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   locking_ptr.hpp
Chris@16:  * \author Andrey Semashev
Chris@16:  * \date   15.07.2009
Chris@16:  *
Chris@16:  * This header is the Boost.Log library implementation, see the library documentation
Chris@16:  * at http://www.boost.org/doc/libs/release/libs/log/doc/html/index.html.
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_LOG_DETAIL_LOCKING_PTR_HPP_INCLUDED_
Chris@16: #define BOOST_LOG_DETAIL_LOCKING_PTR_HPP_INCLUDED_
Chris@16: 
Chris@16: #include <boost/smart_ptr/shared_ptr.hpp>
Chris@16: #include <boost/log/detail/config.hpp>
Chris@16: #include <boost/utility/explicit_operator_bool.hpp>
Chris@16: #include <boost/log/detail/header.hpp>
Chris@16: 
Chris@16: #ifdef BOOST_HAS_PRAGMA_ONCE
Chris@16: #pragma once
Chris@16: #endif
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16: BOOST_LOG_OPEN_NAMESPACE
Chris@16: 
Chris@16: namespace aux {
Chris@16: 
Chris@16: //! Shared lock object to support locking_ptr
Chris@16: struct BOOST_LOG_NO_VTABLE locking_ptr_counter_base
Chris@16: {
Chris@16:     unsigned int m_RefCounter;
Chris@16: 
Chris@16:     locking_ptr_counter_base() : m_RefCounter(0)
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     virtual ~locking_ptr_counter_base() {}
Chris@16:     virtual void lock() = 0;
Chris@16:     virtual bool try_lock() = 0;
Chris@16:     virtual void unlock() = 0;
Chris@16: 
Chris@16: private:
Chris@16:     locking_ptr_counter_base(locking_ptr_counter_base const&);
Chris@16:     locking_ptr_counter_base& operator= (locking_ptr_counter_base const&);
Chris@16: };
Chris@16: 
Chris@16: struct try_lock_tag {};
Chris@16: BOOST_CONSTEXPR_OR_CONST try_lock_tag try_lock = {};
Chris@16: 
Chris@16: //! A pointer type that locks the backend until it's destroyed
Chris@16: template< typename T >
Chris@16: class locking_ptr
Chris@16: {
Chris@16: public:
Chris@16:     //! Pointed type
Chris@16:     typedef T element_type;
Chris@16: 
Chris@16: private:
Chris@16:     //! The pointer to the backend
Chris@16:     shared_ptr< element_type > m_pElement;
Chris@16:     //! Reference to the shared lock control object
Chris@16:     locking_ptr_counter_base* m_pLock;
Chris@16: 
Chris@16: public:
Chris@16:     //! Constructor
Chris@16:     locking_ptr(shared_ptr< element_type > const& p, locking_ptr_counter_base& l)
Chris@16:         : m_pElement(p), m_pLock(&l)
Chris@16:     {
Chris@16:         if (m_pLock->m_RefCounter == 0)
Chris@16:             m_pLock->lock();
Chris@16:         ++m_pLock->m_RefCounter;
Chris@16:     }
Chris@16:     //! Constructor
Chris@16:     locking_ptr(shared_ptr< element_type > const& p, locking_ptr_counter_base& l, try_lock_tag const&)
Chris@16:         : m_pElement(p), m_pLock(&l)
Chris@16:     {
Chris@16:         if (m_pLock->m_RefCounter > 0 || m_pLock->try_lock())
Chris@16:         {
Chris@16:             ++m_pLock->m_RefCounter;
Chris@16:         }
Chris@16:         else
Chris@16:         {
Chris@16:             m_pElement.reset();
Chris@16:             m_pLock = NULL;
Chris@16:         }
Chris@16:     }
Chris@16:     //! Copy constructor
Chris@16:     locking_ptr(locking_ptr const& that) : m_pElement(that.m_pElement), m_pLock(that.m_pLock)
Chris@16:     {
Chris@16:         if (m_pLock)
Chris@16:             ++m_pLock->m_RefCounter;
Chris@16:     }
Chris@16:     //! Destructor
Chris@16:     ~locking_ptr()
Chris@16:     {
Chris@16:         if (m_pLock && --m_pLock->m_RefCounter == 0)
Chris@16:             m_pLock->unlock();
Chris@16:     }
Chris@16: 
Chris@16:     //! Assignment
Chris@16:     locking_ptr& operator= (locking_ptr that)
Chris@16:     {
Chris@16:         this->swap(that);
Chris@16:         return *this;
Chris@16:     }
Chris@16: 
Chris@16:     //! Indirection
Chris@16:     element_type* operator-> () const { return m_pElement.get(); }
Chris@16:     //! Dereferencing
Chris@16:     element_type& operator* () const { return *m_pElement; }
Chris@16: 
Chris@16:     //! Accessor to the raw pointer
Chris@16:     element_type* get() const { return m_pElement.get(); }
Chris@16: 
Chris@16:     //! Checks for null pointer
Chris@16:     BOOST_EXPLICIT_OPERATOR_BOOL()
Chris@16:     //! Checks for null pointer
Chris@16:     bool operator! () const { return !m_pElement; }
Chris@16: 
Chris@16:     //! Swaps two pointers
Chris@16:     void swap(locking_ptr& that)
Chris@16:     {
Chris@16:         m_pElement.swap(that.m_pElement);
Chris@16:         register locking_ptr_counter_base* p = m_pLock;
Chris@16:         m_pLock = that.m_pLock;
Chris@16:         that.m_pLock = p;
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: //! Free raw pointer getter to assist generic programming
Chris@16: template< typename T >
Chris@16: inline T* get_pointer(locking_ptr< T > const& p)
Chris@16: {
Chris@16:     return p.get();
Chris@16: }
Chris@16: //! Free swap operation
Chris@16: template< typename T >
Chris@16: inline void swap(locking_ptr< T >& left, locking_ptr< T >& right)
Chris@16: {
Chris@16:     left.swap(right);
Chris@16: }
Chris@16: 
Chris@16: } // namespace aux
Chris@16: 
Chris@16: BOOST_LOG_CLOSE_NAMESPACE // namespace log
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #include <boost/log/detail/footer.hpp>
Chris@16: 
Chris@16: #endif // BOOST_LOG_DETAIL_LOCKING_PTR_HPP_INCLUDED_