1 #ifndef BOOST_CORE_REF_HPP
2 #define BOOST_CORE_REF_HPP
3
4 // MS compatible compilers support #pragma once
5
6 #if defined(_MSC_VER) && (_MSC_VER >= 1020)
7 # pragma once
8 #endif
9
10 #include <boost/config.hpp>
11 #include <boost/config/workaround.hpp>
12 #include <boost/core/addressof.hpp>
13
14 //
15 // ref.hpp - ref/cref, useful helper functions
16 //
17 // Copyright (C) 1999, 2000 Jaakko Jarvi (jaakko.jarvi@cs.utu.fi)
18 // Copyright (C) 2001, 2002 Peter Dimov
19 // Copyright (C) 2002 David Abrahams
20 //
21 // Copyright (C) 2014 Glen Joseph Fernandes
22 // (glenjofe@gmail.com)
23 //
24 // Copyright (C) 2014 Agustin Berge
25 //
26 // Distributed under the Boost Software License, Version 1.0. (See
27 // accompanying file LICENSE_1_0.txt or copy at
28 // http://www.boost.org/LICENSE_1_0.txt)
29 //
30 // See http://www.boost.org/libs/core/doc/html/core/ref.html for documentation.
31 //
32
33 /**
34 @file
35 */
36
37 /**
38 Boost namespace.
39 */
40 namespace boost
41 {
42
43 #if defined( BOOST_MSVC ) && BOOST_WORKAROUND( BOOST_MSVC, == 1600 )
44
45 struct ref_workaround_tag {};
46
47 #endif
48
49 // reference_wrapper
50
51 /**
52 @brief Contains a reference to an object of type `T`.
53
54 `reference_wrapper` is primarily used to "feed" references to
55 function templates (algorithms) that take their parameter by
56 value. It provides an implicit conversion to `T&`, which
57 usually allows the function templates to work on references
58 unmodified.
59 */
60 template<class T> class reference_wrapper
61 {
62 public:
63 /**
64 Type `T`.
65 */
66 typedef T type;
67
68 /**
69 Constructs a `reference_wrapper` object that stores a
70 reference to `t`.
71
72 @remark Does not throw.
73 */
reference_wrapper(T & t)74 BOOST_FORCEINLINE explicit reference_wrapper(T& t): t_(boost::addressof(t)) {}
75
76 #if defined( BOOST_MSVC ) && BOOST_WORKAROUND( BOOST_MSVC, == 1600 )
77
reference_wrapper(T & t,ref_workaround_tag)78 BOOST_FORCEINLINE explicit reference_wrapper( T & t, ref_workaround_tag ): t_( boost::addressof( t ) ) {}
79
80 #endif
81
82 #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
83 /**
84 @remark Construction from a temporary object is disabled.
85 */
86 BOOST_DELETED_FUNCTION(reference_wrapper(T&& t))
87 public:
88 #endif
89
90 /**
91 @return The stored reference.
92 @remark Does not throw.
93 */
operator T&() const94 BOOST_FORCEINLINE operator T& () const { return *t_; }
95
96 /**
97 @return The stored reference.
98 @remark Does not throw.
99 */
get() const100 BOOST_FORCEINLINE T& get() const { return *t_; }
101
102 /**
103 @return A pointer to the object referenced by the stored
104 reference.
105 @remark Does not throw.
106 */
get_pointer() const107 BOOST_FORCEINLINE T* get_pointer() const { return t_; }
108
109 private:
110
111 T* t_;
112 };
113
114 // ref
115
116 /**
117 @cond
118 */
119 #if defined( BOOST_BORLANDC ) && BOOST_WORKAROUND( BOOST_BORLANDC, BOOST_TESTED_AT(0x581) )
120 # define BOOST_REF_CONST
121 #else
122 # define BOOST_REF_CONST const
123 #endif
124 /**
125 @endcond
126 */
127
128 /**
129 @return `reference_wrapper<T>(t)`
130 @remark Does not throw.
131 */
ref(T & t)132 template<class T> BOOST_FORCEINLINE reference_wrapper<T> BOOST_REF_CONST ref( T & t )
133 {
134 #if defined( BOOST_MSVC ) && BOOST_WORKAROUND( BOOST_MSVC, == 1600 )
135
136 return reference_wrapper<T>( t, ref_workaround_tag() );
137
138 #else
139
140 return reference_wrapper<T>( t );
141
142 #endif
143 }
144
145 // cref
146
147 /**
148 @return `reference_wrapper<T const>(t)`
149 @remark Does not throw.
150 */
cref(T const & t)151 template<class T> BOOST_FORCEINLINE reference_wrapper<T const> BOOST_REF_CONST cref( T const & t )
152 {
153 return reference_wrapper<T const>(t);
154 }
155
156 #undef BOOST_REF_CONST
157
158 #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
159
160 /**
161 @cond
162 */
163 #if defined(BOOST_NO_CXX11_DELETED_FUNCTIONS)
164 # define BOOST_REF_DELETE
165 #else
166 # define BOOST_REF_DELETE = delete
167 #endif
168 /**
169 @endcond
170 */
171
172 /**
173 @remark Construction from a temporary object is disabled.
174 */
175 template<class T> void ref(T const&&) BOOST_REF_DELETE;
176
177 /**
178 @remark Construction from a temporary object is disabled.
179 */
180 template<class T> void cref(T const&&) BOOST_REF_DELETE;
181
182 #undef BOOST_REF_DELETE
183
184 #endif
185
186 // is_reference_wrapper
187
188 /**
189 @brief Determine if a type `T` is an instantiation of
190 `reference_wrapper`.
191
192 The value static constant will be true if the type `T` is a
193 specialization of `reference_wrapper`.
194 */
195 template<typename T> struct is_reference_wrapper
196 {
197 BOOST_STATIC_CONSTANT( bool, value = false );
198 };
199
200 /**
201 @cond
202 */
203 template<typename T> struct is_reference_wrapper< reference_wrapper<T> >
204 {
205 BOOST_STATIC_CONSTANT( bool, value = true );
206 };
207
208 #if !defined(BOOST_NO_CV_SPECIALIZATIONS)
209
210 template<typename T> struct is_reference_wrapper< reference_wrapper<T> const >
211 {
212 BOOST_STATIC_CONSTANT( bool, value = true );
213 };
214
215 template<typename T> struct is_reference_wrapper< reference_wrapper<T> volatile >
216 {
217 BOOST_STATIC_CONSTANT( bool, value = true );
218 };
219
220 template<typename T> struct is_reference_wrapper< reference_wrapper<T> const volatile >
221 {
222 BOOST_STATIC_CONSTANT( bool, value = true );
223 };
224
225 #endif // !defined(BOOST_NO_CV_SPECIALIZATIONS)
226
227 /**
228 @endcond
229 */
230
231
232 // unwrap_reference
233
234 /**
235 @brief Find the type in a `reference_wrapper`.
236
237 The `typedef` type is `T::type` if `T` is a
238 `reference_wrapper`, `T` otherwise.
239 */
240 template<typename T> struct unwrap_reference
241 {
242 typedef T type;
243 };
244
245 /**
246 @cond
247 */
248 template<typename T> struct unwrap_reference< reference_wrapper<T> >
249 {
250 typedef T type;
251 };
252
253 #if !defined(BOOST_NO_CV_SPECIALIZATIONS)
254
255 template<typename T> struct unwrap_reference< reference_wrapper<T> const >
256 {
257 typedef T type;
258 };
259
260 template<typename T> struct unwrap_reference< reference_wrapper<T> volatile >
261 {
262 typedef T type;
263 };
264
265 template<typename T> struct unwrap_reference< reference_wrapper<T> const volatile >
266 {
267 typedef T type;
268 };
269
270 #endif // !defined(BOOST_NO_CV_SPECIALIZATIONS)
271
272 /**
273 @endcond
274 */
275
276 // unwrap_ref
277
278 /**
279 @return `unwrap_reference<T>::type&(t)`
280 @remark Does not throw.
281 */
unwrap_ref(T & t)282 template<class T> BOOST_FORCEINLINE typename unwrap_reference<T>::type& unwrap_ref( T & t )
283 {
284 return t;
285 }
286
287 // get_pointer
288
289 /**
290 @cond
291 */
get_pointer(reference_wrapper<T> const & r)292 template<class T> BOOST_FORCEINLINE T* get_pointer( reference_wrapper<T> const & r )
293 {
294 return r.get_pointer();
295 }
296 /**
297 @endcond
298 */
299
300 } // namespace boost
301
302 #endif // #ifndef BOOST_CORE_REF_HPP
303