Re: DLL library (Was: [boost] Re: additional boost libraries?)

From: Reece Dunn (msclrhd_at_[hidden])
Date: 2004-07-26 07:27:51

Vladimir Prus wrote:
>Hi Mattias,
> > On Fri, 23 Jul 2004 13:49:22 +0400, Vladimir Prus <ghost_at_[hidden]> 
>wrote:
> > > static imported_function<void()>   apiFunc( "ApiFunc", "OSLib" );
> >
> > Couldn't find a nice point in the thread at which to insert this
> > comment, so I'll just spit it out: Since we have both the name of the
> > function and the function type, and given that a lib such as this
> > should provide a platform-independent interface, would it be useful if
> > the library automatically mangled the name according to the type?
>
>I think you've missed something ;-) Even my initial reply inthe "additional
>boost libraries" thread mentioned the possibility of calling functions 
>which
>are not "extern "C". At least two other persons seems to want this. I find
>this would be nice, though not critical at all.

Would it be possible to have a mangle function, then you could do something 
like:

   static imported_function<void()>   apiFunc( mangle::mwcw( "ApiFunc" ), 
"OSLib" );

This would mean that imported_function need only know how to get the 
function (e.g. using GetProcAddress in Win32) and not worry about the name 
mangling scheme used. The name mangling could then be handled by a 
mangler/demangler library that would be useful in diagnostics, e.g.:

   template< typename T >
   inline void print_type( const T & t )
   {
      std::cout << demangle::gcc3( typeid(t).name());
   }

Also, wouldn't it be better to have import as a function of shared_library, 
so you could do something like:

   boost::shared_library mylib( "user32.dll" )
   typedef ... msgboxA_fn;

   msgboxA_fn mbA = mylib.import< msgboxA_fn >( "MessageBoxA" );
   msgboxW_fn mbW = mylib.import< msgboxW_fn >( "MessageBoxW" );

With the possible Win32 implementation of, but using boost::function:

namespace boost
{
   class shared_library
   {
      private:
         HANDLE hDLL;
      public:
         template< typename Function >
         inline Function * import( const char * fn )
         {
            if( hDLL == 0 ) return( 0 );
            return( reinterpret_cast< Function * >( ::GetProcAddress( hDLL, 
fn )));
         }
      public:
         inline shared_library( const char * fn ): hDLL( ::LoadLibrary( fn 
))
         {
         }
         inline ~shared_library()
         {
           if( hDLL )
            {
               ::FreeLibrary( hDLL );
               hDLL = 0;
            }
         }
   };
}

Regards,
Reece

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