Chris@16: /*
Chris@16:  *          Copyright Andrey Semashev 2007 - 2013.
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: /*!
Chris@16:  * \file   intrusive_ref_counter.hpp
Chris@16:  * \author Andrey Semashev
Chris@16:  * \date   12.03.2009
Chris@16:  *
Chris@16:  * This header contains a reference counter class for \c intrusive_ptr.
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_SMART_PTR_INTRUSIVE_REF_COUNTER_HPP_INCLUDED_
Chris@16: #define BOOST_SMART_PTR_INTRUSIVE_REF_COUNTER_HPP_INCLUDED_
Chris@16: 
Chris@16: #include <boost/config.hpp>
Chris@16: #include <boost/smart_ptr/detail/atomic_count.hpp>
Chris@16: 
Chris@16: #ifdef BOOST_HAS_PRAGMA_ONCE
Chris@16: #pragma once
Chris@16: #endif
Chris@16: 
Chris@16: #if defined(_MSC_VER)
Chris@16: #pragma warning(push)
Chris@16: // This is a bogus MSVC warning, which is flagged by friend declarations of intrusive_ptr_add_ref and intrusive_ptr_release in intrusive_ref_counter:
Chris@16: // 'name' : the inline specifier cannot be used when a friend declaration refers to a specialization of a function template
Chris@16: // Note that there is no inline specifier in the declarations.
Chris@16: #pragma warning(disable: 4396)
Chris@16: #endif
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16: namespace sp_adl_block {
Chris@16: 
Chris@16: /*!
Chris@16:  * \brief Thread unsafe reference counter policy for \c intrusive_ref_counter
Chris@16:  *
Chris@16:  * The policy instructs the \c intrusive_ref_counter base class to implement
Chris@16:  * a reference counter suitable for single threaded use only. Pointers to the same
Chris@16:  * object with this kind of reference counter must not be used by different threads.
Chris@16:  */
Chris@16: struct thread_unsafe_counter
Chris@16: {
Chris@16:     typedef unsigned int type;
Chris@16: 
Chris@16:     static unsigned int load(unsigned int const& counter) BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         return counter;
Chris@16:     }
Chris@16: 
Chris@16:     static void increment(unsigned int& counter) BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         ++counter;
Chris@16:     }
Chris@16: 
Chris@16:     static unsigned int decrement(unsigned int& counter) BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         return --counter;
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: /*!
Chris@16:  * \brief Thread safe reference counter policy for \c intrusive_ref_counter
Chris@16:  *
Chris@16:  * The policy instructs the \c intrusive_ref_counter base class to implement
Chris@16:  * a thread-safe reference counter, if the target platform supports multithreading.
Chris@16:  */
Chris@16: struct thread_safe_counter
Chris@16: {
Chris@16:     typedef boost::detail::atomic_count type;
Chris@16: 
Chris@16:     static unsigned int load(boost::detail::atomic_count const& counter) BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         return static_cast< unsigned int >(static_cast< long >(counter));
Chris@16:     }
Chris@16: 
Chris@16:     static void increment(boost::detail::atomic_count& counter) BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         ++counter;
Chris@16:     }
Chris@16: 
Chris@16:     static unsigned int decrement(boost::detail::atomic_count& counter) BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         return --counter;
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: template< typename DerivedT, typename CounterPolicyT = thread_safe_counter >
Chris@16: class intrusive_ref_counter;
Chris@16: 
Chris@16: template< typename DerivedT, typename CounterPolicyT >
Chris@16: void intrusive_ptr_add_ref(const intrusive_ref_counter< DerivedT, CounterPolicyT >* p) BOOST_NOEXCEPT;
Chris@16: template< typename DerivedT, typename CounterPolicyT >
Chris@16: void intrusive_ptr_release(const intrusive_ref_counter< DerivedT, CounterPolicyT >* p) BOOST_NOEXCEPT;
Chris@16: 
Chris@16: /*!
Chris@16:  * \brief A reference counter base class
Chris@16:  *
Chris@16:  * This base class can be used with user-defined classes to add support
Chris@16:  * for \c intrusive_ptr. The class contains a reference counter defined by the \c CounterPolicyT.
Chris@16:  * Upon releasing the last \c intrusive_ptr referencing the object
Chris@16:  * derived from the \c intrusive_ref_counter class, operator \c delete
Chris@16:  * is automatically called on the pointer to the object.
Chris@16:  *
Chris@16:  * The other template parameter, \c DerivedT, is the user's class that derives from \c intrusive_ref_counter.
Chris@16:  */
Chris@16: template< typename DerivedT, typename CounterPolicyT >
Chris@16: class intrusive_ref_counter
Chris@16: {
Chris@16: private:
Chris@16:     //! Reference counter type
Chris@16:     typedef typename CounterPolicyT::type counter_type;
Chris@16:     //! Reference counter
Chris@16:     mutable counter_type m_ref_counter;
Chris@16: 
Chris@16: public:
Chris@16:     /*!
Chris@16:      * Default constructor
Chris@16:      *
Chris@16:      * \post <tt>use_count() == 0</tt>
Chris@16:      */
Chris@16:     intrusive_ref_counter() BOOST_NOEXCEPT : m_ref_counter(0)
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * Copy constructor
Chris@16:      *
Chris@16:      * \post <tt>use_count() == 0</tt>
Chris@16:      */
Chris@16:     intrusive_ref_counter(intrusive_ref_counter const&) BOOST_NOEXCEPT : m_ref_counter(0)
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * Assignment
Chris@16:      *
Chris@16:      * \post The reference counter is not modified after assignment
Chris@16:      */
Chris@16:     intrusive_ref_counter& operator= (intrusive_ref_counter const&) BOOST_NOEXCEPT { return *this; }
Chris@16: 
Chris@16:     /*!
Chris@16:      * \return The reference counter
Chris@16:      */
Chris@16:     unsigned int use_count() const BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         return CounterPolicyT::load(m_ref_counter);
Chris@16:     }
Chris@16: 
Chris@16: protected:
Chris@16:     /*!
Chris@16:      * Destructor
Chris@16:      */
Chris@16:     BOOST_DEFAULTED_FUNCTION(~intrusive_ref_counter(), {})
Chris@16: 
Chris@16:     friend void intrusive_ptr_add_ref< DerivedT, CounterPolicyT >(const intrusive_ref_counter< DerivedT, CounterPolicyT >* p) BOOST_NOEXCEPT;
Chris@16:     friend void intrusive_ptr_release< DerivedT, CounterPolicyT >(const intrusive_ref_counter< DerivedT, CounterPolicyT >* p) BOOST_NOEXCEPT;
Chris@16: };
Chris@16: 
Chris@16: template< typename DerivedT, typename CounterPolicyT >
Chris@16: inline void intrusive_ptr_add_ref(const intrusive_ref_counter< DerivedT, CounterPolicyT >* p) BOOST_NOEXCEPT
Chris@16: {
Chris@16:     CounterPolicyT::increment(p->m_ref_counter);
Chris@16: }
Chris@16: 
Chris@16: template< typename DerivedT, typename CounterPolicyT >
Chris@16: inline void intrusive_ptr_release(const intrusive_ref_counter< DerivedT, CounterPolicyT >* p) BOOST_NOEXCEPT
Chris@16: {
Chris@16:     if (CounterPolicyT::decrement(p->m_ref_counter) == 0)
Chris@16:         delete static_cast< const DerivedT* >(p);
Chris@16: }
Chris@16: 
Chris@16: } // namespace sp_adl_block
Chris@16: 
Chris@16: using sp_adl_block::intrusive_ref_counter;
Chris@16: using sp_adl_block::thread_unsafe_counter;
Chris@16: using sp_adl_block::thread_safe_counter;
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #if defined(_MSC_VER)
Chris@16: #pragma warning(pop)
Chris@16: #endif
Chris@16: 
Chris@16: #endif // BOOST_SMART_PTR_INTRUSIVE_REF_COUNTER_HPP_INCLUDED_