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1// -*- C++ -*-2//===----------------------------------------------------------------------===//3//4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.5// See https://llvm.org/LICENSE.txt for license information.6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception7//8//===----------------------------------------------------------------------===//9 10#ifndef _LIBCPP___RANGES_TAKE_VIEW_H11#define _LIBCPP___RANGES_TAKE_VIEW_H12 13#include <__algorithm/min.h>14#include <__algorithm/ranges_min.h>15#include <__assert>16#include <__concepts/constructible.h>17#include <__concepts/convertible_to.h>18#include <__config>19#include <__functional/bind_back.h>20#include <__fwd/span.h>21#include <__fwd/string_view.h>22#include <__iterator/concepts.h>23#include <__iterator/counted_iterator.h>24#include <__iterator/default_sentinel.h>25#include <__iterator/distance.h>26#include <__iterator/iterator_traits.h>27#include <__ranges/access.h>28#include <__ranges/all.h>29#include <__ranges/concepts.h>30#include <__ranges/empty_view.h>31#include <__ranges/enable_borrowed_range.h>32#include <__ranges/iota_view.h>33#include <__ranges/range_adaptor.h>34#include <__ranges/repeat_view.h>35#include <__ranges/size.h>36#include <__ranges/subrange.h>37#include <__ranges/view_interface.h>38#include <__type_traits/decay.h>39#include <__type_traits/is_nothrow_constructible.h>40#include <__type_traits/maybe_const.h>41#include <__type_traits/remove_cvref.h>42#include <__utility/auto_cast.h>43#include <__utility/forward.h>44#include <__utility/move.h>45 46#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)47# pragma GCC system_header48#endif49 50_LIBCPP_PUSH_MACROS51#include <__undef_macros>52 53_LIBCPP_BEGIN_NAMESPACE_STD54 55#if _LIBCPP_STD_VER >= 2056 57namespace ranges {58 59template <view _View>60class take_view : public view_interface<take_view<_View>> {61 _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();62 range_difference_t<_View> __count_ = 0;63 64 template <bool>65 class __sentinel;66 67public:68 _LIBCPP_HIDE_FROM_ABI take_view()69 requires default_initializable<_View>70 = default;71 72 _LIBCPP_HIDE_FROM_ABI constexpr _LIBCPP_EXPLICIT_SINCE_CXX2373 take_view(_View __base, range_difference_t<_View> __count)74 : __base_(std::move(__base)), __count_(__count) {75 _LIBCPP_ASSERT_UNCATEGORIZED(__count >= 0, "count has to be greater than or equal to zero");76 }77 78 _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&79 requires copy_constructible<_View>80 {81 return __base_;82 }83 84 _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }85 86 _LIBCPP_HIDE_FROM_ABI constexpr auto begin()87 requires(!__simple_view<_View>)88 {89 if constexpr (sized_range<_View>) {90 if constexpr (random_access_range<_View>) {91 return ranges::begin(__base_);92 } else {93 using _DifferenceT = range_difference_t<_View>;94 auto __size = size();95 return counted_iterator(ranges::begin(__base_), static_cast<_DifferenceT>(__size));96 }97 } else {98 return counted_iterator(ranges::begin(__base_), __count_);99 }100 }101 102 _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const103 requires range<const _View>104 {105 if constexpr (sized_range<const _View>) {106 if constexpr (random_access_range<const _View>) {107 return ranges::begin(__base_);108 } else {109 using _DifferenceT = range_difference_t<const _View>;110 auto __size = size();111 return counted_iterator(ranges::begin(__base_), static_cast<_DifferenceT>(__size));112 }113 } else {114 return counted_iterator(ranges::begin(__base_), __count_);115 }116 }117 118 _LIBCPP_HIDE_FROM_ABI constexpr auto end()119 requires(!__simple_view<_View>)120 {121 if constexpr (sized_range<_View>) {122 if constexpr (random_access_range<_View>) {123 return ranges::begin(__base_) + size();124 } else {125 return default_sentinel;126 }127 } else {128 return __sentinel<false>{ranges::end(__base_)};129 }130 }131 132 _LIBCPP_HIDE_FROM_ABI constexpr auto end() const133 requires range<const _View>134 {135 if constexpr (sized_range<const _View>) {136 if constexpr (random_access_range<const _View>) {137 return ranges::begin(__base_) + size();138 } else {139 return default_sentinel;140 }141 } else {142 return __sentinel<true>{ranges::end(__base_)};143 }144 }145 146 _LIBCPP_HIDE_FROM_ABI constexpr auto size()147 requires sized_range<_View>148 {149 auto __n = ranges::size(__base_);150 return ranges::min(__n, static_cast<decltype(__n)>(__count_));151 }152 153 _LIBCPP_HIDE_FROM_ABI constexpr auto size() const154 requires sized_range<const _View>155 {156 auto __n = ranges::size(__base_);157 return ranges::min(__n, static_cast<decltype(__n)>(__count_));158 }159};160 161template <view _View>162template <bool _Const>163class take_view<_View>::__sentinel {164 using _Base _LIBCPP_NODEBUG = __maybe_const<_Const, _View>;165 template <bool _OtherConst>166 using _Iter _LIBCPP_NODEBUG = counted_iterator<iterator_t<__maybe_const<_OtherConst, _View>>>;167 _LIBCPP_NO_UNIQUE_ADDRESS sentinel_t<_Base> __end_ = sentinel_t<_Base>();168 169 template <bool>170 friend class take_view<_View>::__sentinel;171 172public:173 _LIBCPP_HIDE_FROM_ABI __sentinel() = default;174 175 _LIBCPP_HIDE_FROM_ABI constexpr explicit __sentinel(sentinel_t<_Base> __end) : __end_(std::move(__end)) {}176 177 _LIBCPP_HIDE_FROM_ABI constexpr __sentinel(__sentinel<!_Const> __s)178 requires _Const && convertible_to<sentinel_t<_View>, sentinel_t<_Base>>179 : __end_(std::move(__s.__end_)) {}180 181 _LIBCPP_HIDE_FROM_ABI constexpr sentinel_t<_Base> base() const { return __end_; }182 183 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const _Iter<_Const>& __lhs, const __sentinel& __rhs) {184 return __lhs.count() == 0 || __lhs.base() == __rhs.__end_;185 }186 187 template <bool _OtherConst = !_Const>188 requires sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>189 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const _Iter<_OtherConst>& __lhs, const __sentinel& __rhs) {190 return __lhs.count() == 0 || __lhs.base() == __rhs.__end_;191 }192};193 194template <class _Range>195take_view(_Range&&, range_difference_t<_Range>) -> take_view<views::all_t<_Range>>;196 197template <class _Tp>198inline constexpr bool enable_borrowed_range<take_view<_Tp>> = enable_borrowed_range<_Tp>;199 200namespace views {201namespace __take {202 203template <class _Tp>204inline constexpr bool __is_empty_view = false;205 206template <class _Tp>207inline constexpr bool __is_empty_view<empty_view<_Tp>> = true;208 209template <class _Tp>210inline constexpr bool __is_passthrough_specialization = false;211 212template <class _Tp, size_t _Extent>213inline constexpr bool __is_passthrough_specialization<span<_Tp, _Extent>> = true;214 215template <class _CharT, class _Traits>216inline constexpr bool __is_passthrough_specialization<basic_string_view<_CharT, _Traits>> = true;217 218template <class _Iter, class _Sent, subrange_kind _Kind>219inline constexpr bool __is_passthrough_specialization<subrange<_Iter, _Sent, _Kind>> = true;220 221template <class _Tp>222inline constexpr bool __is_iota_specialization = false;223 224template <class _Np, class _Bound>225inline constexpr bool __is_iota_specialization<iota_view<_Np, _Bound>> = true;226 227template <class _Tp>228struct __passthrough_type;229 230template <class _Tp, size_t _Extent>231struct __passthrough_type<span<_Tp, _Extent>> {232 using type _LIBCPP_NODEBUG = span<_Tp>;233};234 235template <class _CharT, class _Traits>236struct __passthrough_type<basic_string_view<_CharT, _Traits>> {237 using type _LIBCPP_NODEBUG = basic_string_view<_CharT, _Traits>;238};239 240template <class _Iter, class _Sent, subrange_kind _Kind>241 requires requires { typename subrange<_Iter>; }242struct __passthrough_type<subrange<_Iter, _Sent, _Kind>> {243 using type _LIBCPP_NODEBUG = subrange<_Iter>;244};245 246template <class _Tp>247using __passthrough_type_t _LIBCPP_NODEBUG = typename __passthrough_type<_Tp>::type;248 249struct __fn {250 // [range.take.overview]: the `empty_view` case.251 template <class _Range, convertible_to<range_difference_t<_Range>> _Np>252 requires __is_empty_view<remove_cvref_t<_Range>>253 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Np&&) const254 noexcept(noexcept(_LIBCPP_AUTO_CAST(std::forward<_Range>(__range))))255 -> decltype(_LIBCPP_AUTO_CAST(std::forward<_Range>(__range))) {256 return _LIBCPP_AUTO_CAST(std::forward<_Range>(__range));257 }258 259 // [range.take.overview]: the `span | basic_string_view | subrange` case.260 template <class _Range,261 convertible_to<range_difference_t<_Range>> _Np,262 class _RawRange = remove_cvref_t<_Range>,263 class _Dist = range_difference_t<_Range>>264 requires(!__is_empty_view<_RawRange> && random_access_range<_RawRange> && sized_range<_RawRange> &&265 __is_passthrough_specialization<_RawRange>)266 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto267 operator()(_Range&& __rng, _Np&& __n) const noexcept(noexcept(__passthrough_type_t<_RawRange>(268 ranges::begin(__rng), ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)))))269 -> decltype(__passthrough_type_t<_RawRange>(270 // Note: deliberately not forwarding `__rng` to guard against double moves.271 ranges::begin(__rng),272 ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)))) {273 return __passthrough_type_t<_RawRange>(274 ranges::begin(__rng), ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)));275 }276 277 // [range.take.overview]: the `iota_view` case.278 // clang-format off279 template <class _Range,280 convertible_to<range_difference_t<_Range>> _Np,281 class _RawRange = remove_cvref_t<_Range>,282 class _Dist = range_difference_t<_Range>>283 requires (!__is_empty_view<_RawRange> &&284 random_access_range<_RawRange> &&285 sized_range<_RawRange> &&286 __is_iota_specialization<_RawRange>)287 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI288 constexpr auto operator()(_Range&& __rng, _Np&& __n) const289 noexcept(noexcept(ranges::iota_view(290 *ranges::begin(__rng),291 *(ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)))292 )))293 -> decltype( ranges::iota_view(294 // Note: deliberately not forwarding `__rng` to guard against double moves.295 *ranges::begin(__rng),296 *(ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)))297 ))298 { return ranges::iota_view(299 *ranges::begin(__rng),300 *(ranges::begin(__rng) + std::min<_Dist>(ranges::distance(__rng), std::forward<_Np>(__n)))301 ); }302 303#if _LIBCPP_STD_VER >= 23304 // [range.take.overview]: the `repeat_view` "_RawRange models sized_range" case.305 template <class _Range,306 convertible_to<range_difference_t<_Range>> _Np,307 class _RawRange = remove_cvref_t<_Range>,308 class _Dist = range_difference_t<_Range>>309 requires(__is_repeat_specialization<_RawRange> && sized_range<_RawRange>)310 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Np&& __n) const311 noexcept(noexcept(views::repeat(*__range.__value_, std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n)))))312 -> decltype( views::repeat(*__range.__value_, std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n))))313 { return views::repeat(*__range.__value_, std::min<_Dist>(ranges::distance(__range), std::forward<_Np>(__n))); }314 315 // [range.take.overview]: the `repeat_view` "otherwise" case.316 template <class _Range,317 convertible_to<range_difference_t<_Range>> _Np,318 class _RawRange = remove_cvref_t<_Range>,319 class _Dist = range_difference_t<_Range>>320 requires(__is_repeat_specialization<_RawRange> && !sized_range<_RawRange>)321 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Np&& __n) const322 noexcept(noexcept(views::repeat(*__range.__value_, static_cast<_Dist>(__n))))323 -> decltype( views::repeat(*__range.__value_, static_cast<_Dist>(__n)))324 { return views::repeat(*__range.__value_, static_cast<_Dist>(__n)); }325#endif326 // clang-format on327 328 // [range.take.overview]: the "otherwise" case.329 template <class _Range, convertible_to<range_difference_t<_Range>> _Np, class _RawRange = remove_cvref_t<_Range>>330 // Note: without specifically excluding the other cases, GCC sees this overload as ambiguous with the other331 // overloads.332 requires(!(__is_empty_view<_RawRange> ||333# if _LIBCPP_STD_VER >= 23334 __is_repeat_specialization<_RawRange> ||335# endif336 (__is_iota_specialization<_RawRange> && sized_range<_RawRange> && random_access_range<_RawRange>) ||337 (__is_passthrough_specialization<_RawRange> && sized_range<_RawRange> &&338 random_access_range<_RawRange>)))339 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Np&& __n) const340 noexcept(noexcept(take_view(std::forward<_Range>(__range), std::forward<_Np>(__n))))341 -> decltype(take_view(std::forward<_Range>(__range), std::forward<_Np>(__n))) {342 return take_view(std::forward<_Range>(__range), std::forward<_Np>(__n));343 }344 345 template <class _Np>346 requires constructible_from<decay_t<_Np>, _Np>347 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Np&& __n) const348 noexcept(is_nothrow_constructible_v<decay_t<_Np>, _Np>) {349 return __pipeable(std::__bind_back(*this, std::forward<_Np>(__n)));350 }351};352 353} // namespace __take354 355inline namespace __cpo {356inline constexpr auto take = __take::__fn{};357} // namespace __cpo358} // namespace views359 360} // namespace ranges361 362#endif // _LIBCPP_STD_VER >= 20363 364_LIBCPP_END_NAMESPACE_STD365 366_LIBCPP_POP_MACROS367 368#endif // _LIBCPP___RANGES_TAKE_VIEW_H369