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<H1><A NAME="SECTION00420000000000000000">
Loading Plugins</A>
</H1>
Once the File daemon loads the plugins, it asks the OS for the
two entry points (loadPlugin and unloadPlugin) then calls the
<B>loadPlugin</B> entry point (see below).
<P>
Bacula passes information to the plugin through this call and it gets
back information that it needs to use the plugin. Later, Bacula
will call particular functions that are defined by the
<B>loadPlugin</B> interface.
<P>
When Bacula is finished with the plugin
(when Bacula is going to exit), it will call the <B>unloadPlugin</B>
entry point.
<P>
The two entry points are:
<P>
<PRE>
bRC loadPlugin(bInfo *lbinfo, bFuncs *lbfuncs, pInfo **pinfo, pFuncs **pfuncs)
and
bRC unloadPlugin()
</PRE>
<P>
both these external entry points to the shared object are defined as C entry
points to avoid name mangling complications with C++. However, the shared
object can actually be written in any language (preferrably C or C++) providing
that it follows C language calling conventions.
<P>
The definitions for <B>bRC</B> and the arguments are <B>src/filed/fd-plugins.h</B> and so this header file needs to be included in
your plugin. It along with <B>src/lib/plugins.h</B> define basically the whole
plugin interface. Within this header file, it includes the following
files:
<P>
<PRE>
#include <sys/types.h>
#include "config.h"
#include "bc_types.h"
#include "lib/plugins.h"
#include <sys/stat.h>
</PRE>
<P>
Aside from the <B>bc_types.h</B> and <B>confit.h</B> headers, the plugin
definition uses the minimum code from Bacula. The bc_types.h file is required
to ensure that the data type defintions in arguments correspond to the Bacula
core code.
<P>
The return codes are defined as:
<PRE>
typedef enum {
bRC_OK = 0, /* OK */
bRC_Stop = 1, /* Stop calling other plugins */
bRC_Error = 2, /* Some kind of error */
bRC_More = 3, /* More files to backup */
} bRC;
</PRE>
<P>
At a future point in time, we hope to make the Bacula libbac.a into a
shared object so that the plugin can use much more of Bacula's
infrastructure, but for this first cut, we have tried to minimize the
dependence on Bacula.
<P>
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2012-01-24
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