source: Daodan/MSYS2/mingw32/include/c++/11.2.0/span@ 1194

Last change on this file since 1194 was 1166, checked in by rossy, 3 years ago

Daodan: Replace MinGW build env with an up-to-date MSYS2 env
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1// Components for manipulating non-owning sequences of objects -*- C++ -*-
2
3// Copyright (C) 2019-2021 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/** @file span
26 * This is a Standard C++ Library header.
27 */
28
29//
30// P0122 span library
31// Contributed by ThePhD
32//
33
34#ifndef _GLIBCXX_SPAN
35#define _GLIBCXX_SPAN 1
36
37#pragma GCC system_header
38
39#if __cplusplus > 201703L
40
41#include <array>
42#include <cstddef>
43#include <bits/stl_iterator.h>
44#include <bits/ranges_base.h>
45
46#if __cpp_lib_concepts
47namespace std _GLIBCXX_VISIBILITY(default)
48{
49_GLIBCXX_BEGIN_NAMESPACE_VERSION
50
51#define __cpp_lib_span 202002L
52
53 inline constexpr size_t dynamic_extent = static_cast<size_t>(-1);
54
55 template<typename _Type, size_t _Extent>
56 class span;
57
58 namespace __detail
59 {
60 template<typename _Tp>
61 struct __is_std_span : false_type { };
62
63 template<typename _Tp, size_t _Num>
64 struct __is_std_span<span<_Tp, _Num>> : true_type { };
65
66 template<typename _Tp>
67 struct __is_std_array : false_type { };
68
69 template<typename _Tp, size_t _Num>
70 struct __is_std_array<std::array<_Tp, _Num>> : true_type { };
71
72 template<size_t _Extent>
73 class __extent_storage
74 {
75 public:
76 constexpr
77 __extent_storage(size_t) noexcept
78 { }
79
80 static constexpr size_t
81 _M_extent() noexcept
82 { return _Extent; }
83 };
84
85 template<>
86 class __extent_storage<dynamic_extent>
87 {
88 public:
89 constexpr
90 __extent_storage(size_t __extent) noexcept
91 : _M_extent_value(__extent)
92 { }
93
94 constexpr size_t
95 _M_extent() const noexcept
96 { return this->_M_extent_value; }
97
98 private:
99 size_t _M_extent_value;
100 };
101 } // namespace __detail
102
103 template<typename _Type, size_t _Extent = dynamic_extent>
104 class span
105 {
106 template<size_t _Offset, size_t _Count>
107 static constexpr size_t
108 _S_subspan_extent()
109 {
110 if constexpr (_Count != dynamic_extent)
111 return _Count;
112 else if constexpr (extent != dynamic_extent)
113 return _Extent - _Offset;
114 else
115 return dynamic_extent;
116 }
117
118 // _GLIBCXX_RESOLVE_LIB_DEFECTS
119 // 3255. span's array constructor is too strict
120 template<typename _Tp, size_t _ArrayExtent>
121 requires (_Extent == dynamic_extent || _ArrayExtent == _Extent)
122 using __is_compatible_array = __is_array_convertible<_Type, _Tp>;
123
124 template<typename _Ref>
125 using __is_compatible_ref
126 = __is_array_convertible<_Type, remove_reference_t<_Ref>>;
127
128 public:
129 // member types
130 using element_type = _Type;
131 using value_type = remove_cv_t<_Type>;
132 using size_type = size_t;
133 using difference_type = ptrdiff_t;
134 using pointer = _Type*;
135 using const_pointer = const _Type*;
136 using reference = element_type&;
137 using const_reference = const element_type&;
138 using iterator = __gnu_cxx::__normal_iterator<pointer, span>;
139 using reverse_iterator = std::reverse_iterator<iterator>;
140
141 // member constants
142 static constexpr size_t extent = _Extent;
143
144 // constructors, copy and assignment
145
146 constexpr
147 span() noexcept
148 requires ((_Extent + 1u) <= 1u)
149 : _M_ptr(nullptr), _M_extent(0)
150 { }
151
152 template<contiguous_iterator _It>
153 requires __is_compatible_ref<iter_reference_t<_It>>::value
154 constexpr explicit(extent != dynamic_extent)
155 span(_It __first, size_type __count)
156 noexcept
157 : _M_ptr(std::to_address(__first)), _M_extent(__count)
158 {
159 if constexpr (_Extent != dynamic_extent)
160 {
161 __glibcxx_assert(__count == _Extent);
162 }
163 }
164
165 template<contiguous_iterator _It, sized_sentinel_for<_It> _End>
166 requires __is_compatible_ref<iter_reference_t<_It>>::value
167 && (!is_convertible_v<_End, size_type>)
168 constexpr explicit(extent != dynamic_extent)
169 span(_It __first, _End __last)
170 noexcept(noexcept(__last - __first))
171 : _M_ptr(std::to_address(__first)),
172 _M_extent(static_cast<size_type>(__last - __first))
173 {
174 if constexpr (_Extent != dynamic_extent)
175 {
176 __glibcxx_assert((__last - __first) == _Extent);
177 }
178 }
179
180 template<size_t _ArrayExtent>
181 requires (_Extent == dynamic_extent || _ArrayExtent == _Extent)
182 constexpr
183 span(type_identity_t<element_type> (&__arr)[_ArrayExtent]) noexcept
184 : span(static_cast<pointer>(__arr), _ArrayExtent)
185 { }
186
187 template<typename _Tp, size_t _ArrayExtent>
188 requires __is_compatible_array<_Tp, _ArrayExtent>::value
189 constexpr
190 span(array<_Tp, _ArrayExtent>& __arr) noexcept
191 : span(static_cast<pointer>(__arr.data()), _ArrayExtent)
192 { }
193
194 template<typename _Tp, size_t _ArrayExtent>
195 requires __is_compatible_array<const _Tp, _ArrayExtent>::value
196 constexpr
197 span(const array<_Tp, _ArrayExtent>& __arr) noexcept
198 : span(static_cast<pointer>(__arr.data()), _ArrayExtent)
199 { }
200
201 template<typename _Range>
202 requires ranges::contiguous_range<_Range> && ranges::sized_range<_Range>
203 && (ranges::borrowed_range<_Range> || is_const_v<element_type>)
204 && (!__detail::__is_std_span<remove_cvref_t<_Range>>::value)
205 && (!__detail::__is_std_array<remove_cvref_t<_Range>>::value)
206 && (!is_array_v<remove_cvref_t<_Range>>)
207 && __is_compatible_ref<ranges::range_reference_t<_Range>>::value
208 constexpr explicit(extent != dynamic_extent)
209 span(_Range&& __range)
210 noexcept(noexcept(ranges::data(__range))
211 && noexcept(ranges::size(__range)))
212 : span(ranges::data(__range), ranges::size(__range))
213 {
214 if constexpr (extent != dynamic_extent)
215 {
216 __glibcxx_assert(ranges::size(__range) == extent);
217 }
218 }
219
220 constexpr
221 span(const span&) noexcept = default;
222
223 template<typename _OType, size_t _OExtent>
224 requires (_Extent == dynamic_extent || _OExtent == dynamic_extent
225 || _Extent == _OExtent)
226 && (__is_array_convertible<_Type, _OType>::value)
227 constexpr
228 explicit(extent != dynamic_extent && _OExtent == dynamic_extent)
229 span(const span<_OType, _OExtent>& __s) noexcept
230 : _M_extent(__s.size()), _M_ptr(__s.data())
231 {
232 if constexpr (extent != dynamic_extent)
233 {
234 __glibcxx_assert(__s.size() == extent);
235 }
236 }
237
238 ~span() noexcept = default;
239
240 constexpr span&
241 operator=(const span&) noexcept = default;
242
243 // observers
244
245 constexpr size_type
246 size() const noexcept
247 { return this->_M_extent._M_extent(); }
248
249 constexpr size_type
250 size_bytes() const noexcept
251 { return this->_M_extent._M_extent() * sizeof(element_type); }
252
253 [[nodiscard]] constexpr bool
254 empty() const noexcept
255 { return size() == 0; }
256
257 // element access
258
259 constexpr reference
260 front() const noexcept
261 {
262 __glibcxx_assert(!empty());
263 return *this->_M_ptr;
264 }
265
266 constexpr reference
267 back() const noexcept
268 {
269 __glibcxx_assert(!empty());
270 return *(this->_M_ptr + (size() - 1));
271 }
272
273 constexpr reference
274 operator[](size_type __idx) const noexcept
275 {
276 __glibcxx_assert(__idx < size());
277 return *(this->_M_ptr + __idx);
278 }
279
280 constexpr pointer
281 data() const noexcept
282 { return this->_M_ptr; }
283
284 // iterator support
285
286 constexpr iterator
287 begin() const noexcept
288 { return iterator(this->_M_ptr); }
289
290 constexpr iterator
291 end() const noexcept
292 { return iterator(this->_M_ptr + this->size()); }
293
294 constexpr reverse_iterator
295 rbegin() const noexcept
296 { return reverse_iterator(this->end()); }
297
298 constexpr reverse_iterator
299 rend() const noexcept
300 { return reverse_iterator(this->begin()); }
301
302 // subviews
303
304 template<size_t _Count>
305 constexpr span<element_type, _Count>
306 first() const noexcept
307 {
308 if constexpr (_Extent == dynamic_extent)
309 __glibcxx_assert(_Count <= size());
310 else
311 static_assert(_Count <= extent);
312 using _Sp = span<element_type, _Count>;
313 return _Sp{ this->data(), _Count };
314 }
315
316 constexpr span<element_type, dynamic_extent>
317 first(size_type __count) const noexcept
318 {
319 __glibcxx_assert(__count <= size());
320 return { this->data(), __count };
321 }
322
323 template<size_t _Count>
324 constexpr span<element_type, _Count>
325 last() const noexcept
326 {
327 if constexpr (_Extent == dynamic_extent)
328 __glibcxx_assert(_Count <= size());
329 else
330 static_assert(_Count <= extent);
331 using _Sp = span<element_type, _Count>;
332 return _Sp{ this->data() + (this->size() - _Count), _Count };
333 }
334
335 constexpr span<element_type, dynamic_extent>
336 last(size_type __count) const noexcept
337 {
338 __glibcxx_assert(__count <= size());
339 return { this->data() + (this->size() - __count), __count };
340 }
341
342 template<size_t _Offset, size_t _Count = dynamic_extent>
343 constexpr auto
344 subspan() const noexcept
345 -> span<element_type, _S_subspan_extent<_Offset, _Count>()>
346 {
347 if constexpr (_Extent == dynamic_extent)
348 {
349 __glibcxx_assert(_Offset <= size());
350 }
351 else
352 static_assert(_Offset <= extent);
353
354 using _Sp = span<element_type, _S_subspan_extent<_Offset, _Count>()>;
355
356 if constexpr (_Count == dynamic_extent)
357 return _Sp{ this->data() + _Offset, this->size() - _Offset };
358 else
359 {
360 if constexpr (_Extent == dynamic_extent)
361 {
362 __glibcxx_assert(_Count <= size());
363 __glibcxx_assert(_Count <= (size() - _Offset));
364 }
365 else
366 {
367 static_assert(_Count <= extent);
368 static_assert(_Count <= (extent - _Offset));
369 }
370 return _Sp{ this->data() + _Offset, _Count };
371 }
372 }
373
374 constexpr span<element_type, dynamic_extent>
375 subspan(size_type __offset, size_type __count = dynamic_extent) const
376 noexcept
377 {
378 __glibcxx_assert(__offset <= size());
379 if (__count == dynamic_extent)
380 __count = this->size() - __offset;
381 else
382 {
383 __glibcxx_assert(__count <= size());
384 __glibcxx_assert(__offset + __count <= size());
385 }
386 return {this->data() + __offset, __count};
387 }
388
389 private:
390 pointer _M_ptr;
391 [[no_unique_address]] __detail::__extent_storage<extent> _M_extent;
392 };
393
394 // deduction guides
395
396 template<typename _Type, size_t _ArrayExtent>
397 span(_Type(&)[_ArrayExtent]) -> span<_Type, _ArrayExtent>;
398
399 template<typename _Type, size_t _ArrayExtent>
400 span(array<_Type, _ArrayExtent>&) -> span<_Type, _ArrayExtent>;
401
402 template<typename _Type, size_t _ArrayExtent>
403 span(const array<_Type, _ArrayExtent>&)
404 -> span<const _Type, _ArrayExtent>;
405
406 template<contiguous_iterator _Iter, typename _End>
407 span(_Iter, _End)
408 -> span<remove_reference_t<iter_reference_t<_Iter>>>;
409
410 template<typename _Range>
411 span(_Range &&)
412 -> span<remove_reference_t<ranges::range_reference_t<_Range&>>>;
413
414 template<typename _Type, size_t _Extent>
415 inline
416 span<const byte, _Extent == dynamic_extent
417 ? dynamic_extent : _Extent * sizeof(_Type)>
418 as_bytes(span<_Type, _Extent> __sp) noexcept
419 {
420 auto data = reinterpret_cast<const byte*>(__sp.data());
421 auto size = __sp.size_bytes();
422 constexpr auto extent = _Extent == dynamic_extent
423 ? dynamic_extent : _Extent * sizeof(_Type);
424 return span<const byte, extent>{data, size};
425 }
426
427 template<typename _Type, size_t _Extent>
428 requires (!is_const_v<_Type>)
429 inline
430 span<byte, _Extent == dynamic_extent
431 ? dynamic_extent : _Extent * sizeof(_Type)>
432 as_writable_bytes(span<_Type, _Extent> __sp) noexcept
433 {
434 auto data = reinterpret_cast<byte*>(__sp.data());
435 auto size = __sp.size_bytes();
436 constexpr auto extent = _Extent == dynamic_extent
437 ? dynamic_extent : _Extent * sizeof(_Type);
438 return span<byte, extent>{data, size};
439 }
440
441 namespace ranges
442 {
443 // Opt-in to borrowed_range concept
444 template<typename _ElementType, size_t _Extent>
445 inline constexpr bool
446 enable_borrowed_range<span<_ElementType, _Extent>> = true;
447
448 // Opt-in to view concept
449 template<typename _ElementType, size_t _Extent>
450 inline constexpr bool
451 enable_view<span<_ElementType, _Extent>>
452 = _Extent == 0 || _Extent == dynamic_extent;
453 }
454_GLIBCXX_END_NAMESPACE_VERSION
455} // namespace std
456#endif // concepts
457#endif // C++20
458#endif // _GLIBCXX_SPAN
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