Re: [boost] Question regarding logging, persistence, threadcommunication, network messaging and async frameworks

From: Scott Woods (scott.suzuki_at_[hidden])
Date: 2008-05-25 19:26:59

Hi Brian,

Apologies to other list members. I am experiencing very odd mail service 
that
means I am not receiving messages on the Boost list sent by myself. Here's a
brief response to Brian while I try to figure things out.

----- Original Message ----- 
From: "brass goowy" <brass_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Monday, May 26, 2008 10:43 AM
Subject: Re: [boost]Question regarding logging, persistence, 
threadcommunication, network messaging and async frameworks

> Scott Woods writes:
>>Hi,
>>Is there a place in Boost for a library that tackles all of the above? I
>>believe the realistic
>>answer is no but I would be happy to be proven wrong.
>>Work in the different areas mentioned in the subject line recently 
>>collapsed
>>into a single
>>underlying technique. Given the example UDT below;
>>struct person
>>{
>>std::string name;
>>std::vector<unsigned> score;
>>std::set<string> team;
>>};

<snip>

>>actually this is precisely the most compelling thing about the library - 
>>it
>>reduces code
>>that traditionally can be quite difficult into fragments such as those
>>shown.
>
> Shalom
>
>>From what you've shown it looks like the duplication of data members
> in serialization methods is not needed.  Some have been struggling to
> eliminate the need for that duplication --  
> http://preview.tinyurl.com/6kpx8t .
> Maybe more details about codec_object<> would be helpful.

I'm not so sure about that ;-) but in good faith;

    struct object_stack
    {
         typedef file_device device_type;
         typedef transfer_block<device_type> transfer_type;
         typedef binary_run_codec<transfer_type> codec_type;
    };

    // Declaration of the left side (the device+transfer+object)
    // of the transfer.

    template<typename V,typename S=object_stack>
    struct codec_object
    {
         typedef V value_type;
         typedef S::codec_type codec_type;

        type_hash type;
        std::string base_name;
        std::string name_to_open;
        codec_type codec;

        void
        decorate( const std::string &s )
        {
            name_to_open = base_name = s;

            name_to_open += '.';
            name_to_open += codec.codec_tag();
        }

        codec_object() :
        type( type_of<value_type>::hash() )
        {}

        codec_object( const std::string &k ) :
        type( type_of<value_type>::hash() )
        {
            decorate( k );
        }

        void
        change_to( const std::string &k )
        {
            decorate( k );
        }
    };

I looked through the thread at "for each member of a sturcture/class ?" and 
not
sure how to respond; the issue being dealt with in that thread (while 
interesting) is
subordinate to my goals.

I do not have any magic technique for avoiding duplication of member
information. Any C++ type that wishes to play within my library
must define the following two global operators;

    inline network_variant &
    operator<<( network_variant &nv, const person &p )
    {
        network_memory::iterator i = network_output<3>()( nv );
        *i++ << p.name;
        *i++ << p.score;
        *i++ << p.team;
        return nv;
    }

    inline person &
    operator>>( network_variant &nv, person &p )
    {
        network_memory::iterator i = network_input<3>()( nv );
        *i++ >> p.name;
        *i++ >> p.score;
        *i++ >> p.team;
        return p;
    }

My library for persistence, thread communication and network messaging
deals with the movement and representation of "network_variants", i.e.
by providing transform functions as above, the type acquires persistence,
transfer-between-threads and transfer-across-networks capabilities, in
one hit.

There is more to say in this area (type declaration) but I'm not sure that 
either
of us was actually headed there.

Scott.