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Copy pathfunction.hpp
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170 lines (144 loc) · 4.5 KB
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/*
* Copyright Andrey Semashev 2007 - 2015.
* Distributed under the Boost Software License, Version 1.0.
* (See accompanying file LICENSE_1_0.txt or copy at
* http://www.boost.org/LICENSE_1_0.txt)
*/
/*!
* \file function.hpp
* \author Andrey Semashev
* \date 24.06.2007
*
* The header contains implementation of an attribute that calls a third-party function on value acquisition.
*/
#ifndef BOOST_LOG_ATTRIBUTES_FUNCTION_HPP_INCLUDED_
#define BOOST_LOG_ATTRIBUTES_FUNCTION_HPP_INCLUDED_
#include <boost/static_assert.hpp>
#include <boost/utility/result_of.hpp>
#include <boost/type_traits/is_void.hpp>
#include <boost/type_traits/remove_cv.hpp>
#include <boost/type_traits/remove_reference.hpp>
#include <boost/log/detail/config.hpp>
#include <boost/log/attributes/attribute.hpp>
#include <boost/log/attributes/attribute_cast.hpp>
#include <boost/log/attributes/attribute_value_impl.hpp>
#include <boost/log/detail/header.hpp>
#ifdef BOOST_HAS_PRAGMA_ONCE
#pragma once
#endif
namespace boost {
BOOST_LOG_OPEN_NAMESPACE
namespace attributes {
/*!
* \brief A class of an attribute that acquires its value from a third-party function object
*
* The attribute calls a stored nullary function object to acquire each value.
* The result type of the function object is the attribute value type.
*
* It is not recommended to use this class directly. Use \c make_function convenience functions
* to construct the attribute instead.
*/
template< typename R >
class function :
public attribute
{
BOOST_STATIC_ASSERT_MSG(!is_void< R >::value, "Boost.Log: Function object return type must not be void");
public:
//! The attribute value type
typedef R value_type;
protected:
//! Base class for factory implementation
class BOOST_LOG_NO_VTABLE BOOST_SYMBOL_VISIBLE impl :
public attribute::impl
{
};
//! Factory implementation
template< typename T >
class impl_template :
public impl
{
private:
//! Functor that returns attribute values
/*!
* \note The constness signifies that the function object should avoid
* modifying its state since it's not protected against concurrent calls.
*/
const T m_Functor;
public:
/*!
* Constructor with the stored delegate initialization
*/
explicit impl_template(T const& fun) : m_Functor(fun) {}
attribute_value get_value()
{
return attributes::make_attribute_value(m_Functor());
}
};
public:
/*!
* Initializing constructor
*/
template< typename T >
explicit function(T const& fun) : attribute(new impl_template< T >(fun))
{
}
/*!
* Constructor for casting support
*/
explicit function(cast_source const& source) :
attribute(source.as< impl >())
{
}
};
#ifndef BOOST_NO_RESULT_OF
/*!
* The function constructs \c function attribute instance with the provided function object.
*
* \param fun Nullary functional object that returns an actual stored value for an attribute value.
* \return Pointer to the attribute instance
*/
template< typename T >
inline function<
typename remove_cv<
typename remove_reference<
typename boost::result_of< T() >::type
>::type
>::type
> make_function(T const& fun)
{
typedef typename remove_cv<
typename remove_reference<
typename boost::result_of< T() >::type
>::type
>::type result_type;
typedef function< result_type > function_type;
return function_type(fun);
}
#endif // BOOST_NO_RESULT_OF
#ifndef BOOST_LOG_DOXYGEN_PASS
/*!
* The function constructs \c function attribute instance with the provided function object.
* Use this version if your compiler fails to determine the result type of the function object.
*
* \param fun Nullary functional object that returns an actual stored value for an attribute value.
* \return Pointer to the attribute instance
*/
template< typename R, typename T >
inline function<
typename remove_cv<
typename remove_reference< R >::type
>::type
> make_function(T const& fun)
{
typedef typename remove_cv<
typename remove_reference< R >::type
>::type result_type;
typedef function< result_type > function_type;
return function_type(fun);
}
#endif // BOOST_LOG_DOXYGEN_PASS
} // namespace attributes
BOOST_LOG_CLOSE_NAMESPACE // namespace log
} // namespace boost
#include <boost/log/detail/footer.hpp>
#endif // BOOST_LOG_ATTRIBUTES_FUNCTOR_HPP_INCLUDED_