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 
62namespace 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); } 
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 given length. 
162 */ 
163 _Temporary_buffer(_ForwardIterator __seed, size_type __original_len); 
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 __seed, size_type __original_len) 
245 : _M_original_len(__original_len), _M_len(0), _M_buffer(0) 
246 { 
247 __try 
248 { 
249 std::pair<pointer, size_type> __p(std::get_temporary_buffer< 
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 */ 
270