Very Computer

I've been looking at getting OS/2 for my home machine, in part to do some
personal programming.  However, one OS feature I've grown quite fond of
are memory-mapped files.

To date I've not been able to find any documented API for this, although I've
also read that libraries are available to support the Win32 API at the source
level, and memory-mapped files are supported in Win32.

Are memory-mapped files supported by OS/2, and if so, where are they
documented?

                                         James Parker

Quote:>I've been looking at getting OS/2 for my home machine, in part to do some
>personal programming.  However, one OS feature I've grown quite fond of
>are memory-mapped files.

>To date I've not been able to find any documented API for this, although I've
>also read that libraries are available to support the Win32 API at the source
>level, and memory-mapped files are supported in Win32.

>Are memory-mapped files supported by OS/2, and if so, where are they
>documented?

Not at present.  The Win32 API feature is announced, but not in the system
yet.

Since, as far as I know, IBM invented memory-mapped files (it's a key concept
in the AS/400, which has its roots back in the late '70's, and has also been
supported on MVS for years now), I dare say they could add it, if they felt
there were a need.  It is _not_ a common thing on established user OS/2 wish
lists, though.

The Cset++ compiler from IBM does support memory mapped files.
Look at the /Sv+ option.

Panningen
Netherlands

Quote:>Are memory-mapped files supported by OS/2, and if so, where are they
>documented?

James,
  OS/2 doesn't support memory files.  However, the C/Set++ compiler supports
memory mapped files, which are accessable via fopen("File.Nam","rb+, type=memory");

Bob Plyler            IBM Payment Solutions

 b> James,
 b>   OS/2 doesn't support memory files.  However, the
 b> C/Set++ compiler supports
 b> memory mapped files, which are accessable via
 b> fopen("File.Nam","rb+, type=memory");

The Cset++ compiler supports "memory files",  and should not be confused with "memory mapped files".

A memory mapped file is accessed just like memory (via a 'char *',  for example).

Cset++'s cheap <g> memory files are simply file streams (FILE *'s) that do not end up on disk (unless in swapper.dat!).

It is possible,  using OS/2 exceptions,  to write your own memory mapped files -- but you have to make sure the "page not present" exception does not occur in a kernel call -- which makes the whole effort almost useless (since even calling printf() could cause a page fault in DosWrite()).

Adding REAL,  os/2 supplied,  memory mapped files would be so easy -- I wish they would do it;  I added them myself (my first 32bit OS/2 program) and they worked great on the last two OS/2 2.0 betas --- but when OS/2 2.0GA came out,  they decided not to allow page faults on user buffers in kernel calls (the problem I just described above).

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