1 #ifndef BOOST_SMART_PTR_WEAK_PTR_HPP_INCLUDED
2 #define BOOST_SMART_PTR_WEAK_PTR_HPP_INCLUDED
7 // Copyright (c) 2001, 2002, 2003 Peter Dimov
9 // Distributed under the Boost Software License, Version 1.0. (See
10 // accompanying file LICENSE_1_0.txt or copy at
11 // http://www.boost.org/LICENSE_1_0.txt)
13 // See http://www.boost.org/libs/smart_ptr/weak_ptr.htm for documentation.
16 #include <memory> // boost.TR1 include order fix
17 #include <boost/smart_ptr/detail/shared_count.hpp>
18 #include <boost/smart_ptr/shared_ptr.hpp>
20 #ifdef BOOST_MSVC // moved here to work around VC++ compiler crash
21 # pragma warning(push)
22 # pragma warning(disable:4284) // odd return type for operator->
28 template<class T> class weak_ptr
32 // Borland 5.5.1 specific workarounds
33 typedef weak_ptr<T> this_type;
37 typedef T element_type;
39 weak_ptr(): px(0), pn() // never throws in 1.30+
43 // generated copy constructor, assignment, destructor are fine
47 // The "obvious" converting constructor implementation:
50 // weak_ptr(weak_ptr<Y> const & r): px(r.px), pn(r.pn) // never throws
54 // has a serious problem.
56 // r.px may already have been invalidated. The px(r.px)
57 // conversion may require access to *r.px (virtual inheritance).
59 // It is not possible to avoid spurious access violations since
60 // in multithreaded programs r.px may be invalidated at any point.
64 #if !defined( BOOST_SP_NO_SP_CONVERTIBLE )
66 weak_ptr( weak_ptr<Y> const & r, typename boost::detail::sp_enable_if_convertible<Y,T>::type = boost::detail::sp_empty() )
70 weak_ptr( weak_ptr<Y> const & r )
73 : px(r.lock().get()), pn(r.pn) // never throws
77 #if defined( BOOST_HAS_RVALUE_REFS )
80 #if !defined( BOOST_SP_NO_SP_CONVERTIBLE )
82 weak_ptr( weak_ptr<Y> && r, typename boost::detail::sp_enable_if_convertible<Y,T>::type = boost::detail::sp_empty() )
86 weak_ptr( weak_ptr<Y> && r )
89 : px( r.lock().get() ), pn( static_cast< boost::detail::weak_count && >( r.pn ) ) // never throws
94 // for better efficiency in the T == Y case
95 weak_ptr( weak_ptr && r ): px( r.px ), pn( static_cast< boost::detail::weak_count && >( r.pn ) ) // never throws
100 // for better efficiency in the T == Y case
101 weak_ptr & operator=( weak_ptr && r ) // never throws
103 this_type( static_cast< weak_ptr && >( r ) ).swap( *this );
111 #if !defined( BOOST_SP_NO_SP_CONVERTIBLE )
113 weak_ptr( shared_ptr<Y> const & r, typename boost::detail::sp_enable_if_convertible<Y,T>::type = boost::detail::sp_empty() )
117 weak_ptr( shared_ptr<Y> const & r )
120 : px( r.px ), pn( r.pn ) // never throws
124 #if !defined(BOOST_MSVC) || (BOOST_MSVC >= 1300)
127 weak_ptr & operator=(weak_ptr<Y> const & r) // never throws
134 #if defined( BOOST_HAS_RVALUE_REFS )
137 weak_ptr & operator=( weak_ptr<Y> && r )
139 this_type( static_cast< weak_ptr<Y> && >( r ) ).swap( *this );
146 weak_ptr & operator=(shared_ptr<Y> const & r) // never throws
155 shared_ptr<T> lock() const // never throws
157 return shared_ptr<element_type>( *this, boost::detail::sp_nothrow_tag() );
160 long use_count() const // never throws
162 return pn.use_count();
165 bool expired() const // never throws
167 return pn.use_count() == 0;
170 bool _empty() const // extension, not in std::weak_ptr
175 void reset() // never throws in 1.30+
177 this_type().swap(*this);
180 void swap(this_type & other) // never throws
182 std::swap(px, other.px);
186 void _internal_assign(T * px2, boost::detail::shared_count const & pn2)
192 template<class Y> bool _internal_less(weak_ptr<Y> const & rhs) const
197 // Tasteless as this may seem, making all members public allows member templates
198 // to work in the absence of member template friends. (Matthew Langston)
200 #ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS
204 template<class Y> friend class weak_ptr;
205 template<class Y> friend class shared_ptr;
209 T * px; // contained pointer
210 boost::detail::weak_count pn; // reference counter
214 template<class T, class U> inline bool operator<(weak_ptr<T> const & a, weak_ptr<U> const & b)
216 return a._internal_less(b);
219 template<class T> void swap(weak_ptr<T> & a, weak_ptr<T> & b)
227 # pragma warning(pop)
230 #endif // #ifndef BOOST_SMART_PTR_WEAK_PTR_HPP_INCLUDED