Re: Portable Class For Shared Memory
On Sep 30, 12:06 pm, Lance Diduck <lancedid...@nyc.rr.com> wrote:
Other posters have already pointed to Ion Gaztaqaga Interprocess
Libraries, and I have started making my own library using these
interfaces (I can't wait for boost to release 1.35). The offset_ptr is
particularly good tool to have.
What I have found is that it is fairly straightforward to make
wrappers around the various sharem memory implementations (at least
the POSIX and SysV variety) but far harder to ensure that the C++
class you actually want to place in shared memory can be placed in
shared memory.
1. just templatizing a STL containers with a "shared memory allocator"
will not work. There is no guarantee that the memory address assigned
to your shmem segment in one process space is the same for another
process space. All standard container implementations use naked
pointers in one way or another internally --when it is swapped, the
pointer stored in shared memory assigned by process 1 makes no sense
for process 2.
It took me two reads of your post to realize that some people are
actually using shared memory as the memory pool for a generic (perhaps
class-specific) C++ allocator. I never intended to do this, and I
will abstain from criticizing anyone who might walk this path, lest we
open a can of worms. :D
No, I am doing something much simpler: getting block of "system-wide"
shared memory and doing old-fashioned C struct overlay on top of it.
I wanted a portable class because 98% of rest of my code is portable,
and I wanted to avoid contaminating it.
So the class is just to provide portable interface for actually
getting the memory.
-Le Chaud Lapin-
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