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115 lines
3.0 KiB
C++
115 lines
3.0 KiB
C++
#ifndef BOOST_ENABLE_SHARED_FROM_THIS_HPP_INCLUDED
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#define BOOST_ENABLE_SHARED_FROM_THIS_HPP_INCLUDED
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//
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// enable_shared_from_this.hpp
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//
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// Copyright (c) 2002 Peter Dimov
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//
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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//
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// http://www.boost.org/libs/smart_ptr/enable_shared_from_this.html
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//
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#include <boost/weak_ptr.hpp>
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#include <boost/shared_ptr.hpp>
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#include <boost/assert.hpp>
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#include <boost/config.hpp>
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namespace boost
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{
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template<class T> class enable_shared_from_this
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{
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// dynamic cast to template type doesn't work in constructor, so we have
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// to use lazy initialization
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void init_internal_shared_once() const
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{
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if(owned() == false && _internal_shared_this == 0)
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{
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_internal_shared_this = shared_ptr<T>(dynamic_cast<T *>(const_cast<enable_shared_from_this*>(this)),
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detail::sp_deleter_wrapper(), detail::ignore_enable_shared_from_this_tag());
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BOOST_ASSERT(_internal_shared_this.get() == this);
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_internal_weak_this = _internal_shared_this;
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}
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}
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bool owned() const
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{
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return _owned;
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}
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typedef T _internal_element_type; // for bcc 5.5.1
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mutable shared_ptr<_internal_element_type> _internal_shared_this;
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mutable weak_ptr<_internal_element_type> _internal_weak_this;
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mutable bool _owned;
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protected:
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enable_shared_from_this():
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_owned(false)
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{
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}
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enable_shared_from_this(enable_shared_from_this const &):
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_owned(false)
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{
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}
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enable_shared_from_this & operator=(enable_shared_from_this const &)
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{
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return *this;
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}
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// virtual destructor because we need a vtable for dynamic_cast from base to derived to work
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virtual ~enable_shared_from_this()
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{
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// make sure no dangling shared_ptr objects were created by the
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// user calling shared_from_this() but never passing ownership of the object
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// to a shared_ptr.
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BOOST_ASSERT(owned() || _internal_shared_this.use_count() <= 1);
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}
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public:
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shared_ptr<T> shared_from_this()
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{
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init_internal_shared_once();
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shared_ptr<T> p(_internal_weak_this);
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BOOST_ASSERT(p.get() == this);
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return p;
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}
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shared_ptr<T const> shared_from_this() const
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{
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init_internal_shared_once();
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shared_ptr<T const> p(_internal_weak_this);
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BOOST_ASSERT(p.get() == this);
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return p;
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}
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template<typename U>
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void _internal_accept_owner(shared_ptr<U> &owner) const
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{
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init_internal_shared_once();
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if( !_owned )
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{
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detail::sp_deleter_wrapper * pd = get_deleter<detail::sp_deleter_wrapper>(_internal_shared_this);
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BOOST_ASSERT( pd != 0 );
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pd->set_deleter(owner);
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owner.reset( _internal_shared_this, owner.get() );
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_internal_shared_this.reset();
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_owned = true;
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}
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}
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};
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} // namespace boost
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#endif // #ifndef BOOST_ENABLE_SHARED_FROM_THIS_HPP_INCLUDED
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