInfo->VolumeID[i] == '\0')
pVolInfo->VolumeID[i] = '\x020';
}
strncpy(pVolInfo->FileSystemType,achFileSystemType,FILESYS_NAME_SIZE);
for(i=0;i<FILESYS_NAME_SIZE;i++) {
if (pVolInfo->FileSystemType[i] == '\0')
pVolInfo->VolumeID[i] = '\x020';
}
return TRUE;
}
/* demGetDPB - Get Devicr Parameter Block
*
* Entry - Client (AL) - Drive Number (0=A;1=B..etc)
* Client (DS:DI) - Buffer to return information
*
* Exit - SUCCESS
* Client (CF) - 0
*
* FAILURE
* Client (CF) - 1
* Client (AX) - Error code
*
*/
VOID demGetDPB(VOID)
{
BYTE Drive;
DPB UNALIGNED *pDPB;
BYTE Result;
Drive = getAL();
pDPB = (PDPB) GetVDMAddr(getDS(), getDI());
Result = demGetDpbI(Drive, pDPB);
if (Result == FAILURE) {
demClientError(INVALID_HANDLE_VALUE,(CHAR)(Drive + 'A'));
return;
}
else if (Result == NODISK){
setCF(1);
return;
}
setAX(0);
setCF(0);
}
/* demGetDPBI - Worker for GetDPB and GetDPBList
*
* Entry -
* Drive -- Drive Number (0=A;1=B..etc)
* pDPB -- pointer to the location to store the dpb
*
* Exit - SUCCESS
* returns success, fills in DPB
* FAILURE
* returns FAILURE or NODISK
*/
BYTE demGetDpbI(BYTE Drive, DPB UNALIGNED *pDPB)
{
WORD SectorSize, ClusterSize, FreeClusters, TotalClusters;
PBDS pbds;
WORD DirsPerSector;
if (demGetDiskFreeSpace(Drive,
&SectorSize,
&ClusterSize,
&TotalClusters,
&FreeClusters
))
{
pDPB->Next = (PDPB) 0xFFFFFFFF;
pDPB->SectorSize = SectorSize;
pDPB->FreeClusters = FreeClusters;
pDPB->MaxCluster = TotalClusters + 1;
pDPB->ClusterMask = ClusterSize - 1;
pDPB->ClusterShift = 0;
pDPB->DriveNum = pDPB->Unit = Drive;
while ((ClusterSize & 1) == 0) {
ClusterSize >>= 1;
pDPB->ClusterShift++;
}
if (pbds = demGetBDS(Drive)) {
// if the device is a floppy, reload its bpb
if (!(pbds->Flags & NON_REMOVABLE) && !demGetBPB(pbds)) {
return NODISK;
}
pDPB->MediaID = pbds->bpb.MediaID;
pDPB->FATSector = pbds->bpb.ReservedSectors;
pDPB->FATs = pbds->bpb.FATs;
pDPB->RootDirs = pbds->bpb.RootDirs;
pDPB->FATSize = pbds->bpb.FATSize;
pDPB->DirSector = pbds->bpb.FATs * pbds->bpb.FATSize +
pDPB->FATSector;
DirsPerSector = pDPB->SectorSize >> DOS_DIR_ENTRY_LENGTH_SHIFT_COUNT;
pDPB->FirstDataSector = pDPB->DirSector +
((pDPB->RootDirs + DirsPerSector - 1) /
DirsPerSector);
pDPB->DriveAddr = 0x123456;
pDPB->FirstAccess = 10;
}
// if we don't know the drive, fake a DPB for it
else {
pDPB->MediaID = 0xF8;
pDPB->FATSector = 1;
pDPB->FATs = 2;
pDPB->RootDirs = 63;
pDPB->FATSize = 512;
pDPB->DirSector = 1;
pDPB->DriveAddr = 1212L * 64L * 1024L + 1212L;
pDPB->FirstAccess = 10;
}
return SUCCESS;
}
else {
return FAILURE;
}
}
/* demGetComputerName - Get computer name
*
* Entry -
* Client (DS:DX) - 16 byte buffer
*
* Exit - Always Succeeds
* DS:DX is filled with the computer name (NULL terminated).
*/
VOID demGetComputerName (VOID)
{
PCHAR pDOSBuffer;
CHAR ComputerName[MAX_COMPUTERNAME_LENGTH+1];
DWORD BufferSize = MAX_COMPUTERNAME_LENGTH+1;
ULONG i;
pDOSBuffer = (PCHAR) GetVDMAddr(getDS(), getDX());
if (GetComputerNameOem(ComputerName, &BufferSize)){
if (BufferSize <= 15){
for (i = BufferSize ; i < 15 ; i++)
ComputerName [i] = ' ';
ComputerName[15] = '\0';
strcpy (pDOSBuffer, ComputerName);
}
else{
strncpy (pDOSBuffer, ComputerName, 15);
pDOSBuffer [15] = '\0';
}
setCX(0x1ff);
}
else {
*pDOSBuffer = '\0';
setCH(0);
}
}
#define APPS_SPACE_LIMIT 999990*1024 //999990kb to be on the safe side
BOOL demGetDiskFreeSpace(
BYTE Drive,
WORD * BytesPerSector,
WORD * SectorsPerCluster,
WORD * TotalClusters,
WORD * FreeClusters
)
{
CHAR chRoot[]="?:\\";
DWORD dwBytesPerSector;
DWORD dwSectorsPerCluster;
DWORD dwTotalClusters;
DWORD dwFreeClusters;
DWORD dwLostFreeSectors;
DWORD dwLostTotalSectors;
DWORD dwNewSectorPerCluster;
ULONG ulTotal,ulTemp;
// sudeepb 22-Jun-1993;
// Please read this routine with an empty stomach.
// The most common mistake all the apps do when calculating total
// disk space or free space is to neglect overflow. Excel/Winword/Ppnt
// and lots of other apps use "mul cx mul bx" never taking care
// of first multiplication which can overflow. Hence this routine makes
// sure that first multiplication will never overflow by fixing
// appropriate values. Secondly, all these above apps use signed long
// to deal with these free spaces. This puts a limit of 2Gb-1 on
// the final outcome of the multiplication. If its above this the setup
// fails. So here we have to make sure that total should never exceed
// 0x7fffffff. Another bug in above setup program's that if you return
// anything more than 999,999KB then they try to put "999,999KB+\0", but
// unfortunately the buffer is only 10 bytes. Hence it corrupts something
// with the last byte. In our case that is low byte of a segment which
// it later tries to pop and GPF. This shrinks the maximum size that
// we can return is 999,999KB.
chRoot[0]=(CHAR)('A'+ Drive);
if (GetDiskFreeSpaceOem(chRoot,
&dwSectorsPerCluster,
&dwBytesPerSector,
&dwFreeClusters,
&dwTotalClusters) == FALSE)
return FALSE;
/*
* HPFS and NTFS can give num clusters over dos limit
* For these cases increase SectorPerCluster and lower
* cluster number accordingly. If the disk is very large
* even this isn't enuf, so pass max sizes that dos can
* handle.
*
* The following algorithm is accurate within 1 cluster
* (final figure)
*
*/
dwLostFreeSectors = dwLostTotalSectors = 0;
while (dwTotalClusters + dwLostTotalSectors/dwSectorsPerCluster > 0xFFFF)
{
if (dwSectorsPerCluster > 0x7FFF)
{
dwTotalClusters = 0xFFFF;
if (dwFreeClusters > 0xFFFF)
dwFreeClusters = 0xFFFF;
break;
}
if (dwFreeClusters & 1) {
dwLostFreeSectors += dwSectorsPerCluster;
}
if (dwTotalClusters & 1) {
dwLostTotalSectors += dwSectorsPerCluster;
}
dwSectorsPerCluster <<= 1;
dwFreeClusters >>= 1;
dwTotalClusters >>= 1;
}
if (dwTotalClusters < 0xFFFF) {
dwFreeClusters += dwLostFreeSectors/dwSectorsPerCluster;
dwTotalClusters += dwLostTotalSectors/dwSectorsPerCluster;
}
if ((dwNewSectorPerCluster = (0xffff / dwBytesPerSector)) < dwSectorsPerCluster)
dwSectorsPerCluster = dwNewSectorPerCluster;
// finally check for 999,999kb
ulTemp = (ULONG)((USHORT)dwSectorsPerCluster * (USHORT)dwBytesPerSector);
// check that total space does'nt exceed 999,999kb
ulTotal = ulTemp * (USHORT)dwTotalClusters;
if (ulTotal > APPS_SPACE_LIMIT){
if (ulTemp <= APPS_SPACE_LIMIT)
dwTotalClusters = APPS_SPACE_LIMIT / ulTemp;
else
dwTotalClusters = 1;
}
ulTotal = ulTemp * (USHORT)dwFreeClusters;
if (ulTotal > APPS_SPACE_LIMIT) {
if (ulTemp <= APPS_SPACE_LIMIT)
dwFreeClusters = APPS_SPACE_LIMIT / ulTemp;
else
dwFreeClusters = 1;
}
*BytesPerSector = (WORD) dwBytesPerSector;
*SectorsPerCluster = (WORD) dwSectorsPerCluster;
*TotalClusters = (WORD) dwTotalClusters;
*FreeClusters = (WORD) dwFreeClusters;
return TRUE;
}
/* demGetDPBList - Create the list of dpbs
*
* Entry -
* Client(ES:BP) - points to destination for the dpb list
* Exit - SUCCESS
* Client (BP) - points to first byte past dpb list
* FAILURE
* Client (BP) unchanged
*
* Notes:
* For performance reasons, only the drive and unit fields are
* filled in. The only application I know of that depends on the
* dpb list is go.exe (a shareware app installer). Even if we filled
* in the other fields they would likely be incorrect when the app
* looked at them, since ntdos.sys never updates the pdbs in the pdb
* list
*/
VOID demGetDPBList (VOID)
{
UCHAR DriveType;
UCHAR DriveNum;
DPB UNALIGNED *pDpb;
USHORT usDpbOffset, usDpbSeg;
usDpbOffset = getBP();
usDpbSeg = getES();
pDpb = (PDPB)GetVDMAddr(usDpbSeg, usDpbOffset);
//
// Iterate over all of the drive letters.
//
DriveNum = 0;
do {
DriveType = demGetPhysicalDriveType(DriveNum);
//
// Only include the local non cd rom drives ?? ramdisk ???
//
if ((DriveType == DRIVE_REMOVABLE) || (DriveType == DRIVE_FIXED)) {
//
// Fake the Dpb for the drive
//
pDpb->DriveNum = pDpb->Unit = DriveNum;
//
// Link it to the next dpb
//
usDpbOffset += sizeof(DPB);
pDpb->Next = (PDPB)(((ULONG)usDpbSeg) << 16 | usDpbOffset);
//
// Advance to the next dpb
//
pDpb += 1;
ASSERT(usDpbOffset < 0xFFFF);
}
} while (++DriveNum < 26);
//
// Terminate the list if necessary
//
if (usDpbOffset != getBP()) {
pDpb -= 1;
pDpb->Next = (PDPB)-1;
}
//
// Return the new free space pointer
//
setBP(usDpbOffset);
}