Chris@16: //////////////////////////////////////////////////////////////////////////////
Chris@16: //
Chris@16: // This file is the adaptation for Interprocess of boost/weak_ptr.hpp
Chris@16: //
Chris@16: // (C) Copyright Peter Dimov 2001, 2002, 2003
Chris@16: // (C) Copyright Ion Gaztanaga 2006-2012.
Chris@16: // Distributed under the Boost Software License, Version 1.0.
Chris@16: // (See accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: //
Chris@16: // See http://www.boost.org/libs/interprocess for documentation.
Chris@16: //
Chris@16: //////////////////////////////////////////////////////////////////////////////
Chris@16: 
Chris@16: #ifndef BOOST_INTERPROCESS_WEAK_PTR_HPP_INCLUDED
Chris@16: #define BOOST_INTERPROCESS_WEAK_PTR_HPP_INCLUDED
Chris@16: 
Chris@101: #ifndef BOOST_CONFIG_HPP
Chris@101: #  include <boost/config.hpp>
Chris@101: #endif
Chris@101: #
Chris@101: #if defined(BOOST_HAS_PRAGMA_ONCE)
Chris@101: #  pragma once
Chris@101: #endif
Chris@101: 
Chris@16: #include <boost/interprocess/detail/config_begin.hpp>
Chris@16: #include <boost/interprocess/detail/workaround.hpp>
Chris@16: 
Chris@16: #include <boost/interprocess/smart_ptr/shared_ptr.hpp>
Chris@101: #include <boost/core/no_exceptions_support.hpp>
Chris@16: #include <boost/interprocess/allocators/allocator.hpp>
Chris@16: #include <boost/interprocess/smart_ptr/deleter.hpp>
Chris@16: #include <boost/intrusive/pointer_traits.hpp>
Chris@101: #include <boost/move/adl_move_swap.hpp>
Chris@16: 
Chris@16: //!\file
Chris@16: //!Describes the smart pointer weak_ptr.
Chris@16: 
Chris@16: namespace boost{
Chris@16: namespace interprocess{
Chris@16: 
Chris@16: //!The weak_ptr class template stores a "weak reference" to an object
Chris@16: //!that's already managed by a shared_ptr. To access the object, a weak_ptr
Chris@16: //!can be converted to a shared_ptr using  the shared_ptr constructor or the
Chris@16: //!member function  lock. When the last shared_ptr to the object goes away
Chris@16: //!and the object is deleted, the attempt to obtain a shared_ptr from the
Chris@16: //!weak_ptr instances that refer to the deleted object will fail: the constructor
Chris@16: //!will throw an exception of type bad_weak_ptr, and weak_ptr::lock will
Chris@16: //!return an empty shared_ptr.
Chris@16: //!
Chris@16: //!Every weak_ptr meets the CopyConstructible and Assignable requirements
Chris@16: //!of the C++ Standard Library, and so can be used in standard library containers.
Chris@16: //!Comparison operators are supplied so that weak_ptr works with the standard
Chris@16: //!library's associative containers.
Chris@16: //!
Chris@16: //!weak_ptr operations never throw exceptions.
Chris@16: //!
Chris@16: //!The class template is parameterized on T, the type of the object pointed to.
Chris@16: template<class T, class A, class D>
Chris@16: class weak_ptr
Chris@16: {
Chris@101:    #if !defined(BOOST_INTERPROCESS_DOXYGEN_INVOKED)
Chris@16:    private:
Chris@16:    // Borland 5.5.1 specific workarounds
Chris@16:    typedef weak_ptr<T, A, D> this_type;
Chris@16:    typedef typename boost::intrusive::
Chris@16:       pointer_traits<typename A::pointer>::template
Chris@16:          rebind_pointer<T>::type                         pointer;
Chris@16:    typedef typename ipcdetail::add_reference
Chris@16:                      <T>::type            reference;
Chris@16:    typedef typename ipcdetail::add_reference
Chris@16:                      <T>::type            const_reference;
Chris@101:    #endif   //#ifndef BOOST_INTERPROCESS_DOXYGEN_INVOKED
Chris@16: 
Chris@16:    public:
Chris@16:    typedef T element_type;
Chris@16:    typedef T value_type;
Chris@16: 
Chris@16:    //!Effects: Constructs an empty weak_ptr.
Chris@16:    //!Postconditions: use_count() == 0.
Chris@16:    weak_ptr()
Chris@16:    : m_pn() // never throws
Chris@16:    {}
Chris@16:    //  generated copy constructor, assignment, destructor are fine
Chris@16:    //
Chris@16:    //  The "obvious" converting constructor implementation:
Chris@16:    //
Chris@16:    //  template<class Y>
Chris@16:    //  weak_ptr(weak_ptr<Y> const & r): m_px(r.m_px), m_pn(r.m_pn) // never throws
Chris@16:    //  {
Chris@16:    //  }
Chris@16:    //
Chris@16:    //  has a serious problem.
Chris@16:    //
Chris@16:    //  r.m_px may already have been invalidated. The m_px(r.m_px)
Chris@16:    //  conversion may require access to *r.m_px (virtual inheritance).
Chris@16:    //
Chris@16:    //  It is not possible to avoid spurious access violations since
Chris@16:    //  in multithreaded programs r.m_px may be invalidated at any point.
Chris@16: 
Chris@16:    //!Effects: If r is empty, constructs an empty weak_ptr; otherwise,
Chris@16:    //!constructs a weak_ptr that shares ownership with r as if by storing a
Chris@16:    //!copy of the pointer stored in r.
Chris@16:    //!
Chris@16:    //!Postconditions: use_count() == r.use_count().
Chris@16:    //!
Chris@16:    //!Throws: nothing.
Chris@16:    template<class Y>
Chris@16:    weak_ptr(weak_ptr<Y, A, D> const & r)
Chris@16:       : m_pn(r.m_pn) // never throws
Chris@16:    {
Chris@16:       //Construct a temporary shared_ptr so that nobody
Chris@16:       //can destroy the value while constructing this
Chris@16:       const shared_ptr<T, A, D> &ref = r.lock();
Chris@16:       m_pn.set_pointer(ref.get());
Chris@16:    }
Chris@16: 
Chris@16:    //!Effects: If r is empty, constructs an empty weak_ptr; otherwise,
Chris@16:    //!constructs a weak_ptr that shares ownership with r as if by storing a
Chris@16:    //!copy of the pointer stored in r.
Chris@16:    //!
Chris@16:    //!Postconditions: use_count() == r.use_count().
Chris@16:    //!
Chris@16:    //!Throws: nothing.
Chris@16:    template<class Y>
Chris@16:    weak_ptr(shared_ptr<Y, A, D> const & r)
Chris@16:       : m_pn(r.m_pn) // never throws
Chris@16:    {}
Chris@16: 
Chris@16:    //!Effects: Equivalent to weak_ptr(r).swap(*this).
Chris@16:    //!
Chris@16:    //!Throws: nothing.
Chris@16:    //!
Chris@16:    //!Notes: The implementation is free to meet the effects (and the
Chris@16:    //!implied guarantees) via different means, without creating a temporary.
Chris@16:    template<class Y>
Chris@16:    weak_ptr & operator=(weak_ptr<Y, A, D> const & r) // never throws
Chris@16:    {
Chris@16:       //Construct a temporary shared_ptr so that nobody
Chris@16:       //can destroy the value while constructing this
Chris@16:       const shared_ptr<T, A, D> &ref = r.lock();
Chris@16:       m_pn = r.m_pn;
Chris@16:       m_pn.set_pointer(ref.get());
Chris@16:       return *this;
Chris@16:    }
Chris@16: 
Chris@16:    //!Effects: Equivalent to weak_ptr(r).swap(*this).
Chris@16:    //!
Chris@16:    //!Throws: nothing.
Chris@16:    //!
Chris@16:    //!Notes: The implementation is free to meet the effects (and the
Chris@16:    //!implied guarantees) via different means, without creating a temporary.
Chris@16:    template<class Y>
Chris@16:    weak_ptr & operator=(shared_ptr<Y, A, D> const & r) // never throws
Chris@16:    {  m_pn = r.m_pn;  return *this;  }
Chris@16: 
Chris@16:    //!Returns: expired()? shared_ptr<T>(): shared_ptr<T>(*this).
Chris@16:    //!
Chris@16:    //!Throws: nothing.
Chris@16:    shared_ptr<T, A, D> lock() const // never throws
Chris@16:    {
Chris@16:       // optimization: avoid throw overhead
Chris@16:       if(expired()){
Chris@16:          return shared_ptr<element_type, A, D>();
Chris@16:       }
Chris@16:       BOOST_TRY{
Chris@16:          return shared_ptr<element_type, A, D>(*this);
Chris@16:       }
Chris@16:       BOOST_CATCH(bad_weak_ptr const &){
Chris@16:          // Q: how can we get here?
Chris@16:          // A: another thread may have invalidated r after the use_count test above.
Chris@16:          return shared_ptr<element_type, A, D>();
Chris@16:       }
Chris@16:       BOOST_CATCH_END
Chris@16:    }
Chris@16: 
Chris@16:    //!Returns: 0 if *this is empty; otherwise, the number of shared_ptr objects
Chris@16:    //!that share ownership with *this.
Chris@16:    //!
Chris@16:    //!Throws: nothing.
Chris@16:    //!
Chris@16:    //!Notes: use_count() is not necessarily efficient. Use only for debugging and
Chris@16:    //!testing purposes, not for production code.
Chris@16:    long use_count() const // never throws
Chris@16:    {  return m_pn.use_count();  }
Chris@16: 
Chris@16:    //!Returns: Returns: use_count() == 0.
Chris@16:    //!
Chris@16:    //!Throws: nothing.
Chris@16:    //!
Chris@16:    //!Notes: expired() may be faster than use_count().
Chris@16:    bool expired() const // never throws
Chris@16:    {  return m_pn.use_count() == 0;   }
Chris@16: 
Chris@16:    //!Effects: Equivalent to:
Chris@16:    //!weak_ptr().swap(*this).
Chris@16:    void reset() // never throws in 1.30+
Chris@16:    {  this_type().swap(*this);   }
Chris@16: 
Chris@16:    //!Effects: Exchanges the contents of the two
Chris@16:    //!smart pointers.
Chris@16:    //!
Chris@16:    //!Throws: nothing.
Chris@16:    void swap(this_type & other) // never throws
Chris@101:    {  ::boost::adl_move_swap(m_pn, other.m_pn);   }
Chris@16: 
Chris@101:    #if !defined(BOOST_INTERPROCESS_DOXYGEN_INVOKED)
Chris@16:    template<class T2, class A2, class D2>
Chris@16:    bool _internal_less(weak_ptr<T2, A2, D2> const & rhs) const
Chris@16:    {  return m_pn < rhs.m_pn;  }
Chris@16: 
Chris@16:    template<class Y>
Chris@16:    void _internal_assign(const ipcdetail::shared_count<Y, A, D> & pn2)
Chris@16:    {
Chris@16: 
Chris@16:       m_pn = pn2;
Chris@16:    }
Chris@16: 
Chris@16:    private:
Chris@16: 
Chris@16:    template<class T2, class A2, class D2> friend class shared_ptr;
Chris@16:    template<class T2, class A2, class D2> friend class weak_ptr;
Chris@16: 
Chris@16:    ipcdetail::weak_count<T, A, D> m_pn;      // reference counter
Chris@101:    #endif   //#ifndef BOOST_INTERPROCESS_DOXYGEN_INVOKED
Chris@16: };  // weak_ptr
Chris@16: 
Chris@16: template<class T, class A, class D, class U, class A2, class D2> inline
Chris@16: bool operator<(weak_ptr<T, A, D> const & a, weak_ptr<U, A2, D2> const & b)
Chris@16: {  return a._internal_less(b);   }
Chris@16: 
Chris@16: template<class T, class A, class D> inline
Chris@16: void swap(weak_ptr<T, A, D> & a, weak_ptr<T, A, D> & b)
Chris@16: {  a.swap(b);  }
Chris@16: 
Chris@16: //!Returns the type of a weak pointer
Chris@16: //!of type T with the allocator boost::interprocess::allocator allocator
Chris@16: //!and boost::interprocess::deleter deleter
Chris@16: //!that can be constructed in the given managed segment type.
Chris@16: template<class T, class ManagedMemory>
Chris@16: struct managed_weak_ptr
Chris@16: {
Chris@16:    typedef weak_ptr
Chris@16:    < T
Chris@16:    , typename ManagedMemory::template allocator<void>::type
Chris@16:    , typename ManagedMemory::template deleter<T>::type
Chris@16:    > type;
Chris@16: };
Chris@16: 
Chris@16: //!Returns an instance of a weak pointer constructed
Chris@16: //!with the default allocator and deleter from a pointer
Chris@16: //!of type T that has been allocated in the passed managed segment
Chris@16: template<class T, class ManagedMemory>
Chris@16: inline typename managed_weak_ptr<T, ManagedMemory>::type
Chris@16:    make_managed_weak_ptr(T *constructed_object, ManagedMemory &managed_memory)
Chris@16: {
Chris@16:    return typename managed_weak_ptr<T, ManagedMemory>::type
Chris@16:    ( constructed_object
Chris@16:    , managed_memory.template get_allocator<void>()
Chris@16:    , managed_memory.template get_deleter<T>()
Chris@16:    );
Chris@16: }
Chris@16: 
Chris@16: } // namespace interprocess
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #include <boost/interprocess/detail/config_end.hpp>
Chris@16: 
Chris@16: #endif  // #ifndef BOOST_INTERPROCESS_WEAK_PTR_HPP_INCLUDED