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