xref: /freebsd/contrib/llvm-project/libcxx/include/span (revision cb14a3fe5122c879eae1fb480ed7ce82a699ddb6)
10b57cec5SDimitry Andric// -*- C++ -*-
2349cc55cSDimitry Andric//===----------------------------------------------------------------------===//
30b57cec5SDimitry Andric//
40b57cec5SDimitry Andric// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
50b57cec5SDimitry Andric// See https://llvm.org/LICENSE.txt for license information.
60b57cec5SDimitry Andric// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
70b57cec5SDimitry Andric//
80b57cec5SDimitry Andric//===---------------------------------------------------------------------===//
90b57cec5SDimitry Andric
100b57cec5SDimitry Andric#ifndef _LIBCPP_SPAN
110b57cec5SDimitry Andric#define _LIBCPP_SPAN
120b57cec5SDimitry Andric
130b57cec5SDimitry Andric/*
140b57cec5SDimitry Andric    span synopsis
150b57cec5SDimitry Andric
160b57cec5SDimitry Andricnamespace std {
170b57cec5SDimitry Andric
180b57cec5SDimitry Andric// constants
190b57cec5SDimitry Andricinline constexpr size_t dynamic_extent = numeric_limits<size_t>::max();
200b57cec5SDimitry Andric
210b57cec5SDimitry Andric// [views.span], class template span
220b57cec5SDimitry Andrictemplate <class ElementType, size_t Extent = dynamic_extent>
230b57cec5SDimitry Andric    class span;
240b57cec5SDimitry Andric
25fe6060f1SDimitry Andrictemplate<class ElementType, size_t Extent>
26fe6060f1SDimitry Andric  inline constexpr bool ranges::enable_view<span<ElementType, Extent>> = true;
27fe6060f1SDimitry Andric
28fe6060f1SDimitry Andrictemplate<class ElementType, size_t Extent>
29fe6060f1SDimitry Andric    inline constexpr bool ranges::enable_borrowed_range<span<ElementType, Extent>> = true;
30fe6060f1SDimitry Andric
310b57cec5SDimitry Andric// [span.objectrep], views of object representation
320b57cec5SDimitry Andrictemplate <class ElementType, size_t Extent>
330b57cec5SDimitry Andric    span<const byte, ((Extent == dynamic_extent) ? dynamic_extent :
340b57cec5SDimitry Andric        (sizeof(ElementType) * Extent))> as_bytes(span<ElementType, Extent> s) noexcept;
350b57cec5SDimitry Andric
360b57cec5SDimitry Andrictemplate <class ElementType, size_t Extent>
370b57cec5SDimitry Andric    span<      byte, ((Extent == dynamic_extent) ? dynamic_extent :
380b57cec5SDimitry Andric        (sizeof(ElementType) * Extent))> as_writable_bytes(span<ElementType, Extent> s) noexcept;
390b57cec5SDimitry Andric
400b57cec5SDimitry Andric
410b57cec5SDimitry Andrictemplate <class ElementType, size_t Extent = dynamic_extent>
420b57cec5SDimitry Andricclass span {
430b57cec5SDimitry Andricpublic:
440b57cec5SDimitry Andric    // constants and types
450b57cec5SDimitry Andric    using element_type = ElementType;
460b57cec5SDimitry Andric    using value_type = remove_cv_t<ElementType>;
47480093f4SDimitry Andric    using size_type = size_t;
480b57cec5SDimitry Andric    using difference_type = ptrdiff_t;
490b57cec5SDimitry Andric    using pointer = element_type*;
500b57cec5SDimitry Andric    using const_pointer = const element_type*;
510b57cec5SDimitry Andric    using reference = element_type&;
520b57cec5SDimitry Andric    using const_reference = const element_type&;
530b57cec5SDimitry Andric    using iterator = implementation-defined;
540b57cec5SDimitry Andric    using reverse_iterator = std::reverse_iterator<iterator>;
55480093f4SDimitry Andric    static constexpr size_type extent = Extent;
560b57cec5SDimitry Andric
570b57cec5SDimitry Andric    // [span.cons], span constructors, copy, assignment, and destructor
580b57cec5SDimitry Andric    constexpr span() noexcept;
59349cc55cSDimitry Andric    template <class It>
60349cc55cSDimitry Andric    constexpr explicit(Extent != dynamic_extent) span(It first, size_type count);
61349cc55cSDimitry Andric    template <class It, class End>
62349cc55cSDimitry Andric    constexpr explicit(Extent != dynamic_extent) span(It first, End last);
630b57cec5SDimitry Andric    template <size_t N>
64349cc55cSDimitry Andric        constexpr span(type_identity_t<element_type> (&arr)[N]) noexcept;
650b57cec5SDimitry Andric    template <size_t N>
660b57cec5SDimitry Andric        constexpr span(array<value_type, N>& arr) noexcept;
670b57cec5SDimitry Andric    template <size_t N>
680b57cec5SDimitry Andric        constexpr span(const array<value_type, N>& arr) noexcept;
69349cc55cSDimitry Andric    template<class R>
70349cc55cSDimitry Andric      constexpr explicit(Extent != dynamic_extent) span(R&& r);
710b57cec5SDimitry Andric    constexpr span(const span& other) noexcept = default;
720b57cec5SDimitry Andric    template <class OtherElementType, size_t OtherExtent>
735ffd83dbSDimitry Andric        constexpr explicit(Extent != dynamic_extent) span(const span<OtherElementType, OtherExtent>& s) noexcept;
740b57cec5SDimitry Andric    constexpr span& operator=(const span& other) noexcept = default;
750b57cec5SDimitry Andric
760b57cec5SDimitry Andric    // [span.sub], span subviews
770b57cec5SDimitry Andric    template <size_t Count>
780b57cec5SDimitry Andric        constexpr span<element_type, Count> first() const;
790b57cec5SDimitry Andric    template <size_t Count>
800b57cec5SDimitry Andric        constexpr span<element_type, Count> last() const;
810b57cec5SDimitry Andric    template <size_t Offset, size_t Count = dynamic_extent>
820b57cec5SDimitry Andric        constexpr span<element_type, see below> subspan() const;
830b57cec5SDimitry Andric
84480093f4SDimitry Andric    constexpr span<element_type, dynamic_extent> first(size_type count) const;
85480093f4SDimitry Andric    constexpr span<element_type, dynamic_extent> last(size_type count) const;
86480093f4SDimitry Andric    constexpr span<element_type, dynamic_extent> subspan(size_type offset, size_type count = dynamic_extent) const;
870b57cec5SDimitry Andric
880b57cec5SDimitry Andric    // [span.obs], span observers
89480093f4SDimitry Andric    constexpr size_type size() const noexcept;
90480093f4SDimitry Andric    constexpr size_type size_bytes() const noexcept;
91349cc55cSDimitry Andric    [[nodiscard]] constexpr bool empty() const noexcept;
920b57cec5SDimitry Andric
930b57cec5SDimitry Andric    // [span.elem], span element access
94480093f4SDimitry Andric    constexpr reference operator[](size_type idx) const;
950b57cec5SDimitry Andric    constexpr reference front() const;
960b57cec5SDimitry Andric    constexpr reference back() const;
970b57cec5SDimitry Andric    constexpr pointer data() const noexcept;
980b57cec5SDimitry Andric
990b57cec5SDimitry Andric    // [span.iterators], span iterator support
1000b57cec5SDimitry Andric    constexpr iterator begin() const noexcept;
1010b57cec5SDimitry Andric    constexpr iterator end() const noexcept;
1020b57cec5SDimitry Andric    constexpr reverse_iterator rbegin() const noexcept;
1030b57cec5SDimitry Andric    constexpr reverse_iterator rend() const noexcept;
1040b57cec5SDimitry Andric
1050b57cec5SDimitry Andricprivate:
1060b57cec5SDimitry Andric    pointer data_;    // exposition only
107480093f4SDimitry Andric    size_type size_;  // exposition only
1080b57cec5SDimitry Andric};
1090b57cec5SDimitry Andric
110349cc55cSDimitry Andrictemplate<class It, class EndOrSize>
111349cc55cSDimitry Andric    span(It, EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>;
112349cc55cSDimitry Andric
1130b57cec5SDimitry Andrictemplate<class T, size_t N>
1140b57cec5SDimitry Andric    span(T (&)[N]) -> span<T, N>;
1150b57cec5SDimitry Andric
1160b57cec5SDimitry Andrictemplate<class T, size_t N>
1170b57cec5SDimitry Andric    span(array<T, N>&) -> span<T, N>;
1180b57cec5SDimitry Andric
1190b57cec5SDimitry Andrictemplate<class T, size_t N>
1200b57cec5SDimitry Andric    span(const array<T, N>&) -> span<const T, N>;
1210b57cec5SDimitry Andric
122349cc55cSDimitry Andrictemplate<class R>
123349cc55cSDimitry Andric    span(R&&) -> span<remove_reference_t<ranges::range_reference_t<R>>>;
1240b57cec5SDimitry Andric
1250b57cec5SDimitry Andric} // namespace std
1260b57cec5SDimitry Andric
1270b57cec5SDimitry Andric*/
1280b57cec5SDimitry Andric
12981ad6265SDimitry Andric#include <__assert> // all public C++ headers provide the assertion handler
1300b57cec5SDimitry Andric#include <__config>
13181ad6265SDimitry Andric#include <__fwd/span.h>
13281ad6265SDimitry Andric#include <__iterator/bounded_iter.h>
133349cc55cSDimitry Andric#include <__iterator/concepts.h>
13481ad6265SDimitry Andric#include <__iterator/iterator_traits.h>
135fe6060f1SDimitry Andric#include <__iterator/wrap_iter.h>
13681ad6265SDimitry Andric#include <__memory/pointer_traits.h>
137349cc55cSDimitry Andric#include <__ranges/concepts.h>
138349cc55cSDimitry Andric#include <__ranges/data.h>
139fe6060f1SDimitry Andric#include <__ranges/enable_borrowed_range.h>
140fe6060f1SDimitry Andric#include <__ranges/enable_view.h>
141349cc55cSDimitry Andric#include <__ranges/size.h>
14206c3fb27SDimitry Andric#include <__type_traits/is_convertible.h>
14306c3fb27SDimitry Andric#include <__type_traits/remove_cvref.h>
14406c3fb27SDimitry Andric#include <__type_traits/remove_reference.h>
14506c3fb27SDimitry Andric#include <__type_traits/type_identity.h>
14681ad6265SDimitry Andric#include <__utility/forward.h>
1470b57cec5SDimitry Andric#include <array>   // for array
1480b57cec5SDimitry Andric#include <cstddef> // for byte
149fe6060f1SDimitry Andric#include <version>
1500b57cec5SDimitry Andric
15181ad6265SDimitry Andric// standard-mandated includes
15281ad6265SDimitry Andric
15381ad6265SDimitry Andric// [iterator.range]
15481ad6265SDimitry Andric#include <__iterator/access.h>
15581ad6265SDimitry Andric#include <__iterator/data.h>
15681ad6265SDimitry Andric#include <__iterator/empty.h>
15781ad6265SDimitry Andric#include <__iterator/reverse_access.h>
15881ad6265SDimitry Andric#include <__iterator/size.h>
15981ad6265SDimitry Andric
1600b57cec5SDimitry Andric#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
1610b57cec5SDimitry Andric#  pragma GCC system_header
1620b57cec5SDimitry Andric#endif
1630b57cec5SDimitry Andric
164e8d8bef9SDimitry Andric_LIBCPP_PUSH_MACROS
165e8d8bef9SDimitry Andric#include <__undef_macros>
166e8d8bef9SDimitry Andric
1670b57cec5SDimitry Andric_LIBCPP_BEGIN_NAMESPACE_STD
1680b57cec5SDimitry Andric
16906c3fb27SDimitry Andric#if _LIBCPP_STD_VER >= 20
1700b57cec5SDimitry Andric
1710b57cec5SDimitry Andrictemplate <class _Tp>
172349cc55cSDimitry Andricstruct __is_std_array : false_type {};
1730b57cec5SDimitry Andric
1740b57cec5SDimitry Andrictemplate <class _Tp, size_t _Sz>
175349cc55cSDimitry Andricstruct __is_std_array<array<_Tp, _Sz>> : true_type {};
1760b57cec5SDimitry Andric
1770b57cec5SDimitry Andrictemplate <class _Tp>
178349cc55cSDimitry Andricstruct __is_std_span : false_type {};
1790b57cec5SDimitry Andric
180349cc55cSDimitry Andrictemplate <class _Tp, size_t _Sz>
181349cc55cSDimitry Andricstruct __is_std_span<span<_Tp, _Sz>> : true_type {};
1820b57cec5SDimitry Andric
183349cc55cSDimitry Andrictemplate <class _Range, class _ElementType>
184349cc55cSDimitry Andricconcept __span_compatible_range =
1855f757f3fSDimitry Andric    ranges::contiguous_range<_Range> &&                            //
1865f757f3fSDimitry Andric    ranges::sized_range<_Range> &&                                 //
1875f757f3fSDimitry Andric    (ranges::borrowed_range<_Range> || is_const_v<_ElementType>)&& //
1885f757f3fSDimitry Andric    !__is_std_span<remove_cvref_t<_Range>>::value &&               //
1895f757f3fSDimitry Andric    !__is_std_array<remove_cvref_t<_Range>>::value &&              //
1905f757f3fSDimitry Andric    !is_array_v<remove_cvref_t<_Range>> &&                         //
191349cc55cSDimitry Andric    is_convertible_v<remove_reference_t<ranges::range_reference_t<_Range>> (*)[], _ElementType (*)[]>;
19281ad6265SDimitry Andric
19381ad6265SDimitry Andrictemplate <class _From, class _To>
19481ad6265SDimitry Andricconcept __span_array_convertible = is_convertible_v<_From (*)[], _To (*)[]>;
19581ad6265SDimitry Andric
19681ad6265SDimitry Andrictemplate <class _It, class _Tp>
197*cb14a3feSDimitry Andricconcept __span_compatible_iterator =
198*cb14a3feSDimitry Andric    contiguous_iterator<_It> && __span_array_convertible<remove_reference_t<iter_reference_t<_It>>, _Tp>;
19981ad6265SDimitry Andric
20081ad6265SDimitry Andrictemplate <class _Sentinel, class _It>
20181ad6265SDimitry Andricconcept __span_compatible_sentinel_for = sized_sentinel_for<_Sentinel, _It> && !is_convertible_v<_Sentinel, size_t>;
2020b57cec5SDimitry Andric
2030b57cec5SDimitry Andrictemplate <typename _Tp, size_t _Extent>
2040b57cec5SDimitry Andricclass _LIBCPP_TEMPLATE_VIS span {
2050b57cec5SDimitry Andricpublic:
2060b57cec5SDimitry Andric  //  constants and types
2070b57cec5SDimitry Andric  using element_type    = _Tp;
2080b57cec5SDimitry Andric  using value_type      = remove_cv_t<_Tp>;
209480093f4SDimitry Andric  using size_type       = size_t;
2100b57cec5SDimitry Andric  using difference_type = ptrdiff_t;
2110b57cec5SDimitry Andric  using pointer         = _Tp*;
2120b57cec5SDimitry Andric  using const_pointer   = const _Tp*;
2130b57cec5SDimitry Andric  using reference       = _Tp&;
2140b57cec5SDimitry Andric  using const_reference = const _Tp&;
21506c3fb27SDimitry Andric#  ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
21681ad6265SDimitry Andric  using iterator = __bounded_iter<pointer>;
217fe6060f1SDimitry Andric#  else
2180b57cec5SDimitry Andric  using iterator = __wrap_iter<pointer>;
219fe6060f1SDimitry Andric#  endif
2205f757f3fSDimitry Andric  using reverse_iterator = std::reverse_iterator<iterator>;
2210b57cec5SDimitry Andric
222480093f4SDimitry Andric  static constexpr size_type extent = _Extent;
2230b57cec5SDimitry Andric
2240b57cec5SDimitry Andric  // [span.cons], span constructors, copy, assignment, and destructor
225*cb14a3feSDimitry Andric  template <size_t _Sz = _Extent>
226*cb14a3feSDimitry Andric    requires(_Sz == 0)
2275f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span() noexcept : __data_{nullptr} {}
2280b57cec5SDimitry Andric
2290b57cec5SDimitry Andric  constexpr span(const span&) noexcept            = default;
2300b57cec5SDimitry Andric  constexpr span& operator=(const span&) noexcept = default;
2310b57cec5SDimitry Andric
23281ad6265SDimitry Andric  template <__span_compatible_iterator<element_type> _It>
233*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_It __first, size_type __count) : __data_{std::to_address(__first)} {
234349cc55cSDimitry Andric    (void)__count;
23506c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Extent == __count, "size mismatch in span's constructor (iterator, len)");
236349cc55cSDimitry Andric  }
2370b57cec5SDimitry Andric
23881ad6265SDimitry Andric  template <__span_compatible_iterator<element_type> _It, __span_compatible_sentinel_for<_It> _End>
239*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_It __first, _End __last) : __data_{std::to_address(__first)} {
24006c3fb27SDimitry Andric    // [span.cons]/10
24106c3fb27SDimitry Andric    // Throws: When and what last - first throws.
24206c3fb27SDimitry Andric    [[maybe_unused]] auto __dist = __last - __first;
24306c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_INPUT_RANGE(__dist >= 0, "invalid range in span's constructor (iterator, sentinel)");
24406c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
24506c3fb27SDimitry Andric        __dist == _Extent, "invalid range in span's constructor (iterator, sentinel): last - first != extent");
246349cc55cSDimitry Andric  }
247349cc55cSDimitry Andric
2485f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span(type_identity_t<element_type> (&__arr)[_Extent]) noexcept : __data_{__arr} {}
2495ffd83dbSDimitry Andric
25081ad6265SDimitry Andric  template <__span_array_convertible<element_type> _OtherElementType>
251*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span(array<_OtherElementType, _Extent>& __arr) noexcept : __data_{__arr.data()} {}
2525ffd83dbSDimitry Andric
25381ad6265SDimitry Andric  template <class _OtherElementType>
25481ad6265SDimitry Andric    requires __span_array_convertible<const _OtherElementType, element_type>
255*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span(const array<_OtherElementType, _Extent>& __arr) noexcept
256*cb14a3feSDimitry Andric      : __data_{__arr.data()} {}
2575ffd83dbSDimitry Andric
258349cc55cSDimitry Andric  template <__span_compatible_range<element_type> _Range>
259*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_Range&& __r) : __data_{ranges::data(__r)} {
260*cb14a3feSDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(ranges::size(__r) == _Extent, "size mismatch in span's constructor (range)");
2615ffd83dbSDimitry Andric  }
2620b57cec5SDimitry Andric
26381ad6265SDimitry Andric  template <__span_array_convertible<element_type> _OtherElementType>
264*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span(const span<_OtherElementType, _Extent>& __other) : __data_{__other.data()} {}
2650b57cec5SDimitry Andric
26681ad6265SDimitry Andric  template <__span_array_convertible<element_type> _OtherElementType>
267*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr explicit span(const span<_OtherElementType, dynamic_extent>& __other) noexcept
26806c3fb27SDimitry Andric      : __data_{__other.data()} {
269*cb14a3feSDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Extent == __other.size(), "size mismatch in span's constructor (other span)");
27006c3fb27SDimitry Andric  }
2710b57cec5SDimitry Andric
2720b57cec5SDimitry Andric  template <size_t _Count>
273*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> first() const noexcept {
27481ad6265SDimitry Andric    static_assert(_Count <= _Extent, "span<T, N>::first<Count>(): Count out of range");
2755ffd83dbSDimitry Andric    return span<element_type, _Count>{data(), _Count};
2760b57cec5SDimitry Andric  }
2770b57cec5SDimitry Andric
2780b57cec5SDimitry Andric  template <size_t _Count>
279*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> last() const noexcept {
28081ad6265SDimitry Andric    static_assert(_Count <= _Extent, "span<T, N>::last<Count>(): Count out of range");
2815ffd83dbSDimitry Andric    return span<element_type, _Count>{data() + size() - _Count, _Count};
2820b57cec5SDimitry Andric  }
2830b57cec5SDimitry Andric
284*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept {
28506c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T, N>::first(count): count out of range");
2860b57cec5SDimitry Andric    return {data(), __count};
2870b57cec5SDimitry Andric  }
2880b57cec5SDimitry Andric
289*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept {
29006c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T, N>::last(count): count out of range");
2910b57cec5SDimitry Andric    return {data() + size() - __count, __count};
2920b57cec5SDimitry Andric  }
2930b57cec5SDimitry Andric
2940b57cec5SDimitry Andric  template <size_t _Offset, size_t _Count = dynamic_extent>
295*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr auto subspan() const noexcept
296*cb14a3feSDimitry Andric      -> span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset> {
29781ad6265SDimitry Andric    static_assert(_Offset <= _Extent, "span<T, N>::subspan<Offset, Count>(): Offset out of range");
298*cb14a3feSDimitry Andric    static_assert(_Count == dynamic_extent || _Count <= _Extent - _Offset,
299*cb14a3feSDimitry Andric                  "span<T, N>::subspan<Offset, Count>(): Offset + Count out of range");
3005ffd83dbSDimitry Andric
3015ffd83dbSDimitry Andric    using _ReturnType = span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>;
3025ffd83dbSDimitry Andric    return _ReturnType{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
3030b57cec5SDimitry Andric  }
3040b57cec5SDimitry Andric
305*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent>
306*cb14a3feSDimitry Andric  subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept {
307*cb14a3feSDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__offset <= size(), "span<T, N>::subspan(offset, count): offset out of range");
3080b57cec5SDimitry Andric    if (__count == dynamic_extent)
3090b57cec5SDimitry Andric      return {data() + __offset, size() - __offset};
31006c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
31106c3fb27SDimitry Andric        __count <= size() - __offset, "span<T, N>::subspan(offset, count): offset + count out of range");
3120b57cec5SDimitry Andric    return {data() + __offset, __count};
3130b57cec5SDimitry Andric  }
3140b57cec5SDimitry Andric
3155f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr size_type size() const noexcept { return _Extent; }
3165f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr size_type size_bytes() const noexcept { return _Extent * sizeof(element_type); }
3175f757f3fSDimitry Andric  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const noexcept { return _Extent == 0; }
3180b57cec5SDimitry Andric
319*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](size_type __idx) const noexcept {
32006c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__idx < size(), "span<T, N>::operator[](index): index out of range");
321bdd1243dSDimitry Andric    return __data_[__idx];
3220b57cec5SDimitry Andric  }
3230b57cec5SDimitry Andric
324*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr reference front() const noexcept {
32506c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T, N>::front() on empty span");
326bdd1243dSDimitry Andric    return __data_[0];
3270b57cec5SDimitry Andric  }
3280b57cec5SDimitry Andric
329*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr reference back() const noexcept {
33006c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T, N>::back() on empty span");
331bdd1243dSDimitry Andric    return __data_[size() - 1];
3320b57cec5SDimitry Andric  }
3330b57cec5SDimitry Andric
3345f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr pointer data() const noexcept { return __data_; }
3350b57cec5SDimitry Andric
3360b57cec5SDimitry Andric  // [span.iter], span iterator support
3375f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr iterator begin() const noexcept {
33806c3fb27SDimitry Andric#  ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
33981ad6265SDimitry Andric    return std::__make_bounded_iter(data(), data(), data() + size());
34081ad6265SDimitry Andric#  else
34106c3fb27SDimitry Andric    return iterator(data());
34281ad6265SDimitry Andric#  endif
34381ad6265SDimitry Andric  }
3445f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr iterator end() const noexcept {
34506c3fb27SDimitry Andric#  ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
34681ad6265SDimitry Andric    return std::__make_bounded_iter(data() + size(), data(), data() + size());
34781ad6265SDimitry Andric#  else
34806c3fb27SDimitry Andric    return iterator(data() + size());
34981ad6265SDimitry Andric#  endif
35081ad6265SDimitry Andric  }
3515f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); }
3525f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); }
3530b57cec5SDimitry Andric
354*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI span<const byte, _Extent * sizeof(element_type)> __as_bytes() const noexcept {
355*cb14a3feSDimitry Andric    return span<const byte, _Extent * sizeof(element_type)>{reinterpret_cast<const byte*>(data()), size_bytes()};
356*cb14a3feSDimitry Andric  }
3570b57cec5SDimitry Andric
358*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI span<byte, _Extent * sizeof(element_type)> __as_writable_bytes() const noexcept {
359*cb14a3feSDimitry Andric    return span<byte, _Extent * sizeof(element_type)>{reinterpret_cast<byte*>(data()), size_bytes()};
360*cb14a3feSDimitry Andric  }
3610b57cec5SDimitry Andric
3620b57cec5SDimitry Andricprivate:
363bdd1243dSDimitry Andric  pointer __data_;
3640b57cec5SDimitry Andric};
3650b57cec5SDimitry Andric
3660b57cec5SDimitry Andrictemplate <typename _Tp>
3670b57cec5SDimitry Andricclass _LIBCPP_TEMPLATE_VIS span<_Tp, dynamic_extent> {
3680b57cec5SDimitry Andricpublic:
3690b57cec5SDimitry Andric  //  constants and types
3700b57cec5SDimitry Andric  using element_type    = _Tp;
3710b57cec5SDimitry Andric  using value_type      = remove_cv_t<_Tp>;
372480093f4SDimitry Andric  using size_type       = size_t;
3730b57cec5SDimitry Andric  using difference_type = ptrdiff_t;
3740b57cec5SDimitry Andric  using pointer         = _Tp*;
3750b57cec5SDimitry Andric  using const_pointer   = const _Tp*;
3760b57cec5SDimitry Andric  using reference       = _Tp&;
3770b57cec5SDimitry Andric  using const_reference = const _Tp&;
37806c3fb27SDimitry Andric#  ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
37981ad6265SDimitry Andric  using iterator = __bounded_iter<pointer>;
380fe6060f1SDimitry Andric#  else
3810b57cec5SDimitry Andric  using iterator = __wrap_iter<pointer>;
382fe6060f1SDimitry Andric#  endif
3835f757f3fSDimitry Andric  using reverse_iterator = std::reverse_iterator<iterator>;
3840b57cec5SDimitry Andric
385480093f4SDimitry Andric  static constexpr size_type extent = dynamic_extent;
3860b57cec5SDimitry Andric
3870b57cec5SDimitry Andric  // [span.cons], span constructors, copy, assignment, and destructor
3885f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span() noexcept : __data_{nullptr}, __size_{0} {}
3890b57cec5SDimitry Andric
3900b57cec5SDimitry Andric  constexpr span(const span&) noexcept            = default;
3910b57cec5SDimitry Andric  constexpr span& operator=(const span&) noexcept = default;
3920b57cec5SDimitry Andric
39381ad6265SDimitry Andric  template <__span_compatible_iterator<element_type> _It>
394*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, size_type __count)
3955f757f3fSDimitry Andric      : __data_{std::to_address(__first)}, __size_{__count} {}
396349cc55cSDimitry Andric
39781ad6265SDimitry Andric  template <__span_compatible_iterator<element_type> _It, __span_compatible_sentinel_for<_It> _End>
3985f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, _End __last)
3995f757f3fSDimitry Andric      : __data_(std::to_address(__first)), __size_(__last - __first) {
400*cb14a3feSDimitry Andric    _LIBCPP_ASSERT_VALID_INPUT_RANGE(__last - __first >= 0, "invalid range in span's constructor (iterator, sentinel)");
401a4a491e2SDimitry Andric  }
4020b57cec5SDimitry Andric
4030b57cec5SDimitry Andric  template <size_t _Sz>
404*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span(type_identity_t<element_type> (&__arr)[_Sz]) noexcept
405*cb14a3feSDimitry Andric      : __data_{__arr}, __size_{_Sz} {}
4060b57cec5SDimitry Andric
40781ad6265SDimitry Andric  template <__span_array_convertible<element_type> _OtherElementType, size_t _Sz>
408*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span(array<_OtherElementType, _Sz>& __arr) noexcept
409*cb14a3feSDimitry Andric      : __data_{__arr.data()}, __size_{_Sz} {}
4100b57cec5SDimitry Andric
41181ad6265SDimitry Andric  template <class _OtherElementType, size_t _Sz>
41281ad6265SDimitry Andric    requires __span_array_convertible<const _OtherElementType, element_type>
413*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span(const array<_OtherElementType, _Sz>& __arr) noexcept
414*cb14a3feSDimitry Andric      : __data_{__arr.data()}, __size_{_Sz} {}
4150b57cec5SDimitry Andric
416349cc55cSDimitry Andric  template <__span_compatible_range<element_type> _Range>
417*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span(_Range&& __r) : __data_(ranges::data(__r)), __size_{ranges::size(__r)} {}
4180b57cec5SDimitry Andric
41981ad6265SDimitry Andric  template <__span_array_convertible<element_type> _OtherElementType, size_t _OtherExtent>
420*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span(const span<_OtherElementType, _OtherExtent>& __other) noexcept
421bdd1243dSDimitry Andric      : __data_{__other.data()}, __size_{__other.size()} {}
4220b57cec5SDimitry Andric
4230b57cec5SDimitry Andric  template <size_t _Count>
424*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> first() const noexcept {
42506c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count <= size(), "span<T>::first<Count>(): Count out of range");
4265ffd83dbSDimitry Andric    return span<element_type, _Count>{data(), _Count};
4270b57cec5SDimitry Andric  }
4280b57cec5SDimitry Andric
4290b57cec5SDimitry Andric  template <size_t _Count>
430*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> last() const noexcept {
43106c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count <= size(), "span<T>::last<Count>(): Count out of range");
4325ffd83dbSDimitry Andric    return span<element_type, _Count>{data() + size() - _Count, _Count};
4330b57cec5SDimitry Andric  }
4340b57cec5SDimitry Andric
435*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept {
43606c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T>::first(count): count out of range");
4370b57cec5SDimitry Andric    return {data(), __count};
4380b57cec5SDimitry Andric  }
4390b57cec5SDimitry Andric
440*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept {
44106c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T>::last(count): count out of range");
4420b57cec5SDimitry Andric    return {data() + size() - __count, __count};
4430b57cec5SDimitry Andric  }
4440b57cec5SDimitry Andric
4450b57cec5SDimitry Andric  template <size_t _Offset, size_t _Count = dynamic_extent>
446*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> subspan() const noexcept {
447*cb14a3feSDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Offset <= size(), "span<T>::subspan<Offset, Count>(): Offset out of range");
44806c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count == dynamic_extent || _Count <= size() - _Offset,
44906c3fb27SDimitry Andric                                        "span<T>::subspan<Offset, Count>(): Offset + Count out of range");
4505ffd83dbSDimitry Andric    return span<element_type, _Count>{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
4510b57cec5SDimitry Andric  }
4520b57cec5SDimitry Andric
453*cb14a3feSDimitry Andric  constexpr span<element_type, dynamic_extent> _LIBCPP_HIDE_FROM_ABI
454*cb14a3feSDimitry Andric  subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept {
45506c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__offset <= size(), "span<T>::subspan(offset, count): offset out of range");
4560b57cec5SDimitry Andric    if (__count == dynamic_extent)
4570b57cec5SDimitry Andric      return {data() + __offset, size() - __offset};
45806c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
45906c3fb27SDimitry Andric        __count <= size() - __offset, "span<T>::subspan(offset, count): offset + count out of range");
4600b57cec5SDimitry Andric    return {data() + __offset, __count};
4610b57cec5SDimitry Andric  }
4620b57cec5SDimitry Andric
4635f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr size_type size() const noexcept { return __size_; }
4645f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr size_type size_bytes() const noexcept { return __size_ * sizeof(element_type); }
4655f757f3fSDimitry Andric  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const noexcept { return __size_ == 0; }
4660b57cec5SDimitry Andric
467*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](size_type __idx) const noexcept {
46806c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__idx < size(), "span<T>::operator[](index): index out of range");
469bdd1243dSDimitry Andric    return __data_[__idx];
4700b57cec5SDimitry Andric  }
4710b57cec5SDimitry Andric
472*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr reference front() const noexcept {
47306c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T>::front() on empty span");
474bdd1243dSDimitry Andric    return __data_[0];
4750b57cec5SDimitry Andric  }
4760b57cec5SDimitry Andric
477*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr reference back() const noexcept {
47806c3fb27SDimitry Andric    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T>::back() on empty span");
479bdd1243dSDimitry Andric    return __data_[size() - 1];
4800b57cec5SDimitry Andric  }
4810b57cec5SDimitry Andric
4825f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr pointer data() const noexcept { return __data_; }
4830b57cec5SDimitry Andric
4840b57cec5SDimitry Andric  // [span.iter], span iterator support
4855f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr iterator begin() const noexcept {
48606c3fb27SDimitry Andric#  ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
48781ad6265SDimitry Andric    return std::__make_bounded_iter(data(), data(), data() + size());
48881ad6265SDimitry Andric#  else
48906c3fb27SDimitry Andric    return iterator(data());
49081ad6265SDimitry Andric#  endif
49181ad6265SDimitry Andric  }
4925f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr iterator end() const noexcept {
49306c3fb27SDimitry Andric#  ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
49481ad6265SDimitry Andric    return std::__make_bounded_iter(data() + size(), data(), data() + size());
49581ad6265SDimitry Andric#  else
49606c3fb27SDimitry Andric    return iterator(data() + size());
49781ad6265SDimitry Andric#  endif
49881ad6265SDimitry Andric  }
4995f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); }
5005f757f3fSDimitry Andric  _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); }
5010b57cec5SDimitry Andric
502*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI span<const byte, dynamic_extent> __as_bytes() const noexcept {
503*cb14a3feSDimitry Andric    return {reinterpret_cast<const byte*>(data()), size_bytes()};
504*cb14a3feSDimitry Andric  }
5050b57cec5SDimitry Andric
506*cb14a3feSDimitry Andric  _LIBCPP_HIDE_FROM_ABI span<byte, dynamic_extent> __as_writable_bytes() const noexcept {
507*cb14a3feSDimitry Andric    return {reinterpret_cast<byte*>(data()), size_bytes()};
508*cb14a3feSDimitry Andric  }
5090b57cec5SDimitry Andric
5100b57cec5SDimitry Andricprivate:
511bdd1243dSDimitry Andric  pointer __data_;
512bdd1243dSDimitry Andric  size_type __size_;
5130b57cec5SDimitry Andric};
5140b57cec5SDimitry Andric
515fe6060f1SDimitry Andrictemplate <class _Tp, size_t _Extent>
516fe6060f1SDimitry Andricinline constexpr bool ranges::enable_borrowed_range<span<_Tp, _Extent> > = true;
517fe6060f1SDimitry Andric
518fe6060f1SDimitry Andrictemplate <class _ElementType, size_t _Extent>
519fe6060f1SDimitry Andricinline constexpr bool ranges::enable_view<span<_ElementType, _Extent>> = true;
520fe6060f1SDimitry Andric
5210b57cec5SDimitry Andric//  as_bytes & as_writable_bytes
5220b57cec5SDimitry Andrictemplate <class _Tp, size_t _Extent>
523*cb14a3feSDimitry Andric_LIBCPP_HIDE_FROM_ABI auto as_bytes(span<_Tp, _Extent> __s) noexcept {
524*cb14a3feSDimitry Andric  return __s.__as_bytes();
525*cb14a3feSDimitry Andric}
5260b57cec5SDimitry Andric
527*cb14a3feSDimitry Andrictemplate <class _Tp, size_t _Extent>
528*cb14a3feSDimitry Andric  requires(!is_const_v<_Tp>)
529*cb14a3feSDimitry Andric_LIBCPP_HIDE_FROM_ABI auto as_writable_bytes(span<_Tp, _Extent> __s) noexcept {
530*cb14a3feSDimitry Andric  return __s.__as_writable_bytes();
531*cb14a3feSDimitry Andric}
5320b57cec5SDimitry Andric
53306c3fb27SDimitry Andric#  if _LIBCPP_STD_VER >= 20
534349cc55cSDimitry Andrictemplate <contiguous_iterator _It, class _EndOrSize>
535349cc55cSDimitry Andricspan(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>;
53606c3fb27SDimitry Andric#  endif // _LIBCPP_STD_VER >= 20
537349cc55cSDimitry Andric
5380b57cec5SDimitry Andrictemplate <class _Tp, size_t _Sz>
5390b57cec5SDimitry Andricspan(_Tp (&)[_Sz]) -> span<_Tp, _Sz>;
5400b57cec5SDimitry Andric
5410b57cec5SDimitry Andrictemplate <class _Tp, size_t _Sz>
5420b57cec5SDimitry Andricspan(array<_Tp, _Sz>&) -> span<_Tp, _Sz>;
5430b57cec5SDimitry Andric
5440b57cec5SDimitry Andrictemplate <class _Tp, size_t _Sz>
5450b57cec5SDimitry Andricspan(const array<_Tp, _Sz>&) -> span<const _Tp, _Sz>;
5460b57cec5SDimitry Andric
547349cc55cSDimitry Andrictemplate <ranges::contiguous_range _Range>
548349cc55cSDimitry Andricspan(_Range&&) -> span<remove_reference_t<ranges::range_reference_t<_Range>>>;
5490b57cec5SDimitry Andric
55006c3fb27SDimitry Andric#endif // _LIBCPP_STD_VER >= 20
5510b57cec5SDimitry Andric
5520b57cec5SDimitry Andric_LIBCPP_END_NAMESPACE_STD
5530b57cec5SDimitry Andric
554e8d8bef9SDimitry Andric_LIBCPP_POP_MACROS
555e8d8bef9SDimitry Andric
556bdd1243dSDimitry Andric#if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
557bdd1243dSDimitry Andric#  include <concepts>
558bdd1243dSDimitry Andric#  include <functional>
559bdd1243dSDimitry Andric#  include <iterator>
56006c3fb27SDimitry Andric#  include <type_traits>
561bdd1243dSDimitry Andric#endif
562bdd1243dSDimitry Andric
5630b57cec5SDimitry Andric#endif // _LIBCPP_SPAN
564