1// auto_ptr implementation -*- C++ -*-
2
3// Copyright (C) 2007, 2008, 2009, 2010 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      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      ~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, <em>no longer owns
175       *  anything</em> 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      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 */
293