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// Components for manipulating non-owning sequences of objects -*- C++ -*- |
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|
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// Copyright (C) 2019-2021 Free Software Foundation, Inc. |
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// |
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// This file is part of the GNU ISO C++ Library. This library is free |
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// software; you can redistribute it and/or modify it under the |
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// terms of the GNU General Public License as published by the |
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// Free Software Foundation; either version 3, or (at your option) |
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// any later version. |
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|
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// This library is distributed in the hope that it will be useful, |
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// but WITHOUT ANY WARRANTY; without even the implied warranty of |
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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// GNU General Public License for more details. |
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|
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// Under Section 7 of GPL version 3, you are granted additional |
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// permissions described in the GCC Runtime Library Exception, version |
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// 3.1, as published by the Free Software Foundation. |
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|
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// You should have received a copy of the GNU General Public License and |
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// a copy of the GCC Runtime Library Exception along with this program; |
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
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// <http://www.gnu.org/licenses/>. |
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|
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/** @file span |
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* This is a Standard C++ Library header. |
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*/ |
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|
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// |
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// P0122 span library |
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// Contributed by ThePhD |
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// |
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|
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#ifndef _GLIBCXX_SPAN |
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#define _GLIBCXX_SPAN 1 |
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|
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#pragma GCC system_header |
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|
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#if __cplusplus > 201703L |
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|
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#include <array> |
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#include <cstddef> |
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#include <bits/stl_iterator.h> |
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#include <bits/ranges_base.h> |
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|
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#if __cpp_lib_concepts |
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namespace std _GLIBCXX_VISIBILITY(default) |
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{ |
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_GLIBCXX_BEGIN_NAMESPACE_VERSION |
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|
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#define __cpp_lib_span 202002L |
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|
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inline constexpr size_t dynamic_extent = static_cast<size_t>(-1); |
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|
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template<typename _Type, size_t _Extent> |
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class span; |
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|
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namespace __detail |
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{ |
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template<typename _Tp> |
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struct __is_std_span : false_type { }; |
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|
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template<typename _Tp, size_t _Num> |
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struct __is_std_span<span<_Tp, _Num>> : true_type { }; |
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|
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template<typename _Tp> |
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struct __is_std_array : false_type { }; |
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|
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template<typename _Tp, size_t _Num> |
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struct __is_std_array<std::array<_Tp, _Num>> : true_type { }; |
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|
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template<size_t _Extent> |
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class __extent_storage |
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{ |
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public: |
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constexpr |
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__extent_storage(size_t) noexcept |
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{ } |
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|
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static constexpr size_t |
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_M_extent() noexcept |
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{ return _Extent; } |
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}; |
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|
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template<> |
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class __extent_storage<dynamic_extent> |
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{ |
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public: |
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constexpr |
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__extent_storage(size_t __extent) noexcept |
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: _M_extent_value(__extent) |
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{ } |
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|
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constexpr size_t |
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_M_extent() const noexcept |
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{ return this->_M_extent_value; } |
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|
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private: |
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size_t _M_extent_value; |
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}; |
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} // namespace __detail |
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|
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template<typename _Type, size_t _Extent = dynamic_extent> |
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class span |
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{ |
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template<size_t _Offset, size_t _Count> |
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static constexpr size_t |
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_S_subspan_extent() |
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{ |
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if constexpr (_Count != dynamic_extent) |
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return _Count; |
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else if constexpr (extent != dynamic_extent) |
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return _Extent - _Offset; |
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else |
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return dynamic_extent; |
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} |
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|
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// _GLIBCXX_RESOLVE_LIB_DEFECTS |
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// 3255. span's array constructor is too strict |
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template<typename _Tp, size_t _ArrayExtent> |
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requires (_Extent == dynamic_extent || _ArrayExtent == _Extent) |
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using __is_compatible_array = __is_array_convertible<_Type, _Tp>; |
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|
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template<typename _Ref> |
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using __is_compatible_ref |
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= __is_array_convertible<_Type, remove_reference_t<_Ref>>; |
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|
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public: |
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// member types |
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using element_type = _Type; |
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using value_type = remove_cv_t<_Type>; |
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using size_type = size_t; |
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using difference_type = ptrdiff_t; |
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using pointer = _Type*; |
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using const_pointer = const _Type*; |
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using reference = element_type&; |
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using const_reference = const element_type&; |
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using iterator = __gnu_cxx::__normal_iterator<pointer, span>; |
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using reverse_iterator = std::reverse_iterator<iterator>; |
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|
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// member constants |
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static constexpr size_t extent = _Extent; |
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|
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// constructors, copy and assignment |
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|
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constexpr |
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span() noexcept |
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requires ((_Extent + 1u) <= 1u) |
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: _M_ptr(nullptr), _M_extent(0) |
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{ } |
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|
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template<contiguous_iterator _It> |
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requires __is_compatible_ref<iter_reference_t<_It>>::value |
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constexpr explicit(extent != dynamic_extent) |
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span(_It __first, size_type __count) |
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noexcept |
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: _M_ptr(std::to_address(__first)), _M_extent(__count) |
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{ |
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if constexpr (_Extent != dynamic_extent) |
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{ |
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__glibcxx_assert(__count == _Extent); |
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} |
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} |
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|
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template<contiguous_iterator _It, sized_sentinel_for<_It> _End> |
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requires __is_compatible_ref<iter_reference_t<_It>>::value |
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&& (!is_convertible_v<_End, size_type>) |
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constexpr explicit(extent != dynamic_extent) |
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span(_It __first, _End __last) |
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noexcept(noexcept(__last - __first)) |
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: _M_ptr(std::to_address(__first)), |
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_M_extent(static_cast<size_type>(__last - __first)) |
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{ |
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if constexpr (_Extent != dynamic_extent) |
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{ |
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__glibcxx_assert((__last - __first) == _Extent); |
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} |
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} |
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|
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template<size_t _ArrayExtent> |
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requires (_Extent == dynamic_extent || _ArrayExtent == _Extent) |
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constexpr |
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span(type_identity_t<element_type> (&__arr)[_ArrayExtent]) noexcept |
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: span(static_cast<pointer>(__arr), _ArrayExtent) |
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{ } |
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|
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template<typename _Tp, size_t _ArrayExtent> |
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requires __is_compatible_array<_Tp, _ArrayExtent>::value |
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constexpr |
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span(array<_Tp, _ArrayExtent>& __arr) noexcept |
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: span(static_cast<pointer>(__arr.data()), _ArrayExtent) |
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{ } |
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|
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template<typename _Tp, size_t _ArrayExtent> |
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requires __is_compatible_array<const _Tp, _ArrayExtent>::value |
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constexpr |
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span(const array<_Tp, _ArrayExtent>& __arr) noexcept |
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: span(static_cast<pointer>(__arr.data()), _ArrayExtent) |
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{ } |
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|
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template<typename _Range> |
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requires ranges::contiguous_range<_Range> && ranges::sized_range<_Range> |
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&& (ranges::borrowed_range<_Range> || is_const_v<element_type>) |
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&& (!__detail::__is_std_span<remove_cvref_t<_Range>>::value) |
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&& (!__detail::__is_std_array<remove_cvref_t<_Range>>::value) |
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&& (!is_array_v<remove_cvref_t<_Range>>) |
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&& __is_compatible_ref<ranges::range_reference_t<_Range>>::value |
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constexpr explicit(extent != dynamic_extent) |
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span(_Range&& __range) |
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noexcept(noexcept(ranges::data(__range)) |
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&& noexcept(ranges::size(__range))) |
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: span(ranges::data(__range), ranges::size(__range)) |
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{ |
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if constexpr (extent != dynamic_extent) |
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{ |
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__glibcxx_assert(ranges::size(__range) == extent); |
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} |
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} |
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|
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constexpr |
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span(const span&) noexcept = default; |
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|
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template<typename _OType, size_t _OExtent> |
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requires (_Extent == dynamic_extent || _OExtent == dynamic_extent |
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|| _Extent == _OExtent) |
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&& (__is_array_convertible<_Type, _OType>::value) |
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constexpr |
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explicit(extent != dynamic_extent && _OExtent == dynamic_extent) |
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span(const span<_OType, _OExtent>& __s) noexcept |
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: _M_extent(__s.size()), _M_ptr(__s.data()) |
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{ |
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if constexpr (extent != dynamic_extent) |
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{ |
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__glibcxx_assert(__s.size() == extent); |
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} |
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} |
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|
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~span() noexcept = default; |
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|
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constexpr span& |
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operator=(const span&) noexcept = default; |
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|
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// observers |
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|
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constexpr size_type |
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size() const noexcept |
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{ return this->_M_extent._M_extent(); } |
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|
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constexpr size_type |
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size_bytes() const noexcept |
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{ return this->_M_extent._M_extent() * sizeof(element_type); } |
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|
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[[nodiscard]] constexpr bool |
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empty() const noexcept |
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{ return size() == 0; } |
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|
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// element access |
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|
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constexpr reference |
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front() const noexcept |
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{ |
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__glibcxx_assert(!empty()); |
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return *this->_M_ptr; |
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} |
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|
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constexpr reference |
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back() const noexcept |
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{ |
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__glibcxx_assert(!empty()); |
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return *(this->_M_ptr + (size() - 1)); |
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} |
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|
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constexpr reference |
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operator[](size_type __idx) const noexcept |
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{ |
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__glibcxx_assert(__idx < size()); |
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return *(this->_M_ptr + __idx); |
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} |
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|
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constexpr pointer |
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data() const noexcept |
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{ return this->_M_ptr; } |
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|
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// iterator support |
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|
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constexpr iterator |
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begin() const noexcept |
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{ return iterator(this->_M_ptr); } |
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|
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constexpr iterator |
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end() const noexcept |
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{ return iterator(this->_M_ptr + this->size()); } |
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|
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constexpr reverse_iterator |
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rbegin() const noexcept |
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{ return reverse_iterator(this->end()); } |
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|
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constexpr reverse_iterator |
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rend() const noexcept |
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{ return reverse_iterator(this->begin()); } |
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|
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// subviews |
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|
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template<size_t _Count> |
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constexpr span<element_type, _Count> |
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first() const noexcept |
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{ |
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if constexpr (_Extent == dynamic_extent) |
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__glibcxx_assert(_Count <= size()); |
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else |
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static_assert(_Count <= extent); |
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using _Sp = span<element_type, _Count>; |
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return _Sp{ this->data(), _Count }; |
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} |
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|
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constexpr span<element_type, dynamic_extent> |
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first(size_type __count) const noexcept |
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{ |
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__glibcxx_assert(__count <= size()); |
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return { this->data(), __count }; |
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} |
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|
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template<size_t _Count> |
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constexpr span<element_type, _Count> |
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last() const noexcept |
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{ |
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if constexpr (_Extent == dynamic_extent) |
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__glibcxx_assert(_Count <= size()); |
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else |
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static_assert(_Count <= extent); |
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using _Sp = span<element_type, _Count>; |
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return _Sp{ this->data() + (this->size() - _Count), _Count }; |
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} |
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|
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constexpr span<element_type, dynamic_extent> |
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last(size_type __count) const noexcept |
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{ |
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__glibcxx_assert(__count <= size()); |
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return { this->data() + (this->size() - __count), __count }; |
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} |
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|
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template<size_t _Offset, size_t _Count = dynamic_extent> |
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constexpr auto |
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subspan() const noexcept |
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-> span<element_type, _S_subspan_extent<_Offset, _Count>()> |
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{ |
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if constexpr (_Extent == dynamic_extent) |
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{ |
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__glibcxx_assert(_Offset <= size()); |
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} |
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else |
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static_assert(_Offset <= extent); |
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|
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using _Sp = span<element_type, _S_subspan_extent<_Offset, _Count>()>; |
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|
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if constexpr (_Count == dynamic_extent) |
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return _Sp{ this->data() + _Offset, this->size() - _Offset }; |
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else |
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{ |
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if constexpr (_Extent == dynamic_extent) |
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{ |
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__glibcxx_assert(_Count <= size()); |
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__glibcxx_assert(_Count <= (size() - _Offset)); |
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} |
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else |
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{ |
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static_assert(_Count <= extent); |
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static_assert(_Count <= (extent - _Offset)); |
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} |
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return _Sp{ this->data() + _Offset, _Count }; |
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} |
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} |
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|
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constexpr span<element_type, dynamic_extent> |
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subspan(size_type __offset, size_type __count = dynamic_extent) const |
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noexcept |
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{ |
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__glibcxx_assert(__offset <= size()); |
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if (__count == dynamic_extent) |
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__count = this->size() - __offset; |
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else |
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{ |
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__glibcxx_assert(__count <= size()); |
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__glibcxx_assert(__offset + __count <= size()); |
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} |
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return {this->data() + __offset, __count}; |
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} |
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|
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private: |
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pointer _M_ptr; |
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[[no_unique_address]] __detail::__extent_storage<extent> _M_extent; |
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}; |
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|
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// deduction guides |
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|
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template<typename _Type, size_t _ArrayExtent> |
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span(_Type(&)[_ArrayExtent]) -> span<_Type, _ArrayExtent>; |
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|
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template<typename _Type, size_t _ArrayExtent> |
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span(array<_Type, _ArrayExtent>&) -> span<_Type, _ArrayExtent>; |
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|
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template<typename _Type, size_t _ArrayExtent> |
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span(const array<_Type, _ArrayExtent>&) |
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-> span<const _Type, _ArrayExtent>; |
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|
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template<contiguous_iterator _Iter, typename _End> |
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span(_Iter, _End) |
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-> span<remove_reference_t<iter_reference_t<_Iter>>>; |
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|
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template<typename _Range> |
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span(_Range &&) |
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-> span<remove_reference_t<ranges::range_reference_t<_Range&>>>; |
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|
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template<typename _Type, size_t _Extent> |
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inline |
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span<const byte, _Extent == dynamic_extent |
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? dynamic_extent : _Extent * sizeof(_Type)> |
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as_bytes(span<_Type, _Extent> __sp) noexcept |
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{ |
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auto data = reinterpret_cast<const byte*>(__sp.data()); |
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auto size = __sp.size_bytes(); |
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constexpr auto extent = _Extent == dynamic_extent |
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? dynamic_extent : _Extent * sizeof(_Type); |
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return span<const byte, extent>{data, size}; |
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} |
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|
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template<typename _Type, size_t _Extent> |
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requires (!is_const_v<_Type>) |
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inline |
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span<byte, _Extent == dynamic_extent |
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? dynamic_extent : _Extent * sizeof(_Type)> |
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as_writable_bytes(span<_Type, _Extent> __sp) noexcept |
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{ |
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auto data = reinterpret_cast<byte*>(__sp.data()); |
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auto size = __sp.size_bytes(); |
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constexpr auto extent = _Extent == dynamic_extent |
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? dynamic_extent : _Extent * sizeof(_Type); |
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return span<byte, extent>{data, size}; |
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} |
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|
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namespace ranges |
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{ |
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// Opt-in to borrowed_range concept |
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template<typename _ElementType, size_t _Extent> |
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inline constexpr bool |
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enable_borrowed_range<span<_ElementType, _Extent>> = true; |
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|
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// Opt-in to view concept |
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template<typename _ElementType, size_t _Extent> |
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inline constexpr bool |
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enable_view<span<_ElementType, _Extent>> |
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= _Extent == 0 || _Extent == dynamic_extent; |
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} |
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_GLIBCXX_END_NAMESPACE_VERSION |
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} // namespace std |
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#endif // concepts |
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#endif // C++20 |
| 458 |
#endif // _GLIBCXX_SPAN |
