Greg Copeland wrote:
>
> Windows does not really have shared memory support. This has been a
> beef with the Win32 API for a long time now. Because it has been a long
> time complaint, it was finally added in Win2000 and later. Likewise,
> I'd like to point out that thinks like sims, shared memory, pipes, etc,
> and other entities commonly used for concurrent programming strategies
> are slower in XP. So, because shared memory really isn't well
> supported, they elected to have what is, in essense, memory mapped
> files. Multiple processes then map the same file and read/write to it
> as needed, more or less as you would shared memory. Unless you plan on
> only targetting on Win 2000 and XP, it sounds like a waste of time.
This is not really true. Under DOS windows, i.e. 95,98, etc. Shared memory can
be done in 16 bit land with a touch of assembly and a DLL. Allocate, with
globalalloc, a shared memory segment. The base selector is a valid 32 bit
selector, and the memory is mapped in the above 2G space shared and mapped to
all 32bit processes.
Under NT through 2K, yes using a memory mapped files is the way to do it, but
you do not actually need to create a file, you can use (HANDLE)0xFFFFFFFF,
which is the NT equivilent of the system memory file. The handle returned is a
system global object which can be shared across processes.
>
