Re: [boost] Re: Re: Interest in library generating streambufs fromobjects

From: Larry Evans (jcampbell3_at_[hidden])
Date: 2003-06-14 08:59:24

Maxim Egorushkin wrote:
> "Larry Evans" <jcampbell3_at_[hidden]> wrote in message
> news:3EE87CC6.9020905_at_prodigy.net...

[snip]

> I've examined col_io. At a high point of view it is the decorator pattern -
> you extend basic_ostream<> interface with identation capabilities. The code
> I posted, particulary input/output_buffer classes, is the adapter pattern -
> it adds basic_streambuf<> interface to a sequence. So, this patterns have
> different purposes.

Thanks very much.  I hadn't realized col_io (or more particularly the
code in test_marg_ostreambuf.zip) was a decorator pattern.  However, I
see now that the correspondence with the "Structure" secion on p. 177
of the GOF '95 _Design Patterns_ book.  More precisely:

    Component -> streambuf
    ConcreteComponent -> the streambuf from the original ostream
    Decorator -> fwd_ostreambuf
    Decorator::Operation -> fwd_ostreambuf::overflow
    ConcreteDecoratorA -> marg_ostreambuf
    ConcreteDecoratorA::addedState -> marg_put

I'll soon upload a commented an simplified version of marg_ostreambuf
and maybe a templatized version to parameterize the addedState. I may
rename it too to decorated_ostreambuf or something similar.

> If I get you right you want to see how one can add identation capabilites to
> a buffer using the adapters. Well, it could be done but it would be somewhat
> onerous. One would have to wrap an existing buffer with a developed sequence

OK.