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0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===---------------------------------------------------------------------===//
0009
0010 #ifndef _LIBCPP___CXX03_SPAN
0011 #define _LIBCPP___CXX03_SPAN
0012
0013 /*
0014 span synopsis
0015
0016 namespace std {
0017
0018 // constants
0019 inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max();
0020
0021 template<class T>
0022 concept integral-constant-like = // exposition only, since C++26
0023 is_integral_v<decltype(T::value)> &&
0024 !is_same_v<bool, remove_const_t<decltype(T::value)>> &&
0025 convertible_to<T, decltype(T::value)> &&
0026 equality_comparable_with<T, decltype(T::value)> &&
0027 bool_constant<T() == T::value>::value &&
0028 bool_constant<static_cast<decltype(T::value)>(T()) == T::value>::value;
0029
0030 template<class T>
0031 constexpr size_t maybe-static-ext = dynamic_extent; // exposition only, since C++26
0032 template<integral-constant-like T>
0033 constexpr size_t maybe-static-ext<T> = {T::value};
0034
0035 // [views.span], class template span
0036 template <class ElementType, size_t Extent = dynamic_extent>
0037 class span;
0038
0039 template<class ElementType, size_t Extent>
0040 inline constexpr bool ranges::enable_view<span<ElementType, Extent>> = true;
0041
0042 template<class ElementType, size_t Extent>
0043 inline constexpr bool ranges::enable_borrowed_range<span<ElementType, Extent>> = true;
0044
0045 // [span.objectrep], views of object representation
0046 template <class ElementType, size_t Extent>
0047 span<const byte, ((Extent == dynamic_extent) ? dynamic_extent :
0048 (sizeof(ElementType) * Extent))> as_bytes(span<ElementType, Extent> s) noexcept;
0049
0050 template <class ElementType, size_t Extent>
0051 span< byte, ((Extent == dynamic_extent) ? dynamic_extent :
0052 (sizeof(ElementType) * Extent))> as_writable_bytes(span<ElementType, Extent> s) noexcept;
0053
0054
0055 template <class ElementType, size_t Extent = dynamic_extent>
0056 class span {
0057 public:
0058 // constants and types
0059 using element_type = ElementType;
0060 using value_type = remove_cv_t<ElementType>;
0061 using size_type = size_t;
0062 using difference_type = ptrdiff_t;
0063 using pointer = element_type*;
0064 using const_pointer = const element_type*;
0065 using reference = element_type&;
0066 using const_reference = const element_type&;
0067 using iterator = implementation-defined;
0068 using reverse_iterator = std::reverse_iterator<iterator>;
0069 static constexpr size_type extent = Extent;
0070
0071 // [span.cons], span constructors, copy, assignment, and destructor
0072 constexpr span() noexcept;
0073 template <class It>
0074 constexpr explicit(Extent != dynamic_extent) span(It first, size_type count);
0075 template <class It, class End>
0076 constexpr explicit(Extent != dynamic_extent) span(It first, End last);
0077 template <size_t N>
0078 constexpr span(type_identity_t<element_type> (&arr)[N]) noexcept;
0079 template <size_t N>
0080 constexpr span(array<value_type, N>& arr) noexcept;
0081 template <size_t N>
0082 constexpr span(const array<value_type, N>& arr) noexcept;
0083 template<class R>
0084 constexpr explicit(Extent != dynamic_extent) span(R&& r);
0085 constexpr explicit(extent != dynamic_extent) span(std::initializer_list<value_type> il); // Since C++26
0086 constexpr span(const span& other) noexcept = default;
0087 template <class OtherElementType, size_t OtherExtent>
0088 constexpr explicit(Extent != dynamic_extent) span(const span<OtherElementType, OtherExtent>& s) noexcept;
0089 constexpr span& operator=(const span& other) noexcept = default;
0090
0091 // [span.sub], span subviews
0092 template <size_t Count>
0093 constexpr span<element_type, Count> first() const;
0094 template <size_t Count>
0095 constexpr span<element_type, Count> last() const;
0096 template <size_t Offset, size_t Count = dynamic_extent>
0097 constexpr span<element_type, see below> subspan() const;
0098
0099 constexpr span<element_type, dynamic_extent> first(size_type count) const;
0100 constexpr span<element_type, dynamic_extent> last(size_type count) const;
0101 constexpr span<element_type, dynamic_extent> subspan(size_type offset, size_type count = dynamic_extent) const;
0102
0103 // [span.obs], span observers
0104 constexpr size_type size() const noexcept;
0105 constexpr size_type size_bytes() const noexcept;
0106 [[nodiscard]] constexpr bool empty() const noexcept;
0107
0108 // [span.elem], span element access
0109 constexpr reference operator[](size_type idx) const;
0110 constexpr reference at(size_type idx) const; // since C++26
0111 constexpr reference front() const;
0112 constexpr reference back() const;
0113 constexpr pointer data() const noexcept;
0114
0115 // [span.iterators], span iterator support
0116 constexpr iterator begin() const noexcept;
0117 constexpr iterator end() const noexcept;
0118 constexpr reverse_iterator rbegin() const noexcept;
0119 constexpr reverse_iterator rend() const noexcept;
0120
0121 private:
0122 pointer data_; // exposition only
0123 size_type size_; // exposition only
0124 };
0125
0126 template<class It, class EndOrSize>
0127 span(It, EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>; // until C++26
0128 template<class It, class EndOrSize>
0129 span(It, EndOrSize) -> span<remove_reference_t<iter_reference_t<It>>, maybe-static-ext<EndOrSize>>; // since C++26
0130
0131 template<class T, size_t N>
0132 span(T (&)[N]) -> span<T, N>;
0133
0134 template<class T, size_t N>
0135 span(array<T, N>&) -> span<T, N>;
0136
0137 template<class T, size_t N>
0138 span(const array<T, N>&) -> span<const T, N>;
0139
0140 template<class R>
0141 span(R&&) -> span<remove_reference_t<ranges::range_reference_t<R>>>;
0142
0143 } // namespace std
0144
0145 */
0146
0147 #include <__cxx03/__assert>
0148 #include <__cxx03/__concepts/convertible_to.h>
0149 #include <__cxx03/__concepts/equality_comparable.h>
0150 #include <__cxx03/__config>
0151 #include <__cxx03/__fwd/array.h>
0152 #include <__cxx03/__fwd/span.h>
0153 #include <__cxx03/__iterator/bounded_iter.h>
0154 #include <__cxx03/__iterator/concepts.h>
0155 #include <__cxx03/__iterator/iterator_traits.h>
0156 #include <__cxx03/__iterator/reverse_iterator.h>
0157 #include <__cxx03/__iterator/wrap_iter.h>
0158 #include <__cxx03/__memory/pointer_traits.h>
0159 #include <__cxx03/__ranges/concepts.h>
0160 #include <__cxx03/__ranges/data.h>
0161 #include <__cxx03/__ranges/enable_borrowed_range.h>
0162 #include <__cxx03/__ranges/enable_view.h>
0163 #include <__cxx03/__ranges/size.h>
0164 #include <__cxx03/__type_traits/integral_constant.h>
0165 #include <__cxx03/__type_traits/is_array.h>
0166 #include <__cxx03/__type_traits/is_const.h>
0167 #include <__cxx03/__type_traits/is_convertible.h>
0168 #include <__cxx03/__type_traits/is_integral.h>
0169 #include <__cxx03/__type_traits/is_same.h>
0170 #include <__cxx03/__type_traits/remove_const.h>
0171 #include <__cxx03/__type_traits/remove_cv.h>
0172 #include <__cxx03/__type_traits/remove_cvref.h>
0173 #include <__cxx03/__type_traits/remove_reference.h>
0174 #include <__cxx03/__type_traits/type_identity.h>
0175 #include <__cxx03/__utility/forward.h>
0176 #include <__cxx03/cstddef> // for byte
0177 #include <__cxx03/initializer_list>
0178 #include <__cxx03/stdexcept>
0179 #include <__cxx03/version>
0180
0181 // standard-mandated includes
0182
0183 // [iterator.range]
0184 #include <__cxx03/__iterator/access.h>
0185 #include <__cxx03/__iterator/data.h>
0186 #include <__cxx03/__iterator/empty.h>
0187 #include <__cxx03/__iterator/reverse_access.h>
0188 #include <__cxx03/__iterator/size.h>
0189
0190 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0191 # pragma GCC system_header
0192 #endif
0193
0194 _LIBCPP_PUSH_MACROS
0195 #include <__cxx03/__undef_macros>
0196
0197 _LIBCPP_BEGIN_NAMESPACE_STD
0198
0199 #if _LIBCPP_STD_VER >= 20
0200
0201 template <class _Tp>
0202 struct __is_std_span : false_type {};
0203
0204 template <class _Tp, size_t _Sz>
0205 struct __is_std_span<span<_Tp, _Sz>> : true_type {};
0206
0207 template <class _Range, class _ElementType>
0208 concept __span_compatible_range =
0209 !__is_std_span<remove_cvref_t<_Range>>::value && //
0210 ranges::contiguous_range<_Range> && //
0211 ranges::sized_range<_Range> && //
0212 (ranges::borrowed_range<_Range> || is_const_v<_ElementType>) && //
0213 !__is_std_array<remove_cvref_t<_Range>>::value && //
0214 !is_array_v<remove_cvref_t<_Range>> && //
0215 is_convertible_v<remove_reference_t<ranges::range_reference_t<_Range>> (*)[], _ElementType (*)[]>;
0216
0217 template <class _From, class _To>
0218 concept __span_array_convertible = is_convertible_v<_From (*)[], _To (*)[]>;
0219
0220 template <class _It, class _Tp>
0221 concept __span_compatible_iterator =
0222 contiguous_iterator<_It> && __span_array_convertible<remove_reference_t<iter_reference_t<_It>>, _Tp>;
0223
0224 template <class _Sentinel, class _It>
0225 concept __span_compatible_sentinel_for = sized_sentinel_for<_Sentinel, _It> && !is_convertible_v<_Sentinel, size_t>;
0226
0227 template <typename _Tp, size_t _Extent>
0228 class _LIBCPP_TEMPLATE_VIS span {
0229 public:
0230 // constants and types
0231 using element_type = _Tp;
0232 using value_type = remove_cv_t<_Tp>;
0233 using size_type = size_t;
0234 using difference_type = ptrdiff_t;
0235 using pointer = _Tp*;
0236 using const_pointer = const _Tp*;
0237 using reference = _Tp&;
0238 using const_reference = const _Tp&;
0239 # ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
0240 using iterator = __bounded_iter<pointer>;
0241 # else
0242 using iterator = __wrap_iter<pointer>;
0243 # endif
0244 using reverse_iterator = std::reverse_iterator<iterator>;
0245
0246 static constexpr size_type extent = _Extent;
0247
0248 // [span.cons], span constructors, copy, assignment, and destructor
0249 template <size_t _Sz = _Extent>
0250 requires(_Sz == 0)
0251 _LIBCPP_HIDE_FROM_ABI constexpr span() noexcept : __data_{nullptr} {}
0252
0253 # if _LIBCPP_STD_VER >= 26
0254 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(std::initializer_list<value_type> __il)
0255 requires is_const_v<element_type>
0256 : __data_{__il.begin()} {
0257 _LIBCPP_ASSERT_VALID_INPUT_RANGE(
0258 _Extent == __il.size(), "Size mismatch in span's constructor _Extent != __il.size().");
0259 }
0260 # endif
0261
0262 constexpr span(const span&) noexcept = default;
0263 constexpr span& operator=(const span&) noexcept = default;
0264
0265 template <__span_compatible_iterator<element_type> _It>
0266 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_It __first, size_type __count) : __data_{std::to_address(__first)} {
0267 (void)__count;
0268 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Extent == __count, "size mismatch in span's constructor (iterator, len)");
0269 }
0270
0271 template <__span_compatible_iterator<element_type> _It, __span_compatible_sentinel_for<_It> _End>
0272 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_It __first, _End __last) : __data_{std::to_address(__first)} {
0273 // [span.cons]/10
0274 // Throws: When and what last - first throws.
0275 [[maybe_unused]] auto __dist = __last - __first;
0276 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__dist >= 0, "invalid range in span's constructor (iterator, sentinel)");
0277 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
0278 __dist == _Extent, "invalid range in span's constructor (iterator, sentinel): last - first != extent");
0279 }
0280
0281 _LIBCPP_HIDE_FROM_ABI constexpr span(type_identity_t<element_type> (&__arr)[_Extent]) noexcept : __data_{__arr} {}
0282
0283 template <__span_array_convertible<element_type> _OtherElementType>
0284 _LIBCPP_HIDE_FROM_ABI constexpr span(array<_OtherElementType, _Extent>& __arr) noexcept : __data_{__arr.data()} {}
0285
0286 template <class _OtherElementType>
0287 requires __span_array_convertible<const _OtherElementType, element_type>
0288 _LIBCPP_HIDE_FROM_ABI constexpr span(const array<_OtherElementType, _Extent>& __arr) noexcept
0289 : __data_{__arr.data()} {}
0290
0291 template <__span_compatible_range<element_type> _Range>
0292 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_Range&& __r) : __data_{ranges::data(__r)} {
0293 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(ranges::size(__r) == _Extent, "size mismatch in span's constructor (range)");
0294 }
0295
0296 template <__span_array_convertible<element_type> _OtherElementType>
0297 _LIBCPP_HIDE_FROM_ABI constexpr span(const span<_OtherElementType, _Extent>& __other) noexcept
0298 : __data_{__other.data()} {}
0299
0300 template <__span_array_convertible<element_type> _OtherElementType>
0301 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(const span<_OtherElementType, dynamic_extent>& __other) noexcept
0302 : __data_{__other.data()} {
0303 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Extent == __other.size(), "size mismatch in span's constructor (other span)");
0304 }
0305
0306 template <size_t _Count>
0307 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> first() const noexcept {
0308 static_assert(_Count <= _Extent, "span<T, N>::first<Count>(): Count out of range");
0309 return span<element_type, _Count>{data(), _Count};
0310 }
0311
0312 template <size_t _Count>
0313 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> last() const noexcept {
0314 static_assert(_Count <= _Extent, "span<T, N>::last<Count>(): Count out of range");
0315 return span<element_type, _Count>{data() + size() - _Count, _Count};
0316 }
0317
0318 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept {
0319 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T, N>::first(count): count out of range");
0320 return {data(), __count};
0321 }
0322
0323 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept {
0324 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T, N>::last(count): count out of range");
0325 return {data() + size() - __count, __count};
0326 }
0327
0328 template <size_t _Offset, size_t _Count = dynamic_extent>
0329 _LIBCPP_HIDE_FROM_ABI constexpr auto
0330 subspan() const noexcept -> span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset> {
0331 static_assert(_Offset <= _Extent, "span<T, N>::subspan<Offset, Count>(): Offset out of range");
0332 static_assert(_Count == dynamic_extent || _Count <= _Extent - _Offset,
0333 "span<T, N>::subspan<Offset, Count>(): Offset + Count out of range");
0334
0335 using _ReturnType = span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>;
0336 return _ReturnType{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
0337 }
0338
0339 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent>
0340 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept {
0341 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__offset <= size(), "span<T, N>::subspan(offset, count): offset out of range");
0342 if (__count == dynamic_extent)
0343 return {data() + __offset, size() - __offset};
0344 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
0345 __count <= size() - __offset, "span<T, N>::subspan(offset, count): offset + count out of range");
0346 return {data() + __offset, __count};
0347 }
0348
0349 _LIBCPP_HIDE_FROM_ABI constexpr size_type size() const noexcept { return _Extent; }
0350 _LIBCPP_HIDE_FROM_ABI constexpr size_type size_bytes() const noexcept { return _Extent * sizeof(element_type); }
0351 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const noexcept { return _Extent == 0; }
0352
0353 _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](size_type __idx) const noexcept {
0354 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__idx < size(), "span<T, N>::operator[](index): index out of range");
0355 return __data_[__idx];
0356 }
0357
0358 # if _LIBCPP_STD_VER >= 26
0359 _LIBCPP_HIDE_FROM_ABI constexpr reference at(size_type __index) const {
0360 if (__index >= size())
0361 std::__throw_out_of_range("span");
0362 return __data_[__index];
0363 }
0364 # endif
0365
0366 _LIBCPP_HIDE_FROM_ABI constexpr reference front() const noexcept {
0367 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T, N>::front() on empty span");
0368 return __data_[0];
0369 }
0370
0371 _LIBCPP_HIDE_FROM_ABI constexpr reference back() const noexcept {
0372 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T, N>::back() on empty span");
0373 return __data_[size() - 1];
0374 }
0375
0376 _LIBCPP_HIDE_FROM_ABI constexpr pointer data() const noexcept { return __data_; }
0377
0378 // [span.iter], span iterator support
0379 _LIBCPP_HIDE_FROM_ABI constexpr iterator begin() const noexcept {
0380 # ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
0381 return std::__make_bounded_iter(data(), data(), data() + size());
0382 # else
0383 return iterator(data());
0384 # endif
0385 }
0386 _LIBCPP_HIDE_FROM_ABI constexpr iterator end() const noexcept {
0387 # ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
0388 return std::__make_bounded_iter(data() + size(), data(), data() + size());
0389 # else
0390 return iterator(data() + size());
0391 # endif
0392 }
0393 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); }
0394 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); }
0395
0396 _LIBCPP_HIDE_FROM_ABI span<const byte, _Extent * sizeof(element_type)> __as_bytes() const noexcept {
0397 return span<const byte, _Extent * sizeof(element_type)>{reinterpret_cast<const byte*>(data()), size_bytes()};
0398 }
0399
0400 _LIBCPP_HIDE_FROM_ABI span<byte, _Extent * sizeof(element_type)> __as_writable_bytes() const noexcept {
0401 return span<byte, _Extent * sizeof(element_type)>{reinterpret_cast<byte*>(data()), size_bytes()};
0402 }
0403
0404 private:
0405 pointer __data_;
0406 };
0407
0408 template <typename _Tp>
0409 class _LIBCPP_TEMPLATE_VIS span<_Tp, dynamic_extent> {
0410 public:
0411 // constants and types
0412 using element_type = _Tp;
0413 using value_type = remove_cv_t<_Tp>;
0414 using size_type = size_t;
0415 using difference_type = ptrdiff_t;
0416 using pointer = _Tp*;
0417 using const_pointer = const _Tp*;
0418 using reference = _Tp&;
0419 using const_reference = const _Tp&;
0420 # ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
0421 using iterator = __bounded_iter<pointer>;
0422 # else
0423 using iterator = __wrap_iter<pointer>;
0424 # endif
0425 using reverse_iterator = std::reverse_iterator<iterator>;
0426
0427 static constexpr size_type extent = dynamic_extent;
0428
0429 // [span.cons], span constructors, copy, assignment, and destructor
0430 _LIBCPP_HIDE_FROM_ABI constexpr span() noexcept : __data_{nullptr}, __size_{0} {}
0431
0432 # if _LIBCPP_STD_VER >= 26
0433 _LIBCPP_HIDE_FROM_ABI constexpr span(std::initializer_list<value_type> __il)
0434 requires is_const_v<element_type>
0435 : __data_{__il.begin()}, __size_{__il.size()} {}
0436 # endif
0437
0438 constexpr span(const span&) noexcept = default;
0439 constexpr span& operator=(const span&) noexcept = default;
0440
0441 template <__span_compatible_iterator<element_type> _It>
0442 _LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, size_type __count)
0443 : __data_{std::to_address(__first)}, __size_{__count} {}
0444
0445 template <__span_compatible_iterator<element_type> _It, __span_compatible_sentinel_for<_It> _End>
0446 _LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, _End __last)
0447 : __data_(std::to_address(__first)), __size_(__last - __first) {
0448 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__last - __first >= 0, "invalid range in span's constructor (iterator, sentinel)");
0449 }
0450
0451 template <size_t _Sz>
0452 _LIBCPP_HIDE_FROM_ABI constexpr span(type_identity_t<element_type> (&__arr)[_Sz]) noexcept
0453 : __data_{__arr}, __size_{_Sz} {}
0454
0455 template <__span_array_convertible<element_type> _OtherElementType, size_t _Sz>
0456 _LIBCPP_HIDE_FROM_ABI constexpr span(array<_OtherElementType, _Sz>& __arr) noexcept
0457 : __data_{__arr.data()}, __size_{_Sz} {}
0458
0459 template <class _OtherElementType, size_t _Sz>
0460 requires __span_array_convertible<const _OtherElementType, element_type>
0461 _LIBCPP_HIDE_FROM_ABI constexpr span(const array<_OtherElementType, _Sz>& __arr) noexcept
0462 : __data_{__arr.data()}, __size_{_Sz} {}
0463
0464 template <__span_compatible_range<element_type> _Range>
0465 _LIBCPP_HIDE_FROM_ABI constexpr span(_Range&& __r) : __data_(ranges::data(__r)), __size_{ranges::size(__r)} {}
0466
0467 template <__span_array_convertible<element_type> _OtherElementType, size_t _OtherExtent>
0468 _LIBCPP_HIDE_FROM_ABI constexpr span(const span<_OtherElementType, _OtherExtent>& __other) noexcept
0469 : __data_{__other.data()}, __size_{__other.size()} {}
0470
0471 template <size_t _Count>
0472 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> first() const noexcept {
0473 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count <= size(), "span<T>::first<Count>(): Count out of range");
0474 return span<element_type, _Count>{data(), _Count};
0475 }
0476
0477 template <size_t _Count>
0478 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> last() const noexcept {
0479 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count <= size(), "span<T>::last<Count>(): Count out of range");
0480 return span<element_type, _Count>{data() + size() - _Count, _Count};
0481 }
0482
0483 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept {
0484 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T>::first(count): count out of range");
0485 return {data(), __count};
0486 }
0487
0488 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept {
0489 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T>::last(count): count out of range");
0490 return {data() + size() - __count, __count};
0491 }
0492
0493 template <size_t _Offset, size_t _Count = dynamic_extent>
0494 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> subspan() const noexcept {
0495 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Offset <= size(), "span<T>::subspan<Offset, Count>(): Offset out of range");
0496 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count == dynamic_extent || _Count <= size() - _Offset,
0497 "span<T>::subspan<Offset, Count>(): Offset + Count out of range");
0498 return span<element_type, _Count>{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
0499 }
0500
0501 constexpr span<element_type, dynamic_extent> _LIBCPP_HIDE_FROM_ABI
0502 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept {
0503 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__offset <= size(), "span<T>::subspan(offset, count): offset out of range");
0504 if (__count == dynamic_extent)
0505 return {data() + __offset, size() - __offset};
0506 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
0507 __count <= size() - __offset, "span<T>::subspan(offset, count): offset + count out of range");
0508 return {data() + __offset, __count};
0509 }
0510
0511 _LIBCPP_HIDE_FROM_ABI constexpr size_type size() const noexcept { return __size_; }
0512 _LIBCPP_HIDE_FROM_ABI constexpr size_type size_bytes() const noexcept { return __size_ * sizeof(element_type); }
0513 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const noexcept { return __size_ == 0; }
0514
0515 _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](size_type __idx) const noexcept {
0516 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__idx < size(), "span<T>::operator[](index): index out of range");
0517 return __data_[__idx];
0518 }
0519
0520 # if _LIBCPP_STD_VER >= 26
0521 _LIBCPP_HIDE_FROM_ABI constexpr reference at(size_type __index) const {
0522 if (__index >= size())
0523 std::__throw_out_of_range("span");
0524 return __data_[__index];
0525 }
0526 # endif
0527
0528 _LIBCPP_HIDE_FROM_ABI constexpr reference front() const noexcept {
0529 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T>::front() on empty span");
0530 return __data_[0];
0531 }
0532
0533 _LIBCPP_HIDE_FROM_ABI constexpr reference back() const noexcept {
0534 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T>::back() on empty span");
0535 return __data_[size() - 1];
0536 }
0537
0538 _LIBCPP_HIDE_FROM_ABI constexpr pointer data() const noexcept { return __data_; }
0539
0540 // [span.iter], span iterator support
0541 _LIBCPP_HIDE_FROM_ABI constexpr iterator begin() const noexcept {
0542 # ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
0543 return std::__make_bounded_iter(data(), data(), data() + size());
0544 # else
0545 return iterator(data());
0546 # endif
0547 }
0548 _LIBCPP_HIDE_FROM_ABI constexpr iterator end() const noexcept {
0549 # ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
0550 return std::__make_bounded_iter(data() + size(), data(), data() + size());
0551 # else
0552 return iterator(data() + size());
0553 # endif
0554 }
0555 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); }
0556 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); }
0557
0558 _LIBCPP_HIDE_FROM_ABI span<const byte, dynamic_extent> __as_bytes() const noexcept {
0559 return {reinterpret_cast<const byte*>(data()), size_bytes()};
0560 }
0561
0562 _LIBCPP_HIDE_FROM_ABI span<byte, dynamic_extent> __as_writable_bytes() const noexcept {
0563 return {reinterpret_cast<byte*>(data()), size_bytes()};
0564 }
0565
0566 private:
0567 pointer __data_;
0568 size_type __size_;
0569 };
0570
0571 template <class _Tp, size_t _Extent>
0572 inline constexpr bool ranges::enable_borrowed_range<span<_Tp, _Extent> > = true;
0573
0574 template <class _ElementType, size_t _Extent>
0575 inline constexpr bool ranges::enable_view<span<_ElementType, _Extent>> = true;
0576
0577 // as_bytes & as_writable_bytes
0578 template <class _Tp, size_t _Extent>
0579 _LIBCPP_HIDE_FROM_ABI auto as_bytes(span<_Tp, _Extent> __s) noexcept {
0580 return __s.__as_bytes();
0581 }
0582
0583 template <class _Tp, size_t _Extent>
0584 requires(!is_const_v<_Tp>)
0585 _LIBCPP_HIDE_FROM_ABI auto as_writable_bytes(span<_Tp, _Extent> __s) noexcept {
0586 return __s.__as_writable_bytes();
0587 }
0588
0589 # if _LIBCPP_STD_VER >= 26
0590 template <class _Tp>
0591 concept __integral_constant_like =
0592 is_integral_v<decltype(_Tp::value)> && !is_same_v<bool, remove_const_t<decltype(_Tp::value)>> &&
0593 convertible_to<_Tp, decltype(_Tp::value)> && equality_comparable_with<_Tp, decltype(_Tp::value)> &&
0594 bool_constant<_Tp() == _Tp::value>::value &&
0595 bool_constant<static_cast<decltype(_Tp::value)>(_Tp()) == _Tp::value>::value;
0596
0597 template <class _Tp>
0598 inline constexpr size_t __maybe_static_ext = dynamic_extent;
0599
0600 template <__integral_constant_like _Tp>
0601 inline constexpr size_t __maybe_static_ext<_Tp> = {_Tp::value};
0602
0603 template <contiguous_iterator _It, class _EndOrSize>
0604 span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>, __maybe_static_ext<_EndOrSize>>;
0605 # else
0606 template <contiguous_iterator _It, class _EndOrSize>
0607 span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>;
0608 # endif
0609
0610 template <class _Tp, size_t _Sz>
0611 span(_Tp (&)[_Sz]) -> span<_Tp, _Sz>;
0612
0613 template <class _Tp, size_t _Sz>
0614 span(array<_Tp, _Sz>&) -> span<_Tp, _Sz>;
0615
0616 template <class _Tp, size_t _Sz>
0617 span(const array<_Tp, _Sz>&) -> span<const _Tp, _Sz>;
0618
0619 template <ranges::contiguous_range _Range>
0620 span(_Range&&) -> span<remove_reference_t<ranges::range_reference_t<_Range>>>;
0621
0622 #endif // _LIBCPP_STD_VER >= 20
0623
0624 _LIBCPP_END_NAMESPACE_STD
0625
0626 _LIBCPP_POP_MACROS
0627
0628 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
0629 # include <__cxx03/array>
0630 # include <__cxx03/concepts>
0631 # include <__cxx03/functional>
0632 # include <__cxx03/iterator>
0633 # include <__cxx03/type_traits>
0634 #endif
0635
0636 #endif // _LIBCPP___CXX03_SPAN
