123 lines
3.3 KiB
C++
123 lines
3.3 KiB
C++
/*
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* Copyright Andrey Semashev 2007 - 2014.
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* Distributed under the Boost Software License, Version 1.0.
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* (See accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*/
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/*!
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* \file constant.hpp
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* \author Andrey Semashev
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* \date 15.04.2007
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*
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* The header contains implementation of a constant attribute.
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*/
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#ifndef BOOST_LOG_ATTRIBUTES_CONSTANT_HPP_INCLUDED_
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#define BOOST_LOG_ATTRIBUTES_CONSTANT_HPP_INCLUDED_
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#include <boost/move/core.hpp>
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#include <boost/move/utility.hpp>
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#include <boost/type_traits/remove_reference.hpp>
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#include <boost/log/detail/config.hpp>
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#include <boost/log/detail/embedded_string_type.hpp>
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#include <boost/log/attributes/attribute.hpp>
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#include <boost/log/attributes/attribute_cast.hpp>
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#include <boost/log/attributes/attribute_value_impl.hpp>
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#include <boost/log/detail/header.hpp>
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#ifdef BOOST_HAS_PRAGMA_ONCE
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#pragma once
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#endif
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namespace boost {
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BOOST_LOG_OPEN_NAMESPACE
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namespace attributes {
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/*!
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* \brief A class of an attribute that holds a single constant value
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*
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* The constant is a simplest and one of the most frequently used types of attributes.
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* It stores a constant value, which it eventually returns as its value each time
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* requested.
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*/
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template< typename T >
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class constant :
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public attribute
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{
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public:
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//! Attribute value type
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typedef T value_type;
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protected:
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//! Factory implementation
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class BOOST_SYMBOL_VISIBLE impl :
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public attribute_value_impl< value_type >
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{
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//! Base type
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typedef attribute_value_impl< value_type > base_type;
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public:
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/*!
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* Constructor with the stored value initialization
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*/
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explicit impl(value_type const& value) : base_type(value) {}
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/*!
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* Constructor with the stored value initialization
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*/
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explicit impl(BOOST_RV_REF(value_type) value) : base_type(boost::move(value)) {}
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};
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public:
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/*!
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* Constructor with the stored value initialization
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*/
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explicit constant(value_type const& value) : attribute(new impl(value)) {}
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/*!
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* Constructor with the stored value initialization
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*/
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explicit constant(BOOST_RV_REF(value_type) value) : attribute(new impl(boost::move(value))) {}
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/*!
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* Constructor for casting support
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*/
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explicit constant(cast_source const& source) : attribute(source.as< impl >())
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{
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}
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/*!
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* \return Reference to the contained value.
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*/
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value_type const& get() const
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{
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return static_cast< impl* >(this->get_impl())->get();
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}
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};
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/*!
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* The function constructs a \c constant attribute containing the provided value.
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* The function automatically converts C string arguments to \c std::basic_string objects.
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*/
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template< typename T >
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inline constant<
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typename boost::log::aux::make_embedded_string_type<
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typename remove_reference< T >::type
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>::type
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> make_constant(BOOST_FWD_REF(T) val)
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{
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typedef typename boost::log::aux::make_embedded_string_type<
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typename remove_reference< T >::type
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>::type value_type;
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return constant< value_type >(boost::forward< T >(val));
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}
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} // namespace attributes
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BOOST_LOG_CLOSE_NAMESPACE // namespace log
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} // namespace boost
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#include <boost/log/detail/footer.hpp>
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#endif // BOOST_LOG_ATTRIBUTES_CONSTANT_HPP_INCLUDED_
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