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_go32_info_block
================

Syntax
------

     #include <go32.h>
     
     extern __Go32_Info_Block _go32_info_block;

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

The go32 information block is a mechanism for `go32' to pass
information to the application.  Some of this information is generally
useful, such as the pid or the transfer buffer, while some is used
internally to `libc.a' only.

The structure has this format:

     typedef struct {
       unsigned long  size_of_this_structure_in_bytes;
       unsigned long  linear_address_of_primary_screen;
       unsigned long  linear_address_of_secondary_screen;
       unsigned long  linear_address_of_transfer_buffer;
       unsigned long  size_of_transfer_buffer;
       unsigned long  pid;
       unsigned char  master_interrupt_controller_base;
       unsigned char  slave_interrupt_controller_base;
       unsigned short selector_for_linear_memory;
       unsigned long  linear_address_of_stub_info_structure;
       unsigned long  linear_address_of_original_psp;
       unsigned short run_mode;
       unsigned short run_mode_info;
     } Go32_Info_Block;

The linear address fields provide values that are suitable for
`dosmemget', `dosmemput', and `movedata'.  The
selector_for_linear_memory is suitable for `<sys/farptr.h>' selector
parameters.

Due to the length of these fields, and their popularity, the following
macros are available:

`_dos_ds'
     This expands to _go32_info_block.selector_for_linear_memory

`__tb'
     This expands to _go32_info_block.linear_address_of_transfer_buffer

The `run_mode' field indicates the mode that the program is running in.
The following modes are defined:

`_GO32_RUN_MODE_UNDEF'
     This indicates that the extender did not (or could not) determine
     or provide the mode information.  The most probable reason is that
     it's an older extender that does not support this field.  The
     program should not assume anything about the run mode if it is
     this value.

`_GO32_RUN_MODE_RAW'
     This indicates that no CPU manager is being used, and no XMS
     manager is present.  The CPU is being managed directly from the
     extender, and memory was allocated from the extended memory pool.

`_GO32_RUN_MODE_XMS'
     This indicates that the extender is managing the CPU, but an XMS
     driver is managing the memory pool.

`_GO32_RUN_MODE_VCPI'
     This indicates that a VCPI server (like `emm386' or `qemm') is
     managing both the CPU and the memory.

`_GO32_RUN_MODE_DPMI'
     This indicates that a DPMI server (like `qdpmi' or Windows) is
     managing both the CPU and memory.  Programs may rely on this value
     to determine if it is safe to use DPMI 0.9 functions.

     If this value is set, the `run_mode_info' field has the DPMI
     specification version, in hex, shifted eight bits.  For example,
     DPMI 0.9 has 0x005A in the `run_mode_info' field.

Note that the program should not assume that the value will be one of
the listed values.  If the program is running with an extender that
provides some other mode (say, a newly released extender) then the
program should be able to handle that case gracefully.

Example
-------

     dosmemget(_go32_info_block.linear_address_of_primary_screen, 80*25*2, buf);