[29] | 1 | /* Copyright 2003-2006 Joaquín M López Muñoz. |
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| 2 | * Distributed under the Boost Software License, Version 1.0. |
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| 3 | * (See accompanying file LICENSE_1_0.txt or copy at |
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| 4 | * http://www.boost.org/LICENSE_1_0.txt) |
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| 5 | * |
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| 6 | * See http://www.boost.org/libs/multi_index for library home page. |
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| 7 | */ |
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| 8 | |
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| 9 | #ifndef BOOST_MULTI_INDEX_IDENTITY_HPP |
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| 10 | #define BOOST_MULTI_INDEX_IDENTITY_HPP |
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| 11 | |
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| 12 | #if defined(_MSC_VER)&&(_MSC_VER>=1200) |
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| 13 | #pragma once |
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| 14 | #endif |
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| 15 | |
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| 16 | #include <boost/config.hpp> |
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| 17 | #include <boost/mpl/if.hpp> |
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| 18 | #include <boost/multi_index/identity_fwd.hpp> |
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| 19 | #include <boost/type_traits/is_const.hpp> |
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| 20 | #include <boost/type_traits/remove_const.hpp> |
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| 21 | #include <boost/utility/enable_if.hpp> |
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| 22 | |
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| 23 | #if !defined(BOOST_NO_SFINAE) |
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| 24 | #include <boost/type_traits/is_convertible.hpp> |
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| 25 | #endif |
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| 26 | |
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| 27 | namespace boost{ |
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| 28 | |
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| 29 | template<class Type> class reference_wrapper; /* fwd decl. */ |
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| 30 | |
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| 31 | namespace multi_index{ |
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| 32 | |
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| 33 | namespace detail{ |
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| 34 | |
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| 35 | /* identity is a do-nothing key extractor that returns the [const] Type& |
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| 36 | * object passed. |
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| 37 | * Additionally, identity is overloaded to support referece_wrappers |
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| 38 | * of Type and "chained pointers" to Type's. By chained pointer to Type we |
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| 39 | * mean a type P such that, given a p of type P |
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| 40 | * *...n...*x is convertible to Type&, for some n>=1. |
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| 41 | * Examples of chained pointers are raw and smart pointers, iterators and |
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| 42 | * arbitrary combinations of these (vg. Type** or auto_ptr<Type*>.) |
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| 43 | */ |
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| 44 | |
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| 45 | /* NB. Some overloads of operator() have an extra dummy parameter int=0. |
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| 46 | * This disambiguator serves several purposes: |
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| 47 | * - Without it, MSVC++ 6.0 incorrectly regards some overloads as |
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| 48 | * specializations of a previous member function template. |
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| 49 | * - MSVC++ 6.0/7.0 seem to incorrectly treat some different memfuns |
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| 50 | * as if they have the same signature. |
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| 51 | * - If remove_const is broken due to lack of PTS, int=0 avoids the |
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| 52 | * declaration of memfuns with identical signature. |
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| 53 | */ |
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| 54 | |
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| 55 | template<typename Type> |
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| 56 | struct const_identity_base |
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| 57 | { |
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| 58 | typedef Type result_type; |
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| 59 | |
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| 60 | template<typename ChainedPtr> |
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| 61 | |
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| 62 | #if !defined(BOOST_NO_SFINAE) |
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| 63 | typename disable_if<is_convertible<const ChainedPtr&,Type&>,Type&>::type |
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| 64 | #else |
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| 65 | Type& |
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| 66 | #endif |
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| 67 | |
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| 68 | operator()(const ChainedPtr& x)const |
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| 69 | { |
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| 70 | return operator()(*x); |
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| 71 | } |
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| 72 | |
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| 73 | Type& operator()(Type& x)const |
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| 74 | { |
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| 75 | return x; |
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| 76 | } |
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| 77 | |
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| 78 | Type& operator()(const reference_wrapper<Type>& x)const |
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| 79 | { |
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| 80 | return x.get(); |
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| 81 | } |
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| 82 | |
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| 83 | Type& operator()( |
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| 84 | const reference_wrapper<typename remove_const<Type>::type>& x,int=0)const |
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| 85 | { |
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| 86 | return x.get(); |
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| 87 | } |
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| 88 | }; |
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| 89 | |
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| 90 | template<typename Type> |
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| 91 | struct non_const_identity_base |
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| 92 | { |
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| 93 | typedef Type result_type; |
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| 94 | |
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| 95 | /* templatized for pointer-like types */ |
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| 96 | |
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| 97 | template<typename ChainedPtr> |
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| 98 | |
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| 99 | #if !defined(BOOST_NO_SFINAE) |
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| 100 | typename disable_if< |
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| 101 | is_convertible<const ChainedPtr&,const Type&>,Type&>::type |
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| 102 | #else |
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| 103 | Type& |
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| 104 | #endif |
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| 105 | |
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| 106 | operator()(const ChainedPtr& x)const |
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| 107 | { |
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| 108 | return operator()(*x); |
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| 109 | } |
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| 110 | |
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| 111 | const Type& operator()(const Type& x,int=0)const |
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| 112 | { |
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| 113 | return x; |
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| 114 | } |
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| 115 | |
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| 116 | Type& operator()(Type& x)const |
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| 117 | { |
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| 118 | return x; |
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| 119 | } |
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| 120 | |
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| 121 | const Type& operator()(const reference_wrapper<const Type>& x,int=0)const |
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| 122 | { |
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| 123 | return x.get(); |
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| 124 | } |
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| 125 | |
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| 126 | Type& operator()(const reference_wrapper<Type>& x)const |
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| 127 | { |
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| 128 | return x.get(); |
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| 129 | } |
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| 130 | }; |
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| 131 | |
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| 132 | } /* namespace multi_index::detail */ |
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| 133 | |
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| 134 | template<class Type> |
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| 135 | struct identity: |
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| 136 | mpl::if_c< |
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| 137 | is_const<Type>::value, |
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| 138 | detail::const_identity_base<Type>,detail::non_const_identity_base<Type> |
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| 139 | >::type |
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| 140 | { |
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| 141 | }; |
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| 142 | |
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| 143 | } /* namespace multi_index */ |
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| 144 | |
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| 145 | } /* namespace boost */ |
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| 146 | |
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| 147 | #endif |
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