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<!-- $Id$ -->
<HTML>
<HEAD>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
<META NAME="Author" CONTENT="James CE Johnson">
<TITLE>ACE Tutorial 019</TITLE>
</HEAD>
<BODY TEXT="#000000" BGCOLOR="#FFFFFF" LINK="#000FFF" VLINK="#FF0F0F">
<CENTER><B><FONT SIZE=+2>ACE Tutorial 019</FONT></B></CENTER>
<CENTER><B><FONT SIZE=+2>Sharing your Memories</FONT></B></CENTER>
<P>
<HR WIDTH="100%">
Did you ever wish you could read someone's mind? Or that they could
read yours?
<p>
Well, we won't be doing that here but we'll try to get close by
letting your code do something similar: Shared Memory.
<p>
What we're going to do is ask the operating system to set
aside a part of RAM that we can share with another process. By
doing this, we can allow our applications to swap data very
efficiently.
<p>
Along the way, we'll have to come up with some sort of
coordination betweent the processes. That is the most
difficult part of a shared memory system. In the tutorial we're
just going to take a simplistic approach (eg -- busy loop) but
real-world applications will need to take a serious look at
process-level synch mechanisms such as ACE_*_Semaphore.
<P>
Caveat: I've barely begun to use shared memory
myself. This tutorial and the next are very simple-minded and
primitive. Anyone who wants to provide more realistic
replacements is encouraged to drop me a note
(<A HREF="mailto:jcej@lads.com">jcej@lads.com</A>).
<P>
A tutorial wouldn't be complete without Kirthika's abstract:
<UL>
This tutorial shows how to use memory as a shared resource between the
client and server processes. ACE_Shared_Memory_SV has been used for
creating
the shared memory segment. Two different approaches have been used. One
uses the malloc () method to allocate memory while the other uses the
placement new expression (C++) of allocating a memory chunk in advance
and using it on demand.
<P>
The server has a string of alphabets from a-z which are converted to
uppercase
by the client proving that the same memory locations are being shared
between
the two processes. The syncronisation between the server and client is
done
using the ACE_OS::sleep () instead of a semaphore/mutexes with the aim
of keeping our first dive into shared memory usage simple and easy to
fathom.
</UL>
<P><HR WIDTH="100%">
<CENTER>[<A HREF="../online-tutorials.html">Tutorial Index</A>] [<A HREF="page02.html">Continue This Tutorial</A>]</CENTER>
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