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1 | // auto_ptr implementation -*- C++ -*- | |
2 | ||
3 | // Copyright (C) 2007, 2008 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 2, 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 | // You should have received a copy of the GNU General Public License | |
17 | // along with this library; see the file COPYING. If not, write to | |
18 | // the Free Software Foundation, 51 Franklin Street, Fifth Floor, | |
19 | // Boston, MA 02110-1301, USA. | |
20 | ||
21 | // As a special exception, you may use this file as part of a free software | |
22 | // library without restriction. Specifically, if other files instantiate | |
23 | // templates or use macros or inline functions from this file, or you compile | |
24 | // this file and link it with other files to produce an executable, this | |
25 | // file does not by itself cause the resulting executable to be covered by | |
26 | // the GNU General Public License. This exception does not however | |
27 | // invalidate any other reasons why the executable file might be covered by | |
28 | // the GNU General Public License. | |
29 | ||
30 | /** @file backward/auto_ptr.h | |
31 | * This is an internal header file, included by other library headers. | |
32 | * You should not attempt to use it directly. | |
33 | */ | |
34 | ||
35 | #ifndef _STL_AUTO_PTR_H | |
36 | #define _STL_AUTO_PTR_H 1 | |
37 | ||
38 | #include <bits/c++config.h> | |
39 | #include <debug/debug.h> | |
40 | ||
41 | _GLIBCXX_BEGIN_NAMESPACE(std) | |
42 | ||
43 | /** | |
44 | * A wrapper class to provide auto_ptr with reference semantics. | |
45 | * For example, an auto_ptr can be assigned (or constructed from) | |
46 | * the result of a function which returns an auto_ptr by value. | |
47 | * | |
48 | * All the auto_ptr_ref stuff should happen behind the scenes. | |
49 | */ | |
50 | template<typename _Tp1> | |
51 | struct auto_ptr_ref | |
52 | { | |
53 | _Tp1* _M_ptr; | |
54 | ||
55 | explicit | |
56 | auto_ptr_ref(_Tp1* __p): _M_ptr(__p) { } | |
57 | } _GLIBCXX_DEPRECATED_ATTR; | |
58 | ||
59 | ||
60 | /** | |
61 | * @brief A simple smart pointer providing strict ownership semantics. | |
62 | * | |
63 | * The Standard says: | |
64 | * <pre> | |
65 | * An @c auto_ptr owns the object it holds a pointer to. Copying | |
66 | * an @c auto_ptr copies the pointer and transfers ownership to the | |
67 | * destination. If more than one @c auto_ptr owns the same object | |
68 | * at the same time the behavior of the program is undefined. | |
69 | * | |
70 | * The uses of @c auto_ptr include providing temporary | |
71 | * exception-safety for dynamically allocated memory, passing | |
72 | * ownership of dynamically allocated memory to a function, and | |
73 | * returning dynamically allocated memory from a function. @c | |
74 | * auto_ptr does not meet the CopyConstructible and Assignable | |
75 | * requirements for Standard Library <a | |
76 | * href="tables.html#65">container</a> elements and thus | |
77 | * instantiating a Standard Library container with an @c auto_ptr | |
78 | * results in undefined behavior. | |
79 | * </pre> | |
80 | * Quoted from [20.4.5]/3. | |
81 | * | |
82 | * Good examples of what can and cannot be done with auto_ptr can | |
83 | * be found in the libstdc++ testsuite. | |
84 | * | |
85 | * _GLIBCXX_RESOLVE_LIB_DEFECTS | |
86 | * 127. auto_ptr<> conversion issues | |
87 | * These resolutions have all been incorporated. | |
88 | */ | |
89 | template<typename _Tp> | |
90 | class auto_ptr | |
91 | { | |
92 | private: | |
93 | _Tp* _M_ptr; | |
94 | ||
95 | public: | |
96 | /// The pointed-to type. | |
97 | typedef _Tp element_type; | |
98 | ||
99 | /** | |
100 | * @brief An %auto_ptr is usually constructed from a raw pointer. | |
101 | * @param p A pointer (defaults to NULL). | |
102 | * | |
103 | * This object now @e owns the object pointed to by @a p. | |
104 | */ | |
105 | explicit | |
106 | auto_ptr(element_type* __p = 0) throw() : _M_ptr(__p) { } | |
107 | ||
108 | /** | |
109 | * @brief An %auto_ptr can be constructed from another %auto_ptr. | |
110 | * @param a Another %auto_ptr of the same type. | |
111 | * | |
112 | * This object now @e owns the object previously owned by @a a, | |
113 | * which has given up ownsership. | |
114 | */ | |
115 | auto_ptr(auto_ptr& __a) throw() : _M_ptr(__a.release()) { } | |
116 | ||
117 | /** | |
118 | * @brief An %auto_ptr can be constructed from another %auto_ptr. | |
119 | * @param a Another %auto_ptr of a different but related type. | |
120 | * | |
121 | * A pointer-to-Tp1 must be convertible to a | |
122 | * pointer-to-Tp/element_type. | |
123 | * | |
124 | * This object now @e owns the object previously owned by @a a, | |
125 | * which has given up ownsership. | |
126 | */ | |
127 | template<typename _Tp1> | |
128 | auto_ptr(auto_ptr<_Tp1>& __a) throw() : _M_ptr(__a.release()) { } | |
129 | ||
130 | /** | |
131 | * @brief %auto_ptr assignment operator. | |
132 | * @param a Another %auto_ptr of the same type. | |
133 | * | |
134 | * This object now @e owns the object previously owned by @a a, | |
135 | * which has given up ownsership. The object that this one @e | |
136 | * used to own and track has been deleted. | |
137 | */ | |
138 | auto_ptr& | |
139 | operator=(auto_ptr& __a) throw() | |
140 | { | |
141 | reset(__a.release()); | |
142 | return *this; | |
143 | } | |
144 | ||
145 | /** | |
146 | * @brief %auto_ptr assignment operator. | |
147 | * @param a Another %auto_ptr of a different but related type. | |
148 | * | |
149 | * A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type. | |
150 | * | |
151 | * This object now @e owns the object previously owned by @a a, | |
152 | * which has given up ownsership. The object that this one @e | |
153 | * used to own and track has been deleted. | |
154 | */ | |
155 | template<typename _Tp1> | |
156 | auto_ptr& | |
157 | operator=(auto_ptr<_Tp1>& __a) throw() | |
158 | { | |
159 | reset(__a.release()); | |
160 | return *this; | |
161 | } | |
162 | ||
163 | /** | |
164 | * When the %auto_ptr goes out of scope, the object it owns is | |
165 | * deleted. If it no longer owns anything (i.e., @c get() is | |
166 | * @c NULL), then this has no effect. | |
167 | * | |
168 | * The C++ standard says there is supposed to be an empty throw | |
169 | * specification here, but omitting it is standard conforming. Its | |
170 | * presence can be detected only if _Tp::~_Tp() throws, but this is | |
171 | * prohibited. [17.4.3.6]/2 | |
172 | */ | |
173 | ~auto_ptr() { delete _M_ptr; } | |
174 | ||
175 | /** | |
176 | * @brief Smart pointer dereferencing. | |
177 | * | |
178 | * If this %auto_ptr no longer owns anything, then this | |
179 | * operation will crash. (For a smart pointer, "no longer owns | |
180 | * anything" is the same as being a null pointer, and you know | |
181 | * what happens when you dereference one of those...) | |
182 | */ | |
183 | element_type& | |
184 | operator*() const throw() | |
185 | { | |
186 | _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0); | |
187 | return *_M_ptr; | |
188 | } | |
189 | ||
190 | /** | |
191 | * @brief Smart pointer dereferencing. | |
192 | * | |
193 | * This returns the pointer itself, which the language then will | |
194 | * automatically cause to be dereferenced. | |
195 | */ | |
196 | element_type* | |
197 | operator->() const throw() | |
198 | { | |
199 | _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0); | |
200 | return _M_ptr; | |
201 | } | |
202 | ||
203 | /** | |
204 | * @brief Bypassing the smart pointer. | |
205 | * @return The raw pointer being managed. | |
206 | * | |
207 | * You can get a copy of the pointer that this object owns, for | |
208 | * situations such as passing to a function which only accepts | |
209 | * a raw pointer. | |
210 | * | |
211 | * @note This %auto_ptr still owns the memory. | |
212 | */ | |
213 | element_type* | |
214 | get() const throw() { return _M_ptr; } | |
215 | ||
216 | /** | |
217 | * @brief Bypassing the smart pointer. | |
218 | * @return The raw pointer being managed. | |
219 | * | |
220 | * You can get a copy of the pointer that this object owns, for | |
221 | * situations such as passing to a function which only accepts | |
222 | * a raw pointer. | |
223 | * | |
224 | * @note This %auto_ptr no longer owns the memory. When this object | |
225 | * goes out of scope, nothing will happen. | |
226 | */ | |
227 | element_type* | |
228 | release() throw() | |
229 | { | |
230 | element_type* __tmp = _M_ptr; | |
231 | _M_ptr = 0; | |
232 | return __tmp; | |
233 | } | |
234 | ||
235 | /** | |
236 | * @brief Forcibly deletes the managed object. | |
237 | * @param p A pointer (defaults to NULL). | |
238 | * | |
239 | * This object now @e owns the object pointed to by @a p. The | |
240 | * previous object has been deleted. | |
241 | */ | |
242 | void | |
243 | reset(element_type* __p = 0) throw() | |
244 | { | |
245 | if (__p != _M_ptr) | |
246 | { | |
247 | delete _M_ptr; | |
248 | _M_ptr = __p; | |
249 | } | |
250 | } | |
251 | ||
252 | /** | |
253 | * @brief Automatic conversions | |
254 | * | |
255 | * These operations convert an %auto_ptr into and from an auto_ptr_ref | |
256 | * automatically as needed. This allows constructs such as | |
257 | * @code | |
258 | * auto_ptr<Derived> func_returning_auto_ptr(.....); | |
259 | * ... | |
260 | * auto_ptr<Base> ptr = func_returning_auto_ptr(.....); | |
261 | * @endcode | |
262 | */ | |
263 | auto_ptr(auto_ptr_ref<element_type> __ref) throw() | |
264 | : _M_ptr(__ref._M_ptr) { } | |
265 | ||
266 | auto_ptr& | |
267 | operator=(auto_ptr_ref<element_type> __ref) throw() | |
268 | { | |
269 | if (__ref._M_ptr != this->get()) | |
270 | { | |
271 | delete _M_ptr; | |
272 | _M_ptr = __ref._M_ptr; | |
273 | } | |
274 | return *this; | |
275 | } | |
276 | ||
277 | template<typename _Tp1> | |
278 | operator auto_ptr_ref<_Tp1>() throw() | |
279 | { return auto_ptr_ref<_Tp1>(this->release()); } | |
280 | ||
281 | template<typename _Tp1> | |
282 | operator auto_ptr<_Tp1>() throw() | |
283 | { return auto_ptr<_Tp1>(this->release()); } | |
284 | } _GLIBCXX_DEPRECATED_ATTR; | |
285 | ||
286 | // _GLIBCXX_RESOLVE_LIB_DEFECTS | |
287 | // 541. shared_ptr template assignment and void | |
288 | template<> | |
289 | class auto_ptr<void> | |
290 | { | |
291 | public: | |
292 | typedef void element_type; | |
293 | } _GLIBCXX_DEPRECATED_ATTR; | |
294 | ||
295 | _GLIBCXX_END_NAMESPACE | |
296 | ||
297 | #endif /* _STL_AUTO_PTR_H */ |