🚀 go-pugleaf

"Vladimir Afanasyev" <avv@systema.kiev.ua> wrote in message
news:3ec37cee$1@newsgroups.borland.com...

> It can be so if name of the file-mapping object is
> known for all processes that want to use it. But process
> can create file mapping with name that is defines via
> random generator. In this case another process can't
> connect to file mapping via OpenFileMapping because
> name is unknown.

Well, of course.  But the whole point of sharing memory that is the other
processes know about it, thus they will know the name of the mapping and can
use Create/OpenFileMapping to get at it.  However, that is not the issue
being discussed.  The original question was how to restrict access to
read-only for other processes who do want to use the shared memory.  In that
regard, the answer is as stated earlier - the process who initially creates
the memory can't control that aspect of the memory, as each process
obtaining a pointer to the memory can specify their own individual settings
for how they want to access the memory.  Each process is only responsible
for its own local pointers to the memory, to to other process's pointers.

> If to return to question:
> >> Is there a way to share the memory, but to make
> >> it read-only to other processes?
> The answer is yes and DuplicateHandle just for it.

That can only work if you are actually passing the duplicated handle to the
other process directly, which I get the feeling is not the actual case in
MWP's situation, but that the other processes are accessing his mapped
memory directly.  DuplicateHandle() does not copy the new handle to other
processes, and certainly is not doing so in your examples.  To do that, the
other process would have to not be allowed to know the memory's mapped name
(aka, make it random), and the other process would have to know the process
handle of the memory's initial owner as well as the numeric value of the
original read-only handle inside that process.  That last step is not one
you have shown yet in your examples, as the other process has to make the
call to DuplicateHandle() passing it the original process's information.


Gambit