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_go32_dpmi_allocate_real_mode_callback_iret
===========================================

Syntax
------

     #include <dpmi.h>
     
     int _go32_dpmi_allocate_real_mode_callback_iret(_go32_dpmi_seginfo *info, _go32_dpmi_registers *regs);

Description
-----------

DPMI Overview:    

This function allocates a "real-mode callback".  Fill in the
`pm_offset' field of INFO and call this function.  It will fill in the
`rm_segment' and `rm_offset' fields.  Any time a real-mode program
calls the real-mode address, your function gets called.  The registers
in affect will be stored in REGS, which should be a global, and will be
passed to your function.  Any changes in REGS will be reflected back
into real mode.  A wrapper will be added to your function to simulate
the effects of an `iret' instruction, so this function is useful for
trapping real-mode software interrupts (like 0x1b - `Ctrl-Break' hit).

Return Value
------------

Zero on success, nonzero on failure.

Example
-------

     _go32_dpmi_registers regs;
     
     my_handler(_go32_dpmi_registers *r)
     {
       r.d.eax = 4;
     }
     
     setup()
     {
       _go32_dpmi_seginfo info;
       _go32_dpmi_seginfo old_vector;
       _go32_dpmi_get_real_mode_interrupt_vector(0x84, &old_vector);
       info.pm_offset = my_handler;
       _go32_dpmi_allocate_real_mode_callback_iret(&info, &regs);
       _go32_dpmi_set_real_mode_interrupt_vector(0x84, &info);
       do_stuff();
       _go32_dpmi_set_real_mode_interrupt_vector(0x84, &old_vector);
       _go32_dpmi_free_real_mode_callback(&info);
     }