@c ----------------------------------------------------------------------
@node __djgpp_nearptr_enable, memory
@subheading Syntax

@example
#include <sys/nearptr.h>

int __djgpp_nearptr_enable(void);
@end example

@subheading Description

This function enables "near pointers" to be used to access the DOS
memory arena.  Sort of.  When you call this function, it will return
nonzero if it has successfully enabled near pointers.  If so, you must
add the value @code{__djgpp_conventional_base} to the linear address
of the physical memory.  For example:

@example
if (__djgpp_nearptr_enable())
@{
  short *screen = (short *)(__djgpp_conventional_base + 0xb8000);
  for (i=0; i<80*24*2; i++)
    screen[i] = 0x0720;
  __djgpp_nearptr_disable();
@}
@end example

The variable @code{__djgpp_base_address} contains the linear base
address of the application's data segment.  You can subtract this
value from other linear addresses that DPMI functions might return
in order to obtain a near pointer to those linear regions as well.

If using the Unix-like sbrk algorithm, near pointers are only valid 
until the next @code{malloc}, @code{system}, @code{spawn*}, or 
@code{exec*} function call, since the linear base address of the 
application may be changed by these calls.

WARNING: When you enable near pointers, you disable all the protection
that the system is providing.  If you are not careful, your
application may destroy the data in your computer.  USE AT YOUR OWN
RISK!

@subheading Return Value

Returns 0 if near pointers are not available, or nonzero if they are.

@subheading Portability

@portability !ansi, !posix

@c ----------------------------------------------------------------------
@node __djgpp_nearptr_disable, memory
@subheading Syntax

@example
#include <sys/nearptr.h>

void __djgpp_nearptr_disable(void);
@end example

@subheading Description

This function disables near pointers, and re-enables protection.
@xref{__djgpp_nearptr_enable}.

@subheading Portability

@portability !ansi, !posix