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
56 666 : 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
106 666 : 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 ownership.
114 : */
115 590 : 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 ownership.
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 ownership. 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 ownership. 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 1922 : ~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*
197 590 : operator->() const throw()
198 : {
199 : _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
200 590 : 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 1256 : 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 1256 : release() throw()
229 : {
230 1256 : element_type* __tmp = _M_ptr;
231 1256 : _M_ptr = 0;
232 1256 : 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 : */
263 666 : auto_ptr(auto_ptr_ref<element_type> __ref) throw()
264 666 : : _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>
278 666 : operator auto_ptr_ref<_Tp1>() throw()
279 666 : { 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 */
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