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1 | // auto_ptr implementation -*- C++ -*- | |
2 | ||
3 | // Copyright (C) 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc. | |
4 | // | |
5 | // This file is part of the GNU ISO C++ Library. This library is free | |
6 | // software; you can redistribute it and/or modify it under the | |
7 | // terms of the GNU General Public License as published by the | |
8 | // Free Software Foundation; either version 3, or (at your option) | |
9 | // any later version. | |
10 | ||
11 | // This library is distributed in the hope that it will be useful, | |
12 | // but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | // GNU General Public License for more details. | |
15 | ||
16 | // Under Section 7 of GPL version 3, you are granted additional | |
17 | // permissions described in the GCC Runtime Library Exception, version | |
18 | // 3.1, as published by the Free Software Foundation. | |
19 | ||
20 | // You should have received a copy of the GNU General Public License and | |
21 | // a copy of the GCC Runtime Library Exception along with this program; | |
22 | // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see | |
23 | // <http://www.gnu.org/licenses/>. | |
24 | ||
25 | /** @file backward/auto_ptr.h | |
26 | * This is an internal header file, included by other library headers. | |
27 | * Do not attempt to use it directly. @headername{memory} | |
28 | */ | |
29 | ||
30 | #ifndef _BACKWARD_AUTO_PTR_H | |
31 | #define _BACKWARD_AUTO_PTR_H 1 | |
32 | ||
33 | #include <bits/c++config.h> | |
34 | #include <debug/debug.h> | |
35 | ||
36 | namespace std _GLIBCXX_VISIBILITY(default) | |
37 | { | |
38 | _GLIBCXX_BEGIN_NAMESPACE_VERSION | |
39 | ||
40 | /** | |
41 | * A wrapper class to provide auto_ptr with reference semantics. | |
42 | * For example, an auto_ptr can be assigned (or constructed from) | |
43 | * the result of a function which returns an auto_ptr by value. | |
44 | * | |
45 | * All the auto_ptr_ref stuff should happen behind the scenes. | |
46 | */ | |
47 | template<typename _Tp1> | |
48 | struct auto_ptr_ref | |
49 | { | |
50 | _Tp1* _M_ptr; | |
51 | ||
52 | explicit | |
53 | auto_ptr_ref(_Tp1* __p): _M_ptr(__p) { } | |
54 | } _GLIBCXX_DEPRECATED; | |
55 | ||
56 | ||
57 | /** | |
58 | * @brief A simple smart pointer providing strict ownership semantics. | |
59 | * | |
60 | * The Standard says: | |
61 | * <pre> | |
62 | * An @c auto_ptr owns the object it holds a pointer to. Copying | |
63 | * an @c auto_ptr copies the pointer and transfers ownership to the | |
64 | * destination. If more than one @c auto_ptr owns the same object | |
65 | * at the same time the behavior of the program is undefined. | |
66 | * | |
67 | * The uses of @c auto_ptr include providing temporary | |
68 | * exception-safety for dynamically allocated memory, passing | |
69 | * ownership of dynamically allocated memory to a function, and | |
70 | * returning dynamically allocated memory from a function. @c | |
71 | * auto_ptr does not meet the CopyConstructible and Assignable | |
72 | * requirements for Standard Library <a | |
73 | * href="tables.html#65">container</a> elements and thus | |
74 | * instantiating a Standard Library container with an @c auto_ptr | |
75 | * results in undefined behavior. | |
76 | * </pre> | |
77 | * Quoted from [20.4.5]/3. | |
78 | * | |
79 | * Good examples of what can and cannot be done with auto_ptr can | |
80 | * be found in the libstdc++ testsuite. | |
81 | * | |
82 | * _GLIBCXX_RESOLVE_LIB_DEFECTS | |
83 | * 127. auto_ptr<> conversion issues | |
84 | * These resolutions have all been incorporated. | |
85 | */ | |
86 | template<typename _Tp> | |
87 | class auto_ptr | |
88 | { | |
89 | private: | |
90 | _Tp* _M_ptr; | |
91 | ||
92 | public: | |
93 | /// The pointed-to type. | |
94 | typedef _Tp element_type; | |
95 | ||
96 | /** | |
97 | * @brief An %auto_ptr is usually constructed from a raw pointer. | |
98 | * @param __p A pointer (defaults to NULL). | |
99 | * | |
100 | * This object now @e owns the object pointed to by @a __p. | |
101 | */ | |
102 | explicit | |
103 | auto_ptr(element_type* __p = 0) throw() : _M_ptr(__p) { } | |
104 | ||
105 | /** | |
106 | * @brief An %auto_ptr can be constructed from another %auto_ptr. | |
107 | * @param __a Another %auto_ptr of the same type. | |
108 | * | |
109 | * This object now @e owns the object previously owned by @a __a, | |
110 | * which has given up ownership. | |
111 | */ | |
112 | auto_ptr(auto_ptr& __a) throw() : _M_ptr(__a.release()) { } | |
113 | ||
114 | /** | |
115 | * @brief An %auto_ptr can be constructed from another %auto_ptr. | |
116 | * @param __a Another %auto_ptr of a different but related type. | |
117 | * | |
118 | * A pointer-to-Tp1 must be convertible to a | |
119 | * pointer-to-Tp/element_type. | |
120 | * | |
121 | * This object now @e owns the object previously owned by @a __a, | |
122 | * which has given up ownership. | |
123 | */ | |
124 | template<typename _Tp1> | |
125 | auto_ptr(auto_ptr<_Tp1>& __a) throw() : _M_ptr(__a.release()) { } | |
126 | ||
127 | /** | |
128 | * @brief %auto_ptr assignment operator. | |
129 | * @param __a Another %auto_ptr of the same type. | |
130 | * | |
131 | * This object now @e owns the object previously owned by @a __a, | |
132 | * which has given up ownership. The object that this one @e | |
133 | * used to own and track has been deleted. | |
134 | */ | |
135 | auto_ptr& | |
136 | operator=(auto_ptr& __a) throw() | |
137 | { | |
138 | reset(__a.release()); | |
139 | return *this; | |
140 | } | |
141 | ||
142 | /** | |
143 | * @brief %auto_ptr assignment operator. | |
144 | * @param __a Another %auto_ptr of a different but related type. | |
145 | * | |
146 | * A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type. | |
147 | * | |
148 | * This object now @e owns the object previously owned by @a __a, | |
149 | * which has given up ownership. The object that this one @e | |
150 | * used to own and track has been deleted. | |
151 | */ | |
152 | template<typename _Tp1> | |
153 | auto_ptr& | |
154 | operator=(auto_ptr<_Tp1>& __a) throw() | |
155 | { | |
156 | reset(__a.release()); | |
157 | return *this; | |
158 | } | |
159 | ||
160 | /** | |
161 | * When the %auto_ptr goes out of scope, the object it owns is | |
162 | * deleted. If it no longer owns anything (i.e., @c get() is | |
163 | * @c NULL), then this has no effect. | |
164 | * | |
165 | * The C++ standard says there is supposed to be an empty throw | |
166 | * specification here, but omitting it is standard conforming. Its | |
167 | * presence can be detected only if _Tp::~_Tp() throws, but this is | |
168 | * prohibited. [17.4.3.6]/2 | |
169 | */ | |
170 | ~auto_ptr() { delete _M_ptr; } | |
171 | ||
172 | /** | |
173 | * @brief Smart pointer dereferencing. | |
174 | * | |
175 | * If this %auto_ptr no longer owns anything, then this | |
176 | * operation will crash. (For a smart pointer, <em>no longer owns | |
177 | * anything</em> is the same as being a null pointer, and you know | |
178 | * what happens when you dereference one of those...) | |
179 | */ | |
180 | element_type& | |
181 | operator*() const throw() | |
182 | { | |
183 | _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0); | |
184 | return *_M_ptr; | |
185 | } | |
186 | ||
187 | /** | |
188 | * @brief Smart pointer dereferencing. | |
189 | * | |
190 | * This returns the pointer itself, which the language then will | |
191 | * automatically cause to be dereferenced. | |
192 | */ | |
193 | element_type* | |
194 | operator->() const throw() | |
195 | { | |
196 | _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0); | |
197 | return _M_ptr; | |
198 | } | |
199 | ||
200 | /** | |
201 | * @brief Bypassing the smart pointer. | |
202 | * @return The raw pointer being managed. | |
203 | * | |
204 | * You can get a copy of the pointer that this object owns, for | |
205 | * situations such as passing to a function which only accepts | |
206 | * a raw pointer. | |
207 | * | |
208 | * @note This %auto_ptr still owns the memory. | |
209 | */ | |
210 | element_type* | |
211 | get() const throw() { return _M_ptr; } | |
212 | ||
213 | /** | |
214 | * @brief Bypassing the smart pointer. | |
215 | * @return The raw pointer being managed. | |
216 | * | |
217 | * You can get a copy of the pointer that this object owns, for | |
218 | * situations such as passing to a function which only accepts | |
219 | * a raw pointer. | |
220 | * | |
221 | * @note This %auto_ptr no longer owns the memory. When this object | |
222 | * goes out of scope, nothing will happen. | |
223 | */ | |
224 | element_type* | |
225 | release() throw() | |
226 | { | |
227 | element_type* __tmp = _M_ptr; | |
228 | _M_ptr = 0; | |
229 | return __tmp; | |
230 | } | |
231 | ||
232 | /** | |
233 | * @brief Forcibly deletes the managed object. | |
234 | * @param __p A pointer (defaults to NULL). | |
235 | * | |
236 | * This object now @e owns the object pointed to by @a __p. The | |
237 | * previous object has been deleted. | |
238 | */ | |
239 | void | |
240 | reset(element_type* __p = 0) throw() | |
241 | { | |
242 | if (__p != _M_ptr) | |
243 | { | |
244 | delete _M_ptr; | |
245 | _M_ptr = __p; | |
246 | } | |
247 | } | |
248 | ||
249 | /** | |
250 | * @brief Automatic conversions | |
251 | * | |
252 | * These operations convert an %auto_ptr into and from an auto_ptr_ref | |
253 | * automatically as needed. This allows constructs such as | |
254 | * @code | |
255 | * auto_ptr<Derived> func_returning_auto_ptr(.....); | |
256 | * ... | |
257 | * auto_ptr<Base> ptr = func_returning_auto_ptr(.....); | |
258 | * @endcode | |
259 | */ | |
260 | auto_ptr(auto_ptr_ref<element_type> __ref) throw() | |
261 | : _M_ptr(__ref._M_ptr) { } | |
262 | ||
263 | auto_ptr& | |
264 | operator=(auto_ptr_ref<element_type> __ref) throw() | |
265 | { | |
266 | if (__ref._M_ptr != this->get()) | |
267 | { | |
268 | delete _M_ptr; | |
269 | _M_ptr = __ref._M_ptr; | |
270 | } | |
271 | return *this; | |
272 | } | |
273 | ||
274 | template<typename _Tp1> | |
275 | operator auto_ptr_ref<_Tp1>() throw() | |
276 | { return auto_ptr_ref<_Tp1>(this->release()); } | |
277 | ||
278 | template<typename _Tp1> | |
279 | operator auto_ptr<_Tp1>() throw() | |
280 | { return auto_ptr<_Tp1>(this->release()); } | |
281 | } _GLIBCXX_DEPRECATED; | |
282 | ||
283 | // _GLIBCXX_RESOLVE_LIB_DEFECTS | |
284 | // 541. shared_ptr template assignment and void | |
285 | template<> | |
286 | class auto_ptr<void> | |
287 | { | |
288 | public: | |
289 | typedef void element_type; | |
290 | } _GLIBCXX_DEPRECATED; | |
291 | ||
292 | _GLIBCXX_END_NAMESPACE_VERSION | |
293 | } // namespace | |
294 | ||
295 | #endif /* _BACKWARD_AUTO_PTR_H */ |