mirror of
https://github.com/jart/cosmopolitan.git
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329 lines
13 KiB
C++
329 lines
13 KiB
C++
// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___RANGES_DROP_VIEW_H
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#define _LIBCPP___RANGES_DROP_VIEW_H
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#include <__algorithm/min.h>
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#include <__assert>
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#include <__concepts/constructible.h>
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#include <__concepts/convertible_to.h>
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#include <__config>
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#include <__functional/bind_back.h>
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#include <__fwd/span.h>
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#include <__fwd/string_view.h>
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#include <__iterator/concepts.h>
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#include <__iterator/distance.h>
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#include <__iterator/iterator_traits.h>
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#include <__iterator/next.h>
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#include <__ranges/access.h>
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#include <__ranges/all.h>
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#include <__ranges/concepts.h>
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#include <__ranges/empty_view.h>
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#include <__ranges/enable_borrowed_range.h>
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#include <__ranges/iota_view.h>
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#include <__ranges/non_propagating_cache.h>
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#include <__ranges/range_adaptor.h>
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#include <__ranges/repeat_view.h>
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#include <__ranges/size.h>
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#include <__ranges/subrange.h>
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#include <__ranges/view_interface.h>
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#include <__type_traits/conditional.h>
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#include <__type_traits/decay.h>
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#include <__type_traits/is_nothrow_constructible.h>
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#include <__type_traits/make_unsigned.h>
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#include <__type_traits/remove_cvref.h>
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#include <__utility/auto_cast.h>
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#include <__utility/forward.h>
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#include <__utility/move.h>
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#include <cstddef>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_PUSH_MACROS
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#include <__undef_macros>
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_LIBCPP_BEGIN_NAMESPACE_STD
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#if _LIBCPP_STD_VER >= 20
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namespace ranges {
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template <view _View>
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class drop_view : public view_interface<drop_view<_View>> {
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// We cache begin() whenever ranges::next is not guaranteed O(1) to provide an
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// amortized O(1) begin() method. If this is an input_range, then we cannot cache
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// begin because begin is not equality preserving.
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// Note: drop_view<input-range>::begin() is still trivially amortized O(1) because
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// one can't call begin() on it more than once.
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static constexpr bool _UseCache = forward_range<_View> && !(random_access_range<_View> && sized_range<_View>);
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using _Cache = _If<_UseCache, __non_propagating_cache<iterator_t<_View>>, __empty_cache>;
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_LIBCPP_NO_UNIQUE_ADDRESS _Cache __cached_begin_ = _Cache();
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range_difference_t<_View> __count_ = 0;
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_View __base_ = _View();
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public:
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_LIBCPP_HIDE_FROM_ABI drop_view()
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requires default_initializable<_View>
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= default;
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_LIBCPP_HIDE_FROM_ABI constexpr _LIBCPP_EXPLICIT_SINCE_CXX23
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drop_view(_View __base, range_difference_t<_View> __count)
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: __count_(__count), __base_(std::move(__base)) {
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_LIBCPP_ASSERT_UNCATEGORIZED(__count_ >= 0, "count must be greater than or equal to zero.");
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}
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_LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
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requires copy_constructible<_View>
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{
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return __base_;
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}
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_LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
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_LIBCPP_HIDE_FROM_ABI constexpr auto begin()
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requires(!(__simple_view<_View> && random_access_range<const _View> && sized_range<const _View>))
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{
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if constexpr (random_access_range<_View> && sized_range<_View>) {
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const auto __dist = std::min(ranges::distance(__base_), __count_);
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return ranges::begin(__base_) + __dist;
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}
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if constexpr (_UseCache)
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if (__cached_begin_.__has_value())
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return *__cached_begin_;
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auto __tmp = ranges::next(ranges::begin(__base_), __count_, ranges::end(__base_));
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if constexpr (_UseCache)
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__cached_begin_.__emplace(__tmp);
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return __tmp;
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}
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_LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
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requires random_access_range<const _View> && sized_range<const _View>
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{
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const auto __dist = std::min(ranges::distance(__base_), __count_);
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return ranges::begin(__base_) + __dist;
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}
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_LIBCPP_HIDE_FROM_ABI constexpr auto end()
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requires(!__simple_view<_View>)
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{
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return ranges::end(__base_);
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}
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_LIBCPP_HIDE_FROM_ABI constexpr auto end() const
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requires range<const _View>
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{
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return ranges::end(__base_);
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}
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_LIBCPP_HIDE_FROM_ABI static constexpr auto __size(auto& __self) {
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const auto __s = ranges::size(__self.__base_);
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const auto __c = static_cast<decltype(__s)>(__self.__count_);
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return __s < __c ? 0 : __s - __c;
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}
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_LIBCPP_HIDE_FROM_ABI constexpr auto size()
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requires sized_range<_View>
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{
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return __size(*this);
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}
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_LIBCPP_HIDE_FROM_ABI constexpr auto size() const
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requires sized_range<const _View>
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{
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return __size(*this);
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}
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};
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template <class _Range>
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drop_view(_Range&&, range_difference_t<_Range>) -> drop_view<views::all_t<_Range>>;
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template <class _Tp>
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inline constexpr bool enable_borrowed_range<drop_view<_Tp>> = enable_borrowed_range<_Tp>;
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namespace views {
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namespace __drop {
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template <class _Tp>
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inline constexpr bool __is_empty_view = false;
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template <class _Tp>
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inline constexpr bool __is_empty_view<empty_view<_Tp>> = true;
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template <class _Tp>
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inline constexpr bool __is_passthrough_specialization = false;
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template <class _Tp, size_t _Extent>
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inline constexpr bool __is_passthrough_specialization<span<_Tp, _Extent>> = true;
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template <class _CharT, class _Traits>
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inline constexpr bool __is_passthrough_specialization<basic_string_view<_CharT, _Traits>> = true;
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template <class _Np, class _Bound>
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inline constexpr bool __is_passthrough_specialization<iota_view<_Np, _Bound>> = true;
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template <class _Iter, class _Sent, subrange_kind _Kind>
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inline constexpr bool __is_passthrough_specialization<subrange<_Iter, _Sent, _Kind>> =
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!subrange<_Iter, _Sent, _Kind>::_StoreSize;
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template <class _Tp>
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inline constexpr bool __is_subrange_specialization_with_store_size = false;
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template <class _Iter, class _Sent, subrange_kind _Kind>
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inline constexpr bool __is_subrange_specialization_with_store_size<subrange<_Iter, _Sent, _Kind>> =
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subrange<_Iter, _Sent, _Kind>::_StoreSize;
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template <class _Tp>
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struct __passthrough_type;
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template <class _Tp, size_t _Extent>
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struct __passthrough_type<span<_Tp, _Extent>> {
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using type = span<_Tp>;
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};
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template <class _CharT, class _Traits>
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struct __passthrough_type<basic_string_view<_CharT, _Traits>> {
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using type = basic_string_view<_CharT, _Traits>;
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};
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template <class _Np, class _Bound>
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struct __passthrough_type<iota_view<_Np, _Bound>> {
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using type = iota_view<_Np, _Bound>;
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};
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template <class _Iter, class _Sent, subrange_kind _Kind>
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struct __passthrough_type<subrange<_Iter, _Sent, _Kind>> {
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using type = subrange<_Iter, _Sent, _Kind>;
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};
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template <class _Tp>
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using __passthrough_type_t = typename __passthrough_type<_Tp>::type;
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struct __fn {
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// [range.drop.overview]: the `empty_view` case.
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template <class _Range, convertible_to<range_difference_t<_Range>> _Np>
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requires __is_empty_view<remove_cvref_t<_Range>>
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Np&&) const
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noexcept(noexcept(_LIBCPP_AUTO_CAST(std::forward<_Range>(__range))))
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-> decltype(_LIBCPP_AUTO_CAST(std::forward<_Range>(__range))) {
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return _LIBCPP_AUTO_CAST(std::forward<_Range>(__range));
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}
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// [range.drop.overview]: the `span | basic_string_view | iota_view | subrange (StoreSize == false)` case.
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template <class _Range,
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convertible_to<range_difference_t<_Range>> _Np,
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class _RawRange = remove_cvref_t<_Range>,
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class _Dist = range_difference_t<_Range>>
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requires(!__is_empty_view<_RawRange> && random_access_range<_RawRange> && sized_range<_RawRange> &&
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__is_passthrough_specialization<_RawRange>)
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __rng, _Np&& __n) const
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noexcept(noexcept(__passthrough_type_t<_RawRange>(
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ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)), ranges::end(__rng))))
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-> decltype(__passthrough_type_t<_RawRange>(
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// Note: deliberately not forwarding `__rng` to guard against double moves.
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ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)),
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ranges::end(__rng))) {
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return __passthrough_type_t<_RawRange>(
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ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)), ranges::end(__rng));
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}
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// [range.drop.overview]: the `subrange (StoreSize == true)` case.
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template <class _Range,
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convertible_to<range_difference_t<_Range>> _Np,
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class _RawRange = remove_cvref_t<_Range>,
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class _Dist = range_difference_t<_Range>>
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requires(!__is_empty_view<_RawRange> && random_access_range<_RawRange> && sized_range<_RawRange> &&
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__is_subrange_specialization_with_store_size<_RawRange>)
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __rng, _Np&& __n) const noexcept(noexcept(
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_RawRange(ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)),
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ranges::end(__rng),
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std::__to_unsigned_like(ranges::distance(__rng) -
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std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n))))))
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-> decltype(_RawRange(
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// Note: deliberately not forwarding `__rng` to guard against double moves.
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ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)),
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ranges::end(__rng),
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std::__to_unsigned_like(ranges::distance(__rng) -
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std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n))))) {
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// Introducing local variables avoids calculating `min` and `distance` twice (at the cost of diverging from the
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// expression used in the `noexcept` clause and the return statement).
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auto __dist = ranges::distance(__rng);
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auto __clamped = std::min<_Dist>(__dist, std::forward<_Np>(__n));
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return _RawRange(ranges::begin(__rng) + __clamped, ranges::end(__rng), std::__to_unsigned_like(__dist - __clamped));
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}
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// clang-format off
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#if _LIBCPP_STD_VER >= 23
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// [range.drop.overview]: the `repeat_view` "_RawRange models sized_range" case.
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template <class _Range,
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convertible_to<range_difference_t<_Range>> _Np,
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class _RawRange = remove_cvref_t<_Range>,
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class _Dist = range_difference_t<_Range>>
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requires (__is_repeat_specialization<_RawRange> && sized_range<_RawRange>)
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Np&& __n) const
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noexcept(noexcept(views::repeat(*__range.__value_, ranges::distance(__range) - std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n)))))
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-> decltype( views::repeat(*__range.__value_, ranges::distance(__range) - std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n))))
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{ return views::repeat(*__range.__value_, ranges::distance(__range) - std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n))); }
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// [range.drop.overview]: the `repeat_view` "otherwise" case.
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template <class _Range,
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convertible_to<range_difference_t<_Range>> _Np,
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class _RawRange = remove_cvref_t<_Range>,
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class _Dist = range_difference_t<_Range>>
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requires (__is_repeat_specialization<_RawRange> && !sized_range<_RawRange>)
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI
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constexpr auto operator()(_Range&& __range, _Np&&) const
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noexcept(noexcept(_LIBCPP_AUTO_CAST(std::forward<_Range>(__range))))
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-> decltype( _LIBCPP_AUTO_CAST(std::forward<_Range>(__range)))
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{ return _LIBCPP_AUTO_CAST(std::forward<_Range>(__range)); }
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#endif
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// clang-format on
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// [range.drop.overview]: the "otherwise" case.
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template <class _Range, convertible_to<range_difference_t<_Range>> _Np, class _RawRange = remove_cvref_t<_Range>>
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// Note: without specifically excluding the other cases, GCC sees this overload as ambiguous with the other
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// overloads.
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requires(!(__is_empty_view<_RawRange> ||
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# if _LIBCPP_STD_VER >= 23
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__is_repeat_specialization<_RawRange> ||
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# endif
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(__is_subrange_specialization_with_store_size<_RawRange> && sized_range<_RawRange> &&
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random_access_range<_RawRange>) ||
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(__is_passthrough_specialization<_RawRange> && sized_range<_RawRange> &&
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random_access_range<_RawRange>)))
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Np&& __n) const
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noexcept(noexcept(drop_view(std::forward<_Range>(__range), std::forward<_Np>(__n))))
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-> decltype(drop_view(std::forward<_Range>(__range), std::forward<_Np>(__n))) {
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return drop_view(std::forward<_Range>(__range), std::forward<_Np>(__n));
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}
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template <class _Np>
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requires constructible_from<decay_t<_Np>, _Np>
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Np&& __n) const
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noexcept(is_nothrow_constructible_v<decay_t<_Np>, _Np>) {
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return __range_adaptor_closure_t(std::__bind_back(*this, std::forward<_Np>(__n)));
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}
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};
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} // namespace __drop
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inline namespace __cpo {
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inline constexpr auto drop = __drop::__fn{};
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} // namespace __cpo
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} // namespace views
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} // namespace ranges
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#endif // _LIBCPP_STD_VER >= 20
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_LIBCPP_END_NAMESPACE_STD
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___RANGES_DROP_VIEW_H
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