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From: Peter Dimov (pdimov_at_[hidden])
Date: 2005-12-19 17:05:11

Christopher Kohlhoff wrote:


> Basically I would add a new static function
> basic_demuxer<>::global(), which returns a reference to the
> singleton demuxer object. Constructors would look something
> like:
> basic_stream_socket(demuxer_type& d = demuxer_type::global())
> Synchronous-only code could then be written without knowledge of
> the demuxer:
> ipv4::host_resolver r;
> stream_socket s;
> deadline_timer t;
> etc...
> However, unlike Jeremy's dummy demuxer suggestion, the async
> operations would still be allowed.


> I generally dislike singletons because of the issues to do with
> the order of cosntruction and cleanup.

You should dislike singletons because they are global variables.

The problem with the above apporach is that most code will end up using the
global demuxer because this is the path of least resistance. When it turns
out that the code needs to be refactored to use a specific demuxer, the
programmers would need to go over it with a fine-toothed comb and replace
every implicit reference to the global demuxer with an explicit demuxer
reference, passing that reference wherever necessary. It'd be a pain, and
it'd be easy to miss some. Not to mention that the code that implicitly uses
the global demuxer may be in a library for which the source is not

So yes, the easy case will be easier, but the hard case will be harder.

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