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<div class="sect1">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="libgtop-white-paper-overview"></a>Overview</h2></div></div></div>
<p>This section should give you a short overview on how LibGTop
was developed, which things needed to be considered and how it
works.</p>
<div class="sect2">
<div class="titlepage"><div><div><h3 class="title">
<a name="libgtop-white-paper-overview-design"></a>Interface Design: Things that need to be considered</h3></div></div></div>
<p>
At the very beginning, it was necessary to collect all the data the library part
should provide and put them into some C structures. This was not that easiy as it
might sound since LibGTop should be portable to any modern UNIX system with a common
library part on all those systems, but the data that should be returned vary from
system to system. For instance some systems support shared memory, but some others
may not.</p>
<p>
The header files where we define these C structures (which are system-independent) are
shared between client and server. This way we can call the system dependent code
directly where we do not need any special privileges to do so.</p>
<p>
All of those structures contain a @code{flags} member which is interpreted as a bit
mask and tells the caller of the library functions which of the fields in the returned
structure are valid and which are not.</p>
</div>
<div class="sect2">
<div class="titlepage"><div><div><h3 class="title">
<a name="libgtop-white-paper-overview-server"></a>Server Implementation: The LibGTop "server"</h3></div></div></div>
<p>
The LibGTop @dfn{server} is a setgid/setuid binary which contains all the system
dependent code which needs special privileges. It is only build if it's required
on the current system (for instance, the Linux kernel provides all the required
data via its @file{/proc} filesystem so we do not need the server at all) and it
only contains the @dfn{features} which need privileges.</p>
<p>
Whenever we do not need any privileges to get all the data for some of the requested
structures (here called @dfn{features}) the library calls the sysdeps code directly
rather than using the server.</p>
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