Re: [boost] [smart_ptr] shared_ptr template type

Subject: Re: [boost] [smart_ptr] shared_ptr template type
From: Sid Sacek (ssacek_at_[hidden])
Date: 2009-07-09 12:50:33

> I wonder if it might be better/possible to have a shared_ptr<T> that
didn't 
> assume its corresponding "raw" pointer type was T* but rather T.

If I'm not mistaken, the C++0x committee is setting the 'shared_ptr<>'
class in stone as we speak. I seriously doubt that can be changed this
late in the game, considering the amount of code that is already using
this class as-is.

See if this type of code works for you:

#include <boost/shared_ptr.hpp>

using boost::shared_ptr;

struct mutex
{
        void lock() {}
        void unlock() {}
};

template< typename T > class monitor;

template< typename T > class locker
{
        mutex        & mutex_;
        monitor< T > * monitor_;
public:
         locker( monitor< T > * mt, mutex & mx ) : mutex_( mx ),
monitor_( mt )
         {
                 mutex_.lock();
         }
        ~locker()
        {
                mutex_.unlock(); 
        }
        monitor< T > * operator->()
        {
                return monitor_;
        }
};

template< typename T > class monitor
{
        mutex mutex_;
public:
        shared_ptr< T > obj_ptr;

        monitor( T * t ) : obj_ptr( shared_ptr< T >( t ) )
        { }

        locker< T > operator->()
        {
                return locker< T >( this, mutex_ );
        }
};

int main( int argc, char * argv[] )
{
        char * buf = new char[ 3 ];
        memset( buf, 0, 3 );

        monitor< char > m( buf );
        *m->obj_ptr = 'A';

        return 0;
}