master
1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#ifndef _LIBCPP___ALGORITHM_LEXICOGRAPHICAL_COMPARE_H
10#define _LIBCPP___ALGORITHM_LEXICOGRAPHICAL_COMPARE_H
11
12#include <__algorithm/comp.h>
13#include <__algorithm/min.h>
14#include <__algorithm/mismatch.h>
15#include <__algorithm/simd_utils.h>
16#include <__algorithm/unwrap_iter.h>
17#include <__config>
18#include <__functional/identity.h>
19#include <__iterator/iterator_traits.h>
20#include <__string/constexpr_c_functions.h>
21#include <__type_traits/desugars_to.h>
22#include <__type_traits/enable_if.h>
23#include <__type_traits/invoke.h>
24#include <__type_traits/is_equality_comparable.h>
25#include <__type_traits/is_integral.h>
26#include <__type_traits/is_trivially_lexicographically_comparable.h>
27#include <__type_traits/is_volatile.h>
28
29#if _LIBCPP_HAS_WIDE_CHARACTERS
30# include <cwchar>
31#endif
32
33#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
34# pragma GCC system_header
35#endif
36
37_LIBCPP_PUSH_MACROS
38#include <__undef_macros>
39
40_LIBCPP_BEGIN_NAMESPACE_STD
41
42template <class _Iter1, class _Sent1, class _Iter2, class _Sent2, class _Proj1, class _Proj2, class _Comp>
43_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool __lexicographical_compare(
44 _Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Sent2 __last2, _Comp& __comp, _Proj1& __proj1, _Proj2& __proj2) {
45 while (__first2 != __last2) {
46 if (__first1 == __last1 ||
47 std::__invoke(__comp, std::__invoke(__proj1, *__first1), std::__invoke(__proj2, *__first2)))
48 return true;
49 if (std::__invoke(__comp, std::__invoke(__proj2, *__first2), std::__invoke(__proj1, *__first1)))
50 return false;
51 ++__first1;
52 ++__first2;
53 }
54 return false;
55}
56
57#if _LIBCPP_STD_VER >= 14
58
59// If the comparison operation is equivalent to < and that is a total order, we know that we can use equality comparison
60// on that type instead to extract some information. Furthermore, if equality comparison on that type is trivial, the
61// user can't observe that we're calling it. So instead of using the user-provided total order, we use std::mismatch,
62// which uses equality comparison (and is vertorized). Additionally, if the type is trivially lexicographically
63// comparable, we can go one step further and use std::memcmp directly instead of calling std::mismatch.
64template <class _Tp,
65 class _Proj1,
66 class _Proj2,
67 class _Comp,
68 __enable_if_t<__desugars_to_v<__totally_ordered_less_tag, _Comp, _Tp, _Tp> && !is_volatile<_Tp>::value &&
69 __libcpp_is_trivially_equality_comparable<_Tp, _Tp>::value &&
70 __is_identity<_Proj1>::value && __is_identity<_Proj2>::value,
71 int> = 0>
72_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
73__lexicographical_compare(_Tp* __first1, _Tp* __last1, _Tp* __first2, _Tp* __last2, _Comp&, _Proj1&, _Proj2&) {
74 if constexpr (__is_trivially_lexicographically_comparable_v<_Tp, _Tp>) {
75 auto __res =
76 std::__constexpr_memcmp(__first1, __first2, __element_count(std::min(__last1 - __first1, __last2 - __first2)));
77 if (__res == 0)
78 return __last1 - __first1 < __last2 - __first2;
79 return __res < 0;
80 }
81# if _LIBCPP_HAS_WIDE_CHARACTERS
82 else if constexpr (is_same<__remove_cv_t<_Tp>, wchar_t>::value) {
83 auto __res = std::__constexpr_wmemcmp(__first1, __first2, std::min(__last1 - __first1, __last2 - __first2));
84 if (__res == 0)
85 return __last1 - __first1 < __last2 - __first2;
86 return __res < 0;
87 }
88# endif // _LIBCPP_HAS_WIDE_CHARACTERS
89 else {
90 auto __res = std::mismatch(__first1, __last1, __first2, __last2);
91 if (__res.second == __last2)
92 return false;
93 if (__res.first == __last1)
94 return true;
95 return *__res.first < *__res.second;
96 }
97}
98
99#endif // _LIBCPP_STD_VER >= 14
100
101template <class _InputIterator1, class _InputIterator2, class _Compare>
102[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool lexicographical_compare(
103 _InputIterator1 __first1,
104 _InputIterator1 __last1,
105 _InputIterator2 __first2,
106 _InputIterator2 __last2,
107 _Compare __comp) {
108 __identity __proj;
109 return std::__lexicographical_compare(
110 std::__unwrap_iter(__first1),
111 std::__unwrap_iter(__last1),
112 std::__unwrap_iter(__first2),
113 std::__unwrap_iter(__last2),
114 __comp,
115 __proj,
116 __proj);
117}
118
119template <class _InputIterator1, class _InputIterator2>
120[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool lexicographical_compare(
121 _InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _InputIterator2 __last2) {
122 return std::lexicographical_compare(__first1, __last1, __first2, __last2, __less<>());
123}
124
125_LIBCPP_END_NAMESPACE_STD
126
127_LIBCPP_POP_MACROS
128
129#endif // _LIBCPP___ALGORITHM_LEXICOGRAPHICAL_COMPARE_H