#ifndef BOOST_SMART_PTR_WEAK_PTR_HPP_INCLUDED #define BOOST_SMART_PTR_WEAK_PTR_HPP_INCLUDED // // weak_ptr.hpp // // Copyright (c) 2001, 2002, 2003 Peter Dimov // // Distributed under the Boost Software License, Version 1.0. (See // accompanying file LICENSE_1_0.txt or copy at // http://www.boost.org/LICENSE_1_0.txt) // // See http://www.boost.org/libs/smart_ptr/weak_ptr.htm for documentation. // #include <memory> // boost.TR1 include order fix #include <boost/smart_ptr/detail/shared_count.hpp> #include <boost/smart_ptr/shared_ptr.hpp> namespace boost { template<class T> class weak_ptr { private: // Borland 5.5.1 specific workarounds typedef weak_ptr<T> this_type; public: typedef T element_type; weak_ptr(): px(0), pn() // never throws in 1.30+ { } // generated copy constructor, assignment, destructor are fine... #if defined( BOOST_HAS_RVALUE_REFS ) // ... except in C++0x, move disables the implicit copy weak_ptr( weak_ptr const & r ): px( r.px ), pn( r.pn ) // never throws { } weak_ptr & operator=( weak_ptr const & r ) // never throws { px = r.px; pn = r.pn; return *this; } #endif // // The "obvious" converting constructor implementation: // // template<class Y> // weak_ptr(weak_ptr<Y> const & r): px(r.px), pn(r.pn) // never throws // { // } // // has a serious problem. // // r.px may already have been invalidated. The px(r.px) // conversion may require access to *r.px (virtual inheritance). // // It is not possible to avoid spurious access violations since // in multithreaded programs r.px may be invalidated at any point. // template<class Y> #if !defined( BOOST_SP_NO_SP_CONVERTIBLE ) weak_ptr( weak_ptr<Y> const & r, typename boost::detail::sp_enable_if_convertible<Y,T>::type = boost::detail::sp_empty() ) #else weak_ptr( weak_ptr<Y> const & r ) #endif : px(r.lock().get()), pn(r.pn) // never throws { } #if defined( BOOST_HAS_RVALUE_REFS ) template<class Y> #if !defined( BOOST_SP_NO_SP_CONVERTIBLE ) weak_ptr( weak_ptr<Y> && r, typename boost::detail::sp_enable_if_convertible<Y,T>::type = boost::detail::sp_empty() ) #else weak_ptr( weak_ptr<Y> && r ) #endif : px( r.lock().get() ), pn( static_cast< boost::detail::weak_count && >( r.pn ) ) // never throws { r.px = 0; } // for better efficiency in the T == Y case weak_ptr( weak_ptr && r ): px( r.px ), pn( static_cast< boost::detail::weak_count && >( r.pn ) ) // never throws { r.px = 0; } // for better efficiency in the T == Y case weak_ptr & operator=( weak_ptr && r ) // never throws { this_type( static_cast< weak_ptr && >( r ) ).swap( *this ); return *this; } #endif template<class Y> #if !defined( BOOST_SP_NO_SP_CONVERTIBLE ) weak_ptr( shared_ptr<Y> const & r, typename boost::detail::sp_enable_if_convertible<Y,T>::type = boost::detail::sp_empty() ) #else weak_ptr( shared_ptr<Y> const & r ) #endif : px( r.px ), pn( r.pn ) // never throws { } #if !defined(BOOST_MSVC) || (BOOST_MSVC >= 1300) template<class Y> weak_ptr & operator=(weak_ptr<Y> const & r) // never throws { px = r.lock().get(); pn = r.pn; return *this; } #if defined( BOOST_HAS_RVALUE_REFS ) template<class Y> weak_ptr & operator=( weak_ptr<Y> && r ) { this_type( static_cast< weak_ptr<Y> && >( r ) ).swap( *this ); return *this; } #endif template<class Y> weak_ptr & operator=(shared_ptr<Y> const & r) // never throws { px = r.px; pn = r.pn; return *this; } #endif shared_ptr<T> lock() const // never throws { return shared_ptr<element_type>( *this, boost::detail::sp_nothrow_tag() ); } long use_count() const // never throws { return pn.use_count(); } bool expired() const // never throws { return pn.use_count() == 0; } bool _empty() const // extension, not in std::weak_ptr { return pn.empty(); } void reset() // never throws in 1.30+ { this_type().swap(*this); } void swap(this_type & other) // never throws { std::swap(px, other.px); pn.swap(other.pn); } void _internal_assign(T * px2, boost::detail::shared_count const & pn2) { px = px2; pn = pn2; } template<class Y> bool owner_before( weak_ptr<Y> const & rhs ) const { return pn < rhs.pn; } template<class Y> bool owner_before( shared_ptr<Y> const & rhs ) const { return pn < rhs.pn; } // Tasteless as this may seem, making all members public allows member templates // to work in the absence of member template friends. (Matthew Langston) #ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS private: template<class Y> friend class weak_ptr; template<class Y> friend class shared_ptr; #endif T * px; // contained pointer boost::detail::weak_count pn; // reference counter }; // weak_ptr template<class T, class U> inline bool operator<(weak_ptr<T> const & a, weak_ptr<U> const & b) { return a.owner_before( b ); } template<class T> void swap(weak_ptr<T> & a, weak_ptr<T> & b) { a.swap(b); } } // namespace boost #endif // #ifndef BOOST_SMART_PTR_WEAK_PTR_HPP_INCLUDED