1// Components for manipulating non-owning sequences of objects -*- C++ -*-
3// Copyright (C) 2019-2024 Free Software Foundation, Inc.
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)
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.
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.
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/>.
26 * This is a Standard C++ Library header.
31// Contributed by ThePhD
35#define _GLIBCXX_SPAN 1
37#pragma GCC system_header
39#define __glibcxx_want_span
40#include <bits/version.h>
42#ifdef __cpp_lib_span // C++ >= 20 && concepts
45#include <bits/stl_iterator.h>
46#include <bits/ranges_base.h>
47namespace std _GLIBCXX_VISIBILITY(default)
49_GLIBCXX_BEGIN_NAMESPACE_VERSION
51 inline constexpr size_t dynamic_extent = static_cast<size_t>(-1);
53 template<typename _Type, size_t _Extent>
58 template<typename _Tp>
59 inline constexpr bool __is_span = false;
61 template<typename _Tp, size_t _Num>
62 inline constexpr bool __is_span<span<_Tp, _Num>> = true;
64 template<typename _Tp>
65 inline constexpr bool __is_std_array = false;
67 template<typename _Tp, size_t _Num>
68 inline constexpr bool __is_std_array<std::array<_Tp, _Num>> = true;
70 template<size_t _Extent>
71 class __extent_storage
75 __extent_storage(size_t) noexcept
78 static constexpr size_t
84 class __extent_storage<dynamic_extent>
88 __extent_storage(size_t __extent) noexcept
89 : _M_extent_value(__extent)
93 _M_extent() const noexcept
94 { return this->_M_extent_value; }
97 size_t _M_extent_value;
99 } // namespace __detail
101 template<typename _Type, size_t _Extent = dynamic_extent>
104 template<size_t _Offset, size_t _Count>
105 static constexpr size_t
108 if constexpr (_Count != dynamic_extent)
110 else if constexpr (extent != dynamic_extent)
111 return _Extent - _Offset;
113 return dynamic_extent;
116 // _GLIBCXX_RESOLVE_LIB_DEFECTS
117 // 3255. span's array constructor is too strict
118 template<typename _Tp, size_t _ArrayExtent>
119 requires (_Extent == dynamic_extent || _ArrayExtent == _Extent)
120 using __is_compatible_array = __is_array_convertible<_Type, _Tp>;
122 template<typename _Ref>
123 using __is_compatible_ref
124 = __is_array_convertible<_Type, remove_reference_t<_Ref>>;
128 using element_type = _Type;
129 using value_type = remove_cv_t<_Type>;
130 using size_type = size_t;
131 using difference_type = ptrdiff_t;
132 using pointer = _Type*;
133 using const_pointer = const _Type*;
134 using reference = element_type&;
135 using const_reference = const element_type&;
136 using iterator = __gnu_cxx::__normal_iterator<pointer, span>;
137 using reverse_iterator = std::reverse_iterator<iterator>;
138#if __cplusplus > 202002L
139 using const_iterator = std::const_iterator<iterator>;
140 using const_reverse_iterator = std::const_iterator<reverse_iterator>;
144 static constexpr size_t extent = _Extent;
146 // constructors, copy and assignment
150 requires (_Extent == dynamic_extent || _Extent == 0)
151 : _M_ptr(nullptr), _M_extent(0)
154 template<contiguous_iterator _It>
155 requires __is_compatible_ref<iter_reference_t<_It>>::value
156 constexpr explicit(extent != dynamic_extent)
157 span(_It __first, size_type __count)
159 : _M_ptr(std::to_address(__first)), _M_extent(__count)
161 if constexpr (_Extent != dynamic_extent)
163 __glibcxx_assert(__count == _Extent);
165 __glibcxx_requires_valid_range(__first, __first + __count);
168 template<contiguous_iterator _It, sized_sentinel_for<_It> _End>
169 requires __is_compatible_ref<iter_reference_t<_It>>::value
170 && (!is_convertible_v<_End, size_type>)
171 constexpr explicit(extent != dynamic_extent)
172 span(_It __first, _End __last)
173 noexcept(noexcept(__last - __first))
174 : _M_ptr(std::to_address(__first)),
175 _M_extent(static_cast<size_type>(__last - __first))
177 if constexpr (_Extent != dynamic_extent)
179 __glibcxx_assert((__last - __first) == _Extent);
181 __glibcxx_requires_valid_range(__first, __last);
184 template<size_t _ArrayExtent>
185 requires (_Extent == dynamic_extent || _ArrayExtent == _Extent)
187 span(type_identity_t<element_type> (&__arr)[_ArrayExtent]) noexcept
188 : _M_ptr(__arr), _M_extent(_ArrayExtent)
191 template<typename _Tp, size_t _ArrayExtent>
192 requires __is_compatible_array<_Tp, _ArrayExtent>::value
194 span(array<_Tp, _ArrayExtent>& __arr) noexcept
195 : _M_ptr(__arr.data()), _M_extent(_ArrayExtent)
198 template<typename _Tp, size_t _ArrayExtent>
199 requires __is_compatible_array<const _Tp, _ArrayExtent>::value
201 span(const array<_Tp, _ArrayExtent>& __arr) noexcept
202 : _M_ptr(__arr.data()), _M_extent(_ArrayExtent)
205 template<typename _Range>
206 requires (!__detail::__is_span<remove_cvref_t<_Range>>)
207 && (!__detail::__is_std_array<remove_cvref_t<_Range>>)
208 && (!is_array_v<remove_cvref_t<_Range>>)
209 && ranges::contiguous_range<_Range> && ranges::sized_range<_Range>
210 && (ranges::borrowed_range<_Range> || is_const_v<element_type>)
211 && __is_compatible_ref<ranges::range_reference_t<_Range>>::value
212 constexpr explicit(extent != dynamic_extent)
213 span(_Range&& __range)
214 noexcept(noexcept(ranges::data(__range))
215 && noexcept(ranges::size(__range)))
216 : _M_ptr(ranges::data(__range)), _M_extent(ranges::size(__range))
218 if constexpr (extent != dynamic_extent)
220 __glibcxx_assert(ranges::size(__range) == extent);
225 span(const span&) noexcept = default;
227 template<typename _OType, size_t _OExtent>
228 requires (_Extent == dynamic_extent || _OExtent == dynamic_extent
229 || _Extent == _OExtent)
230 && (__is_array_convertible<_Type, _OType>::value)
232 explicit(extent != dynamic_extent && _OExtent == dynamic_extent)
233 span(const span<_OType, _OExtent>& __s) noexcept
234 : _M_ptr(__s.data()), _M_extent(__s.size())
236 if constexpr (extent != dynamic_extent)
238 __glibcxx_assert(__s.size() == extent);
242 ~span() noexcept = default;
245 operator=(const span&) noexcept = default;
251 size() const noexcept
252 { return this->_M_extent._M_extent(); }
256 size_bytes() const noexcept
257 { return this->_M_extent._M_extent() * sizeof(element_type); }
261 empty() const noexcept
262 { return size() == 0; }
268 front() const noexcept
270 __glibcxx_assert(!empty());
271 return *this->_M_ptr;
276 back() const noexcept
278 __glibcxx_assert(!empty());
279 return *(this->_M_ptr + (size() - 1));
284 operator[](size_type __idx) const noexcept
286 __glibcxx_assert(__idx < size());
287 return *(this->_M_ptr + __idx);
290#if __cpp_lib_span >= 202311L // >= C++26
293 at(size_type __idx) const
296 __throw_out_of_range_fmt(__N("span::at(%zu) out-of-range for span "
297 "of size %zu"), __idx, this->size());
298 return *(this->_M_ptr + __idx);
304 data() const noexcept
305 { return this->_M_ptr; }
311 begin() const noexcept
312 { return iterator(this->_M_ptr); }
317 { return iterator(this->_M_ptr + this->size()); }
320 constexpr reverse_iterator
321 rbegin() const noexcept
322 { return reverse_iterator(this->end()); }
325 constexpr reverse_iterator
326 rend() const noexcept
327 { return reverse_iterator(this->begin()); }
329#if __cplusplus > 202002L
331 constexpr const_iterator
332 cbegin() const noexcept
336 constexpr const_iterator
337 cend() const noexcept
341 constexpr const_reverse_iterator
342 crbegin() const noexcept
346 constexpr const_reverse_iterator
347 crend() const noexcept
353 template<size_t _Count>
355 constexpr span<element_type, _Count>
356 first() const noexcept
358 if constexpr (_Extent == dynamic_extent)
359 __glibcxx_assert(_Count <= size());
361 static_assert(_Count <= extent);
362 using _Sp = span<element_type, _Count>;
363 return _Sp{ this->data(), _Count };
367 constexpr span<element_type, dynamic_extent>
368 first(size_type __count) const noexcept
370 __glibcxx_assert(__count <= size());
371 return { this->data(), __count };
374 template<size_t _Count>
376 constexpr span<element_type, _Count>
377 last() const noexcept
379 if constexpr (_Extent == dynamic_extent)
380 __glibcxx_assert(_Count <= size());
382 static_assert(_Count <= extent);
383 using _Sp = span<element_type, _Count>;
384 return _Sp{ this->data() + (this->size() - _Count), _Count };
388 constexpr span<element_type, dynamic_extent>
389 last(size_type __count) const noexcept
391 __glibcxx_assert(__count <= size());
392 return { this->data() + (this->size() - __count), __count };
395 template<size_t _Offset, size_t _Count = dynamic_extent>
398 subspan() const noexcept
399 -> span<element_type, _S_subspan_extent<_Offset, _Count>()>
401 if constexpr (_Extent == dynamic_extent)
403 __glibcxx_assert(_Offset <= size());
406 static_assert(_Offset <= extent);
408 using _Sp = span<element_type, _S_subspan_extent<_Offset, _Count>()>;
410 if constexpr (_Count == dynamic_extent)
411 return _Sp{ this->data() + _Offset, this->size() - _Offset };
414 if constexpr (_Extent == dynamic_extent)
416 __glibcxx_assert(_Count <= size());
417 __glibcxx_assert(_Count <= (size() - _Offset));
421 static_assert(_Count <= extent);
422 static_assert(_Count <= (extent - _Offset));
424 return _Sp{ this->data() + _Offset, _Count };
429 constexpr span<element_type, dynamic_extent>
430 subspan(size_type __offset, size_type __count = dynamic_extent) const
433 __glibcxx_assert(__offset <= size());
434 if (__count == dynamic_extent)
435 __count = this->size() - __offset;
438 __glibcxx_assert(__count <= size());
439 __glibcxx_assert(__offset + __count <= size());
441 return {this->data() + __offset, __count};
446 [[no_unique_address]] __detail::__extent_storage<extent> _M_extent;
451 template<typename _Type, size_t _ArrayExtent>
452 span(_Type(&)[_ArrayExtent]) -> span<_Type, _ArrayExtent>;
454 template<typename _Type, size_t _ArrayExtent>
455 span(array<_Type, _ArrayExtent>&) -> span<_Type, _ArrayExtent>;
457 template<typename _Type, size_t _ArrayExtent>
458 span(const array<_Type, _ArrayExtent>&)
459 -> span<const _Type, _ArrayExtent>;
461 template<contiguous_iterator _Iter, typename _End>
463 -> span<remove_reference_t<iter_reference_t<_Iter>>>;
465 template<ranges::contiguous_range _Range>
467 -> span<remove_reference_t<ranges::range_reference_t<_Range&>>>;
469 template<typename _Type, size_t _Extent>
472 span<const byte, _Extent == dynamic_extent
473 ? dynamic_extent : _Extent * sizeof(_Type)>
474 as_bytes(span<_Type, _Extent> __sp) noexcept
476 auto data = reinterpret_cast<const byte*>(__sp.data());
477 auto size = __sp.size_bytes();
478 constexpr auto extent = _Extent == dynamic_extent
479 ? dynamic_extent : _Extent * sizeof(_Type);
480 return span<const byte, extent>{data, size};
483 template<typename _Type, size_t _Extent>
484 requires (!is_const_v<_Type>)
486 span<byte, _Extent == dynamic_extent
487 ? dynamic_extent : _Extent * sizeof(_Type)>
488 as_writable_bytes [[nodiscard]] (span<_Type, _Extent> __sp) noexcept
490 auto data = reinterpret_cast<byte*>(__sp.data());
491 auto size = __sp.size_bytes();
492 constexpr auto extent = _Extent == dynamic_extent
493 ? dynamic_extent : _Extent * sizeof(_Type);
494 return span<byte, extent>{data, size};
499 // Opt-in to borrowed_range concept
500 template<typename _ElementType, size_t _Extent>
501 inline constexpr bool
502 enable_borrowed_range<span<_ElementType, _Extent>> = true;
504 // Opt-in to view concept
505 template<typename _ElementType, size_t _Extent>
506 inline constexpr bool
507 enable_view<span<_ElementType, _Extent>> = true;
509_GLIBCXX_END_NAMESPACE_VERSION
511#endif // __cpp_lib_span
512#endif // _GLIBCXX_SPAN