1 | // Temporary buffer implementation -*- C++ -*- |
2 | |
3 | // Copyright (C) 2001-2017 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 |
112 | return_temporary_buffer(_Tp* __p) |
113 | { ::operator delete(__p, std::nothrow); } |
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> |
122 | class _Temporary_buffer |
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 |
146 | requested_size() const |
147 | { return _M_original_len; } |
148 | |
149 | /// As per Table mumble. |
150 | iterator |
151 | begin() |
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 size of the given range. |
162 | */ |
163 | _Temporary_buffer(_ForwardIterator __first, _ForwardIterator __last); |
164 | |
165 | ~_Temporary_buffer() |
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. |
173 | _Temporary_buffer(const _Temporary_buffer&); |
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 | { |
194 | std::_Construct(std::__addressof(*__first), |
195 | _GLIBCXX_MOVE(*__seed)); |
196 | _Pointer __prev = __cur; |
197 | ++__cur; |
198 | for(; __cur != __last; ++__cur, ++__prev) |
199 | std::_Construct(std::__addressof(*__cur), |
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> |
243 | _Temporary_buffer<_ForwardIterator, _Tp>:: |
244 | _Temporary_buffer(_ForwardIterator __first, _ForwardIterator __last) |
245 | : _M_original_len(std::distance(__first, __last)), |
246 | _M_len(0), _M_buffer(0) |
247 | { |
248 | __try |
249 | { |
250 | std::pair<pointer, size_type> __p(std::get_temporary_buffer< |
251 | value_type>(_M_original_len)); |
252 | _M_buffer = __p.first; |
253 | _M_len = __p.second; |
254 | if (_M_buffer) |
255 | std::__uninitialized_construct_buf(_M_buffer, _M_buffer + _M_len, |
256 | __first); |
257 | } |
258 | __catch(...) |
259 | { |
260 | std::return_temporary_buffer(_M_buffer); |
261 | _M_buffer = 0; |
262 | _M_len = 0; |
263 | __throw_exception_again; |
264 | } |
265 | } |
266 | |
267 | _GLIBCXX_END_NAMESPACE_VERSION |
268 | } // namespace |
269 | |
270 | #endif /* _STL_TEMPBUF_H */ |
271 | |
272 | |