Date: Thu, 17 Aug 1995 13:26:36 +1100
From: Bill Currie <BILLC AT teleng1 DOT tait DOT co DOT nz>
Subject: mem locking and rm callbacks
To: djgpp AT sun DOT soe DOT clarkson DOT edu
Organization: Tait Electronics Ltd.

I am implementing a mouse class and I'm having problems with the
callback function (0xC).  I have locked down all the memory except
the stack and I am still getting page access errors.  I imagine this
is from the stack not being locked down, but I don't know where it
is.  Below is the relavent code for anyone to look over.  The 
likely cause of the errors is in TMouse::setUserFunction.

TIA
Bill

#ifndef __tmouse_h
#define __tmouse_h

#pragma interface

#ifndef __dj_include_dpmi_h_
#include <dpmi.h>
#endif

class TMouse {
protected:
	unsigned
		present:1;
	int numButtons;
	static __dpmi_raddr callBack;
	static __dpmi_regs regs;
	static void mouse_func();
	static void (*mouseCallback)(short,short,short,short,short,short);
public:
	TMouse();
	~TMouse();
    int	    getButtons();
    void    showCursor();
    void    hideCursor();
    short   getPos(short &x, short &y);
    void    setPos(short x, short y);
    void    getPress(short &c, short &x, short &y, short &s);
    void    getRelease(short &c, short &x, short &y, short &s);
    void    setHRange(short mi, short ma);
    void    setVRange(short mi, short ma);
    void setUserFunction(void (*func)(short,short,short,
                                      short,short,short),short mask);
};

extern TMouse Mouse;

#endif	// __tmouse_h

#pragma implementation "tmouse.h"
#include <sys/segments.h>
#include "tui.h"

TMouse Mouse;
void (*TMouse::mouseCallback)(short,short,short,short,short,short);
__dpmi_regs TMouse::regs;
__dpmi_raddr TMouse::callBack;

void TMouse::mouse_func()
{
//  if (mouseCallback)
//      mouseCallback(regs.x.ax,regs.x.cx,regs.x.dx,regs.x.di,regs.x.si,regs.x.bx);
}

static void eofunc(){}

/* stolen from sb03_dj2 by Joel H. Hunter*/
int lock_memory(const void *ptr, unsigned long bytes) {
  unsigned long base;

  if(__dpmi_get_segment_base_address(_my_ds(),&base)!=-1) {
	__dpmi_meminfo mem;
	mem.handle=0;
	mem.size=bytes;
	mem.address=(unsigned long)((char *)ptr+base);
	if(__dpmi_lock_linear_region(&mem)!=-1)
	  return 1;
  }

  return -1;
}

[irrelevant code clipped]

void TMouse::setUserFunction(void (*func)(short,short,short,
										  short,short,short),short mask)
{
    __dpmi_regs r;
    if (!callBack.segment) {
        lock_memory(mouse_func,(unsigned long)eofunc-(unsigned long)mouse_func);
        lock_memory(&callBack,sizeof(callBack));
        lock_memory(&mouseCallback,sizeof(mouseCallback));
        lock_memory(&regs,sizeof(regs));
        __dpmi_allocate_real_mode_callback(mouse_func,&regs,&callBack);
    }
    mouseCallback=func;
    r.x.ax=0x000c;
    r.x.es=callBack.segment;
    r.x.dx=callBack.offset16;
    r.x.cx=mask;
    __dpmi_simulate_real_mode_interrupt(0x33,&r);
}
+--------------+-----------------------------------+
|Bill Currie   | "Watch that first step..."        |
|Christchurch  | Jump trooper motto.               |
|New Zealand   |                                   |
+--------------+-----------------------------------+