1 | // Temporary buffer implementation -*- C++ -*- |
2 | |
3 | // Copyright (C) 2001-2021 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 | namespace __detail |
67 | { |
68 | template<typename _Tp> |
69 | inline void |
70 | __return_temporary_buffer(_Tp* __p, |
71 | size_t __len __attribute__((__unused__))) |
72 | { |
73 | #if __cpp_sized_deallocation |
74 | ::operator delete(__p, __len * sizeof(_Tp)); |
75 | #else |
76 | ::operator delete(__p); |
77 | #endif |
78 | } |
79 | } |
80 | |
81 | /** |
82 | * @brief Allocates a temporary buffer. |
83 | * @param __len The number of objects of type Tp. |
84 | * @return See full description. |
85 | * |
86 | * Reinventing the wheel, but this time with prettier spokes! |
87 | * |
88 | * This function tries to obtain storage for @c __len adjacent Tp |
89 | * objects. The objects themselves are not constructed, of course. |
90 | * A pair<> is returned containing <em>the buffer s address and |
91 | * capacity (in the units of sizeof(_Tp)), or a pair of 0 values if |
92 | * no storage can be obtained.</em> Note that the capacity obtained |
93 | * may be less than that requested if the memory is unavailable; |
94 | * you should compare len with the .second return value. |
95 | * |
96 | * Provides the nothrow exception guarantee. |
97 | */ |
98 | template<typename _Tp> |
99 | pair<_Tp*, ptrdiff_t> |
100 | get_temporary_buffer(ptrdiff_t __len) _GLIBCXX_NOEXCEPT |
101 | { |
102 | const ptrdiff_t __max = |
103 | __gnu_cxx::__numeric_traits<ptrdiff_t>::__max / sizeof(_Tp); |
104 | if (__len > __max) |
105 | __len = __max; |
106 | |
107 | while (__len > 0) |
108 | { |
109 | _Tp* __tmp = static_cast<_Tp*>(::operator new(__len * sizeof(_Tp), |
110 | std::nothrow)); |
111 | if (__tmp != 0) |
112 | return std::pair<_Tp*, ptrdiff_t>(__tmp, __len); |
113 | __len = __len == 1 ? 0 : ((__len + 1) / 2); |
114 | } |
115 | return std::pair<_Tp*, ptrdiff_t>(static_cast<_Tp*>(0), 0); |
116 | } |
117 | |
118 | /** |
119 | * @brief The companion to get_temporary_buffer(). |
120 | * @param __p A buffer previously allocated by get_temporary_buffer. |
121 | * @return None. |
122 | * |
123 | * Frees the memory pointed to by __p. |
124 | */ |
125 | template<typename _Tp> |
126 | inline void |
127 | return_temporary_buffer(_Tp* __p) |
128 | { ::operator delete(__p); } |
129 | |
130 | /** |
131 | * This class is used in two places: stl_algo.h and ext/memory, |
132 | * where it is wrapped as the temporary_buffer class. See |
133 | * temporary_buffer docs for more notes. |
134 | */ |
135 | template<typename _ForwardIterator, typename _Tp> |
136 | class _Temporary_buffer |
137 | { |
138 | // concept requirements |
139 | __glibcxx_class_requires(_ForwardIterator, _ForwardIteratorConcept) |
140 | |
141 | public: |
142 | typedef _Tp value_type; |
143 | typedef value_type* pointer; |
144 | typedef pointer iterator; |
145 | typedef ptrdiff_t size_type; |
146 | |
147 | protected: |
148 | size_type _M_original_len; |
149 | size_type _M_len; |
150 | pointer _M_buffer; |
151 | |
152 | public: |
153 | /// As per Table mumble. |
154 | size_type |
155 | size() const |
156 | { return _M_len; } |
157 | |
158 | /// Returns the size requested by the constructor; may be >size(). |
159 | size_type |
160 | requested_size() const |
161 | { return _M_original_len; } |
162 | |
163 | /// As per Table mumble. |
164 | iterator |
165 | begin() |
166 | { return _M_buffer; } |
167 | |
168 | /// As per Table mumble. |
169 | iterator |
170 | end() |
171 | { return _M_buffer + _M_len; } |
172 | |
173 | /** |
174 | * Constructs a temporary buffer of a size somewhere between |
175 | * zero and the given length. |
176 | */ |
177 | _Temporary_buffer(_ForwardIterator __seed, size_type __original_len); |
178 | |
179 | ~_Temporary_buffer() |
180 | { |
181 | std::_Destroy(_M_buffer, _M_buffer + _M_len); |
182 | std::__detail::__return_temporary_buffer(_M_buffer, _M_len); |
183 | } |
184 | |
185 | private: |
186 | // Disable copy constructor and assignment operator. |
187 | _Temporary_buffer(const _Temporary_buffer&); |
188 | |
189 | void |
190 | operator=(const _Temporary_buffer&); |
191 | }; |
192 | |
193 | |
194 | template<bool> |
195 | struct __uninitialized_construct_buf_dispatch |
196 | { |
197 | template<typename _Pointer, typename _ForwardIterator> |
198 | static void |
199 | __ucr(_Pointer __first, _Pointer __last, |
200 | _ForwardIterator __seed) |
201 | { |
202 | if (__first == __last) |
203 | return; |
204 | |
205 | _Pointer __cur = __first; |
206 | __try |
207 | { |
208 | std::_Construct(std::__addressof(*__first), |
209 | _GLIBCXX_MOVE(*__seed)); |
210 | _Pointer __prev = __cur; |
211 | ++__cur; |
212 | for(; __cur != __last; ++__cur, ++__prev) |
213 | std::_Construct(std::__addressof(*__cur), |
214 | _GLIBCXX_MOVE(*__prev)); |
215 | *__seed = _GLIBCXX_MOVE(*__prev); |
216 | } |
217 | __catch(...) |
218 | { |
219 | std::_Destroy(__first, __cur); |
220 | __throw_exception_again; |
221 | } |
222 | } |
223 | }; |
224 | |
225 | template<> |
226 | struct __uninitialized_construct_buf_dispatch<true> |
227 | { |
228 | template<typename _Pointer, typename _ForwardIterator> |
229 | static void |
230 | __ucr(_Pointer, _Pointer, _ForwardIterator) { } |
231 | }; |
232 | |
233 | // Constructs objects in the range [first, last). |
234 | // Note that while these new objects will take valid values, |
235 | // their exact value is not defined. In particular they may |
236 | // be 'moved from'. |
237 | // |
238 | // While *__seed may be altered during this algorithm, it will have |
239 | // the same value when the algorithm finishes, unless one of the |
240 | // constructions throws. |
241 | // |
242 | // Requirements: _Pointer::value_type(_Tp&&) is valid. |
243 | template<typename _Pointer, typename _ForwardIterator> |
244 | inline void |
245 | __uninitialized_construct_buf(_Pointer __first, _Pointer __last, |
246 | _ForwardIterator __seed) |
247 | { |
248 | typedef typename std::iterator_traits<_Pointer>::value_type |
249 | _ValueType; |
250 | |
251 | std::__uninitialized_construct_buf_dispatch< |
252 | __has_trivial_constructor(_ValueType)>:: |
253 | __ucr(__first, __last, __seed); |
254 | } |
255 | |
256 | template<typename _ForwardIterator, typename _Tp> |
257 | _Temporary_buffer<_ForwardIterator, _Tp>:: |
258 | _Temporary_buffer(_ForwardIterator __seed, size_type __original_len) |
259 | : _M_original_len(__original_len), _M_len(0), _M_buffer(0) |
260 | { |
261 | std::pair<pointer, size_type> __p( |
262 | std::get_temporary_buffer<value_type>(_M_original_len)); |
263 | |
264 | if (__p.first) |
265 | { |
266 | __try |
267 | { |
268 | std::__uninitialized_construct_buf(__p.first, __p.first + __p.second, |
269 | __seed); |
270 | _M_buffer = __p.first; |
271 | _M_len = __p.second; |
272 | } |
273 | __catch(...) |
274 | { |
275 | std::__detail::__return_temporary_buffer(__p.first, __p.second); |
276 | __throw_exception_again; |
277 | } |
278 | } |
279 | } |
280 | |
281 | _GLIBCXX_END_NAMESPACE_VERSION |
282 | } // namespace |
283 | |
284 | #endif /* _STL_TEMPBUF_H */ |
285 | |