🚀 go-pugleaf

To: wagner@main.mndly.umn.edu

29 Aug 92, Rick Wagner writes to All:

 RW> Set AX=4310h and INT 2F.  This will return the address of the XMS
 RW> driver in ES:BX.  I can call this function with an INT86x and get the
 RW> address returned (confirmed) but I can't figure out how to call the XMS
 RW> driver at ES:BX.  I read the longjump stuff in the manual and I'm now
 RW> totally confused.
 RW>

1. Longjmp() has got nothing to do with this... it is for unwinding the stack after a failed operation 57 function calls deep or for switching tasks in pseudo-multitaskers.

2. Take a look at this...

typedef void far (*XF)() = 0;

unsigned short  usXMSSeg = 0;
unsigned short  usXMSOff = 0;
XF              xfXMS = (XF)0;

int GetXMSPtr()
{
        _AX=0x4310;
        geninterrupt(0x2f);
        usXMSOff = _BX;
        usXMSSeg = _ES;
        xfXMS = (XF)MK_FP(usXMSSeg, usXMSOff);
        return xfXMS != 0;
};

// example to call XMS driver with AX set to some value

int XMSCall(unsigned short axval)
{
        _AX=axval;
        xfXMS();
        return _AX;
}

Hope this clears up some of the confusion for you.

Alan

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