boost shared_ptr计数分析
boost::shared_ptr
boost::detail::shared_count pn; // reference counter
template
explicit shared_ptr( Y * p ): px( p ), pn( p )// Y must be complete
{
boost::detail::sp_enable_shared_from_this( this, p, p );
}
template
{
pi_ = new sp_counted_impl_p
if( pi_ == 0 )
{
boost::checked_delete( p );
boost::throw_exception( std::bad_alloc() );
}
}
explicit sp_counted_impl_p( X * px ): px_( px )
{
}
boost::shared_ptr
shared_ptr( shared_ptr const & r ): px( r.px ), pn( r.pn ) // never throws
{
}
shared_count(shared_countconst & r): pi_(r.pi_) // nothrow
{
if( pi_ != 0 ) pi_->add_ref_copy();
}
void sp_counted_base::add_ref_copy()
{
BOOST_INTERLOCKED_INCREMENT(&use_count_ );
}
boost::~shared_ptr
~shared_count() // nothrow
{
if( pi_ != 0 ) pi_->release();
}
void sp_counted_base::release()// nothrow
{
if( BOOST_INTERLOCKED_DECREMENT(&use_count_ ) == 0 )
{
dispose();
weak_release();
}
}
virtual void sp_counted_impl_p::dispose() // nothrow
{
boost::checked_delete( px_ );
}
void sp_counted_base::weak_release() //nothrow
{
if( BOOST_INTERLOCKED_DECREMENT(&weak_count_ ) == 0 )
{
destroy();
}
}
virtual void sp_counted_base::destroy() // nothrow
{
delete this;
}