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- #ifndef BOOSTER_SMART_PTR_WEAK_PTR_HPP_INCLUDED
- #define BOOSTER_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 <booster/auto_ptr_inc.h> // boost.TR1 include order fix
- #include <booster/smart_ptr/shared_count.h>
- #include <booster/shared_ptr.h>
-
- #ifdef BOOSTER_MSVC // moved here to work around VC++ compiler crash
- # pragma warning(push)
- # pragma warning(disable:4284) // odd return type for operator->
- #endif
-
- namespace booster
- {
-
- 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
-
-
- //
- // 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>
- weak_ptr( weak_ptr<Y> const & r, typename detail::sp_enable_if_convertible<Y,T>::type = detail::sp_empty() )
- : px(r.lock().get()), pn(r.pn) // never throws
- {
- }
-
-
- template<class Y>
- weak_ptr( shared_ptr<Y> const & r, typename detail::sp_enable_if_convertible<Y,T>::type = detail::sp_empty() )
- : px( r.px ), pn( r.pn ) // never throws
- {
- }
-
- template<class Y>
- weak_ptr & operator=(weak_ptr<Y> const & r) // never throws
- {
- px = r.lock().get();
- pn = r.pn;
- return *this;
- }
-
- template<class Y>
- weak_ptr & operator=(shared_ptr<Y> const & r) // never throws
- {
- px = r.px;
- pn = r.pn;
- return *this;
- }
-
- shared_ptr<T> lock() const // never throws
- {
- return shared_ptr<element_type>( *this, booster::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, booster::detail::shared_count const & pn2)
- {
- px = px2;
- pn = pn2;
- }
-
- template<class Y> bool _internal_less(weak_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)
-
- private:
-
- template<class Y> friend class weak_ptr;
- template<class Y> friend class shared_ptr;
-
- T * px; // contained pointer
- booster::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._internal_less(b);
- }
-
- template<class T> void swap(weak_ptr<T> & a, weak_ptr<T> & b)
- {
- a.swap(b);
- }
-
- } // namespace boost
-
- #ifdef BOOSTER_MSVC
- # pragma warning(pop)
- #endif
-
- #endif // #ifndef BOOST_SMART_PTR_WEAK_PTR_HPP_INCLUDED
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