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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_SPAN
0011 #define _LIBCPP_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 #if __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
0148 # include <__cxx03/span>
0149 #else
0150 # include <__assert>
0151 # include <__concepts/convertible_to.h>
0152 # include <__concepts/equality_comparable.h>
0153 # include <__config>
0154 # include <__cstddef/byte.h>
0155 # include <__cstddef/ptrdiff_t.h>
0156 # include <__fwd/array.h>
0157 # include <__fwd/span.h>
0158 # include <__iterator/bounded_iter.h>
0159 # include <__iterator/concepts.h>
0160 # include <__iterator/iterator_traits.h>
0161 # include <__iterator/reverse_iterator.h>
0162 # include <__iterator/wrap_iter.h>
0163 # include <__memory/pointer_traits.h>
0164 # include <__ranges/concepts.h>
0165 # include <__ranges/data.h>
0166 # include <__ranges/enable_borrowed_range.h>
0167 # include <__ranges/enable_view.h>
0168 # include <__ranges/size.h>
0169 # include <__type_traits/integral_constant.h>
0170 # include <__type_traits/is_array.h>
0171 # include <__type_traits/is_const.h>
0172 # include <__type_traits/is_convertible.h>
0173 # include <__type_traits/is_integral.h>
0174 # include <__type_traits/is_same.h>
0175 # include <__type_traits/remove_const.h>
0176 # include <__type_traits/remove_cv.h>
0177 # include <__type_traits/remove_cvref.h>
0178 # include <__type_traits/remove_reference.h>
0179 # include <__type_traits/type_identity.h>
0180 # include <__utility/forward.h>
0181 # include <initializer_list>
0182 # include <stdexcept>
0183 # include <version>
0184
0185 // standard-mandated includes
0186
0187 // [iterator.range]
0188 # include <__iterator/access.h>
0189 # include <__iterator/data.h>
0190 # include <__iterator/empty.h>
0191 # include <__iterator/reverse_access.h>
0192 # include <__iterator/size.h>
0193
0194 # if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0195 # pragma GCC system_header
0196 # endif
0197
0198 _LIBCPP_PUSH_MACROS
0199 # include <__undef_macros>
0200
0201 _LIBCPP_BEGIN_NAMESPACE_STD
0202
0203 # if _LIBCPP_STD_VER >= 20
0204
0205 template <class _Tp>
0206 struct __is_std_span : false_type {};
0207
0208 template <class _Tp, size_t _Sz>
0209 struct __is_std_span<span<_Tp, _Sz>> : true_type {};
0210
0211 template <class _Range, class _ElementType>
0212 concept __span_compatible_range =
0213 !__is_std_span<remove_cvref_t<_Range>>::value && //
0214 ranges::contiguous_range<_Range> && //
0215 ranges::sized_range<_Range> && //
0216 (ranges::borrowed_range<_Range> || is_const_v<_ElementType>) && //
0217 !__is_std_array_v<remove_cvref_t<_Range>> && //
0218 !is_array_v<remove_cvref_t<_Range>> && //
0219 is_convertible_v<remove_reference_t<ranges::range_reference_t<_Range>> (*)[], _ElementType (*)[]>;
0220
0221 template <class _From, class _To>
0222 concept __span_array_convertible = is_convertible_v<_From (*)[], _To (*)[]>;
0223
0224 template <class _It, class _Tp>
0225 concept __span_compatible_iterator =
0226 contiguous_iterator<_It> && __span_array_convertible<remove_reference_t<iter_reference_t<_It>>, _Tp>;
0227
0228 template <class _Sentinel, class _It>
0229 concept __span_compatible_sentinel_for = sized_sentinel_for<_Sentinel, _It> && !is_convertible_v<_Sentinel, size_t>;
0230
0231 template <typename _Tp, size_t _Extent>
0232 class _LIBCPP_TEMPLATE_VIS span {
0233 public:
0234 // constants and types
0235 using element_type = _Tp;
0236 using value_type = remove_cv_t<_Tp>;
0237 using size_type = size_t;
0238 using difference_type = ptrdiff_t;
0239 using pointer = _Tp*;
0240 using const_pointer = const _Tp*;
0241 using reference = _Tp&;
0242 using const_reference = const _Tp&;
0243 # ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
0244 using iterator = __bounded_iter<pointer>;
0245 # else
0246 using iterator = __wrap_iter<pointer>;
0247 # endif
0248 using reverse_iterator = std::reverse_iterator<iterator>;
0249
0250 static constexpr size_type extent = _Extent;
0251
0252 // [span.cons], span constructors, copy, assignment, and destructor
0253 template <size_t _Sz = _Extent>
0254 requires(_Sz == 0)
0255 _LIBCPP_HIDE_FROM_ABI constexpr span() noexcept : __data_{nullptr} {}
0256
0257 # if _LIBCPP_STD_VER >= 26
0258 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(std::initializer_list<value_type> __il)
0259 requires is_const_v<element_type>
0260 : __data_{__il.begin()} {
0261 _LIBCPP_ASSERT_VALID_INPUT_RANGE(
0262 _Extent == __il.size(), "Size mismatch in span's constructor _Extent != __il.size().");
0263 }
0264 # endif
0265
0266 constexpr span(const span&) noexcept = default;
0267 constexpr span& operator=(const span&) noexcept = default;
0268
0269 template <__span_compatible_iterator<element_type> _It>
0270 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_It __first, size_type __count) : __data_{std::to_address(__first)} {
0271 (void)__count;
0272 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Extent == __count, "size mismatch in span's constructor (iterator, len)");
0273 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__count == 0 || std::to_address(__first) != nullptr,
0274 "passed nullptr with non-zero length in span's constructor (iterator, len)");
0275 }
0276
0277 template <__span_compatible_iterator<element_type> _It, __span_compatible_sentinel_for<_It> _End>
0278 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_It __first, _End __last) : __data_{std::to_address(__first)} {
0279 // [span.cons]/10
0280 // Throws: When and what last - first throws.
0281 [[maybe_unused]] auto __dist = __last - __first;
0282 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__dist >= 0, "invalid range in span's constructor (iterator, sentinel)");
0283 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
0284 __dist == _Extent, "invalid range in span's constructor (iterator, sentinel): last - first != extent");
0285 }
0286
0287 _LIBCPP_HIDE_FROM_ABI constexpr span(type_identity_t<element_type> (&__arr)[_Extent]) noexcept : __data_{__arr} {}
0288
0289 template <__span_array_convertible<element_type> _OtherElementType>
0290 _LIBCPP_HIDE_FROM_ABI constexpr span(array<_OtherElementType, _Extent>& __arr) noexcept : __data_{__arr.data()} {}
0291
0292 template <class _OtherElementType>
0293 requires __span_array_convertible<const _OtherElementType, element_type>
0294 _LIBCPP_HIDE_FROM_ABI constexpr span(const array<_OtherElementType, _Extent>& __arr) noexcept
0295 : __data_{__arr.data()} {}
0296
0297 template <__span_compatible_range<element_type> _Range>
0298 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_Range&& __r) : __data_{ranges::data(__r)} {
0299 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(ranges::size(__r) == _Extent, "size mismatch in span's constructor (range)");
0300 }
0301
0302 template <__span_array_convertible<element_type> _OtherElementType>
0303 _LIBCPP_HIDE_FROM_ABI constexpr span(const span<_OtherElementType, _Extent>& __other) noexcept
0304 : __data_{__other.data()} {}
0305
0306 template <__span_array_convertible<element_type> _OtherElementType>
0307 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(const span<_OtherElementType, dynamic_extent>& __other) noexcept
0308 : __data_{__other.data()} {
0309 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Extent == __other.size(), "size mismatch in span's constructor (other span)");
0310 }
0311
0312 template <size_t _Count>
0313 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> first() const noexcept {
0314 static_assert(_Count <= _Extent, "span<T, N>::first<Count>(): Count out of range");
0315 return span<element_type, _Count>{data(), _Count};
0316 }
0317
0318 template <size_t _Count>
0319 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> last() const noexcept {
0320 static_assert(_Count <= _Extent, "span<T, N>::last<Count>(): Count out of range");
0321 return span<element_type, _Count>{data() + size() - _Count, _Count};
0322 }
0323
0324 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept {
0325 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T, N>::first(count): count out of range");
0326 return {data(), __count};
0327 }
0328
0329 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept {
0330 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T, N>::last(count): count out of range");
0331 return {data() + size() - __count, __count};
0332 }
0333
0334 template <size_t _Offset, size_t _Count = dynamic_extent>
0335 _LIBCPP_HIDE_FROM_ABI constexpr auto
0336 subspan() const noexcept -> span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset> {
0337 static_assert(_Offset <= _Extent, "span<T, N>::subspan<Offset, Count>(): Offset out of range");
0338 static_assert(_Count == dynamic_extent || _Count <= _Extent - _Offset,
0339 "span<T, N>::subspan<Offset, Count>(): Offset + Count out of range");
0340
0341 using _ReturnType = span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>;
0342 return _ReturnType{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
0343 }
0344
0345 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent>
0346 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept {
0347 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__offset <= size(), "span<T, N>::subspan(offset, count): offset out of range");
0348 if (__count == dynamic_extent)
0349 return {data() + __offset, size() - __offset};
0350 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
0351 __count <= size() - __offset, "span<T, N>::subspan(offset, count): offset + count out of range");
0352 return {data() + __offset, __count};
0353 }
0354
0355 _LIBCPP_HIDE_FROM_ABI constexpr size_type size() const noexcept { return _Extent; }
0356 _LIBCPP_HIDE_FROM_ABI constexpr size_type size_bytes() const noexcept { return _Extent * sizeof(element_type); }
0357 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const noexcept { return _Extent == 0; }
0358
0359 _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](size_type __idx) const noexcept {
0360 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__idx < size(), "span<T, N>::operator[](index): index out of range");
0361 return __data_[__idx];
0362 }
0363
0364 # if _LIBCPP_STD_VER >= 26
0365 _LIBCPP_HIDE_FROM_ABI constexpr reference at(size_type __index) const {
0366 if (__index >= size())
0367 std::__throw_out_of_range("span");
0368 return __data_[__index];
0369 }
0370 # endif
0371
0372 _LIBCPP_HIDE_FROM_ABI constexpr reference front() const noexcept {
0373 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T, N>::front() on empty span");
0374 return __data_[0];
0375 }
0376
0377 _LIBCPP_HIDE_FROM_ABI constexpr reference back() const noexcept {
0378 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T, N>::back() on empty span");
0379 return __data_[size() - 1];
0380 }
0381
0382 _LIBCPP_HIDE_FROM_ABI constexpr pointer data() const noexcept { return __data_; }
0383
0384 // [span.iter], span iterator support
0385 _LIBCPP_HIDE_FROM_ABI constexpr iterator begin() const noexcept {
0386 # ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
0387 return std::__make_bounded_iter(data(), data(), data() + size());
0388 # else
0389 return iterator(data());
0390 # endif
0391 }
0392 _LIBCPP_HIDE_FROM_ABI constexpr iterator end() const noexcept {
0393 # ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
0394 return std::__make_bounded_iter(data() + size(), data(), data() + size());
0395 # else
0396 return iterator(data() + size());
0397 # endif
0398 }
0399 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); }
0400 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); }
0401
0402 _LIBCPP_HIDE_FROM_ABI span<const byte, _Extent * sizeof(element_type)> __as_bytes() const noexcept {
0403 return span<const byte, _Extent * sizeof(element_type)>{reinterpret_cast<const byte*>(data()), size_bytes()};
0404 }
0405
0406 _LIBCPP_HIDE_FROM_ABI span<byte, _Extent * sizeof(element_type)> __as_writable_bytes() const noexcept {
0407 return span<byte, _Extent * sizeof(element_type)>{reinterpret_cast<byte*>(data()), size_bytes()};
0408 }
0409
0410 private:
0411 pointer __data_;
0412 };
0413
0414 template <typename _Tp>
0415 class _LIBCPP_TEMPLATE_VIS span<_Tp, dynamic_extent> {
0416 public:
0417 // constants and types
0418 using element_type = _Tp;
0419 using value_type = remove_cv_t<_Tp>;
0420 using size_type = size_t;
0421 using difference_type = ptrdiff_t;
0422 using pointer = _Tp*;
0423 using const_pointer = const _Tp*;
0424 using reference = _Tp&;
0425 using const_reference = const _Tp&;
0426 # ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
0427 using iterator = __bounded_iter<pointer>;
0428 # else
0429 using iterator = __wrap_iter<pointer>;
0430 # endif
0431 using reverse_iterator = std::reverse_iterator<iterator>;
0432
0433 static constexpr size_type extent = dynamic_extent;
0434
0435 // [span.cons], span constructors, copy, assignment, and destructor
0436 _LIBCPP_HIDE_FROM_ABI constexpr span() noexcept : __data_{nullptr}, __size_{0} {}
0437
0438 # if _LIBCPP_STD_VER >= 26
0439 _LIBCPP_HIDE_FROM_ABI constexpr span(std::initializer_list<value_type> __il)
0440 requires is_const_v<element_type>
0441 : __data_{__il.begin()}, __size_{__il.size()} {}
0442 # endif
0443
0444 constexpr span(const span&) noexcept = default;
0445 constexpr span& operator=(const span&) noexcept = default;
0446
0447 template <__span_compatible_iterator<element_type> _It>
0448 _LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, size_type __count)
0449 : __data_{std::to_address(__first)}, __size_{__count} {
0450 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__count == 0 || std::to_address(__first) != nullptr,
0451 "passed nullptr with non-zero length in span's constructor (iterator, len)");
0452 }
0453
0454 template <__span_compatible_iterator<element_type> _It, __span_compatible_sentinel_for<_It> _End>
0455 _LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, _End __last)
0456 : __data_(std::to_address(__first)), __size_(__last - __first) {
0457 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__last - __first >= 0, "invalid range in span's constructor (iterator, sentinel)");
0458 }
0459
0460 template <size_t _Sz>
0461 _LIBCPP_HIDE_FROM_ABI constexpr span(type_identity_t<element_type> (&__arr)[_Sz]) noexcept
0462 : __data_{__arr}, __size_{_Sz} {}
0463
0464 template <__span_array_convertible<element_type> _OtherElementType, size_t _Sz>
0465 _LIBCPP_HIDE_FROM_ABI constexpr span(array<_OtherElementType, _Sz>& __arr) noexcept
0466 : __data_{__arr.data()}, __size_{_Sz} {}
0467
0468 template <class _OtherElementType, size_t _Sz>
0469 requires __span_array_convertible<const _OtherElementType, element_type>
0470 _LIBCPP_HIDE_FROM_ABI constexpr span(const array<_OtherElementType, _Sz>& __arr) noexcept
0471 : __data_{__arr.data()}, __size_{_Sz} {}
0472
0473 template <__span_compatible_range<element_type> _Range>
0474 _LIBCPP_HIDE_FROM_ABI constexpr span(_Range&& __r) : __data_(ranges::data(__r)), __size_{ranges::size(__r)} {}
0475
0476 template <__span_array_convertible<element_type> _OtherElementType, size_t _OtherExtent>
0477 _LIBCPP_HIDE_FROM_ABI constexpr span(const span<_OtherElementType, _OtherExtent>& __other) noexcept
0478 : __data_{__other.data()}, __size_{__other.size()} {}
0479
0480 template <size_t _Count>
0481 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> first() const noexcept {
0482 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count <= size(), "span<T>::first<Count>(): Count out of range");
0483 return span<element_type, _Count>{data(), _Count};
0484 }
0485
0486 template <size_t _Count>
0487 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> last() const noexcept {
0488 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count <= size(), "span<T>::last<Count>(): Count out of range");
0489 return span<element_type, _Count>{data() + size() - _Count, _Count};
0490 }
0491
0492 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept {
0493 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T>::first(count): count out of range");
0494 return {data(), __count};
0495 }
0496
0497 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept {
0498 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T>::last(count): count out of range");
0499 return {data() + size() - __count, __count};
0500 }
0501
0502 template <size_t _Offset, size_t _Count = dynamic_extent>
0503 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> subspan() const noexcept {
0504 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Offset <= size(), "span<T>::subspan<Offset, Count>(): Offset out of range");
0505 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count == dynamic_extent || _Count <= size() - _Offset,
0506 "span<T>::subspan<Offset, Count>(): Offset + Count out of range");
0507 return span<element_type, _Count>{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
0508 }
0509
0510 constexpr span<element_type, dynamic_extent> _LIBCPP_HIDE_FROM_ABI
0511 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept {
0512 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__offset <= size(), "span<T>::subspan(offset, count): offset out of range");
0513 if (__count == dynamic_extent)
0514 return {data() + __offset, size() - __offset};
0515 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
0516 __count <= size() - __offset, "span<T>::subspan(offset, count): offset + count out of range");
0517 return {data() + __offset, __count};
0518 }
0519
0520 _LIBCPP_HIDE_FROM_ABI constexpr size_type size() const noexcept { return __size_; }
0521 _LIBCPP_HIDE_FROM_ABI constexpr size_type size_bytes() const noexcept { return __size_ * sizeof(element_type); }
0522 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const noexcept { return __size_ == 0; }
0523
0524 _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](size_type __idx) const noexcept {
0525 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__idx < size(), "span<T>::operator[](index): index out of range");
0526 return __data_[__idx];
0527 }
0528
0529 # if _LIBCPP_STD_VER >= 26
0530 _LIBCPP_HIDE_FROM_ABI constexpr reference at(size_type __index) const {
0531 if (__index >= size())
0532 std::__throw_out_of_range("span");
0533 return __data_[__index];
0534 }
0535 # endif
0536
0537 _LIBCPP_HIDE_FROM_ABI constexpr reference front() const noexcept {
0538 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T>::front() on empty span");
0539 return __data_[0];
0540 }
0541
0542 _LIBCPP_HIDE_FROM_ABI constexpr reference back() const noexcept {
0543 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T>::back() on empty span");
0544 return __data_[size() - 1];
0545 }
0546
0547 _LIBCPP_HIDE_FROM_ABI constexpr pointer data() const noexcept { return __data_; }
0548
0549 // [span.iter], span iterator support
0550 _LIBCPP_HIDE_FROM_ABI constexpr iterator begin() const noexcept {
0551 # ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
0552 return std::__make_bounded_iter(data(), data(), data() + size());
0553 # else
0554 return iterator(data());
0555 # endif
0556 }
0557 _LIBCPP_HIDE_FROM_ABI constexpr iterator end() const noexcept {
0558 # ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
0559 return std::__make_bounded_iter(data() + size(), data(), data() + size());
0560 # else
0561 return iterator(data() + size());
0562 # endif
0563 }
0564 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); }
0565 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); }
0566
0567 _LIBCPP_HIDE_FROM_ABI span<const byte, dynamic_extent> __as_bytes() const noexcept {
0568 return {reinterpret_cast<const byte*>(data()), size_bytes()};
0569 }
0570
0571 _LIBCPP_HIDE_FROM_ABI span<byte, dynamic_extent> __as_writable_bytes() const noexcept {
0572 return {reinterpret_cast<byte*>(data()), size_bytes()};
0573 }
0574
0575 private:
0576 pointer __data_;
0577 size_type __size_;
0578 };
0579
0580 template <class _Tp, size_t _Extent>
0581 inline constexpr bool ranges::enable_borrowed_range<span<_Tp, _Extent> > = true;
0582
0583 template <class _ElementType, size_t _Extent>
0584 inline constexpr bool ranges::enable_view<span<_ElementType, _Extent>> = true;
0585
0586 // as_bytes & as_writable_bytes
0587 template <class _Tp, size_t _Extent>
0588 _LIBCPP_HIDE_FROM_ABI auto as_bytes(span<_Tp, _Extent> __s) noexcept {
0589 return __s.__as_bytes();
0590 }
0591
0592 template <class _Tp, size_t _Extent>
0593 requires(!is_const_v<_Tp>)
0594 _LIBCPP_HIDE_FROM_ABI auto as_writable_bytes(span<_Tp, _Extent> __s) noexcept {
0595 return __s.__as_writable_bytes();
0596 }
0597
0598 # if _LIBCPP_STD_VER >= 26
0599 template <class _Tp>
0600 concept __integral_constant_like =
0601 is_integral_v<decltype(_Tp::value)> && !is_same_v<bool, remove_const_t<decltype(_Tp::value)>> &&
0602 convertible_to<_Tp, decltype(_Tp::value)> && equality_comparable_with<_Tp, decltype(_Tp::value)> &&
0603 bool_constant<_Tp() == _Tp::value>::value &&
0604 bool_constant<static_cast<decltype(_Tp::value)>(_Tp()) == _Tp::value>::value;
0605
0606 template <class _Tp>
0607 inline constexpr size_t __maybe_static_ext = dynamic_extent;
0608
0609 template <__integral_constant_like _Tp>
0610 inline constexpr size_t __maybe_static_ext<_Tp> = {_Tp::value};
0611
0612 template <contiguous_iterator _It, class _EndOrSize>
0613 span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>, __maybe_static_ext<_EndOrSize>>;
0614 # else
0615 template <contiguous_iterator _It, class _EndOrSize>
0616 span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>;
0617 # endif
0618
0619 template <class _Tp, size_t _Sz>
0620 span(_Tp (&)[_Sz]) -> span<_Tp, _Sz>;
0621
0622 template <class _Tp, size_t _Sz>
0623 span(array<_Tp, _Sz>&) -> span<_Tp, _Sz>;
0624
0625 template <class _Tp, size_t _Sz>
0626 span(const array<_Tp, _Sz>&) -> span<const _Tp, _Sz>;
0627
0628 template <ranges::contiguous_range _Range>
0629 span(_Range&&) -> span<remove_reference_t<ranges::range_reference_t<_Range>>>;
0630
0631 # endif // _LIBCPP_STD_VER >= 20
0632
0633 _LIBCPP_END_NAMESPACE_STD
0634
0635 _LIBCPP_POP_MACROS
0636
0637 # if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
0638 # include <array>
0639 # include <concepts>
0640 # include <functional>
0641 # include <iterator>
0642 # include <type_traits>
0643 # endif
0644 #endif // __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
0645
0646 #endif // _LIBCPP_SPAN
