sl@0: /* Copyright 2003-2006 Joaquín M López Muñoz.
sl@0:  * Distributed under the Boost Software License, Version 1.0.
sl@0:  * (See accompanying file LICENSE_1_0.txt or copy at
sl@0:  * http://www.boost.org/LICENSE_1_0.txt)
sl@0:  *
sl@0:  * See http://www.boost.org/libs/multi_index for library home page.
sl@0:  */
sl@0: 
sl@0: #ifndef BOOST_MULTI_INDEX_IDENTITY_HPP
sl@0: #define BOOST_MULTI_INDEX_IDENTITY_HPP
sl@0: 
sl@0: #if defined(_MSC_VER)&&(_MSC_VER>=1200)
sl@0: #pragma once
sl@0: #endif
sl@0: 
sl@0: #include <boost/config.hpp>
sl@0: #include <boost/mpl/if.hpp>
sl@0: #include <boost/multi_index/identity_fwd.hpp>
sl@0: #include <boost/type_traits/is_const.hpp>
sl@0: #include <boost/type_traits/remove_const.hpp>
sl@0: #include <boost/utility/enable_if.hpp>
sl@0: 
sl@0: #if !defined(BOOST_NO_SFINAE)
sl@0: #include <boost/type_traits/is_convertible.hpp>
sl@0: #endif
sl@0: 
sl@0: namespace boost{
sl@0: 
sl@0: template<class Type> class reference_wrapper; /* fwd decl. */
sl@0: 
sl@0: namespace multi_index{
sl@0: 
sl@0: namespace detail{
sl@0: 
sl@0: /* identity is a do-nothing key extractor that returns the [const] Type&
sl@0:  * object passed.
sl@0:  * Additionally, identity is overloaded to support referece_wrappers
sl@0:  * of Type and "chained pointers" to Type's. By chained pointer to Type we
sl@0:  * mean a  type  P such that, given a p of type P
sl@0:  *   *...n...*x is convertible to Type&, for some n>=1.
sl@0:  * Examples of chained pointers are raw and smart pointers, iterators and
sl@0:  * arbitrary combinations of these (vg. Type** or auto_ptr<Type*>.)
sl@0:  */
sl@0: 
sl@0: /* NB. Some overloads of operator() have an extra dummy parameter int=0.
sl@0:  * This disambiguator serves several purposes:
sl@0:  *  - Without it, MSVC++ 6.0 incorrectly regards some overloads as
sl@0:  *    specializations of a previous member function template.
sl@0:  *  - MSVC++ 6.0/7.0 seem to incorrectly treat some different memfuns
sl@0:  *    as if they have the same signature.
sl@0:  *  - If remove_const is broken due to lack of PTS, int=0 avoids the
sl@0:  *    declaration of memfuns with identical signature.
sl@0:  */
sl@0: 
sl@0: template<typename Type>
sl@0: struct const_identity_base
sl@0: {
sl@0:   typedef Type result_type;
sl@0: 
sl@0:   template<typename ChainedPtr>
sl@0: 
sl@0: #if !defined(BOOST_NO_SFINAE)
sl@0:   typename disable_if<is_convertible<const ChainedPtr&,Type&>,Type&>::type
sl@0: #else
sl@0:   Type&
sl@0: #endif 
sl@0:   
sl@0:   operator()(const ChainedPtr& x)const
sl@0:   {
sl@0:     return operator()(*x);
sl@0:   }
sl@0: 
sl@0:   Type& operator()(Type& x)const
sl@0:   {
sl@0:     return x;
sl@0:   }
sl@0: 
sl@0:   Type& operator()(const reference_wrapper<Type>& x)const
sl@0:   { 
sl@0:     return x.get();
sl@0:   }
sl@0: 
sl@0:   Type& operator()(
sl@0:     const reference_wrapper<typename remove_const<Type>::type>& x,int=0)const
sl@0:   { 
sl@0:     return x.get();
sl@0:   }
sl@0: };
sl@0: 
sl@0: template<typename Type>
sl@0: struct non_const_identity_base
sl@0: {
sl@0:   typedef Type result_type;
sl@0: 
sl@0:   /* templatized for pointer-like types */
sl@0:   
sl@0:   template<typename ChainedPtr>
sl@0: 
sl@0: #if !defined(BOOST_NO_SFINAE)
sl@0:   typename disable_if<
sl@0:     is_convertible<const ChainedPtr&,const Type&>,Type&>::type
sl@0: #else
sl@0:   Type&
sl@0: #endif 
sl@0:     
sl@0:   operator()(const ChainedPtr& x)const
sl@0:   {
sl@0:     return operator()(*x);
sl@0:   }
sl@0: 
sl@0:   const Type& operator()(const Type& x,int=0)const
sl@0:   {
sl@0:     return x;
sl@0:   }
sl@0: 
sl@0:   Type& operator()(Type& x)const
sl@0:   {
sl@0:     return x;
sl@0:   }
sl@0: 
sl@0:   const Type& operator()(const reference_wrapper<const Type>& x,int=0)const
sl@0:   { 
sl@0:     return x.get();
sl@0:   }
sl@0: 
sl@0:   Type& operator()(const reference_wrapper<Type>& x)const
sl@0:   { 
sl@0:     return x.get();
sl@0:   }
sl@0: };
sl@0: 
sl@0: } /* namespace multi_index::detail */
sl@0: 
sl@0: template<class Type>
sl@0: struct identity:
sl@0:   mpl::if_c<
sl@0:     is_const<Type>::value,
sl@0:     detail::const_identity_base<Type>,detail::non_const_identity_base<Type>
sl@0:   >::type
sl@0: {
sl@0: };
sl@0: 
sl@0: } /* namespace multi_index */
sl@0: 
sl@0: } /* namespace boost */
sl@0: 
sl@0: #endif