Chris@16: /*
Chris@101:  *          Copyright Andrey Semashev 2007 - 2015.
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   mutable_constant.hpp
Chris@16:  * \author Andrey Semashev
Chris@16:  * \date   06.11.2007
Chris@16:  *
Chris@16:  * The header contains implementation of a mutable constant attribute.
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_LOG_ATTRIBUTES_MUTABLE_CONSTANT_HPP_INCLUDED_
Chris@16: #define BOOST_LOG_ATTRIBUTES_MUTABLE_CONSTANT_HPP_INCLUDED_
Chris@16: 
Chris@16: #include <boost/static_assert.hpp>
Chris@16: #include <boost/smart_ptr/intrusive_ptr.hpp>
Chris@16: #include <boost/mpl/if.hpp>
Chris@16: #include <boost/move/core.hpp>
Chris@16: #include <boost/move/utility.hpp>
Chris@16: #include <boost/type_traits/is_void.hpp>
Chris@16: #include <boost/log/detail/config.hpp>
Chris@16: #include <boost/log/detail/locks.hpp>
Chris@16: #include <boost/log/attributes/attribute.hpp>
Chris@16: #include <boost/log/attributes/attribute_cast.hpp>
Chris@16: #include <boost/log/attributes/attribute_value_impl.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 attributes {
Chris@16: 
Chris@16: /*!
Chris@16:  * \brief A class of an attribute that holds a single constant value with ability to change it
Chris@16:  *
Chris@16:  * The mutable_constant attribute stores a single value of type, specified as the first template argument.
Chris@16:  * This value is returned on each attribute value acquisition.
Chris@16:  *
Chris@16:  * The attribute also allows to modify the stored value, even if the attribute is registered in an attribute set.
Chris@16:  * In order to ensure thread safety of such modifications the \c mutable_constant class is also parametrized
Chris@16:  * with three additional template arguments: mutex type, scoped write and scoped read lock types. If not specified,
Chris@16:  * the lock types are automatically deduced based on the mutex type.
Chris@16:  *
Chris@16:  * The implementation may avoid using these types to actually create and use the mutex, if a more efficient synchronization method is
Chris@16:  * available (such as atomic operations on the value type). By default no synchronization is done.
Chris@16:  */
Chris@16: #ifdef BOOST_LOG_DOXYGEN_PASS
Chris@16: template< typename T, typename MutexT = void, typename ScopedWriteLockT = auto, typename ScopedReadLockT = auto >
Chris@16: #else // BOOST_LOG_DOXYGEN_PASS
Chris@16: template<
Chris@16:     typename T,
Chris@16:     typename MutexT = void,
Chris@16:     typename ScopedWriteLockT =
Chris@16: #ifndef BOOST_LOG_NO_THREADS
Chris@16:         typename mpl::if_c<
Chris@16:             boost::log::aux::is_exclusively_lockable< MutexT >::value,
Chris@16:             boost::log::aux::exclusive_lock_guard< MutexT >,
Chris@16:             void
Chris@16:         >::type,
Chris@16: #else
Chris@16:         void,
Chris@16: #endif // BOOST_LOG_NO_THREADS
Chris@16:     typename ScopedReadLockT =
Chris@16: #ifndef BOOST_LOG_NO_THREADS
Chris@16:         typename mpl::if_c<
Chris@16:             boost::log::aux::is_shared_lockable< MutexT >::value,
Chris@16:             boost::log::aux::shared_lock_guard< MutexT >,
Chris@16:             ScopedWriteLockT
Chris@16:         >::type
Chris@16: #else
Chris@16:         ScopedWriteLockT
Chris@16: #endif // BOOST_LOG_NO_THREADS
Chris@16: #endif // BOOST_LOG_DOXYGEN_PASS
Chris@16: >
Chris@16: class mutable_constant :
Chris@16:     public attribute
Chris@16: {
Chris@16: public:
Chris@16:     //! The attribute value type
Chris@16:     typedef T value_type;
Chris@16: 
Chris@16: protected:
Chris@16:     //! Factory implementation
Chris@16:     class BOOST_SYMBOL_VISIBLE impl :
Chris@16:         public attribute::impl
Chris@16:     {
Chris@16:     private:
Chris@16:         //! Mutex type
Chris@16:         typedef MutexT mutex_type;
Chris@16:         //! Shared lock type
Chris@16:         typedef ScopedReadLockT scoped_read_lock;
Chris@16:         //! Exclusive lock type
Chris@16:         typedef ScopedWriteLockT scoped_write_lock;
Chris@16:         BOOST_STATIC_ASSERT_MSG(!(is_void< mutex_type >::value || is_void< scoped_read_lock >::value || is_void< scoped_write_lock >::value), "Boost.Log: Mutex and both lock types either must not be void or must all be void");
Chris@16:         //! Attribute value wrapper
Chris@16:         typedef attribute_value_impl< value_type > attr_value;
Chris@16: 
Chris@16:     private:
Chris@16:         //! Thread protection mutex
Chris@16:         mutable mutex_type m_Mutex;
Chris@16:         //! Pointer to the actual attribute value
Chris@16:         intrusive_ptr< attr_value > m_Value;
Chris@16: 
Chris@16:     public:
Chris@16:         /*!
Chris@16:          * Initializing constructor
Chris@16:          */
Chris@16:         explicit impl(value_type const& value) : m_Value(new attr_value(value))
Chris@16:         {
Chris@16:         }
Chris@16:         /*!
Chris@16:          * Initializing constructor
Chris@16:          */
Chris@16:         explicit impl(BOOST_RV_REF(value_type) value) : m_Value(new attr_value(boost::move(value)))
Chris@16:         {
Chris@16:         }
Chris@16: 
Chris@16:         attribute_value get_value()
Chris@16:         {
Chris@16:             scoped_read_lock lock(m_Mutex);
Chris@16:             return attribute_value(m_Value);
Chris@16:         }
Chris@16: 
Chris@16:         void set(value_type const& value)
Chris@16:         {
Chris@16:             intrusive_ptr< attr_value > p = new attr_value(value);
Chris@16:             scoped_write_lock lock(m_Mutex);
Chris@16:             m_Value.swap(p);
Chris@16:         }
Chris@16: 
Chris@16:         void set(BOOST_RV_REF(value_type) value)
Chris@16:         {
Chris@16:             intrusive_ptr< attr_value > p = new attr_value(boost::move(value));
Chris@16:             scoped_write_lock lock(m_Mutex);
Chris@16:             m_Value.swap(p);
Chris@16:         }
Chris@16: 
Chris@16:         value_type get() const
Chris@16:         {
Chris@16:             scoped_read_lock lock(m_Mutex);
Chris@16:             return m_Value->get();
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16: public:
Chris@16:     /*!
Chris@16:      * Constructor with the stored value initialization
Chris@16:      */
Chris@16:     explicit mutable_constant(value_type const& value) : attribute(new impl(value))
Chris@16:     {
Chris@16:     }
Chris@16:     /*!
Chris@16:      * Constructor with the stored value initialization
Chris@16:      */
Chris@16:     explicit mutable_constant(BOOST_RV_REF(value_type) value) : attribute(new impl(boost::move(value)))
Chris@16:     {
Chris@16:     }
Chris@16:     /*!
Chris@16:      * Constructor for casting support
Chris@16:      */
Chris@16:     explicit mutable_constant(cast_source const& source) : attribute(source.as< impl >())
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * The method sets a new attribute value. The implementation exclusively locks the mutex in order
Chris@16:      * to protect the value assignment.
Chris@16:      */
Chris@16:     void set(value_type const& value)
Chris@16:     {
Chris@16:         get_impl()->set(value);
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * The method sets a new attribute value.
Chris@16:      */
Chris@16:     void set(BOOST_RV_REF(value_type) value)
Chris@16:     {
Chris@16:         get_impl()->set(boost::move(value));
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * The method acquires the current attribute value. The implementation non-exclusively locks the mutex in order
Chris@16:      * to protect the value acquisition.
Chris@16:      */
Chris@16:     value_type get() const
Chris@16:     {
Chris@16:         return get_impl()->get();
Chris@16:     }
Chris@16: 
Chris@16: protected:
Chris@16:     /*!
Chris@16:      * \returns Pointer to the factory implementation
Chris@16:      */
Chris@16:     impl* get_impl() const
Chris@16:     {
Chris@16:         return static_cast< impl* >(attribute::get_impl());
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: /*!
Chris@16:  * \brief Specialization for unlocked case
Chris@16:  *
Chris@16:  * This version of attribute does not perform thread synchronization to access the stored value.
Chris@16:  */
Chris@16: template< typename T >
Chris@16: class mutable_constant< T, void, void, void > :
Chris@16:     public attribute
Chris@16: {
Chris@16: public:
Chris@16:     //! The attribute value type
Chris@16:     typedef T value_type;
Chris@16: 
Chris@16: protected:
Chris@16:     //! Factory implementation
Chris@16:     class BOOST_SYMBOL_VISIBLE impl :
Chris@16:         public attribute::impl
Chris@16:     {
Chris@16:     private:
Chris@16:         //! Attribute value wrapper
Chris@16:         typedef attribute_value_impl< value_type > attr_value;
Chris@16: 
Chris@16:     private:
Chris@16:         //! The actual value
Chris@16:         intrusive_ptr< attr_value > m_Value;
Chris@16: 
Chris@16:     public:
Chris@16:         /*!
Chris@16:          * Initializing constructor
Chris@16:          */
Chris@16:         explicit impl(value_type const& value) : m_Value(new attr_value(value))
Chris@16:         {
Chris@16:         }
Chris@16:         /*!
Chris@16:          * Initializing constructor
Chris@16:          */
Chris@16:         explicit impl(BOOST_RV_REF(value_type) value) : m_Value(new attr_value(boost::move(value)))
Chris@16:         {
Chris@16:         }
Chris@16: 
Chris@16:         attribute_value get_value()
Chris@16:         {
Chris@16:             return attribute_value(m_Value);
Chris@16:         }
Chris@16: 
Chris@16:         void set(value_type const& value)
Chris@16:         {
Chris@16:             m_Value = new attr_value(value);
Chris@16:         }
Chris@16:         void set(BOOST_RV_REF(value_type) value)
Chris@16:         {
Chris@16:             m_Value = new attr_value(boost::move(value));
Chris@16:         }
Chris@16: 
Chris@16:         value_type get() const
Chris@16:         {
Chris@16:             return m_Value->get();
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16: public:
Chris@16:     /*!
Chris@16:      * Constructor with the stored value initialization
Chris@16:      */
Chris@16:     explicit mutable_constant(value_type const& value) : attribute(new impl(value))
Chris@16:     {
Chris@16:     }
Chris@16:     /*!
Chris@16:      * Constructor with the stored value initialization
Chris@16:      */
Chris@16:     explicit mutable_constant(BOOST_RV_REF(value_type) value) : attribute(new impl(boost::move(value)))
Chris@16:     {
Chris@16:     }
Chris@16:     /*!
Chris@16:      * Constructor for casting support
Chris@16:      */
Chris@16:     explicit mutable_constant(cast_source const& source) : attribute(source.as< impl >())
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * The method sets a new attribute value.
Chris@16:      */
Chris@16:     void set(value_type const& value)
Chris@16:     {
Chris@16:         get_impl()->set(value);
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * The method sets a new attribute value.
Chris@16:      */
Chris@16:     void set(BOOST_RV_REF(value_type) value)
Chris@16:     {
Chris@16:         get_impl()->set(boost::move(value));
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * The method acquires the current attribute value.
Chris@16:      */
Chris@16:     value_type get() const
Chris@16:     {
Chris@16:         return get_impl()->get();
Chris@16:     }
Chris@16: 
Chris@16: protected:
Chris@16:     /*!
Chris@16:      * \returns Pointer to the factory implementation
Chris@16:      */
Chris@16:     impl* get_impl() const
Chris@16:     {
Chris@16:         return static_cast< impl* >(attribute::get_impl());
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: } // namespace attributes
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_ATTRIBUTES_MUTABLE_CONSTANT_HPP_INCLUDED_