readme.plugins

multi-line Adjunct Communication Server

With release 0.5, ACS introduces the concept of "plugins".  Plug-ins are
simply loadable shared modules that can be used to extend the
functionality of ACS in a modular fashion at runtime.  This keeps the
size of the primary ACS image small as plug-ins should involve optional or
alternate features. 

ACS plug-ins come in a variety of specialized forms.  Some plugins support
only one active instance,  while others may allow multiple modules to be
loaded.  ACS plug-ins are C++ classes derived from "modules.h".  Currently,
the following plug-in types are defined:

"mod"

This covers all "generic" modules.  Such modules may add one "keyword" to
the script interpreter.

"dba"

A dba plugin implements the insert/delete/search/update script keywords
through a database system.  The most common "dba" would likely be one that
uses gdbm.  A dba module is defined in "database.h" and only one instance
may be loaded.

"mbox"

A mbox plugin implements the commit/mailbox/extension/deliver keywords and
provides the underlying support for both mailbox database management and
transactional objects (class Mailbox).  Only one instance of a mbox may be
loaded at any given time.

notification

A notification module is derived from MWIModule.  It may be loaded as a
generic module, and more than one instance may be loaded.  The module may
export a keyword into the script interpreter like other generic modules.
Notification modules are used to implement message waiting indication and
paging.


Generally, a module is created by defining a dso with at least one global
module initializer derived from one of the module classes, as in:

#include <ACS/module.h>

class MyModule : public Module
{ ... };

MyModule myInstance(..);

The module constructor is created as the class is loaded, and the destructor
is called as the dso is removed from memory.  If the module makes use of
service threads, those should be started and stopped with the start/stop
methods.