libstdc++
stl_tempbuf.h
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1 // Temporary buffer implementation -*- C++ -*-
2 
3 // Copyright (C) 2001-2019 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 /*
26  *
27  * Copyright (c) 1994
28  * Hewlett-Packard Company
29  *
30  * Permission to use, copy, modify, distribute and sell this software
31  * and its documentation for any purpose is hereby granted without fee,
32  * provided that the above copyright notice appear in all copies and
33  * that both that copyright notice and this permission notice appear
34  * in supporting documentation. Hewlett-Packard Company makes no
35  * representations about the suitability of this software for any
36  * purpose. It is provided "as is" without express or implied warranty.
37  *
38  *
39  * Copyright (c) 1996,1997
40  * Silicon Graphics Computer Systems, Inc.
41  *
42  * Permission to use, copy, modify, distribute and sell this software
43  * and its documentation for any purpose is hereby granted without fee,
44  * provided that the above copyright notice appear in all copies and
45  * that both that copyright notice and this permission notice appear
46  * in supporting documentation. Silicon Graphics makes no
47  * representations about the suitability of this software for any
48  * purpose. It is provided "as is" without express or implied warranty.
49  */
50 
51 /** @file bits/stl_tempbuf.h
52  * This is an internal header file, included by other library headers.
53  * Do not attempt to use it directly. @headername{memory}
54  */
55 
56 #ifndef _STL_TEMPBUF_H
57 #define _STL_TEMPBUF_H 1
58 
59 #include <bits/stl_algobase.h>
60 #include <bits/stl_construct.h>
61 
62 namespace std _GLIBCXX_VISIBILITY(default)
63 {
64 _GLIBCXX_BEGIN_NAMESPACE_VERSION
65 
66  /**
67  * @brief Allocates a temporary buffer.
68  * @param __len The number of objects of type Tp.
69  * @return See full description.
70  *
71  * Reinventing the wheel, but this time with prettier spokes!
72  *
73  * This function tries to obtain storage for @c __len adjacent Tp
74  * objects. The objects themselves are not constructed, of course.
75  * A pair<> is returned containing <em>the buffer s address and
76  * capacity (in the units of sizeof(_Tp)), or a pair of 0 values if
77  * no storage can be obtained.</em> Note that the capacity obtained
78  * may be less than that requested if the memory is unavailable;
79  * you should compare len with the .second return value.
80  *
81  * Provides the nothrow exception guarantee.
82  */
83  template<typename _Tp>
84  pair<_Tp*, ptrdiff_t>
85  get_temporary_buffer(ptrdiff_t __len) _GLIBCXX_NOEXCEPT
86  {
87  const ptrdiff_t __max =
88  __gnu_cxx::__numeric_traits<ptrdiff_t>::__max / sizeof(_Tp);
89  if (__len > __max)
90  __len = __max;
91 
92  while (__len > 0)
93  {
94  _Tp* __tmp = static_cast<_Tp*>(::operator new(__len * sizeof(_Tp),
95  std::nothrow));
96  if (__tmp != 0)
97  return std::pair<_Tp*, ptrdiff_t>(__tmp, __len);
98  __len /= 2;
99  }
100  return std::pair<_Tp*, ptrdiff_t>(static_cast<_Tp*>(0), 0);
101  }
102 
103  /**
104  * @brief The companion to get_temporary_buffer().
105  * @param __p A buffer previously allocated by get_temporary_buffer.
106  * @return None.
107  *
108  * Frees the memory pointed to by __p.
109  */
110  template<typename _Tp>
111  inline void
113  { ::operator delete(__p); }
114 
115 
116  /**
117  * This class is used in two places: stl_algo.h and ext/memory,
118  * where it is wrapped as the temporary_buffer class. See
119  * temporary_buffer docs for more notes.
120  */
121  template<typename _ForwardIterator, typename _Tp>
123  {
124  // concept requirements
125  __glibcxx_class_requires(_ForwardIterator, _ForwardIteratorConcept)
126 
127  public:
128  typedef _Tp value_type;
129  typedef value_type* pointer;
130  typedef pointer iterator;
131  typedef ptrdiff_t size_type;
132 
133  protected:
134  size_type _M_original_len;
135  size_type _M_len;
136  pointer _M_buffer;
137 
138  public:
139  /// As per Table mumble.
140  size_type
141  size() const
142  { return _M_len; }
143 
144  /// Returns the size requested by the constructor; may be >size().
145  size_type
147  { return _M_original_len; }
148 
149  /// As per Table mumble.
150  iterator
152  { return _M_buffer; }
153 
154  /// As per Table mumble.
155  iterator
156  end()
157  { return _M_buffer + _M_len; }
158 
159  /**
160  * Constructs a temporary buffer of a size somewhere between
161  * zero and the given length.
162  */
163  _Temporary_buffer(_ForwardIterator __seed, size_type __original_len);
164 
166  {
167  std::_Destroy(_M_buffer, _M_buffer + _M_len);
168  std::return_temporary_buffer(_M_buffer);
169  }
170 
171  private:
172  // Disable copy constructor and assignment operator.
174 
175  void
176  operator=(const _Temporary_buffer&);
177  };
178 
179 
180  template<bool>
181  struct __uninitialized_construct_buf_dispatch
182  {
183  template<typename _Pointer, typename _ForwardIterator>
184  static void
185  __ucr(_Pointer __first, _Pointer __last,
186  _ForwardIterator __seed)
187  {
188  if(__first == __last)
189  return;
190 
191  _Pointer __cur = __first;
192  __try
193  {
195  _GLIBCXX_MOVE(*__seed));
196  _Pointer __prev = __cur;
197  ++__cur;
198  for(; __cur != __last; ++__cur, ++__prev)
200  _GLIBCXX_MOVE(*__prev));
201  *__seed = _GLIBCXX_MOVE(*__prev);
202  }
203  __catch(...)
204  {
205  std::_Destroy(__first, __cur);
206  __throw_exception_again;
207  }
208  }
209  };
210 
211  template<>
212  struct __uninitialized_construct_buf_dispatch<true>
213  {
214  template<typename _Pointer, typename _ForwardIterator>
215  static void
216  __ucr(_Pointer, _Pointer, _ForwardIterator) { }
217  };
218 
219  // Constructs objects in the range [first, last).
220  // Note that while these new objects will take valid values,
221  // their exact value is not defined. In particular they may
222  // be 'moved from'.
223  //
224  // While *__seed may be altered during this algorithm, it will have
225  // the same value when the algorithm finishes, unless one of the
226  // constructions throws.
227  //
228  // Requirements: _Pointer::value_type(_Tp&&) is valid.
229  template<typename _Pointer, typename _ForwardIterator>
230  inline void
231  __uninitialized_construct_buf(_Pointer __first, _Pointer __last,
232  _ForwardIterator __seed)
233  {
234  typedef typename std::iterator_traits<_Pointer>::value_type
235  _ValueType;
236 
237  std::__uninitialized_construct_buf_dispatch<
238  __has_trivial_constructor(_ValueType)>::
239  __ucr(__first, __last, __seed);
240  }
241 
242  template<typename _ForwardIterator, typename _Tp>
244  _Temporary_buffer(_ForwardIterator __seed, size_type __original_len)
245  : _M_original_len(__original_len), _M_len(0), _M_buffer(0)
246  {
247  __try
248  {
250  value_type>(_M_original_len));
251  _M_buffer = __p.first;
252  _M_len = __p.second;
253  if (_M_buffer)
254  std::__uninitialized_construct_buf(_M_buffer, _M_buffer + _M_len,
255  __seed);
256  }
257  __catch(...)
258  {
259  std::return_temporary_buffer(_M_buffer);
260  _M_buffer = 0;
261  _M_len = 0;
262  __throw_exception_again;
263  }
264  }
265 
266 _GLIBCXX_END_NAMESPACE_VERSION
267 } // namespace
268 
269 #endif /* _STL_TEMPBUF_H */
_T2 second
first is a copy of the first object
Definition: stl_pair.h:215
_Temporary_buffer(_ForwardIterator __seed, size_type __original_len)
Definition: stl_tempbuf.h:244
ISO C++ entities toplevel namespace is std.
iterator end()
As per Table mumble.
Definition: stl_tempbuf.h:156
pair< _Tp *, ptrdiff_t > get_temporary_buffer(ptrdiff_t __len) noexcept
Allocates a temporary buffer.
Definition: stl_tempbuf.h:85
_T1 first
second_type is the second bound type
Definition: stl_pair.h:214
Common iterator class.
size_type requested_size() const
Returns the size requested by the constructor; may be >size().
Definition: stl_tempbuf.h:146
void return_temporary_buffer(_Tp *__p)
The companion to get_temporary_buffer().
Definition: stl_tempbuf.h:112
iterator begin()
As per Table mumble.
Definition: stl_tempbuf.h:151
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition: move.h:47
size_type size() const
As per Table mumble.
Definition: stl_tempbuf.h:141
void _Construct(_T1 *__p, _Args &&... __args)
Definition: stl_construct.h:74
Struct holding two objects of arbitrary type.
Definition: stl_pair.h:208
void _Destroy(_Tp *__pointer)
Definition: stl_construct.h:97