boost/smart_ptr/enable_shared_from_this.hpp

   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
  28     enable_shared_from_this()
  29     {
  30     }
  31
  32     enable_shared_from_this(enable_shared_from_this const &)
  33     {
  34     }
  35
  36     enable_shared_from_this & operator=(enable_shared_from_this const &)
  37     {
  38         return *this;
  39     }
  40
  41     ~enable_shared_from_this()
  42     {
  43     }
  44
  45 public:
  46
  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
  54     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
  61 public: // actually private, but avoids compiler template friendship issues
  62
  63     // Note: invoked automatically by shared_ptr; do not call
  64     template<class X, class Y> void _internal_accept_owner( shared_ptr<X> const * ppx, Y * py ) const
  65     {
  66         if( weak_this_.expired() )
  67         {
  68             weak_this_ = shared_ptr<T>( *ppx, py );
  69         }
  70     }
  71
  72 private:
  73
  74     mutable weak_ptr<T> weak_this_;
  75 };
  76
  77 } // namespace boost
  78
  79 #endif  // #ifndef BOOST_SMART_PTR_ENABLE_SHARED_FROM_THIS_HPP_INCLUDED