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   function.hpp
Chris@16:  * \author Andrey Semashev
Chris@16:  * \date   24.06.2007
Chris@16:  *
Chris@16:  * The header contains implementation of an attribute that calls a third-party function on value acquisition.
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_LOG_ATTRIBUTES_FUNCTION_HPP_INCLUDED_
Chris@16: #define BOOST_LOG_ATTRIBUTES_FUNCTION_HPP_INCLUDED_
Chris@16: 
Chris@16: #include <boost/static_assert.hpp>
Chris@16: #include <boost/utility/result_of.hpp>
Chris@16: #include <boost/type_traits/is_void.hpp>
Chris@16: #include <boost/type_traits/remove_cv.hpp>
Chris@16: #include <boost/type_traits/remove_reference.hpp>
Chris@16: #include <boost/log/detail/config.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 acquires its value from a third-party function object
Chris@16:  *
Chris@16:  * The attribute calls a stored nullary function object to acquire each value.
Chris@16:  * The result type of the function object is the attribute value type.
Chris@16:  *
Chris@16:  * It is not recommended to use this class directly. Use \c make_function convenience functions
Chris@16:  * to construct the attribute instead.
Chris@16:  */
Chris@16: template< typename R >
Chris@16: class function :
Chris@16:     public attribute
Chris@16: {
Chris@16:     BOOST_STATIC_ASSERT_MSG(!is_void< R >::value, "Boost.Log: Function object return type must not be void");
Chris@16: 
Chris@16: public:
Chris@16:     //! The attribute value type
Chris@16:     typedef R value_type;
Chris@16: 
Chris@16: protected:
Chris@16:     //! Base class for factory implementation
Chris@16:     class BOOST_LOG_NO_VTABLE BOOST_SYMBOL_VISIBLE impl :
Chris@16:         public attribute::impl
Chris@16:     {
Chris@16:     };
Chris@16: 
Chris@16:     //! Factory implementation
Chris@16:     template< typename T >
Chris@16:     class impl_template :
Chris@16:         public impl
Chris@16:     {
Chris@16:     private:
Chris@16:         //! Functor that returns attribute values
Chris@16:         /*!
Chris@16:          * \note The constness signifies that the function object should avoid
Chris@16:          *       modifying its state since it's not protected against concurrent calls.
Chris@16:          */
Chris@16:         const T m_Functor;
Chris@16: 
Chris@16:     public:
Chris@16:         /*!
Chris@16:          * Constructor with the stored delegate initialization
Chris@16:          */
Chris@16:         explicit impl_template(T const& fun) : m_Functor(fun) {}
Chris@16: 
Chris@16:         attribute_value get_value()
Chris@16:         {
Chris@16:             return attributes::make_attribute_value(m_Functor());
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16: public:
Chris@16:     /*!
Chris@16:      * Initializing constructor
Chris@16:      */
Chris@16:     template< typename T >
Chris@16:     explicit function(T const& fun) : attribute(new impl_template< T >(fun))
Chris@16:     {
Chris@16:     }
Chris@16:     /*!
Chris@16:      * Constructor for casting support
Chris@16:      */
Chris@16:     explicit function(cast_source const& source) :
Chris@16:         attribute(source.as< impl >())
Chris@16:     {
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: #ifndef BOOST_NO_RESULT_OF
Chris@16: 
Chris@16: /*!
Chris@16:  * The function constructs \c function attribute instance with the provided function object.
Chris@16:  *
Chris@16:  * \param fun Nullary functional object that returns an actual stored value for an attribute value.
Chris@16:  * \return Pointer to the attribute instance
Chris@16:  */
Chris@16: template< typename T >
Chris@16: inline function<
Chris@16:     typename remove_cv<
Chris@16:         typename remove_reference<
Chris@16:             typename boost::result_of< T() >::type
Chris@16:         >::type
Chris@16:     >::type
Chris@16: > make_function(T const& fun)
Chris@16: {
Chris@16:     typedef typename remove_cv<
Chris@16:         typename remove_reference<
Chris@16:             typename boost::result_of< T() >::type
Chris@16:         >::type
Chris@16:     >::type result_type;
Chris@16: 
Chris@16:     typedef function< result_type > function_type;
Chris@16:     return function_type(fun);
Chris@16: }
Chris@16: 
Chris@16: #endif // BOOST_NO_RESULT_OF
Chris@16: 
Chris@16: #ifndef BOOST_LOG_DOXYGEN_PASS
Chris@16: 
Chris@16: /*!
Chris@16:  * The function constructs \c function attribute instance with the provided function object.
Chris@16:  * Use this version if your compiler fails to determine the result type of the function object.
Chris@16:  *
Chris@16:  * \param fun Nullary functional object that returns an actual stored value for an attribute value.
Chris@16:  * \return Pointer to the attribute instance
Chris@16:  */
Chris@16: template< typename R, typename T >
Chris@16: inline function<
Chris@16:     typename remove_cv<
Chris@16:         typename remove_reference< R >::type
Chris@16:     >::type
Chris@16: > make_function(T const& fun)
Chris@16: {
Chris@16:     typedef typename remove_cv<
Chris@16:         typename remove_reference< R >::type
Chris@16:     >::type result_type;
Chris@16: 
Chris@16:     typedef function< result_type > function_type;
Chris@16:     return function_type(fun);
Chris@16: }
Chris@16: 
Chris@16: #endif // BOOST_LOG_DOXYGEN_PASS
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_FUNCTOR_HPP_INCLUDED_