Filename: //usr/include//c++/10/span

// 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 ranges::contiguous_range<_Range> && ranges::sized_range<_Range> && (ranges::borrowed_range<_Range> || is_const_v<element_type>) && (!__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>>) && __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<typename _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> 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>> = _Extent == 0 || _Extent == dynamic_extent; } _GLIBCXX_END_NAMESPACE_VERSION } // namespace std #endif // concepts #endif // C++20 #endif // _GLIBCXX_SPAN

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