Chris@101: /* Copyright 2003-2013 Joaquin M Lopez Munoz.
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:  * See http://www.boost.org/libs/multi_index for library home page.
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_MULTI_INDEX_IDENTITY_HPP
Chris@16: #define BOOST_MULTI_INDEX_IDENTITY_HPP
Chris@16: 
Chris@101: #if defined(_MSC_VER)
Chris@16: #pragma once
Chris@16: #endif
Chris@16: 
Chris@16: #include <boost/config.hpp>
Chris@16: #include <boost/mpl/if.hpp>
Chris@16: #include <boost/multi_index/identity_fwd.hpp>
Chris@16: #include <boost/type_traits/is_const.hpp>
Chris@16: #include <boost/type_traits/remove_const.hpp>
Chris@16: #include <boost/utility/enable_if.hpp>
Chris@16: 
Chris@16: #if !defined(BOOST_NO_SFINAE)
Chris@16: #include <boost/type_traits/is_convertible.hpp>
Chris@16: #endif
Chris@16: 
Chris@16: namespace boost{
Chris@16: 
Chris@16: template<class Type> class reference_wrapper; /* fwd decl. */
Chris@16: 
Chris@16: namespace multi_index{
Chris@16: 
Chris@16: namespace detail{
Chris@16: 
Chris@16: /* identity is a do-nothing key extractor that returns the [const] Type&
Chris@16:  * object passed.
Chris@16:  * Additionally, identity is overloaded to support referece_wrappers
Chris@16:  * of Type and "chained pointers" to Type's. By chained pointer to Type we
Chris@16:  * mean a  type  P such that, given a p of type P
Chris@16:  *   *...n...*x is convertible to Type&, for some n>=1.
Chris@16:  * Examples of chained pointers are raw and smart pointers, iterators and
Chris@16:  * arbitrary combinations of these (vg. Type** or auto_ptr<Type*>.)
Chris@16:  */
Chris@16: 
Chris@16: template<typename Type>
Chris@16: struct const_identity_base
Chris@16: {
Chris@16:   typedef Type result_type;
Chris@16: 
Chris@16:   template<typename ChainedPtr>
Chris@16: 
Chris@16: #if !defined(BOOST_NO_SFINAE)
Chris@16:   typename disable_if<is_convertible<const ChainedPtr&,Type&>,Type&>::type
Chris@16: #else
Chris@16:   Type&
Chris@16: #endif 
Chris@16:   
Chris@16:   operator()(const ChainedPtr& x)const
Chris@16:   {
Chris@16:     return operator()(*x);
Chris@16:   }
Chris@16: 
Chris@16:   Type& operator()(Type& x)const
Chris@16:   {
Chris@16:     return x;
Chris@16:   }
Chris@16: 
Chris@16:   Type& operator()(const reference_wrapper<Type>& x)const
Chris@16:   { 
Chris@16:     return x.get();
Chris@16:   }
Chris@16: 
Chris@16:   Type& operator()(
Chris@101:     const reference_wrapper<typename remove_const<Type>::type>& x)const
Chris@16:   { 
Chris@16:     return x.get();
Chris@16:   }
Chris@16: };
Chris@16: 
Chris@16: template<typename Type>
Chris@16: struct non_const_identity_base
Chris@16: {
Chris@16:   typedef Type result_type;
Chris@16: 
Chris@16:   /* templatized for pointer-like types */
Chris@16:   
Chris@16:   template<typename ChainedPtr>
Chris@16: 
Chris@16: #if !defined(BOOST_NO_SFINAE)
Chris@16:   typename disable_if<
Chris@16:     is_convertible<const ChainedPtr&,const Type&>,Type&>::type
Chris@16: #else
Chris@16:   Type&
Chris@16: #endif 
Chris@16:     
Chris@16:   operator()(const ChainedPtr& x)const
Chris@16:   {
Chris@16:     return operator()(*x);
Chris@16:   }
Chris@16: 
Chris@101:   const Type& operator()(const Type& x)const
Chris@16:   {
Chris@16:     return x;
Chris@16:   }
Chris@16: 
Chris@16:   Type& operator()(Type& x)const
Chris@16:   {
Chris@16:     return x;
Chris@16:   }
Chris@16: 
Chris@101:   const Type& operator()(const reference_wrapper<const Type>& x)const
Chris@16:   { 
Chris@16:     return x.get();
Chris@16:   }
Chris@16: 
Chris@16:   Type& operator()(const reference_wrapper<Type>& x)const
Chris@16:   { 
Chris@16:     return x.get();
Chris@16:   }
Chris@16: };
Chris@16: 
Chris@16: } /* namespace multi_index::detail */
Chris@16: 
Chris@16: template<class Type>
Chris@16: struct identity:
Chris@16:   mpl::if_c<
Chris@16:     is_const<Type>::value,
Chris@16:     detail::const_identity_base<Type>,detail::non_const_identity_base<Type>
Chris@16:   >::type
Chris@16: {
Chris@16: };
Chris@16: 
Chris@16: } /* namespace multi_index */
Chris@16: 
Chris@16: } /* namespace boost */
Chris@16: 
Chris@16: #endif