sl@0: #ifndef BOOST_WEAK_PTR_HPP_INCLUDED
sl@0: #define BOOST_WEAK_PTR_HPP_INCLUDED
sl@0: 
sl@0: //
sl@0: //  weak_ptr.hpp
sl@0: //
sl@0: //  Copyright (c) 2001, 2002, 2003 Peter Dimov
sl@0: //
sl@0: // Distributed under the Boost Software License, Version 1.0. (See
sl@0: // accompanying file LICENSE_1_0.txt or copy at
sl@0: // http://www.boost.org/LICENSE_1_0.txt)
sl@0: //
sl@0: //  See http://www.boost.org/libs/smart_ptr/weak_ptr.htm for documentation.
sl@0: //
sl@0: 
sl@0: #include <memory> // boost.TR1 include order fix
sl@0: #include <boost/detail/shared_count.hpp>
sl@0: #include <boost/shared_ptr.hpp>
sl@0: 
sl@0: #ifdef BOOST_MSVC  // moved here to work around VC++ compiler crash
sl@0: # pragma warning(push)
sl@0: # pragma warning(disable:4284) // odd return type for operator->
sl@0: #endif
sl@0: 
sl@0: namespace boost
sl@0: {
sl@0: 
sl@0: template<class T> class weak_ptr
sl@0: {
sl@0: private:
sl@0: 
sl@0:     // Borland 5.5.1 specific workarounds
sl@0:     typedef weak_ptr<T> this_type;
sl@0: 
sl@0: public:
sl@0: 
sl@0:     typedef T element_type;
sl@0: 
sl@0:     weak_ptr(): px(0), pn() // never throws in 1.30+
sl@0:     {
sl@0:     }
sl@0: 
sl@0: //  generated copy constructor, assignment, destructor are fine
sl@0: 
sl@0: 
sl@0: //
sl@0: //  The "obvious" converting constructor implementation:
sl@0: //
sl@0: //  template<class Y>
sl@0: //  weak_ptr(weak_ptr<Y> const & r): px(r.px), pn(r.pn) // never throws
sl@0: //  {
sl@0: //  }
sl@0: //
sl@0: //  has a serious problem.
sl@0: //
sl@0: //  r.px may already have been invalidated. The px(r.px)
sl@0: //  conversion may require access to *r.px (virtual inheritance).
sl@0: //
sl@0: //  It is not possible to avoid spurious access violations since
sl@0: //  in multithreaded programs r.px may be invalidated at any point.
sl@0: //
sl@0: 
sl@0:     template<class Y>
sl@0:     weak_ptr(weak_ptr<Y> const & r): pn(r.pn) // never throws
sl@0:     {
sl@0:         px = r.lock().get();
sl@0:     }
sl@0: 
sl@0:     template<class Y>
sl@0:     weak_ptr(shared_ptr<Y> const & r): px(r.px), pn(r.pn) // never throws
sl@0:     {
sl@0:     }
sl@0: 
sl@0: #if !defined(BOOST_MSVC) || (BOOST_MSVC >= 1300)
sl@0: 
sl@0:     template<class Y>
sl@0:     weak_ptr & operator=(weak_ptr<Y> const & r) // never throws
sl@0:     {
sl@0:         px = r.lock().get();
sl@0:         pn = r.pn;
sl@0:         return *this;
sl@0:     }
sl@0: 
sl@0:     template<class Y>
sl@0:     weak_ptr & operator=(shared_ptr<Y> const & r) // never throws
sl@0:     {
sl@0:         px = r.px;
sl@0:         pn = r.pn;
sl@0:         return *this;
sl@0:     }
sl@0: 
sl@0: #endif
sl@0: 
sl@0:     shared_ptr<T> lock() const // never throws
sl@0:     {
sl@0: #if defined(BOOST_HAS_THREADS)
sl@0: 
sl@0:         // optimization: avoid throw overhead
sl@0:         if(expired())
sl@0:         {
sl@0:             return shared_ptr<element_type>();
sl@0:         }
sl@0: 
sl@0:         try
sl@0:         {
sl@0:             return shared_ptr<element_type>(*this);
sl@0:         }
sl@0:         catch(bad_weak_ptr const &)
sl@0:         {
sl@0:             // Q: how can we get here?
sl@0:             // A: another thread may have invalidated r after the use_count test above.
sl@0:             return shared_ptr<element_type>();
sl@0:         }
sl@0: 
sl@0: #else
sl@0: 
sl@0:         // optimization: avoid try/catch overhead when single threaded
sl@0:         return expired()? shared_ptr<element_type>(): shared_ptr<element_type>(*this);
sl@0: 
sl@0: #endif
sl@0:     }
sl@0: 
sl@0:     long use_count() const // never throws
sl@0:     {
sl@0:         return pn.use_count();
sl@0:     }
sl@0: 
sl@0:     bool expired() const // never throws
sl@0:     {
sl@0:         return pn.use_count() == 0;
sl@0:     }
sl@0: 
sl@0:     void reset() // never throws in 1.30+
sl@0:     {
sl@0:         this_type().swap(*this);
sl@0:     }
sl@0: 
sl@0:     void swap(this_type & other) // never throws
sl@0:     {
sl@0:         std::swap(px, other.px);
sl@0:         pn.swap(other.pn);
sl@0:     }
sl@0: 
sl@0:     void _internal_assign(T * px2, boost::detail::shared_count const & pn2)
sl@0:     {
sl@0:         px = px2;
sl@0:         pn = pn2;
sl@0:     }
sl@0: 
sl@0:     template<class Y> bool _internal_less(weak_ptr<Y> const & rhs) const
sl@0:     {
sl@0:         return pn < rhs.pn;
sl@0:     }
sl@0: 
sl@0: // Tasteless as this may seem, making all members public allows member templates
sl@0: // to work in the absence of member template friends. (Matthew Langston)
sl@0: 
sl@0: #ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS
sl@0: 
sl@0: private:
sl@0: 
sl@0:     template<class Y> friend class weak_ptr;
sl@0:     template<class Y> friend class shared_ptr;
sl@0: 
sl@0: #endif
sl@0: 
sl@0:     T * px;                       // contained pointer
sl@0:     boost::detail::weak_count pn; // reference counter
sl@0: 
sl@0: };  // weak_ptr
sl@0: 
sl@0: template<class T, class U> inline bool operator<(weak_ptr<T> const & a, weak_ptr<U> const & b)
sl@0: {
sl@0:     return a._internal_less(b);
sl@0: }
sl@0: 
sl@0: template<class T> void swap(weak_ptr<T> & a, weak_ptr<T> & b)
sl@0: {
sl@0:     a.swap(b);
sl@0: }
sl@0: 
sl@0: // deprecated, provided for backward compatibility
sl@0: template<class T> shared_ptr<T> make_shared(weak_ptr<T> const & r)
sl@0: {
sl@0:     return r.lock();
sl@0: }
sl@0: 
sl@0: } // namespace boost
sl@0: 
sl@0: #ifdef BOOST_MSVC
sl@0: # pragma warning(pop)
sl@0: #endif    
sl@0: 
sl@0: #endif  // #ifndef BOOST_WEAK_PTR_HPP_INCLUDED