1 #ifndef BOOST_SMART_PTR_ENABLE_SHARED_FROM_THIS_HPP_INCLUDED
2 #define BOOST_SMART_PTR_ENABLE_SHARED_FROM_THIS_HPP_INCLUDED
3 
4 //
5 //  enable_shared_from_this.hpp
6 //
7 //  Copyright 2002, 2009 Peter Dimov
8 //
9 //  Distributed under the Boost Software License, Version 1.0.
10 //  See accompanying file LICENSE_1_0.txt or copy at
11 //  http://www.boost.org/LICENSE_1_0.txt
12 //
13 //  http://www.boost.org/libs/smart_ptr/enable_shared_from_this.html
14 //
15 
16 #include <boost/smart_ptr/weak_ptr.hpp>
17 #include <boost/smart_ptr/shared_ptr.hpp>
18 #include <boost/assert.hpp>
19 #include <boost/config.hpp>
20 
21 namespace boost
22 {
23 
24 template<class T> class enable_shared_from_this
25 {
26 protected:
27 
enable_shared_from_this()28     enable_shared_from_this() BOOST_NOEXCEPT
29     {
30     }
31 
enable_shared_from_this(enable_shared_from_this const &)32     enable_shared_from_this(enable_shared_from_this const &) BOOST_NOEXCEPT
33     {
34     }
35 
operator =(enable_shared_from_this const &)36     enable_shared_from_this & operator=(enable_shared_from_this const &) BOOST_NOEXCEPT
37     {
38         return *this;
39     }
40 
~enable_shared_from_this()41     ~enable_shared_from_this() BOOST_NOEXCEPT // ~weak_ptr<T> newer throws, so this call also must not throw
42     {
43     }
44 
45 public:
46 
shared_from_this()47     shared_ptr<T> shared_from_this()
48     {
49         shared_ptr<T> p( weak_this_ );
50         BOOST_ASSERT( p.get() == this );
51         return p;
52     }
53 
shared_from_this() const54     shared_ptr<T const> shared_from_this() const
55     {
56         shared_ptr<T const> p( weak_this_ );
57         BOOST_ASSERT( p.get() == this );
58         return p;
59     }
60 
weak_from_this()61     weak_ptr<T> weak_from_this() BOOST_NOEXCEPT
62     {
63         return weak_this_;
64     }
65 
weak_from_this() const66     weak_ptr<T const> weak_from_this() const BOOST_NOEXCEPT
67     {
68         return weak_this_;
69     }
70 
71 public: // actually private, but avoids compiler template friendship issues
72 
73     // Note: invoked automatically by shared_ptr; do not call
_internal_accept_owner(shared_ptr<X> const * ppx,Y * py) const74     template<class X, class Y> void _internal_accept_owner( shared_ptr<X> const * ppx, Y * py ) const
75     {
76         if( weak_this_.expired() )
77         {
78             weak_this_ = shared_ptr<T>( *ppx, py );
79         }
80     }
81 
82 private:
83 
84     mutable weak_ptr<T> weak_this_;
85 };
86 
87 } // namespace boost
88 
89 #endif  // #ifndef BOOST_SMART_PTR_ENABLE_SHARED_FROM_THIS_HPP_INCLUDED
90