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1 : // auto_ptr implementation -*- C++ -*-
2 :
3 : // Copyright (C) 2007, 2008, 2009 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 : * You should not attempt to use it directly.
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 : _GLIBCXX_BEGIN_NAMESPACE(std)
37 :
38 : /**
39 : * A wrapper class to provide auto_ptr with reference semantics.
40 : * For example, an auto_ptr can be assigned (or constructed from)
41 : * the result of a function which returns an auto_ptr by value.
42 : *
43 : * All the auto_ptr_ref stuff should happen behind the scenes.
44 : */
45 : template<typename _Tp1>
46 : struct auto_ptr_ref
47 : {
48 : _Tp1* _M_ptr;
49 :
50 : explicit
51 : auto_ptr_ref(_Tp1* __p): _M_ptr(__p) { }
52 : } _GLIBCXX_DEPRECATED_ATTR;
53 :
54 :
55 : /**
56 : * @brief A simple smart pointer providing strict ownership semantics.
57 : *
58 : * The Standard says:
59 : * <pre>
60 : * An @c auto_ptr owns the object it holds a pointer to. Copying
61 : * an @c auto_ptr copies the pointer and transfers ownership to the
62 : * destination. If more than one @c auto_ptr owns the same object
63 : * at the same time the behavior of the program is undefined.
64 : *
65 : * The uses of @c auto_ptr include providing temporary
66 : * exception-safety for dynamically allocated memory, passing
67 : * ownership of dynamically allocated memory to a function, and
68 : * returning dynamically allocated memory from a function. @c
69 : * auto_ptr does not meet the CopyConstructible and Assignable
70 : * requirements for Standard Library <a
71 : * href="tables.html#65">container</a> elements and thus
72 : * instantiating a Standard Library container with an @c auto_ptr
73 : * results in undefined behavior.
74 : * </pre>
75 : * Quoted from [20.4.5]/3.
76 : *
77 : * Good examples of what can and cannot be done with auto_ptr can
78 : * be found in the libstdc++ testsuite.
79 : *
80 : * _GLIBCXX_RESOLVE_LIB_DEFECTS
81 : * 127. auto_ptr<> conversion issues
82 : * These resolutions have all been incorporated.
83 : */
84 : template<typename _Tp>
85 : class auto_ptr
86 : {
87 : private:
88 : _Tp* _M_ptr;
89 :
90 : public:
91 : /// The pointed-to type.
92 : typedef _Tp element_type;
93 :
94 : /**
95 : * @brief An %auto_ptr is usually constructed from a raw pointer.
96 : * @param p A pointer (defaults to NULL).
97 : *
98 : * This object now @e owns the object pointed to by @a p.
99 : */
100 : explicit
101 0 : auto_ptr(element_type* __p = 0) throw() : _M_ptr(__p) { }
102 :
103 : /**
104 : * @brief An %auto_ptr can be constructed from another %auto_ptr.
105 : * @param a Another %auto_ptr of the same type.
106 : *
107 : * This object now @e owns the object previously owned by @a a,
108 : * which has given up ownership.
109 : */
110 : auto_ptr(auto_ptr& __a) throw() : _M_ptr(__a.release()) { }
111 :
112 : /**
113 : * @brief An %auto_ptr can be constructed from another %auto_ptr.
114 : * @param a Another %auto_ptr of a different but related type.
115 : *
116 : * A pointer-to-Tp1 must be convertible to a
117 : * pointer-to-Tp/element_type.
118 : *
119 : * This object now @e owns the object previously owned by @a a,
120 : * which has given up ownership.
121 : */
122 : template<typename _Tp1>
123 : auto_ptr(auto_ptr<_Tp1>& __a) throw() : _M_ptr(__a.release()) { }
124 :
125 : /**
126 : * @brief %auto_ptr assignment operator.
127 : * @param a Another %auto_ptr of the same type.
128 : *
129 : * This object now @e owns the object previously owned by @a a,
130 : * which has given up ownership. The object that this one @e
131 : * used to own and track has been deleted.
132 : */
133 : auto_ptr&
134 : operator=(auto_ptr& __a) throw()
135 : {
136 : reset(__a.release());
137 : return *this;
138 : }
139 :
140 : /**
141 : * @brief %auto_ptr assignment operator.
142 : * @param a Another %auto_ptr of a different but related type.
143 : *
144 : * A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type.
145 : *
146 : * This object now @e owns the object previously owned by @a a,
147 : * which has given up ownership. The object that this one @e
148 : * used to own and track has been deleted.
149 : */
150 : template<typename _Tp1>
151 : auto_ptr&
152 : operator=(auto_ptr<_Tp1>& __a) throw()
153 : {
154 : reset(__a.release());
155 : return *this;
156 : }
157 :
158 : /**
159 : * When the %auto_ptr goes out of scope, the object it owns is
160 : * deleted. If it no longer owns anything (i.e., @c get() is
161 : * @c NULL), then this has no effect.
162 : *
163 : * The C++ standard says there is supposed to be an empty throw
164 : * specification here, but omitting it is standard conforming. Its
165 : * presence can be detected only if _Tp::~_Tp() throws, but this is
166 : * prohibited. [17.4.3.6]/2
167 : */
168 0 : ~auto_ptr() { delete _M_ptr; }
169 :
170 : /**
171 : * @brief Smart pointer dereferencing.
172 : *
173 : * If this %auto_ptr no longer owns anything, then this
174 : * operation will crash. (For a smart pointer, "no longer owns
175 : * anything" is the same as being a null pointer, and you know
176 : * what happens when you dereference one of those...)
177 : */
178 : element_type&
179 : operator*() const throw()
180 : {
181 : _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
182 : return *_M_ptr;
183 : }
184 :
185 : /**
186 : * @brief Smart pointer dereferencing.
187 : *
188 : * This returns the pointer itself, which the language then will
189 : * automatically cause to be dereferenced.
190 : */
191 : element_type*
192 : operator->() const throw()
193 : {
194 : _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
195 : return _M_ptr;
196 : }
197 :
198 : /**
199 : * @brief Bypassing the smart pointer.
200 : * @return The raw pointer being managed.
201 : *
202 : * You can get a copy of the pointer that this object owns, for
203 : * situations such as passing to a function which only accepts
204 : * a raw pointer.
205 : *
206 : * @note This %auto_ptr still owns the memory.
207 : */
208 : element_type*
209 0 : get() const throw() { return _M_ptr; }
210 :
211 : /**
212 : * @brief Bypassing the smart pointer.
213 : * @return The raw pointer being managed.
214 : *
215 : * You can get a copy of the pointer that this object owns, for
216 : * situations such as passing to a function which only accepts
217 : * a raw pointer.
218 : *
219 : * @note This %auto_ptr no longer owns the memory. When this object
220 : * goes out of scope, nothing will happen.
221 : */
222 : element_type*
223 : release() throw()
224 : {
225 : element_type* __tmp = _M_ptr;
226 : _M_ptr = 0;
227 : return __tmp;
228 : }
229 :
230 : /**
231 : * @brief Forcibly deletes the managed object.
232 : * @param p A pointer (defaults to NULL).
233 : *
234 : * This object now @e owns the object pointed to by @a p. The
235 : * previous object has been deleted.
236 : */
237 : void
238 : reset(element_type* __p = 0) throw()
239 : {
240 : if (__p != _M_ptr)
241 : {
242 : delete _M_ptr;
243 : _M_ptr = __p;
244 : }
245 : }
246 :
247 : /**
248 : * @brief Automatic conversions
249 : *
250 : * These operations convert an %auto_ptr into and from an auto_ptr_ref
251 : * automatically as needed. This allows constructs such as
252 : * @code
253 : * auto_ptr<Derived> func_returning_auto_ptr(.....);
254 : * ...
255 : * auto_ptr<Base> ptr = func_returning_auto_ptr(.....);
256 : * @endcode
257 : */
258 : auto_ptr(auto_ptr_ref<element_type> __ref) throw()
259 : : _M_ptr(__ref._M_ptr) { }
260 :
261 : auto_ptr&
262 : operator=(auto_ptr_ref<element_type> __ref) throw()
263 : {
264 : if (__ref._M_ptr != this->get())
265 : {
266 : delete _M_ptr;
267 : _M_ptr = __ref._M_ptr;
268 : }
269 : return *this;
270 : }
271 :
272 : template<typename _Tp1>
273 : operator auto_ptr_ref<_Tp1>() throw()
274 : { return auto_ptr_ref<_Tp1>(this->release()); }
275 :
276 : template<typename _Tp1>
277 : operator auto_ptr<_Tp1>() throw()
278 : { return auto_ptr<_Tp1>(this->release()); }
279 : } _GLIBCXX_DEPRECATED_ATTR;
280 :
281 : // _GLIBCXX_RESOLVE_LIB_DEFECTS
282 : // 541. shared_ptr template assignment and void
283 : template<>
284 : class auto_ptr<void>
285 : {
286 : public:
287 : typedef void element_type;
288 : } _GLIBCXX_DEPRECATED_ATTR;
289 :
290 : _GLIBCXX_END_NAMESPACE
291 :
292 : #endif /* _BACKWARD_AUTO_PTR_H */
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