1// See http://www.boost.org/libs/any for Documentation.
2
3#ifndef BOOST_ANY_INCLUDED
4#define BOOST_ANY_INCLUDED
5
6#include <boost/config.hpp>
7#ifdef BOOST_HAS_PRAGMA_ONCE
8# pragma once
9#endif
10
11/// \file boost/any.hpp
12/// \brief \copybrief boost::any
13
14// what: variant type boost::any
15// who: contributed by Kevlin Henney,
16// with features contributed and bugs found by
17// Antony Polukhin, Ed Brey, Mark Rodgers,
18// Peter Dimov, and James Curran
19// when: July 2001, April 2013 - 2020
20
21#include <boost/any/bad_any_cast.hpp>
22#include <boost/any/fwd.hpp>
23#include <boost/any/detail/placeholder.hpp>
24#include <boost/throw_exception.hpp>
25#include <boost/type_index.hpp>
26
27#include <memory> // for std::addressof
28#include <type_traits>
29
30namespace boost
31{
32 /// \brief A class whose instances can hold instances of any
33 /// type that satisfies \forcedlink{ValueType} requirements.
34 class any
35 {
36 public:
37
38 /// \post this->empty() is true.
39 constexpr any() noexcept
40 : content(0)
41 {
42 }
43
44 /// Makes a copy of `value`, so
45 /// that the initial content of the new instance is equivalent
46 /// in both type and value to `value`.
47 ///
48 /// \throws std::bad_alloc or any exceptions arising from the copy
49 /// constructor of the contained type.
50 template<typename ValueType>
51 any(const ValueType & value)
52 : content(new holder<
53 typename std::remove_cv<typename std::decay<const ValueType>::type>::type
54 >(value))
55 {
56 static_assert(
57 !anys::detail::is_basic_any<ValueType>::value,
58 "boost::any shall not be constructed from boost::anys::basic_any"
59 );
60 }
61
62 /// Copy constructor that copies content of
63 /// `other` into new instance, so that any content
64 /// is equivalent in both type and value to the content of
65 /// `other`, or empty if `other` is empty.
66 ///
67 /// \throws May fail with a `std::bad_alloc`
68 /// exception or any exceptions arising from the copy
69 /// constructor of the contained type.
70 any(const any & other)
71 : content(other.content ? other.content->clone() : 0)
72 {
73 }
74
75 /// Move constructor that moves content of
76 /// `other` into new instance and leaves `other` empty.
77 ///
78 /// \post other->empty() is true
79 /// \throws Nothing.
80 any(any&& other) noexcept
81 : content(other.content)
82 {
83 other.content = 0;
84 }
85
86 /// Forwards `value`, so
87 /// that the initial content of the new instance is equivalent
88 /// in both type and value to `value` before the forward.
89 ///
90 /// \throws std::bad_alloc or any exceptions arising from the move or
91 /// copy constructor of the contained type.
92 template<typename ValueType>
93 any(ValueType&& value
94 , typename std::enable_if<!std::is_same<any&, ValueType>::value >::type* = 0 // disable if value has type `any&`
95 , typename std::enable_if<!std::is_const<ValueType>::value >::type* = 0) // disable if value has type `const ValueType&&`
96 : content(new holder< typename std::decay<ValueType>::type >(std::forward<ValueType>(value)))
97 {
98 static_assert(
99 !anys::detail::is_basic_any<typename std::decay<ValueType>::type>::value,
100 "boost::any shall not be constructed from boost::anys::basic_any"
101 );
102 }
103
104 /// Releases any and all resources used in management of instance.
105 ///
106 /// \throws Nothing.
107 ~any() noexcept
108 {
109 delete content;
110 }
111
112 public: // modifiers
113
114 /// Exchange of the contents of `*this` and `rhs`.
115 ///
116 /// \returns `*this`
117 /// \throws Nothing.
118 any & swap(any & rhs) noexcept
119 {
120 placeholder* tmp = content;
121 content = rhs.content;
122 rhs.content = tmp;
123 return *this;
124 }
125
126 /// Copies content of `rhs` into
127 /// current instance, discarding previous content, so that the
128 /// new content is equivalent in both type and value to the
129 /// content of `rhs`, or empty if `rhs.empty()`.
130 ///
131 /// \throws std::bad_alloc
132 /// or any exceptions arising from the copy constructor of the
133 /// contained type. Assignment satisfies the strong guarantee
134 /// of exception safety.
135 any & operator=(const any& rhs)
136 {
137 any(rhs).swap(rhs&: *this);
138 return *this;
139 }
140
141 /// Moves content of `rhs` into
142 /// current instance, discarding previous content, so that the
143 /// new content is equivalent in both type and value to the
144 /// content of `rhs` before move, or empty if
145 /// `rhs.empty()`.
146 ///
147 /// \post `rhs->empty()` is true
148 /// \throws Nothing.
149 any & operator=(any&& rhs) noexcept
150 {
151 rhs.swap(rhs&: *this);
152 any().swap(rhs);
153 return *this;
154 }
155
156 /// Forwards `rhs`,
157 /// discarding previous content, so that the new content of is
158 /// equivalent in both type and value to
159 /// `rhs` before forward.
160 ///
161 /// \throws std::bad_alloc
162 /// or any exceptions arising from the move or copy constructor of the
163 /// contained type. Assignment satisfies the strong guarantee
164 /// of exception safety.
165 template <class ValueType>
166 any & operator=(ValueType&& rhs)
167 {
168 static_assert(
169 !anys::detail::is_basic_any<typename std::decay<ValueType>::type>::value,
170 "boost::anys::basic_any shall not be assigned into boost::any"
171 );
172 any(std::forward<ValueType>(rhs)).swap(rhs&: *this);
173 return *this;
174 }
175
176 public: // queries
177
178 /// \returns `true` if instance is empty, otherwise `false`.
179 /// \throws Nothing.
180 bool empty() const noexcept
181 {
182 return !content;
183 }
184
185 /// \post this->empty() is true
186 void clear() noexcept
187 {
188 any().swap(rhs&: *this);
189 }
190
191 /// \returns the `typeid` of the
192 /// contained value if instance is non-empty, otherwise
193 /// `typeid(void)`.
194 ///
195 /// Useful for querying against types known either at compile time or
196 /// only at runtime.
197 const boost::typeindex::type_info& type() const noexcept
198 {
199 return content ? content->type() : boost::typeindex::type_id<void>().type_info();
200 }
201
202 private: // types
203 /// @cond
204 class BOOST_SYMBOL_VISIBLE placeholder: public boost::anys::detail::placeholder
205 {
206 public:
207 virtual placeholder * clone() const = 0;
208 };
209
210 template<typename ValueType>
211 class holder final
212 : public placeholder
213 {
214 public: // structors
215
216 holder(const ValueType & value)
217 : held(value)
218 {
219 }
220
221 holder(ValueType&& value)
222 : held(static_cast< ValueType&& >(value))
223 {
224 }
225
226 public: // queries
227
228 const boost::typeindex::type_info& type() const noexcept override
229 {
230 return boost::typeindex::type_id<ValueType>().type_info();
231 }
232
233 placeholder * clone() const BOOST_OVERRIDE
234 {
235 return new holder(held);
236 }
237
238 public: // representation
239
240 ValueType held;
241
242 private: // intentionally left unimplemented
243 holder & operator=(const holder &);
244 };
245
246 private: // representation
247 template<typename ValueType>
248 friend ValueType * unsafe_any_cast(any *) noexcept;
249
250 friend class boost::anys::unique_any;
251
252 placeholder * content;
253 /// @endcond
254 };
255
256 /// Exchange of the contents of `lhs` and `rhs`.
257 /// \throws Nothing.
258 inline void swap(any & lhs, any & rhs) noexcept
259 {
260 lhs.swap(rhs);
261 }
262
263 /// @cond
264
265 // Note: The "unsafe" versions of any_cast are not part of the
266 // public interface and may be removed at any time. They are
267 // required where we know what type is stored in the any and can't
268 // use typeid() comparison, e.g., when our types may travel across
269 // different shared libraries.
270 template<typename ValueType>
271 inline ValueType * unsafe_any_cast(any * operand) noexcept
272 {
273 return std::addressof(
274 static_cast<any::holder<ValueType> *>(operand->content)->held
275 );
276 }
277
278 template<typename ValueType>
279 inline const ValueType * unsafe_any_cast(const any * operand) noexcept
280 {
281 return boost::unsafe_any_cast<ValueType>(const_cast<any *>(operand));
282 }
283 /// @endcond
284
285 /// \returns Pointer to a ValueType stored in `operand`, nullptr if
286 /// `operand` does not contain specified `ValueType`.
287 template<typename ValueType>
288 ValueType * any_cast(any * operand) noexcept
289 {
290 return operand && operand->type() == boost::typeindex::type_id<ValueType>()
291 ? boost::unsafe_any_cast<typename std::remove_cv<ValueType>::type>(operand)
292 : 0;
293 }
294
295 /// \returns Const pointer to a ValueType stored in `operand`, nullptr if
296 /// `operand` does not contain specified `ValueType`.
297 template<typename ValueType>
298 inline const ValueType * any_cast(const any * operand) noexcept
299 {
300 return boost::any_cast<ValueType>(const_cast<any *>(operand));
301 }
302
303 /// \returns ValueType stored in `operand`
304 /// \throws boost::bad_any_cast if `operand` does not contain
305 /// specified ValueType.
306 template<typename ValueType>
307 ValueType any_cast(any & operand)
308 {
309 typedef typename std::remove_reference<ValueType>::type nonref;
310
311 nonref * result = boost::any_cast<nonref>(std::addressof(r&: operand));
312 if(!result)
313 boost::throw_exception(e: bad_any_cast());
314
315 // Attempt to avoid construction of a temporary object in cases when
316 // `ValueType` is not a reference. Example:
317 // `static_cast<std::string>(*result);`
318 // which is equal to `std::string(*result);`
319 typedef typename std::conditional<
320 std::is_reference<ValueType>::value,
321 ValueType,
322 typename std::add_lvalue_reference<ValueType>::type
323 >::type ref_type;
324
325#ifdef BOOST_MSVC
326# pragma warning(push)
327# pragma warning(disable: 4172) // "returning address of local variable or temporary" but *result is not local!
328#endif
329 return static_cast<ref_type>(*result);
330#ifdef BOOST_MSVC
331# pragma warning(pop)
332#endif
333 }
334
335 /// \returns `ValueType` stored in `operand`
336 /// \throws boost::bad_any_cast if `operand` does not contain
337 /// specified `ValueType`.
338 template<typename ValueType>
339 inline ValueType any_cast(const any & operand)
340 {
341 typedef typename std::remove_reference<ValueType>::type nonref;
342 return boost::any_cast<const nonref &>(const_cast<any &>(operand));
343 }
344
345 /// \returns `ValueType` stored in `operand`, leaving the `operand` empty.
346 /// \throws boost::bad_any_cast if `operand` does not contain
347 /// specified `ValueType`.
348 template<typename ValueType>
349 inline ValueType any_cast(any&& operand)
350 {
351 static_assert(
352 std::is_rvalue_reference<ValueType&&>::value /*true if ValueType is rvalue or just a value*/
353 || std::is_const< typename std::remove_reference<ValueType>::type >::value,
354 "boost::any_cast shall not be used for getting nonconst references to temporary objects"
355 );
356 return boost::any_cast<ValueType>(operand);
357 }
358}
359
360// Copyright Kevlin Henney, 2000, 2001, 2002. All rights reserved.
361// Copyright Antony Polukhin, 2013-2024.
362//
363// Distributed under the Boost Software License, Version 1.0. (See
364// accompanying file LICENSE_1_0.txt or copy at
365// http://www.boost.org/LICENSE_1_0.txt)
366
367#endif
368

source code of boost/libs/any/include/boost/any.hpp