RE: [boost] Re: static sized strings (struct hack)

From: Reece Dunn (msclrhd_at_[hidden])
Date: 2004-06-12 16:20:20

John Nagle wrote:
>    I think we're back to using an abstract base class.
>The hacks to get around it introduce worse problems.

I would agree. I have been trying to find a way around the problem and have 
(sortof) by having a base class:

   template< typename CharT >
   class string_base
   {
      private:
         size_t len, cap; // length & capacity
         CharT * buf; // data buffer
      public:
         string_base( CharT * b, size_t c, size_t l ):
            len( l ), cap( c ), buf( b ){}
         // non-virtual implementation
   };

   template< size_t n, typename CharT >
   class fixed_string: public string_base
   {
      private:
         CharT data[ n + 1 ];
      public:
         fixed_string(): string_base( data, n + 1 ){}
   };

The problems with this revolve around swapping/construction/copying and 
interfacing with (in my case) basic_string_impl. I cannot find a way around 
these problems without sacrificing something.

>    Take a look at my approach at
>http://www.animats.com/source/index.html
>
>That's a straightforward approach.  The only
>fundamental objection is that you take a virtual function
>call overhead on some operations.

That's the same with both approaches. Both designs are fundamentally the 
same and I don't see a way around this. It would be interesting to do a 
comparison with the 3 approaches (raw strcpy, etc on a char[ n ] buffer; 
your approach and mine) in virtual and non-virtual situations to compare 
performance.

>What needs to be done to that?

Are you aiming at supporting basic_string operations? If so, the class needs 
more work (all the find functions, for instance). If, however, you are just 
going for C-string replacement it is fine. One point on naming: the 
wide-character operations are wcscpy (strcpy), wcscat (strcat), wcscmp 
(strcmp), wcslen (strlen) and [v]swprintf (sprintf).

>Should I check it into the Boost sandbox, and
>if so, how?  Comments, please.  Thanks.

Go for it! You need a sourceforge account with CVS write access to the 
boost-sandbox. There is documentation at the sourceforge site for setting it 
up and pointers to the various tools. You will need to contact an 
administrator for write access once you have the sourceforge stuff setup.

Regards,
Reece

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