refining the factory model

[stephan b. <st...@s1...>]

Yo, libfactory!

martin, i know you're on holiday, but i want to go ahead and send this 
while i'm thinking about it...

As part of the pclasses.com/s11n.net colaboration, Christian Prochnow 
(project lead) asked me if i would like to rewrite their Factory layer 
for their 1.x ==> 2.x rewrite. Maybe they were just kidding, but i 
happily accepted. i looked over their Factory implementation, then took 
what i learned from their code and applied it to the basic model laid 
out by s11n's factory.

So far, i'm extremely pleased with the results. i've gotten some great 
re-use out of the Factory class in the rest of the P tree, replacing 
the various P1.x Factories/PluginManagers with simple subclasses or 
typedefs of this implementation. Currently it provides the plugin 
support for MimeTypes, Serializers, and arbitrary client-side types, 
and will later support the IOManger layer, to dispatch to i/o handlers 
based on URL protocols.

Attached is what the base factory looks like. i've also included a 
couple supplemental headers it currently needs.

You'll notice that it doesn't have dll support. That's all fine and 
good, because clients can plug in their own by providing a template 
specialization of FactoryInstanceHook<FactoryT>. This how i've done it 
in the P tree: the DLL-aware layer (not part of the core module) plugs 
in it's own handler, such that Factory<T>::instance() returns a 
DLL-aware Factory instance.

The factory registration supermacro is in FactoryReg.h.

i really like P's "SharedLib" abstraction, and will implement something 
similar to abstract away the platform-specific details of opening a DLL 
for libfactory. P currently supports 5 or 6 different DLL loaders using 
their model, and i believe i can support libltdl, libdl and Win32 (the 
others are obscure platforms i won't have access to).

Please give a look to the Factory class and let me know if this seems 
like a usable model for libfactory. As part of s11n 1.1 i will be 
cleaning up the factory interface so we can plug in libfac to it.

See ya!

-- 
----- st...@s1...   http://s11n.net
"...pleasure is a grace and is not obedient to the commands
of the will." -- Alan W. Watts