Re: [dbus-cplusplus-devel] dbus-c++ project on sourceforge created

[Andreas V. <li...@br...>]

Am Sun, 17 Aug 2008 15:34:49 +0200 schrieb P. Durante:

> On Sun, Aug 17, 2008 at 11:21 AM, Christopher Lang
> <chr...@ac...> wrote:
> >
> > Paolo,
> >
> > a question on your code:
> >
> > what is that "private" stuff all about? For example in class
> > "Connection" you are using this:
> >
> > class DXXAPI Connection
> > ...
> > 59      struct Private;
> > 60
> > 61      typedef std::list<Private*> PrivatePList;
> > 62
> > 63      Connection( Private* );
> >
> > Could you provide a little bit of rationale about this? It somehow
> > confuses me. Is this simply a "private" dbus connection for example
> > "app to app" connection? Or is this some (to me unknown) technique
> > to produce c++ quasi private members in the "public" section?
> >
> > many thanks
> >
> > Chris
> >
> >
> 
> it's not a private connection, it's the "private data" of that
> particular class, objects and messages have private data too
> 
> it's the typical pimpl pattern
> 
> http://en.wikipedia.org/wiki/Pimpl
> 
> and it serves two purposes:
> 
> -copying semantics-
> DBus::Connection objects (and any object implementing the same idiom)
> can be copied and all copies will refer to the same, internal, libdbus
> connection, reference counting is greatly simplified (look at the copy
> constructor in connection.cpp)
> 
> -isolation-
> the public interface of the library (that is, the files under
> include/) does not depend on libdbus, <dbus/dbus.h> is ONLY EVER
> included from implementation files (under src/)


Thanks for your explanations. I never used that design pattern. But it
sounds interesting. I'll implement some samples the next days to get
deeper into this design principle.

As I understood it we could maybe solve that pthread runtime problem
with the Pimpl design. In eventloop.h is this:

class DXXAPI DefaultMutex
{
public:

        DefaultMutex();

        ~DefaultMutex();

        void lock();

        void unlock();

private:

#if defined HAVE_PTHREAD_H

        pthread_mutex_t _mutex;

#elif defined HAVE_WIN32

//TODO: use a critical section

#endif
};

This was the reason for the private config header. Because if you
compile dbus-c++ with HAVE_PTHREAD_H and then the app without you'll
get a silent crash. Wouldn't a Pimpl implementation help here to avoid
the private config header?

regards
Andreas