| // Components for manipulating non-owning sequences of objects -*- C++ -*- |
| |
| // Copyright (C) 2019-2020 Free Software Foundation, Inc. |
| // |
| // This file is part of the GNU ISO C++ Library. This library is free |
| // software; you can redistribute it and/or modify it under the |
| // terms of the GNU General Public License as published by the |
| // Free Software Foundation; either version 3, or (at your option) |
| // any later version. |
| |
| // This library is distributed in the hope that it will be useful, |
| // but WITHOUT ANY WARRANTY; without even the implied warranty of |
| // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| // GNU General Public License for more details. |
| |
| // Under Section 7 of GPL version 3, you are granted additional |
| // permissions described in the GCC Runtime Library Exception, version |
| // 3.1, as published by the Free Software Foundation. |
| |
| // You should have received a copy of the GNU General Public License and |
| // a copy of the GCC Runtime Library Exception along with this program; |
| // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
| // <http://www.gnu.org/licenses/>. |
| |
| /** @file span |
| * This is a Standard C++ Library header. |
| */ |
| |
| // |
| // P0122 span library |
| // Contributed by ThePhD |
| // |
| |
| #ifndef _GLIBCXX_SPAN |
| #define _GLIBCXX_SPAN 1 |
| |
| #pragma GCC system_header |
| |
| #if __cplusplus > 201703L |
| |
| #include <type_traits> |
| #include <array> |
| #include <bits/stl_iterator.h> |
| #include <bits/range_access.h> |
| |
| #if __cpp_lib_concepts |
| namespace std _GLIBCXX_VISIBILITY(default) |
| { |
| _GLIBCXX_BEGIN_NAMESPACE_VERSION |
| |
| #define __cpp_lib_span 202002L |
| |
| inline constexpr size_t dynamic_extent = static_cast<size_t>(-1); |
| |
| template<typename _Type, size_t _Extent> |
| class span; |
| |
| namespace __detail |
| { |
| template<typename _Tp> |
| struct __is_std_span : false_type { }; |
| |
| template<typename _Tp, size_t _Num> |
| struct __is_std_span<span<_Tp, _Num>> : true_type { }; |
| |
| template<typename _Tp> |
| struct __is_std_array : false_type { }; |
| |
| template<typename _Tp, size_t _Num> |
| struct __is_std_array<_GLIBCXX_STD_C::array<_Tp, _Num>> : true_type { }; |
| |
| #ifdef _GLIBCXX_DEBUG |
| template<typename _Tp, size_t _Num> |
| struct __is_std_array<__debug::array<_Tp, _Num>> : true_type { }; |
| #endif |
| |
| template<size_t _Extent> |
| class __extent_storage |
| { |
| public: |
| constexpr |
| __extent_storage(size_t) noexcept |
| { } |
| |
| static constexpr size_t |
| _M_extent() noexcept |
| { return _Extent; } |
| }; |
| |
| template<> |
| class __extent_storage<dynamic_extent> |
| { |
| public: |
| constexpr |
| __extent_storage(size_t __extent) noexcept |
| : _M_extent_value(__extent) |
| { } |
| |
| constexpr size_t |
| _M_extent() const noexcept |
| { return this->_M_extent_value; } |
| |
| private: |
| size_t _M_extent_value; |
| }; |
| } // namespace __detail |
| |
| template<typename _Type, size_t _Extent = dynamic_extent> |
| class span |
| { |
| template<size_t _Offset, size_t _Count> |
| static constexpr size_t |
| _S_subspan_extent() |
| { |
| if constexpr (_Count != dynamic_extent) |
| return _Count; |
| else if constexpr (extent != dynamic_extent) |
| return _Extent - _Offset; |
| else |
| return dynamic_extent; |
| } |
| |
| // _GLIBCXX_RESOLVE_LIB_DEFECTS |
| // 3255. span's array constructor is too strict |
| template<typename _Tp, size_t _ArrayExtent> |
| requires (_Extent == dynamic_extent || _ArrayExtent == _Extent) |
| using __is_compatible_array = __is_array_convertible<_Type, _Tp>; |
| |
| template<typename _Ref> |
| using __is_compatible_ref |
| = __is_array_convertible<_Type, remove_reference_t<_Ref>>; |
| |
| public: |
| // member types |
| using element_type = _Type; |
| using value_type = remove_cv_t<_Type>; |
| using size_type = size_t; |
| using difference_type = ptrdiff_t; |
| using pointer = _Type*; |
| using const_pointer = const _Type*; |
| using reference = element_type&; |
| using const_reference = const element_type&; |
| using iterator = __gnu_cxx::__normal_iterator<pointer, span>; |
| using reverse_iterator = std::reverse_iterator<iterator>; |
| |
| // member constants |
| static constexpr size_t extent = _Extent; |
| |
| // constructors, copy and assignment |
| |
| constexpr |
| span() noexcept |
| requires ((_Extent + 1u) <= 1u) |
| : _M_extent(0), _M_ptr(nullptr) |
| { } |
| |
| template<contiguous_iterator _It> |
| requires __is_compatible_ref<iter_reference_t<_It>>::value |
| constexpr explicit(extent != dynamic_extent) |
| span(_It __first, size_type __count) |
| noexcept |
| : _M_extent(__count), _M_ptr(std::to_address(__first)) |
| { |
| if constexpr (_Extent != dynamic_extent) |
| { |
| __glibcxx_assert(__count == _Extent); |
| } |
| } |
| |
| template<contiguous_iterator _It, sized_sentinel_for<_It> _End> |
| requires __is_compatible_ref<iter_reference_t<_It>>::value |
| && (!is_convertible_v<_End, size_type>) |
| constexpr explicit(extent != dynamic_extent) |
| span(_It __first, _End __last) |
| noexcept(noexcept(__last - __first)) |
| : _M_extent(static_cast<size_type>(__last - __first)), |
| _M_ptr(std::to_address(__first)) |
| { |
| if constexpr (_Extent != dynamic_extent) |
| { |
| __glibcxx_assert((__last - __first) == _Extent); |
| } |
| } |
| |
| template<size_t _ArrayExtent> |
| requires (_Extent == dynamic_extent || _ArrayExtent == _Extent) |
| constexpr |
| span(type_identity_t<element_type> (&__arr)[_ArrayExtent]) noexcept |
| : span(static_cast<pointer>(__arr), _ArrayExtent) |
| { } |
| |
| template<typename _Tp, size_t _ArrayExtent> |
| requires __is_compatible_array<_Tp, _ArrayExtent>::value |
| constexpr |
| span(array<_Tp, _ArrayExtent>& __arr) noexcept |
| : span(static_cast<pointer>(__arr.data()), _ArrayExtent) |
| { } |
| |
| template<typename _Tp, size_t _ArrayExtent> |
| requires __is_compatible_array<const _Tp, _ArrayExtent>::value |
| constexpr |
| span(const array<_Tp, _ArrayExtent>& __arr) noexcept |
| : span(static_cast<pointer>(__arr.data()), _ArrayExtent) |
| { } |
| |
| template<typename _Range> |
| requires (!__detail::__is_std_span<remove_cvref_t<_Range>>::value) |
| && (!__detail::__is_std_array<remove_cvref_t<_Range>>::value) |
| && (!is_array_v<remove_cvref_t<_Range>>) |
| && ranges::contiguous_range<_Range> && ranges::sized_range<_Range> |
| && (ranges::borrowed_range<_Range> || is_const_v<element_type>) |
| && __is_compatible_ref<ranges::range_reference_t<_Range>>::value |
| constexpr explicit(extent != dynamic_extent) |
| span(_Range&& __range) |
| noexcept(noexcept(ranges::data(__range)) |
| && noexcept(ranges::size(__range))) |
| : span(ranges::data(__range), ranges::size(__range)) |
| { |
| if constexpr (extent != dynamic_extent) |
| { |
| __glibcxx_assert(ranges::size(__range) == extent); |
| } |
| } |
| |
| constexpr |
| span(const span&) noexcept = default; |
| |
| template<typename _OType, size_t _OExtent> |
| requires (_Extent == dynamic_extent || _OExtent == dynamic_extent |
| || _Extent == _OExtent) |
| && (__is_array_convertible<_Type, _OType>::value) |
| constexpr |
| explicit(extent != dynamic_extent && _OExtent == dynamic_extent) |
| span(const span<_OType, _OExtent>& __s) noexcept |
| : _M_extent(__s.size()), _M_ptr(__s.data()) |
| { |
| if constexpr (extent != dynamic_extent) |
| { |
| __glibcxx_assert(__s.size() == extent); |
| } |
| } |
| |
| ~span() noexcept = default; |
| |
| constexpr span& |
| operator=(const span&) noexcept = default; |
| |
| // observers |
| |
| constexpr size_type |
| size() const noexcept |
| { return this->_M_extent._M_extent(); } |
| |
| constexpr size_type |
| size_bytes() const noexcept |
| { return this->_M_extent._M_extent() * sizeof(element_type); } |
| |
| [[nodiscard]] constexpr bool |
| empty() const noexcept |
| { return size() == 0; } |
| |
| // element access |
| |
| constexpr reference |
| front() const noexcept |
| { |
| __glibcxx_assert(!empty()); |
| return *this->_M_ptr; |
| } |
| |
| constexpr reference |
| back() const noexcept |
| { |
| __glibcxx_assert(!empty()); |
| return *(this->_M_ptr + (size() - 1)); |
| } |
| |
| constexpr reference |
| operator[](size_type __idx) const noexcept |
| { |
| __glibcxx_assert(__idx < size()); |
| return *(this->_M_ptr + __idx); |
| } |
| |
| constexpr pointer |
| data() const noexcept |
| { return this->_M_ptr; } |
| |
| // iterator support |
| |
| constexpr iterator |
| begin() const noexcept |
| { return iterator(this->_M_ptr); } |
| |
| constexpr iterator |
| end() const noexcept |
| { return iterator(this->_M_ptr + this->size()); } |
| |
| constexpr reverse_iterator |
| rbegin() const noexcept |
| { return reverse_iterator(this->end()); } |
| |
| constexpr reverse_iterator |
| rend() const noexcept |
| { return reverse_iterator(this->begin()); } |
| |
| // subviews |
| |
| template<size_t _Count> |
| constexpr span<element_type, _Count> |
| first() const noexcept |
| { |
| if constexpr (_Extent == dynamic_extent) |
| __glibcxx_assert(_Count <= size()); |
| else |
| static_assert(_Count <= extent); |
| using _Sp = span<element_type, _Count>; |
| return _Sp{ this->data(), _Count }; |
| } |
| |
| constexpr span<element_type, dynamic_extent> |
| first(size_type __count) const noexcept |
| { |
| __glibcxx_assert(__count <= size()); |
| return { this->data(), __count }; |
| } |
| |
| template<size_t _Count> |
| constexpr span<element_type, _Count> |
| last() const noexcept |
| { |
| if constexpr (_Extent == dynamic_extent) |
| __glibcxx_assert(_Count <= size()); |
| else |
| static_assert(_Count <= extent); |
| using _Sp = span<element_type, _Count>; |
| return _Sp{ this->data() + (this->size() - _Count), _Count }; |
| } |
| |
| constexpr span<element_type, dynamic_extent> |
| last(size_type __count) const noexcept |
| { |
| __glibcxx_assert(__count <= size()); |
| return { this->data() + (this->size() - __count), __count }; |
| } |
| |
| template<size_t _Offset, size_t _Count = dynamic_extent> |
| constexpr auto |
| subspan() const noexcept |
| -> span<element_type, _S_subspan_extent<_Offset, _Count>()> |
| { |
| if constexpr (_Extent == dynamic_extent) |
| { |
| __glibcxx_assert(_Offset <= size()); |
| } |
| else |
| static_assert(_Offset <= extent); |
| |
| using _Sp = span<element_type, _S_subspan_extent<_Offset, _Count>()>; |
| |
| if constexpr (_Count == dynamic_extent) |
| return _Sp{ this->data() + _Offset, this->size() - _Offset }; |
| else |
| { |
| if constexpr (_Extent == dynamic_extent) |
| { |
| __glibcxx_assert(_Count <= size()); |
| __glibcxx_assert(_Count <= (size() - _Offset)); |
| } |
| else |
| { |
| static_assert(_Count <= extent); |
| static_assert(_Count <= (extent - _Offset)); |
| } |
| return _Sp{ this->data() + _Offset, _Count }; |
| } |
| } |
| |
| constexpr span<element_type, dynamic_extent> |
| subspan(size_type __offset, size_type __count = dynamic_extent) const |
| noexcept |
| { |
| __glibcxx_assert(__offset <= size()); |
| if (__count == dynamic_extent) |
| __count = this->size() - __offset; |
| else |
| { |
| __glibcxx_assert(__count <= size()); |
| __glibcxx_assert(__offset + __count <= size()); |
| } |
| return {this->data() + __offset, __count}; |
| } |
| |
| private: |
| [[no_unique_address]] __detail::__extent_storage<extent> _M_extent; |
| pointer _M_ptr; |
| }; |
| |
| // deduction guides |
| |
| template<typename _Type, size_t _ArrayExtent> |
| span(_Type(&)[_ArrayExtent]) -> span<_Type, _ArrayExtent>; |
| |
| template<typename _Type, size_t _ArrayExtent> |
| span(array<_Type, _ArrayExtent>&) -> span<_Type, _ArrayExtent>; |
| |
| template<typename _Type, size_t _ArrayExtent> |
| span(const array<_Type, _ArrayExtent>&) |
| -> span<const _Type, _ArrayExtent>; |
| |
| template<contiguous_iterator _Iter, typename _End> |
| span(_Iter, _End) |
| -> span<remove_reference_t<iter_reference_t<_Iter>>>; |
| |
| template<ranges::contiguous_range _Range> |
| span(_Range &&) |
| -> span<remove_reference_t<ranges::range_reference_t<_Range&>>>; |
| |
| template<typename _Type, size_t _Extent> |
| inline |
| span<const byte, _Extent == dynamic_extent |
| ? dynamic_extent : _Extent * sizeof(_Type)> |
| as_bytes(span<_Type, _Extent> __sp) noexcept |
| { |
| auto data = reinterpret_cast<const byte*>(__sp.data()); |
| auto size = __sp.size_bytes(); |
| constexpr auto extent = _Extent == dynamic_extent |
| ? dynamic_extent : _Extent * sizeof(_Type); |
| return span<const byte, extent>{data, size}; |
| } |
| |
| template<typename _Type, size_t _Extent> |
| requires (!is_const_v<_Type>) |
| inline |
| span<byte, _Extent == dynamic_extent |
| ? dynamic_extent : _Extent * sizeof(_Type)> |
| as_writable_bytes(span<_Type, _Extent> __sp) noexcept |
| { |
| auto data = reinterpret_cast<byte*>(__sp.data()); |
| auto size = __sp.size_bytes(); |
| constexpr auto extent = _Extent == dynamic_extent |
| ? dynamic_extent : _Extent * sizeof(_Type); |
| return span<byte, extent>{data, size}; |
| } |
| |
| namespace ranges |
| { |
| // Opt-in to borrowed_range concept |
| template<typename _ElementType, size_t _Extent> |
| inline constexpr bool |
| enable_borrowed_range<span<_ElementType, _Extent>> = true; |
| |
| // Opt-in to view concept |
| template<typename _ElementType, size_t _Extent> |
| inline constexpr bool |
| enable_view<span<_ElementType, _Extent>> = true; |
| } |
| _GLIBCXX_END_NAMESPACE_VERSION |
| } // namespace std |
| #endif // concepts |
| #endif // C++20 |
| #endif // _GLIBCXX_SPAN |