| /* Copyright 2003-2008 Joaquin M Lopez Munoz. |
| * 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) |
| * |
| * See http://www.boost.org/libs/multi_index for library home page. |
| */ |
| |
| #ifndef BOOST_MULTI_INDEX_IDENTITY_HPP |
| #define BOOST_MULTI_INDEX_IDENTITY_HPP |
| |
| #if defined(_MSC_VER)&&(_MSC_VER>=1200) |
| #pragma once |
| #endif |
| |
| #include <boost/config.hpp> |
| #include <boost/mpl/if.hpp> |
| #include <boost/multi_index/identity_fwd.hpp> |
| #include <boost/type_traits/is_const.hpp> |
| #include <boost/type_traits/remove_const.hpp> |
| #include <boost/utility/enable_if.hpp> |
| |
| #if !defined(BOOST_NO_SFINAE) |
| #include <boost/type_traits/is_convertible.hpp> |
| #endif |
| |
| namespace boost{ |
| |
| template<class Type> class reference_wrapper; /* fwd decl. */ |
| |
| namespace multi_index{ |
| |
| namespace detail{ |
| |
| /* identity is a do-nothing key extractor that returns the [const] Type& |
| * object passed. |
| * Additionally, identity is overloaded to support referece_wrappers |
| * of Type and "chained pointers" to Type's. By chained pointer to Type we |
| * mean a type P such that, given a p of type P |
| * *...n...*x is convertible to Type&, for some n>=1. |
| * Examples of chained pointers are raw and smart pointers, iterators and |
| * arbitrary combinations of these (vg. Type** or auto_ptr<Type*>.) |
| */ |
| |
| /* NB. Some overloads of operator() have an extra dummy parameter int=0. |
| * This disambiguator serves several purposes: |
| * - Without it, MSVC++ 6.0 incorrectly regards some overloads as |
| * specializations of a previous member function template. |
| * - MSVC++ 6.0/7.0 seem to incorrectly treat some different memfuns |
| * as if they have the same signature. |
| * - If remove_const is broken due to lack of PTS, int=0 avoids the |
| * declaration of memfuns with identical signature. |
| */ |
| |
| template<typename Type> |
| struct const_identity_base |
| { |
| typedef Type result_type; |
| |
| template<typename ChainedPtr> |
| |
| #if !defined(BOOST_NO_SFINAE) |
| typename disable_if<is_convertible<const ChainedPtr&,Type&>,Type&>::type |
| #else |
| Type& |
| #endif |
| |
| operator()(const ChainedPtr& x)const |
| { |
| return operator()(*x); |
| } |
| |
| Type& operator()(Type& x)const |
| { |
| return x; |
| } |
| |
| Type& operator()(const reference_wrapper<Type>& x)const |
| { |
| return x.get(); |
| } |
| |
| Type& operator()( |
| const reference_wrapper<typename remove_const<Type>::type>& x,int=0)const |
| { |
| return x.get(); |
| } |
| }; |
| |
| template<typename Type> |
| struct non_const_identity_base |
| { |
| typedef Type result_type; |
| |
| /* templatized for pointer-like types */ |
| |
| template<typename ChainedPtr> |
| |
| #if !defined(BOOST_NO_SFINAE) |
| typename disable_if< |
| is_convertible<const ChainedPtr&,const Type&>,Type&>::type |
| #else |
| Type& |
| #endif |
| |
| operator()(const ChainedPtr& x)const |
| { |
| return operator()(*x); |
| } |
| |
| const Type& operator()(const Type& x,int=0)const |
| { |
| return x; |
| } |
| |
| Type& operator()(Type& x)const |
| { |
| return x; |
| } |
| |
| const Type& operator()(const reference_wrapper<const Type>& x,int=0)const |
| { |
| return x.get(); |
| } |
| |
| Type& operator()(const reference_wrapper<Type>& x)const |
| { |
| return x.get(); |
| } |
| }; |
| |
| } /* namespace multi_index::detail */ |
| |
| template<class Type> |
| struct identity: |
| mpl::if_c< |
| is_const<Type>::value, |
| detail::const_identity_base<Type>,detail::non_const_identity_base<Type> |
| >::type |
| { |
| }; |
| |
| } /* namespace multi_index */ |
| |
| } /* namespace boost */ |
| |
| #endif |