| //===----------------------------------------------------------------------===// |
| // |
| // 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___ALGORITHM_LEXICOGRAPHICAL_COMPARE_THREE_WAY_H |
| #define _LIBCPP___ALGORITHM_LEXICOGRAPHICAL_COMPARE_THREE_WAY_H |
| |
| #include <__algorithm/min.h> |
| #include <__algorithm/three_way_comp_ref_type.h> |
| #include <__compare/compare_three_way.h> |
| #include <__compare/ordering.h> |
| #include <__concepts/arithmetic.h> |
| #include <__config> |
| #include <__iterator/iterator_traits.h> |
| #include <__type_traits/common_type.h> |
| #include <__type_traits/is_copy_constructible.h> |
| #include <__utility/move.h> |
| |
| #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 >= 20 |
| |
| // Fast path for random access iterators which computes the number of loop iterations up-front and |
| // then skips the iterator comparisons inside the loop. |
| template <class _InputIterator1, class _InputIterator2, class _Cmp> |
| _LIBCPP_HIDE_FROM_ABI constexpr auto __lexicographical_compare_three_way_fast_path( |
| _InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _InputIterator2 __last2, _Cmp& __comp) |
| -> decltype(__comp(*__first1, *__first2)) { |
| static_assert( |
| signed_integral<__iter_diff_t<_InputIterator1>>, "Using a non-integral difference_type is undefined behavior."); |
| static_assert( |
| signed_integral<__iter_diff_t<_InputIterator2>>, "Using a non-integral difference_type is undefined behavior."); |
| |
| using _Len1 = __iter_diff_t<_InputIterator1>; |
| using _Len2 = __iter_diff_t<_InputIterator2>; |
| using _Common = common_type_t<_Len1, _Len2>; |
| |
| _Len1 __len1 = __last1 - __first1; |
| _Len2 __len2 = __last2 - __first2; |
| _Common __min_len = std::min<_Common>(__len1, __len2); |
| |
| for (_Common __i = 0; __i < __min_len; ++__i) { |
| auto __c = __comp(*__first1, *__first2); |
| if (__c != 0) { |
| return __c; |
| } |
| ++__first1; |
| ++__first2; |
| } |
| |
| return __len1 <=> __len2; |
| } |
| |
| // Unoptimized implementation which compares the iterators against the end in every loop iteration |
| template <class _InputIterator1, class _InputIterator2, class _Cmp> |
| _LIBCPP_HIDE_FROM_ABI constexpr auto __lexicographical_compare_three_way_slow_path( |
| _InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _InputIterator2 __last2, _Cmp& __comp) |
| -> decltype(__comp(*__first1, *__first2)) { |
| while (true) { |
| bool __exhausted1 = __first1 == __last1; |
| bool __exhausted2 = __first2 == __last2; |
| |
| if (__exhausted1 || __exhausted2) { |
| if (!__exhausted1) |
| return strong_ordering::greater; |
| if (!__exhausted2) |
| return strong_ordering::less; |
| return strong_ordering::equal; |
| } |
| |
| auto __c = __comp(*__first1, *__first2); |
| if (__c != 0) { |
| return __c; |
| } |
| |
| ++__first1; |
| ++__first2; |
| } |
| } |
| |
| template <class _InputIterator1, class _InputIterator2, class _Cmp> |
| _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr auto lexicographical_compare_three_way( |
| _InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _InputIterator2 __last2, _Cmp __comp) |
| -> decltype(__comp(*__first1, *__first2)) { |
| static_assert(__comparison_category<decltype(__comp(*__first1, *__first2))>, |
| "The comparator passed to lexicographical_compare_three_way must return a comparison category type."); |
| static_assert(std::is_copy_constructible_v<_InputIterator1>, "Iterators must be copy constructible."); |
| static_assert(std::is_copy_constructible_v<_InputIterator2>, "Iterators must be copy constructible."); |
| __three_way_comp_ref_type<_Cmp> __wrapped_comp_ref(__comp); |
| if constexpr (__is_cpp17_random_access_iterator<_InputIterator1>::value && |
| __is_cpp17_random_access_iterator<_InputIterator2>::value) { |
| return std::__lexicographical_compare_three_way_fast_path( |
| std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2), __wrapped_comp_ref); |
| } else { |
| // Unoptimized implementation which compares the iterators against the end in every loop iteration |
| return std::__lexicographical_compare_three_way_slow_path( |
| std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2), __wrapped_comp_ref); |
| } |
| } |
| |
| template <class _InputIterator1, class _InputIterator2> |
| _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr auto lexicographical_compare_three_way( |
| _InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _InputIterator2 __last2) { |
| return std::lexicographical_compare_three_way( |
| std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2), std::compare_three_way()); |
| } |
| |
| #endif // _LIBCPP_STD_VER >= 20 |
| |
| _LIBCPP_END_NAMESPACE_STD |
| |
| _LIBCPP_POP_MACROS |
| |
| #endif // _LIBCPP___ALGORITHM_LEXICOGRAPHICAL_COMPARE_THREE_WAY_H |