Category : Files from Magazines
Archive   : DDJ0292.ZIP
Filename : UNDOCWIN.ASC

 
Output of file : UNDOCWIN.ASC contained in archive : DDJ0292.ZIP
_MAKING UNDOCUMENTED DOS CALLS FROM WINDOWS 3_
by Paul Chui

[LISTING ONE]

#define NOCOMM
#include
#include
#include
#include "getdrvx.h"

#define CDS_SUBST (0x1000)

#define DOS3_CDS_SIZE 81
#define DOS4_CDS_SIZE 88
#define CDS_PATH 0x00
#define CDS_FLAGS 0x43
#define CDS_DPB 0x45

#define DPB_FATS 8

#define MK_FP(seg,ofs) ((void far *) (((unsigned long)(seg) << 16) | (unsigned)(ofs)))
#define _DS GetDS()

/* Documented Windows functions not declared in WINDOWS.H */
DWORD FAR PASCAL GlobalDosAlloc(DWORD dwBytes);
WORD FAR PASCAL GlobalDosFree(WORD wSelector);

/* Undocumented Windows functions */
VOID FAR PASCAL SetSelectorBase(WORD wSelector, DWORD dwBase);
VOID FAR PASCAL SetSelectorLimit(WORD wSelector, DWORD dwLimit);

/* Global Variables */
WORD _wSelector; // a data selector

/* Types */
// DOS list of lists structure (for DOS 3.1 or better)
typedef struct {
BYTE x[22]; // (don't care)
BYTE far* cds;
BYTE xx[7]; // (don't care)
BYTE lastdrive;
// ... the rest of DOS List of Lists
} DOSLISTS;

// DPMI real-mode call structure
typedef struct {
DWORD edi, esi, ebp, reserved, ebx, edx, ecx, eax;
WORD flags, es, ds, fs, gs, ip, cs, sp, ss;
} REALMODECALL;


int GetDosVersionMajor(void)
{
int dosver;

_asm mov ah, 0x30;
_asm int 0x21;
_asm mov dosver, ax;

return (BYTE)dosver;
}

unsigned GetDS(void)
{
_asm mov ax, ds;
return; // return value in AX
}


/****************************************************************************
BOOL DPMI_RealModeInt(int intno, REALMODECALL far* r)

PURPOSE: DPMI simulate real-mode interrupt function. The
following is an excerpt from the DPMI Specification:

PARAMETERS:
int intno real-mode interrupt to simulate
REALMODECALL far* r

RETURNS: TRUE if interrupt is successful, FALSE on error

NOTES: The following is an excerpt from INTEL's DPMI specs:

To Call

AX = 0300h
BL = Interrupt number
BH = Flags
Bit 0 = 1 resets the interrupt controller and A20
line
Other flags reserved and must be 0
CX = Number of words to copy from protected mode to
real-mode stack
ES:(E)DI = Selector:Offset of real-mode call structure

Returns

If function was successful:
Carry flag is clear.
ES:(E)DI = Selector:Offset of modified real-mode call
structure

If function was not successful:
Carry flag is set.
****************************************************************************/
BOOL DPMI_RealModeInt(int intno, REALMODECALL far* r)
{
intno &= 0x00FF; // reset high byte (flags)

_asm {
push di
mov bx, intno // flags | real-mode interrupt to call
mov cx, 0 // don't copy anything from protected mode stack
les di, r // es:di -> real-mode call structure
mov ax, 0x0300 // DPMI simulate real-mode interrupt function
int 0x31
pop di
jc error
}
return TRUE;

error:
return FALSE;
}

/****************************************************************************
BYTE far* PMODE_ADDR(WORD wSel, BYTE far* RMODE_ADDR)

PURPOSE: Get the Current Directory Structure

PARAMETERS:
WORD wSel A valid selector
BYTE far* RMODE_ADDR A real mode address

RETURNS: a protected-mode address of RMODE_ADDR

NOTES: The base address of selector wSel is set to the segment of
RMODE_ADDR.
*****************************************************************************/
BYTE far* PMODE_ADDR(WORD wSel, BYTE far* RMODE_ADDR)
{
SetSelectorBase(wSel, (DWORD) FP_SEG(RMODE_ADDR) << 4);
return MK_FP(wSel, FP_OFF(RMODE_ADDR));
}

/****************************************************************************
BYTE far* GetCDS(int nDrive)

PURPOSE: Get the Current Directory Structure

PARAMETERS: int nDrive The drive to retrieve

RETURNS: a real-mode pointer to the Current Directory Structure of
drive nDrive.
*****************************************************************************/
BYTE far* GetCDS(int nDrive)
{
DOSLISTS far* doslists;
REALMODECALL r;

// Get DOS list of lists (INT 21h, Function 52h)
_fmemset(&r, 0, sizeof(REALMODECALL));
r.eax = 0x5200;
if (!DPMI_RealModeInt(0x21, &r))
return NULL;

// Pointer to DOS list of lists is returned in ES:BX
doslists = (DOSLISTS far*)
PMODE_ADDR( _wSelector, MK_FP(r.es, LOWORD(r.ebx)) );

if (GetDosVersionMajor() < 4)
return doslists->cds + (nDrive * DOS3_CDS_SIZE);
else
return doslists->cds + (nDrive * DOS4_CDS_SIZE);
}

/****************************************************************************
BOOL isCDROM(int nDrive)

PURPOSE: Tests if nDrive is a CD ROM drive

PARAMETERS: int nDrive The drive to test

RETURNS: TRUE if nDrive is a CD ROM
*****************************************************************************/
BOOL isCDROM(int nDrive)
{
WORD saveAX, saveBX;

_asm mov cx, nDrive;
_asm mov ax, 0x150B;
_asm int 0x2F;
_asm mov saveAX, ax;
_asm mov saveBX, bx;

return saveBX == 0xADAD && saveAX != 0;
}


/****************************************************************************
BOOL isSubstDrive(int nDrive)

PURPOSE: Tests for drives created using the DOS SUBST command

PARAMETERS: int nDrive The drive to test

RETURNS: TRUE if nDrive is a SUBST drive
*****************************************************************************/
BOOL isSubstDrive(int nDrive)
{
BYTE far* cds; // Current Directory Structure
WORD cds_flags;

cds = PMODE_ADDR(_wSelector, GetCDS(nDrive));
cds_flags = *(WORD far*)(cds+CDS_FLAGS);
if (cds_flags & (CDS_SUBST))
return TRUE;

return FALSE;
}

/****************************************************************************
BOOL isRamDrive(int nDrive)

PURPOSE: Tests for Ram drives

PARAMETERS: int nDrive The drive to test

RETURNS: TRUE if nDrive is a ram drive

NOTES: This function tests to see if the drive has only one FAT. It
is assumed that if this is true, then the drive must be a RAM drive.
*****************************************************************************/
BOOL isRamDrive(int nDrive)
{
BYTE far* cds; // Current Directory Structure
BYTE far* dpb; // Drive Parameter Block

cds = PMODE_ADDR(_wSelector, GetCDS(nDrive));

dpb = *(BYTE far* far*)(cds+CDS_DPB);
dpb = PMODE_ADDR(_wSelector, dpb);

if (*(dpb+DPB_FATS) == 1)
return TRUE;

return FALSE;
}

/****************************************************************************
WORD FAR PASCAL GetDriveTypeX(int nDrive)

PURPOSE: Determines drive type

PARAMETERS:
int nDrive The drive number. 0 = A:, 1 = B:,
2 = C:, 3 = D:, ...
RETURNS:
DRIVE_UNKNOWN Unknown drive type
DRIVE_NOTEXIST Drive does not exist
DRIVE_REMOVE Removable (floppy) drive
DRIVE_FIXED Fixed (hard) drive
DRIVE_REMOTE Remote (network) drive
DRIVE_CDROM CD ROM drive
DRIVE_RAM Ram drive
DRIVE_SUBST SUBST drive
*****************************************************************************/
WORD FAR PASCAL GetDriveTypeX(int nDrive)
{
WORD wDriveType;

// Get a new selector, using the current DS as the prototype
_wSelector = AllocSelector(_DS);
SetSelectorLimit(_wSelector, 0xFFFF);

wDriveType = GetDriveType(nDrive);

if (isCDROM(nDrive))
wDriveType = DRIVE_CDROM;
else
if (wDriveType != DRIVE_REMOTE && isSubstDrive(nDrive))
wDriveType = DRIVE_SUBST;
else
if (isRamDrive(nDrive))
wDriveType = DRIVE_RAM;

FreeSelector(_wSelector);
return wDriveType;
}

/****************************************************************************
BOOL FAR PASCAL GetCanonicalPath(LPSTR lpszRelPath, LPSTR lpszTruePath)

PURPOSE: Resolve path string to canonical path string

PARAMETERS:
LPSTR lpszRelPath Relative path string or directory name
LPSTR lpszTruePath Destination for canonical fully qualified
path
RETURNS:
TRUE if successful
*****************************************************************************/
BOOL FAR PASCAL GetCanonicalPath(LPSTR lpszRelPath, LPSTR lpszTruePath)
{
BOOL retval;
DWORD dw;
WORD wSelector;
WORD wSegment;
LPSTR lpszDosBuf;
REALMODECALL r;

dw = GlobalDosAlloc(128);
if (dw == NULL)
return FALSE;

wSelector = LOWORD(dw);
wSegment = HIWORD(dw);

lpszDosBuf = MK_FP(wSelector, 0);
_fmemcpy(lpszDosBuf, lpszRelPath, 128);

r.eax = 0x6000;
r.ds = wSegment;
r.esi = 0;
r.es = wSegment;
r.edi = 0;

retval = DPMI_RealModeInt(0x21, &r);

_fmemcpy(lpszTruePath, lpszDosBuf, 128);
GlobalDosFree(wSelector);

return retval;
}




  3 Responses to “Category : Files from Magazines
Archive   : DDJ0292.ZIP
Filename : UNDOCWIN.ASC

  1. Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!

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