| // -*- C++ -*- |
| //===----------------------------------------------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| #ifndef _LIBCPP___RANGES_TAKE_VIEW_H |
| #define _LIBCPP___RANGES_TAKE_VIEW_H |
| |
| #include <__algorithm/min.h> |
| #include <__algorithm/ranges_min.h> |
| #include <__config> |
| #include <__functional/bind_back.h> |
| #include <__fwd/span.h> |
| #include <__fwd/string_view.h> |
| #include <__iterator/concepts.h> |
| #include <__iterator/counted_iterator.h> |
| #include <__iterator/default_sentinel.h> |
| #include <__iterator/distance.h> |
| #include <__iterator/iterator_traits.h> |
| #include <__ranges/access.h> |
| #include <__ranges/all.h> |
| #include <__ranges/concepts.h> |
| #include <__ranges/empty_view.h> |
| #include <__ranges/enable_borrowed_range.h> |
| #include <__ranges/iota_view.h> |
| #include <__ranges/range_adaptor.h> |
| #include <__ranges/size.h> |
| #include <__ranges/subrange.h> |
| #include <__ranges/view_interface.h> |
| #include <__utility/auto_cast.h> |
| #include <__utility/forward.h> |
| #include <__utility/move.h> |
| #include <concepts> |
| #include <type_traits> |
| |
| #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) |
| # pragma GCC system_header |
| #endif |
| |
| _LIBCPP_PUSH_MACROS |
| #include <__undef_macros> |
| |
| _LIBCPP_BEGIN_NAMESPACE_STD |
| |
| #if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) |
| |
| namespace ranges { |
| |
| template<view _View> |
| class take_view : public view_interface<take_view<_View>> { |
| _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View(); |
| range_difference_t<_View> __count_ = 0; |
| |
| template<bool> class __sentinel; |
| |
| public: |
| _LIBCPP_HIDE_FROM_ABI |
| take_view() requires default_initializable<_View> = default; |
| |
| _LIBCPP_HIDE_FROM_ABI |
| constexpr take_view(_View __base, range_difference_t<_View> __count) |
| : __base_(std::move(__base)), __count_(__count) {} |
| |
| _LIBCPP_HIDE_FROM_ABI |
| constexpr _View base() const& requires copy_constructible<_View> { return __base_; } |
| |
| _LIBCPP_HIDE_FROM_ABI |
| constexpr _View base() && { return std::move(__base_); } |
| |
| _LIBCPP_HIDE_FROM_ABI |
| constexpr auto begin() requires (!__simple_view<_View>) { |
| if constexpr (sized_range<_View>) { |
| if constexpr (random_access_range<_View>) { |
| return ranges::begin(__base_); |
| } else { |
| using _DifferenceT = range_difference_t<_View>; |
| auto __size = size(); |
| return counted_iterator(ranges::begin(__base_), static_cast<_DifferenceT>(__size)); |
| } |
| } else { |
| return counted_iterator(ranges::begin(__base_), __count_); |
| } |
| } |
| |
| _LIBCPP_HIDE_FROM_ABI |
| constexpr auto begin() const requires range<const _View> { |
| if constexpr (sized_range<const _View>) { |
| if constexpr (random_access_range<const _View>) { |
| return ranges::begin(__base_); |
| } else { |
| using _DifferenceT = range_difference_t<const _View>; |
| auto __size = size(); |
| return counted_iterator(ranges::begin(__base_), static_cast<_DifferenceT>(__size)); |
| } |
| } else { |
| return counted_iterator(ranges::begin(__base_), __count_); |
| } |
| } |
| |
| _LIBCPP_HIDE_FROM_ABI |
| constexpr auto end() requires (!__simple_view<_View>) { |
| if constexpr (sized_range<_View>) { |
| if constexpr (random_access_range<_View>) { |
| return ranges::begin(__base_) + size(); |
| } else { |
| return default_sentinel; |
| } |
| } else { |
| return __sentinel<false>{ranges::end(__base_)}; |
| } |
| } |
| |
| _LIBCPP_HIDE_FROM_ABI |
| constexpr auto end() const requires range<const _View> { |
| if constexpr (sized_range<const _View>) { |
| if constexpr (random_access_range<const _View>) { |
| return ranges::begin(__base_) + size(); |
| } else { |
| return default_sentinel; |
| } |
| } else { |
| return __sentinel<true>{ranges::end(__base_)}; |
| } |
| } |
| |
| _LIBCPP_HIDE_FROM_ABI |
| constexpr auto size() requires sized_range<_View> { |
| auto __n = ranges::size(__base_); |
| return ranges::min(__n, static_cast<decltype(__n)>(__count_)); |
| } |
| |
| _LIBCPP_HIDE_FROM_ABI |
| constexpr auto size() const requires sized_range<const _View> { |
| auto __n = ranges::size(__base_); |
| return ranges::min(__n, static_cast<decltype(__n)>(__count_)); |
| } |
| }; |
| |
| template<view _View> |
| template<bool _Const> |
| class take_view<_View>::__sentinel { |
| using _Base = __maybe_const<_Const, _View>; |
| template<bool _OtherConst> |
| using _Iter = counted_iterator<iterator_t<__maybe_const<_OtherConst, _View>>>; |
| _LIBCPP_NO_UNIQUE_ADDRESS sentinel_t<_Base> __end_ = sentinel_t<_Base>(); |
| |
| template<bool> |
| friend class take_view<_View>::__sentinel; |
| |
| public: |
| _LIBCPP_HIDE_FROM_ABI |
| __sentinel() = default; |
| |
| _LIBCPP_HIDE_FROM_ABI |
| constexpr explicit __sentinel(sentinel_t<_Base> __end) : __end_(std::move(__end)) {} |
| |
| _LIBCPP_HIDE_FROM_ABI |
| constexpr __sentinel(__sentinel<!_Const> __s) |
| requires _Const && convertible_to<sentinel_t<_View>, sentinel_t<_Base>> |
| : __end_(std::move(__s.__end_)) {} |
| |
| _LIBCPP_HIDE_FROM_ABI |
| constexpr sentinel_t<_Base> base() const { return __end_; } |
| |
| _LIBCPP_HIDE_FROM_ABI |
| friend constexpr bool operator==(const _Iter<_Const>& __lhs, const __sentinel& __rhs) { |
| return __lhs.count() == 0 || __lhs.base() == __rhs.__end_; |
| } |
| |
| template<bool _OtherConst = !_Const> |
| requires sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>> |
| _LIBCPP_HIDE_FROM_ABI |
| friend constexpr bool operator==(const _Iter<_Const>& __lhs, const __sentinel& __rhs) { |
| return __lhs.count() == 0 || __lhs.base() == __rhs.__end_; |
| } |
| }; |
| |
| template<class _Range> |
| take_view(_Range&&, range_difference_t<_Range>) -> take_view<views::all_t<_Range>>; |
| |
| template<class _Tp> |
| inline constexpr bool enable_borrowed_range<take_view<_Tp>> = enable_borrowed_range<_Tp>; |
| |
| namespace views { |
| namespace __take { |
| |
| template <class _Tp> |
| inline constexpr bool __is_empty_view = false; |
| |
| template <class _Tp> |
| inline constexpr bool __is_empty_view<empty_view<_Tp>> = true; |
| |
| template <class _Tp> |
| inline constexpr bool __is_passthrough_specialization = false; |
| |
| template <class _Tp, size_t _Extent> |
| inline constexpr bool __is_passthrough_specialization<span<_Tp, _Extent>> = true; |
| |
| template <class _CharT, class _Traits> |
| inline constexpr bool __is_passthrough_specialization<basic_string_view<_CharT, _Traits>> = true; |
| |
| template <class _Iter, class _Sent, subrange_kind _Kind> |
| inline constexpr bool __is_passthrough_specialization<subrange<_Iter, _Sent, _Kind>> = true; |
| |
| template <class _Tp> |
| inline constexpr bool __is_iota_specialization = false; |
| |
| template <class _Np, class _Bound> |
| inline constexpr bool __is_iota_specialization<iota_view<_Np, _Bound>> = true; |
| |
| template <class _Tp> |
| struct __passthrough_type; |
| |
| template <class _Tp, size_t _Extent> |
| struct __passthrough_type<span<_Tp, _Extent>> { |
| using type = span<_Tp>; |
| }; |
| |
| template <class _CharT, class _Traits> |
| struct __passthrough_type<basic_string_view<_CharT, _Traits>> { |
| using type = basic_string_view<_CharT, _Traits>; |
| }; |
| |
| template <class _Iter, class _Sent, subrange_kind _Kind> |
| struct __passthrough_type<subrange<_Iter, _Sent, _Kind>> { |
| using type = subrange<_Iter>; |
| }; |
| |
| template <class _Tp> |
| using __passthrough_type_t = typename __passthrough_type<_Tp>::type; |
| |
| struct __fn { |
| // [range.take.overview]: the `empty_view` case. |
| template <class _Range, convertible_to<range_difference_t<_Range>> _Np> |
| requires __is_empty_view<remove_cvref_t<_Range>> |
| [[nodiscard]] _LIBCPP_HIDE_FROM_ABI |
| constexpr auto operator()(_Range&& __range, _Np&&) const |
| noexcept(noexcept(_LIBCPP_AUTO_CAST(std::forward<_Range>(__range)))) |
| -> decltype( _LIBCPP_AUTO_CAST(std::forward<_Range>(__range))) |
| { return _LIBCPP_AUTO_CAST(std::forward<_Range>(__range)); } |
| |
| // [range.take.overview]: the `span | basic_string_view | subrange` case. |
| template <class _Range, |
| convertible_to<range_difference_t<_Range>> _Np, |
| class _RawRange = remove_cvref_t<_Range>, |
| class _Dist = range_difference_t<_Range>> |
| requires (!__is_empty_view<_RawRange> && |
| random_access_range<_RawRange> && |
| sized_range<_RawRange> && |
| __is_passthrough_specialization<_RawRange>) |
| [[nodiscard]] _LIBCPP_HIDE_FROM_ABI |
| constexpr auto operator()(_Range&& __rng, _Np&& __n) const |
| noexcept(noexcept(__passthrough_type_t<_RawRange>( |
| ranges::begin(__rng), |
| ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)) |
| ))) |
| -> decltype( __passthrough_type_t<_RawRange>( |
| // Note: deliberately not forwarding `__rng` to guard against double moves. |
| ranges::begin(__rng), |
| ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)) |
| )) |
| { return __passthrough_type_t<_RawRange>( |
| ranges::begin(__rng), |
| ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)) |
| ); } |
| |
| // [range.take.overview]: the `iota_view` case. |
| template <class _Range, |
| convertible_to<range_difference_t<_Range>> _Np, |
| class _RawRange = remove_cvref_t<_Range>, |
| class _Dist = range_difference_t<_Range>> |
| requires (!__is_empty_view<_RawRange> && |
| random_access_range<_RawRange> && |
| sized_range<_RawRange> && |
| __is_iota_specialization<_RawRange>) |
| [[nodiscard]] _LIBCPP_HIDE_FROM_ABI |
| constexpr auto operator()(_Range&& __rng, _Np&& __n) const |
| noexcept(noexcept(ranges::iota_view( |
| *ranges::begin(__rng), |
| *ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)) |
| ))) |
| -> decltype( ranges::iota_view( |
| // Note: deliberately not forwarding `__rng` to guard against double moves. |
| *ranges::begin(__rng), |
| *ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)) |
| )) |
| { return ranges::iota_view( |
| *ranges::begin(__rng), |
| *ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)) |
| ); } |
| |
| // [range.take.overview]: the "otherwise" case. |
| template <class _Range, convertible_to<range_difference_t<_Range>> _Np, |
| class _RawRange = remove_cvref_t<_Range>> |
| // Note: without specifically excluding the other cases, GCC sees this overload as ambiguous with the other |
| // overloads. |
| requires (!(__is_empty_view<_RawRange> || |
| (__is_iota_specialization<_RawRange> && |
| sized_range<_RawRange> && |
| random_access_range<_RawRange>) || |
| (__is_passthrough_specialization<_RawRange> && |
| sized_range<_RawRange> && |
| random_access_range<_RawRange>) |
| )) |
| [[nodiscard]] _LIBCPP_HIDE_FROM_ABI |
| constexpr auto operator()(_Range&& __range, _Np&& __n) const |
| noexcept(noexcept(take_view(std::forward<_Range>(__range), std::forward<_Np>(__n)))) |
| -> decltype( take_view(std::forward<_Range>(__range), std::forward<_Np>(__n))) |
| { return take_view(std::forward<_Range>(__range), std::forward<_Np>(__n)); } |
| |
| template <class _Np> |
| requires constructible_from<decay_t<_Np>, _Np> |
| [[nodiscard]] _LIBCPP_HIDE_FROM_ABI |
| constexpr auto operator()(_Np&& __n) const |
| noexcept(is_nothrow_constructible_v<decay_t<_Np>, _Np>) |
| { return __range_adaptor_closure_t(std::__bind_back(*this, std::forward<_Np>(__n))); } |
| }; |
| |
| } // namespace __take |
| |
| inline namespace __cpo { |
| inline constexpr auto take = __take::__fn{}; |
| } // namespace __cpo |
| } // namespace views |
| |
| } // namespace ranges |
| |
| #endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) |
| |
| _LIBCPP_END_NAMESPACE_STD |
| |
| _LIBCPP_POP_MACROS |
| |
| #endif // _LIBCPP___RANGES_TAKE_VIEW_H |
