std_memory.h revision 146897 
1// <memory> -*- C++ -*-
2
3// Copyright (C) 2001, 2002, 2004 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 _GLIBCXX_MEMORY
50#define _GLIBCXX_MEMORY 1
51
52#pragma GCC system_header
53
54#include <bits/stl_algobase.h>
55#include <bits/allocator.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#include <debug/debug.h>
61#include <limits>
62
63namespace std
64{
65  /**
66   *  @if maint
67   *  This is a helper function.  The unused second parameter exists to
68   *  permit the real get_temporary_buffer to use template parameter deduction.
69   *
70   *  XXX This should perhaps use the pool.
71   *  @endif
72   */
73  template<typename _Tp>
74    pair<_Tp*, ptrdiff_t>
75    __get_temporary_buffer(ptrdiff_t __len, _Tp*)
76    {
77      const ptrdiff_t __max = numeric_limits<ptrdiff_t>::max() / sizeof(_Tp);
78      if (__len > __max)
79	__len = __max;
80
81      while (__len > 0)
82	{
83	  _Tp* __tmp = static_cast<_Tp*>(::operator new(__len * sizeof(_Tp),
84							nothrow));
85	  if (__tmp != 0)
86	    return pair<_Tp*, ptrdiff_t>(__tmp, __len);
87	  __len /= 2;
88	}
89      return pair<_Tp*, ptrdiff_t>(static_cast<_Tp*>(0), 0);
90    }
91
92  /**
93   *  @brief Allocates a temporary buffer.
94   *  @param  len  The number of objects of type Tp.
95   *  @return See full description.
96   *
97   *  Reinventing the wheel, but this time with prettier spokes!
98   *
99   *  This function tries to obtain storage for @c len adjacent Tp
100   *  objects.  The objects themselves are not constructed, of course.
101   *  A pair<> is returned containing "the buffer s address and
102   *  capacity (in the units of sizeof(Tp)), or a pair of 0 values if
103   *  no storage can be obtained."  Note that the capacity obtained
104   *  may be less than that requested if the memory is unavailable;
105   *  you should compare len with the .second return value.
106   *
107   * Provides the nothrow exception guarantee.
108   */
109  template<typename _Tp>
110    inline pair<_Tp*, ptrdiff_t>
111    get_temporary_buffer(ptrdiff_t __len)
112    { return std::__get_temporary_buffer(__len, static_cast<_Tp*>(0)); }
113
114  /**
115   *  @brief The companion to get_temporary_buffer().
116   *  @param  p  A buffer previously allocated by get_temporary_buffer.
117   *  @return   None.
118   *
119   *  Frees the memory pointed to by p.
120   */
121  template<typename _Tp>
122    void
123    return_temporary_buffer(_Tp* __p)
124    { ::operator delete(__p, nothrow); }
125
126  /**
127   *  A wrapper class to provide auto_ptr with reference semantics.
128   *  For example, an auto_ptr can be assigned (or constructed from)
129   *  the result of a function which returns an auto_ptr by value.
130   *
131   *  All the auto_ptr_ref stuff should happen behind the scenes.
132   */
133  template<typename _Tp1>
134    struct auto_ptr_ref
135    {
136      _Tp1* _M_ptr;
137
138      explicit
139      auto_ptr_ref(_Tp1* __p): _M_ptr(__p) { }
140    };
141
142
143  /**
144   *  @brief  A simple smart pointer providing strict ownership semantics.
145   *
146   *  The Standard says:
147   *  <pre>
148   *  An @c auto_ptr owns the object it holds a pointer to.  Copying
149   *  an @c auto_ptr copies the pointer and transfers ownership to the
150   *  destination.  If more than one @c auto_ptr owns the same object
151   *  at the same time the behavior of the program is undefined.
152   *
153   *  The uses of @c auto_ptr include providing temporary
154   *  exception-safety for dynamically allocated memory, passing
155   *  ownership of dynamically allocated memory to a function, and
156   *  returning dynamically allocated memory from a function.  @c
157   *  auto_ptr does not meet the CopyConstructible and Assignable
158   *  requirements for Standard Library <a
159   *  href="tables.html#65">container</a> elements and thus
160   *  instantiating a Standard Library container with an @c auto_ptr
161   *  results in undefined behavior.
162   *  </pre>
163   *  Quoted from [20.4.5]/3.
164   *
165   *  Good examples of what can and cannot be done with auto_ptr can
166   *  be found in the libstdc++ testsuite.
167   *
168   *  @if maint
169   *  _GLIBCXX_RESOLVE_LIB_DEFECTS
170   *  127.  auto_ptr<> conversion issues
171   *  These resolutions have all been incorporated.
172   *  @endif
173   */
174  template<typename _Tp>
175    class auto_ptr
176    {
177    private:
178      _Tp* _M_ptr;
179
180    public:
181      /// The pointed-to type.
182      typedef _Tp element_type;
183
184      /**
185       *  @brief  An %auto_ptr is usually constructed from a raw pointer.
186       *  @param  p  A pointer (defaults to NULL).
187       *
188       *  This object now @e owns the object pointed to by @a p.
189       */
190      explicit
191      auto_ptr(element_type* __p = 0) throw() : _M_ptr(__p) { }
192
193      /**
194       *  @brief  An %auto_ptr can be constructed from another %auto_ptr.
195       *  @param  a  Another %auto_ptr of the same type.
196       *
197       *  This object now @e owns the object previously owned by @a a,
198       *  which has given up ownsership.
199       */
200      auto_ptr(auto_ptr& __a) throw() : _M_ptr(__a.release()) { }
201
202      /**
203       *  @brief  An %auto_ptr can be constructed from another %auto_ptr.
204       *  @param  a  Another %auto_ptr of a different but related type.
205       *
206       *  A pointer-to-Tp1 must be convertible to a
207       *  pointer-to-Tp/element_type.
208       *
209       *  This object now @e owns the object previously owned by @a a,
210       *  which has given up ownsership.
211       */
212      template<typename _Tp1>
213        auto_ptr(auto_ptr<_Tp1>& __a) throw() : _M_ptr(__a.release()) { }
214
215      /**
216       *  @brief  %auto_ptr assignment operator.
217       *  @param  a  Another %auto_ptr of the same type.
218       *
219       *  This object now @e owns the object previously owned by @a a,
220       *  which has given up ownsership.  The object that this one @e
221       *  used to own and track has been deleted.
222       */
223      auto_ptr&
224      operator=(auto_ptr& __a) throw()
225      {
226	reset(__a.release());
227	return *this;
228      }
229
230      /**
231       *  @brief  %auto_ptr assignment operator.
232       *  @param  a  Another %auto_ptr of a different but related type.
233       *
234       *  A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type.
235       *
236       *  This object now @e owns the object previously owned by @a a,
237       *  which has given up ownsership.  The object that this one @e
238       *  used to own and track has been deleted.
239       */
240      template<typename _Tp1>
241        auto_ptr&
242        operator=(auto_ptr<_Tp1>& __a) throw()
243        {
244	  reset(__a.release());
245	  return *this;
246	}
247
248      /**
249       *  When the %auto_ptr goes out of scope, the object it owns is
250       *  deleted.  If it no longer owns anything (i.e., @c get() is
251       *  @c NULL), then this has no effect.
252       *
253       *  @if maint
254       *  The C++ standard says there is supposed to be an empty throw
255       *  specification here, but omitting it is standard conforming.  Its
256       *  presence can be detected only if _Tp::~_Tp() throws, but this is
257       *  prohibited.  [17.4.3.6]/2
258       *  @end maint
259       */
260      ~auto_ptr() { delete _M_ptr; }
261
262      /**
263       *  @brief  Smart pointer dereferencing.
264       *
265       *  If this %auto_ptr no longer owns anything, then this
266       *  operation will crash.  (For a smart pointer, "no longer owns
267       *  anything" is the same as being a null pointer, and you know
268       *  what happens when you dereference one of those...)
269       */
270      element_type&
271      operator*() const throw()
272      {
273	_GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
274	return *_M_ptr;
275      }
276
277      /**
278       *  @brief  Smart pointer dereferencing.
279       *
280       *  This returns the pointer itself, which the language then will
281       *  automatically cause to be dereferenced.
282       */
283      element_type*
284      operator->() const throw()
285      {
286	_GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
287	return _M_ptr;
288      }
289
290      /**
291       *  @brief  Bypassing the smart pointer.
292       *  @return  The raw pointer being managed.
293       *
294       *  You can get a copy of the pointer that this object owns, for
295       *  situations such as passing to a function which only accepts
296       *  a raw pointer.
297       *
298       *  @note  This %auto_ptr still owns the memory.
299       */
300      element_type*
301      get() const throw() { return _M_ptr; }
302
303      /**
304       *  @brief  Bypassing the smart pointer.
305       *  @return  The raw pointer being managed.
306       *
307       *  You can get a copy of the pointer that this object owns, for
308       *  situations such as passing to a function which only accepts
309       *  a raw pointer.
310       *
311       *  @note  This %auto_ptr no longer owns the memory.  When this object
312       *  goes out of scope, nothing will happen.
313       */
314      element_type*
315      release() throw()
316      {
317	element_type* __tmp = _M_ptr;
318	_M_ptr = 0;
319	return __tmp;
320      }
321
322      /**
323       *  @brief  Forcibly deletes the managed object.
324       *  @param  p  A pointer (defaults to NULL).
325       *
326       *  This object now @e owns the object pointed to by @a p.  The
327       *  previous object has been deleted.
328       */
329      void
330      reset(element_type* __p = 0) throw()
331      {
332	if (__p != _M_ptr)
333	  {
334	    delete _M_ptr;
335	    _M_ptr = __p;
336	  }
337      }
338
339      /** @{
340       *  @brief  Automatic conversions
341       *
342       *  These operations convert an %auto_ptr into and from an auto_ptr_ref
343       *  automatically as needed.  This allows constructs such as
344       *  @code
345       *    auto_ptr<Derived>  func_returning_auto_ptr(.....);
346       *    ...
347       *    auto_ptr<Base> ptr = func_returning_auto_ptr(.....);
348       *  @endcode
349       */
350      auto_ptr(auto_ptr_ref<element_type> __ref) throw()
351      : _M_ptr(__ref._M_ptr) { }
352
353      auto_ptr&
354      operator=(auto_ptr_ref<element_type> __ref) throw()
355      {
356	if (__ref._M_ptr != this->get())
357	  {
358	    delete _M_ptr;
359	    _M_ptr = __ref._M_ptr;
360	  }
361	return *this;
362      }
363
364      template<typename _Tp1>
365        operator auto_ptr_ref<_Tp1>() throw()
366        { return auto_ptr_ref<_Tp1>(this->release()); }
367
368      template<typename _Tp1>
369        operator auto_ptr<_Tp1>() throw()
370        { return auto_ptr<_Tp1>(this->release()); }
371      /** @}  */
372  };
373} // namespace std
374
375#endif /* _GLIBCXX_MEMORY */
376