G4memory.hh

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//
#ifndef G4SHARED_PTR_HH_
#define G4SHARED_PTR_HH_

#include "CLHEP/Utility/memory.h"

#define G4shared_ptr G4::shared_ptr
#define G4weak_ptr G4::weak_ptr
#define G4static_pointer_cast G4::static_pointer_cast
#define G4const_pointer_cast G4::const_pointer_cast
#define G4dynamic_pointer_cast G4::dynamic_pointer_cast
#define G4enable_shared_from_this G4::enable_shared_from_this
#define G4enable_shared_from_this2 G4::enable_shared_from_this2

namespace G4
{
using CLHEP::shared_ptr;
using CLHEP::weak_ptr;
using CLHEP::static_pointer_cast;
using CLHEP::const_pointer_cast;
using CLHEP::dynamic_pointer_cast;
}

namespace CLHEP
{

template< typename T >
class enable_shared_from_this
{
protected:
        enable_shared_from_this()
{ }

        ~enable_shared_from_this()
        { }

        enable_shared_from_this( enable_shared_from_this const & )
        { }

        enable_shared_from_this &
        operator = ( enable_shared_from_this const & )
        {
                return *this;
        }

public:
        shared_ptr<T>
        shared_from_this()
        {
                shared_ptr<T>  p( weak_this_ );
                assert( p.get() == this );
                return p;
        }

        shared_ptr<T const>
        shared_from_this() const
        {
                shared_ptr<T const>  p( weak_this_ );
                assert( p.get() == this );
                return p;
        }

public: // actually private, but avoids compiler template friendship issues

        // Note: invoked automatically by shared_ptr; do not call
        template< typename X, typename Y >
        void
        _internal_accept_owner( shared_ptr<X> const * ppx, Y * py ) const
        {
                if( weak_this_.expired() )
                        weak_this_ = shared_ptr<T>( *ppx, py );
        }

private:
        mutable weak_ptr<T>  weak_this_;
};  // enable_shared_from_this<>


//  enable_shared_from_this2.hpp

namespace detail
{

class esft2_deleter_wrapper
{
private:
        shared_ptr<void>  deleter_;

public:
        esft2_deleter_wrapper(){ }

        template< typename T >
        void
        set_deleter( shared_ptr<T> const & deleter )
        {
                deleter_ = deleter;
        }

        template< typename T >
        void
        operator () ( T* )
        {
                assert( deleter_.use_count() <= 1 );
                deleter_.reset();
        }
};

} // namespace detail

template< typename T >
class enable_shared_from_this2
{
protected:

        enable_shared_from_this2(){ }

        enable_shared_from_this2( enable_shared_from_this2 const & )
        { }

        enable_shared_from_this2 & operator = ( enable_shared_from_this2 const & )
        {
                return *this;
        }

        ~enable_shared_from_this2()
        {
                assert( shared_this_.use_count() <= 1 ); // ensure no dangling shared_ptrs
        }

private:
        mutable  weak_ptr<T>    weak_this_;
        mutable  shared_ptr<T>  shared_this_;

public:

        shared_ptr<T>
        shared_from_this()
        {
                init_weak_once();
                return shared_ptr<T>( weak_this_ );
        }

        shared_ptr<T const>
        shared_from_this() const
        {
                init_weak_once();
                return shared_ptr<T>( weak_this_ );
        }

private:

        void init_weak_once() const
        {
                if( weak_this_._empty() )
                {
                        shared_this_.reset( static_cast< T* >( 0 )
                                        , detail::esft2_deleter_wrapper()
                        );
                        weak_this_ = shared_this_;
                }
        }

public:  // actually private, but avoids compiler template friendship issues

// Note: invoked automatically by shared_ptr; do not call
        template< typename X, typename Y >
        void
        _internal_accept_owner( shared_ptr<X> * ppx, Y * py ) const
        {
                assert( ppx != 0 );

                if( weak_this_.use_count() == 0 )
                        weak_this_ = shared_ptr<T>( *ppx, py );
                else if( shared_this_.use_count() != 0 )
                {
                        assert( ppx->unique() ); // no weak_ptrs should exist either, but there's no way to check that

                        detail::esft2_deleter_wrapper *  pd
                        = //boost::
                                        get_deleter<detail::esft2_deleter_wrapper>( shared_this_ );
                        assert( pd != 0 );

                        pd->set_deleter( *ppx );

                        ppx->reset( shared_this_, ppx->get() );
                        shared_this_.reset();
                }
        }
};  // enable_shared_from_this2<>
}

namespace G4
{
        using CLHEP::enable_shared_from_this;
        using CLHEP::enable_shared_from_this2;
}

#endif /* G4SHARED_PTR_HH_ */