std_memory.h revision 117397 
1// <memory> -*- C++ -*-
2
3// Copyright (C) 2001, 2002 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 along
17// with this library; see the file COPYING.  If not, write to the Free
18// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
19// 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/*
31 * Copyright (c) 1997-1999
32 * Silicon Graphics Computer Systems, Inc.
33 *
34 * Permission to use, copy, modify, distribute and sell this software
35 * and its documentation for any purpose is hereby granted without fee,
36 * provided that the above copyright notice appear in all copies and
37 * that both that copyright notice and this permission notice appear
38 * in supporting documentation.  Silicon Graphics makes no
39 * representations about the suitability of this software for any
40 * purpose.  It is provided "as is" without express or implied warranty.
41 *
42 */
43
44/** @file memory
45 *  This is a Standard C++ Library header.  You should @c #include this header
46 *  in your programs, rather than any of the "st[dl]_*.h" implementation files.
47 */
48
49#ifndef _CPP_MEMORY
50#define _CPP_MEMORY 1
51
52#pragma GCC system_header
53
54#include <bits/stl_algobase.h>
55#include <bits/stl_alloc.h>
56#include <bits/stl_construct.h>
57#include <bits/stl_iterator_base_types.h> //for iterator_traits
58#include <bits/stl_uninitialized.h>
59#include <bits/stl_raw_storage_iter.h>
60
61namespace std
62{
63  /**
64   *  @if maint
65   *  This is a helper function.  The unused second parameter exists to
66   *  permit the real get_temporary_buffer to use template parameter deduction.
67   *
68   *  XXX This should perhaps use the pool.
69   *  @endif
70   */
71  template<typename _Tp>
72    pair<_Tp*, ptrdiff_t>
73    __get_temporary_buffer(ptrdiff_t __len, _Tp*)
74    {
75      if (__len > ptrdiff_t(INT_MAX / sizeof(_Tp)))
76	__len = INT_MAX / sizeof(_Tp);
77
78      while (__len > 0)
79	{
80	  _Tp* __tmp = (_Tp*) std::malloc((std::size_t)__len * sizeof(_Tp));
81	  if (__tmp != 0)
82	    return pair<_Tp*, ptrdiff_t>(__tmp, __len);
83	  __len /= 2;
84	}
85      return pair<_Tp*, ptrdiff_t>((_Tp*)0, 0);
86    }
87
88  /**
89   *  @brief This is a mostly-useless wrapper around malloc().
90   *  @param  len  The number of objects of type Tp.
91   *  @return   See full description.
92   *
93   *  Reinventing the wheel, but this time with prettier spokes!
94   *
95   *  This function tries to obtain storage for @c len adjacent Tp objects.
96   *  The objects themselves are not constructed, of course.  A pair<> is
97   *  returned containing "the buffer s address and capacity (in the units of
98   *  sizeof(Tp)), or a pair of 0 values if no storage can be obtained."
99   *  Note that the capacity obtained may be less than that requested if the
100   *  memory is unavailable; you should compare len with the .second return
101   *  value.
102   */
103  template<typename _Tp>
104    inline pair<_Tp*,ptrdiff_t>
105    get_temporary_buffer(ptrdiff_t __len)
106    { return __get_temporary_buffer(__len, (_Tp*) 0); }
107
108  /**
109   *  @brief The companion to get_temporary_buffer().
110   *  @param  p  A buffer previously allocated by get_temporary_buffer.
111   *  @return   None.
112   *
113   *  Frees the memory pointed to by p.
114   */
115  template<typename _Tp>
116    void
117    return_temporary_buffer(_Tp* __p)
118    { std::free(__p); }
119
120  /**
121   *  A wrapper class to provide auto_ptr with reference semantics.  For
122   *  example, an auto_ptr can be assigned (or constructed from) the result of
123   *  a function which returns an auto_ptr by value.
124   *
125   *  All the auto_ptr_ref stuff should happen behind the scenes.
126   */
127  template<typename _Tp1>
128    struct auto_ptr_ref
129    {
130      _Tp1* _M_ptr;
131
132      explicit
133      auto_ptr_ref(_Tp1* __p): _M_ptr(__p) { }
134    };
135
136
137  /**
138   *  @brief  A simple smart pointer providing strict ownership semantics.
139   *
140   *  The Standard says:
141   *  <pre>
142   *  An @c auto_ptr owns the object it holds a pointer to.  Copying an
143   *  @c auto_ptr copies the pointer and transfers ownership to the destination.
144   *  If more than one @c auto_ptr owns the same object at the same time the
145   *  behavior of the program is undefined.
146   *
147   *  The uses of @c auto_ptr include providing temporary exception-safety for
148   *  dynamically allocated memory, passing ownership of dynamically allocated
149   *  memory to a function, and returning dynamically allocated memory from a
150   *  function.  @c auto_ptr does not meet the CopyConstructible and Assignable
151   *  requirements for Standard Library <a href="tables.html#65">container</a>
152   *  elements and thus instantiating a Standard Library container with an
153   *  @c auto_ptr results in undefined behavior.
154   *  </pre>
155   *  Quoted from [20.4.5]/3.
156   *
157   *  Good examples of what can and cannot be done with auto_ptr can be found
158   *  in the libstdc++ testsuite.
159   *
160   *  @if maint
161   *  _GLIBCPP_RESOLVE_LIB_DEFECTS
162   *  127.  auto_ptr<> conversion issues
163   *  These resolutions have all been incorporated.
164   *  @endif
165   */
166  template<typename _Tp>
167    class auto_ptr
168    {
169    private:
170      _Tp* _M_ptr;
171
172    public:
173      /// The pointed-to type.
174      typedef _Tp element_type;
175
176      /**
177       *  @brief  An %auto_ptr is usually constructed from a raw pointer.
178       *  @param  p  A pointer (defaults to NULL).
179       *
180       *  This object now @e owns the object pointed to by @a p.
181       */
182      explicit
183      auto_ptr(element_type* __p = 0) throw() : _M_ptr(__p) { }
184
185      /**
186       *  @brief  An %auto_ptr can be constructed from another %auto_ptr.
187       *  @param  a  Another %auto_ptr of the same type.
188       *
189       *  This object now @e owns the object previously owned by @a a,
190       *  which has given up ownsership.
191       */
192      auto_ptr(auto_ptr& __a) throw() : _M_ptr(__a.release()) { }
193
194      /**
195       *  @brief  An %auto_ptr can be constructed from another %auto_ptr.
196       *  @param  a  Another %auto_ptr of a different but related type.
197       *
198       *  A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type.
199       *
200       *  This object now @e owns the object previously owned by @a a,
201       *  which has given up ownsership.
202       */
203      template<typename _Tp1>
204        auto_ptr(auto_ptr<_Tp1>& __a) throw() : _M_ptr(__a.release()) { }
205
206      /**
207       *  @brief  %auto_ptr assignment operator.
208       *  @param  a  Another %auto_ptr of the same type.
209       *
210       *  This object now @e owns the object previously owned by @a a,
211       *  which has given up ownsership.  The object that this one @e
212       *  used to own and track has been deleted.
213       */
214      auto_ptr&
215      operator=(auto_ptr& __a) throw()
216      {
217	reset(__a.release());
218	return *this;
219      }
220
221      /**
222       *  @brief  %auto_ptr assignment operator.
223       *  @param  a  Another %auto_ptr of a different but related type.
224       *
225       *  A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type.
226       *
227       *  This object now @e owns the object previously owned by @a a,
228       *  which has given up ownsership.  The object that this one @e
229       *  used to own and track has been deleted.
230       */
231      template<typename _Tp1>
232        auto_ptr&
233        operator=(auto_ptr<_Tp1>& __a) throw()
234        {
235	  reset(__a.release());
236	  return *this;
237	}
238
239      /**
240       *  When the %auto_ptr goes out of scope, the object it owns is deleted.
241       *  If it no longer owns anything (i.e., @c get() is @c NULL), then this
242       *  has no effect.
243       *
244       *  @if maint
245       *  The C++ standard says there is supposed to be an empty throw
246       *  specification here, but omitting it is standard conforming.  Its
247       *  presence can be detected only if _Tp::~_Tp() throws, but this is
248       *  prohibited.  [17.4.3.6]/2
249       *  @end maint
250       */
251      ~auto_ptr() { delete _M_ptr; }
252
253      /**
254       *  @brief  Smart pointer dereferencing.
255       *
256       *  If this %auto_ptr no longer owns anything, then this
257       *  operation will crash.  (For a smart pointer, "no longer owns
258       *  anything" is the same as being a null pointer, and you know
259       *  what happens when you dereference one of those...)
260       */
261      element_type&
262      operator*() const throw() { return *_M_ptr; }
263
264      /**
265       *  @brief  Smart pointer dereferencing.
266       *
267       *  This returns the pointer itself, which the language then will
268       *  automatically cause to be dereferenced.
269       */
270      element_type*
271      operator->() const throw() { return _M_ptr; }
272
273      /**
274       *  @brief  Bypassing the smart pointer.
275       *  @return  The raw pointer being managed.
276       *
277       *  You can get a copy of the pointer that this object owns, for
278       *  situations such as passing to a function which only accepts a raw
279       *  pointer.
280       *
281       *  @note  This %auto_ptr still owns the memory.
282       */
283      element_type*
284      get() const throw() { return _M_ptr; }
285
286      /**
287       *  @brief  Bypassing the smart pointer.
288       *  @return  The raw pointer being managed.
289       *
290       *  You can get a copy of the pointer that this object owns, for
291       *  situations such as passing to a function which only accepts a raw
292       *  pointer.
293       *
294       *  @note  This %auto_ptr no longer owns the memory.  When this object
295       *  goes out of scope, nothing will happen.
296       */
297      element_type*
298      release() throw()
299      {
300	element_type* __tmp = _M_ptr;
301	_M_ptr = 0;
302	return __tmp;
303      }
304
305      /**
306       *  @brief  Forcibly deletes the managed object.
307       *  @param  p  A pointer (defaults to NULL).
308       *
309       *  This object now @e owns the object pointed to by @a p.  The previous
310       *  object has been deleted.
311       */
312      void
313      reset(element_type* __p = 0) throw()
314      {
315	if (__p != _M_ptr)
316	  {
317	    delete _M_ptr;
318	    _M_ptr = __p;
319	  }
320      }
321
322      /** @{
323       *  @brief  Automatic conversions
324       *
325       *  These operations convert an %auto_ptr into and from an auto_ptr_ref
326       *  automatically as needed.  This allows constructs such as
327       *  @code
328       *    auto_ptr<Derived>  func_returning_auto_ptr(.....);
329       *    ...
330       *    auto_ptr<Base> ptr = func_returning_auto_ptr(.....);
331       *  @endcode
332       */
333      auto_ptr(auto_ptr_ref<element_type> __ref) throw()
334      : _M_ptr(__ref._M_ptr) { }
335
336      auto_ptr&
337      operator=(auto_ptr_ref<element_type> __ref) throw()
338      {
339	if (__ref._M_ptr != this->get())
340	  {
341	    delete _M_ptr;
342	    _M_ptr = __ref._M_ptr;
343	  }
344	return *this;
345      }
346
347      template<typename _Tp1>
348        operator auto_ptr_ref<_Tp1>() throw()
349        { return auto_ptr_ref<_Tp1>(this->release()); }
350
351      template<typename _Tp1>
352        operator auto_ptr<_Tp1>() throw()
353        { return auto_ptr<_Tp1>(this->release()); }
354      /** @}  */
355  };
356} // namespace std
357
358#endif
359