Re: [boost] Request for rationale

From: Gregory Dai (gregory.dai_at_[hidden])
Date: 2007-11-03 17:41:14

On 11/3/07, Emil Dotchevski <emil_at_[hidden]> wrote:
>
> > I don't think making file_entry is a lot of work. It's pretty simple and
> > straightforward. And once it's made, you keep it around in your arsenal.
>
> Not to split hairs here, but you could also write:
>
> boost::shared_ptr<FILE> open_file( char const * name, char const * mode )
> {
>   if( FILE * f = fopen(name,mode) )
>     return boost::shared_ptr<FILE>(f,fclose);
>   else
>     throw fopen_error(name,mode);
> }
>
> and keep that in your "arsenal".
>
> In fact, I think this function would be a good addition to boost so
> it's part of everyone's arsenal. :)

This free function looks pretty good, indeed. But again, file_sentry works
with not only shared_ptr, but auto_ptr or other *_ptr's as well. In reality
auto_ptr is lighter and has more applications than shared_ptr. That is,
there are in general more applications of auto_ptr<file_sentry> than of
shared_ptr<file_sentry>. Now we are talking about templatizing this function
and what not.

In another dimension, we have other C pointer types similar to FILE*. This
is harder to templatize than the type of *_ptr, due to differences in
functions such as fopen()/fclose(). In such cases, it seems ideal to have
separate thin wrappers to encapsulate the differences.