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130 lines
5.0 KiB
C++
130 lines
5.0 KiB
C++
//===----------------------------------------------------------------------===//
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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___ALGORITHM_LEXICOGRAPHICAL_COMPARE_H
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#define _LIBCPP___ALGORITHM_LEXICOGRAPHICAL_COMPARE_H
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#include <__algorithm/comp.h>
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#include <__algorithm/min.h>
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#include <__algorithm/mismatch.h>
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#include <__algorithm/simd_utils.h>
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#include <__algorithm/unwrap_iter.h>
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#include <__config>
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#include <__functional/identity.h>
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#include <__iterator/iterator_traits.h>
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#include <__string/constexpr_c_functions.h>
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#include <__type_traits/desugars_to.h>
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#include <__type_traits/enable_if.h>
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#include <__type_traits/invoke.h>
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#include <__type_traits/is_equality_comparable.h>
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#include <__type_traits/is_integral.h>
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#include <__type_traits/is_trivially_lexicographically_comparable.h>
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#include <__type_traits/is_volatile.h>
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#if _LIBCPP_HAS_WIDE_CHARACTERS
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# include <cwchar>
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#endif
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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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template <class _Iter1, class _Sent1, class _Iter2, class _Sent2, class _Proj1, class _Proj2, class _Comp>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool __lexicographical_compare(
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_Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Sent2 __last2, _Comp& __comp, _Proj1& __proj1, _Proj2& __proj2) {
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while (__first2 != __last2) {
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if (__first1 == __last1 ||
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std::__invoke(__comp, std::__invoke(__proj1, *__first1), std::__invoke(__proj2, *__first2)))
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return true;
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if (std::__invoke(__comp, std::__invoke(__proj2, *__first2), std::__invoke(__proj1, *__first1)))
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return false;
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++__first1;
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++__first2;
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}
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return false;
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}
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#if _LIBCPP_STD_VER >= 14
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// If the comparison operation is equivalent to < and that is a total order, we know that we can use equality comparison
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// on that type instead to extract some information. Furthermore, if equality comparison on that type is trivial, the
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// user can't observe that we're calling it. So instead of using the user-provided total order, we use std::mismatch,
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// which uses equality comparison (and is vertorized). Additionally, if the type is trivially lexicographically
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// comparable, we can go one step further and use std::memcmp directly instead of calling std::mismatch.
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template <class _Tp,
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class _Proj1,
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class _Proj2,
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class _Comp,
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__enable_if_t<__desugars_to_v<__totally_ordered_less_tag, _Comp, _Tp, _Tp> && !is_volatile<_Tp>::value &&
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__libcpp_is_trivially_equality_comparable<_Tp, _Tp>::value &&
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__is_identity<_Proj1>::value && __is_identity<_Proj2>::value,
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int> = 0>
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
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__lexicographical_compare(_Tp* __first1, _Tp* __last1, _Tp* __first2, _Tp* __last2, _Comp&, _Proj1&, _Proj2&) {
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if constexpr (__is_trivially_lexicographically_comparable_v<_Tp, _Tp>) {
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auto __res =
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std::__constexpr_memcmp(__first1, __first2, __element_count(std::min(__last1 - __first1, __last2 - __first2)));
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if (__res == 0)
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return __last1 - __first1 < __last2 - __first2;
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return __res < 0;
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}
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# if _LIBCPP_HAS_WIDE_CHARACTERS
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else if constexpr (is_same<__remove_cv_t<_Tp>, wchar_t>::value) {
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auto __res = std::__constexpr_wmemcmp(__first1, __first2, std::min(__last1 - __first1, __last2 - __first2));
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if (__res == 0)
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return __last1 - __first1 < __last2 - __first2;
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return __res < 0;
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}
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# endif // _LIBCPP_HAS_WIDE_CHARACTERS
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else {
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auto __res = std::mismatch(__first1, __last1, __first2, __last2);
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if (__res.second == __last2)
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return false;
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if (__res.first == __last1)
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return true;
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return *__res.first < *__res.second;
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}
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}
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#endif // _LIBCPP_STD_VER >= 14
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template <class _InputIterator1, class _InputIterator2, class _Compare>
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[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool lexicographical_compare(
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_InputIterator1 __first1,
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_InputIterator1 __last1,
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_InputIterator2 __first2,
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_InputIterator2 __last2,
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_Compare __comp) {
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__identity __proj;
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return std::__lexicographical_compare(
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std::__unwrap_iter(__first1),
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std::__unwrap_iter(__last1),
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std::__unwrap_iter(__first2),
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std::__unwrap_iter(__last2),
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__comp,
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__proj,
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__proj);
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}
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template <class _InputIterator1, class _InputIterator2>
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[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool lexicographical_compare(
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_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _InputIterator2 __last2) {
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return std::lexicographical_compare(__first1, __last1, __first2, __last2, __less<>());
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}
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_LIBCPP_END_NAMESPACE_STD
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___ALGORITHM_LEXICOGRAPHICAL_COMPARE_H
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