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   constant.hpp
Chris@16:  * \author Andrey Semashev
Chris@16:  * \date   15.04.2007
Chris@16:  *
Chris@16:  * The header contains implementation of a constant attribute.
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_LOG_ATTRIBUTES_CONSTANT_HPP_INCLUDED_
Chris@16: #define BOOST_LOG_ATTRIBUTES_CONSTANT_HPP_INCLUDED_
Chris@16: 
Chris@16: #include <boost/move/core.hpp>
Chris@16: #include <boost/move/utility.hpp>
Chris@16: #include <boost/type_traits/remove_reference.hpp>
Chris@16: #include <boost/log/detail/config.hpp>
Chris@16: #include <boost/log/detail/embedded_string_type.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
Chris@16:  *
Chris@16:  * The constant is a simplest and one of the most frequently used types of attributes.
Chris@16:  * It stores a constant value, which it eventually returns as its value each time
Chris@16:  * requested.
Chris@16:  */
Chris@16: template< typename T >
Chris@16: class constant :
Chris@16:     public attribute
Chris@16: {
Chris@16: public:
Chris@16:     //! 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_value_impl< value_type >
Chris@16:     {
Chris@16:         //! Base type
Chris@16:         typedef attribute_value_impl< value_type > base_type;
Chris@16: 
Chris@16:     public:
Chris@16:         /*!
Chris@16:          * Constructor with the stored value initialization
Chris@16:          */
Chris@16:         explicit impl(value_type const& value) : base_type(value) {}
Chris@16:         /*!
Chris@16:          * Constructor with the stored value initialization
Chris@16:          */
Chris@16:         explicit impl(BOOST_RV_REF(value_type) value) : base_type(boost::move(value)) {}
Chris@16:     };
Chris@16: 
Chris@16: public:
Chris@16:     /*!
Chris@16:      * Constructor with the stored value initialization
Chris@16:      */
Chris@16:     explicit constant(value_type const& value) : attribute(new impl(value)) {}
Chris@16:     /*!
Chris@16:      * Constructor with the stored value initialization
Chris@16:      */
Chris@16:     explicit constant(BOOST_RV_REF(value_type) value) : attribute(new impl(boost::move(value))) {}
Chris@16:     /*!
Chris@16:      * Constructor for casting support
Chris@16:      */
Chris@16:     explicit constant(cast_source const& source) : attribute(source.as< impl >())
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * \return Reference to the contained value.
Chris@16:      */
Chris@16:     value_type const& get() const
Chris@16:     {
Chris@16:         return static_cast< impl* >(this->get_impl())->get();
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: /*!
Chris@16:  * The function constructs a \c constant attribute containing the provided value.
Chris@16:  * The function automatically converts C string arguments to \c std::basic_string objects.
Chris@16:  */
Chris@16: template< typename T >
Chris@16: inline constant<
Chris@16:     typename boost::log::aux::make_embedded_string_type<
Chris@16:         typename remove_reference< T >::type
Chris@16:     >::type
Chris@16: > make_constant(BOOST_FWD_REF(T) val)
Chris@16: {
Chris@16:     typedef typename boost::log::aux::make_embedded_string_type<
Chris@16:         typename remove_reference< T >::type
Chris@16:     >::type value_type;
Chris@16:     return constant< value_type >(boost::forward< T >(val));
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_CONSTANT_HPP_INCLUDED_