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_RANGES_MERGE_H
10 #define _LIBCPP___ALGORITHM_RANGES_MERGE_H
11 
12 #include <__algorithm/in_in_out_result.h>
13 #include <__algorithm/ranges_copy.h>
14 #include <__config>
15 #include <__functional/identity.h>
16 #include <__functional/invoke.h>
17 #include <__functional/ranges_operations.h>
18 #include <__iterator/concepts.h>
19 #include <__iterator/mergeable.h>
20 #include <__ranges/access.h>
21 #include <__ranges/concepts.h>
22 #include <__ranges/dangling.h>
23 #include <__type_traits/remove_cvref.h>
24 #include <__utility/move.h>
25 
26 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
27 #  pragma GCC system_header
28 #endif
29 
30 #if _LIBCPP_STD_VER >= 20
31 
32 _LIBCPP_BEGIN_NAMESPACE_STD
33 
34 namespace ranges {
35 
36 template <class _InIter1, class _InIter2, class _OutIter>
37 using merge_result = in_in_out_result<_InIter1, _InIter2, _OutIter>;
38 
39 namespace __merge {
40 
41 template < class _InIter1,
42            class _Sent1,
43            class _InIter2,
44            class _Sent2,
45            class _OutIter,
46            class _Comp,
47            class _Proj1,
48            class _Proj2>
49 _LIBCPP_HIDE_FROM_ABI constexpr merge_result<__remove_cvref_t<_InIter1>,
50                                              __remove_cvref_t<_InIter2>,
51                                              __remove_cvref_t<_OutIter>>
52 __merge_impl(_InIter1&& __first1,
53              _Sent1&& __last1,
54              _InIter2&& __first2,
55              _Sent2&& __last2,
56              _OutIter&& __result,
57              _Comp&& __comp,
58              _Proj1&& __proj1,
59              _Proj2&& __proj2) {
60   for (; __first1 != __last1 && __first2 != __last2; ++__result) {
61     if (std::invoke(__comp, std::invoke(__proj2, *__first2), std::invoke(__proj1, *__first1))) {
62       *__result = *__first2;
63       ++__first2;
64     } else {
65       *__result = *__first1;
66       ++__first1;
67     }
68   }
69   auto __ret1 = ranges::copy(std::move(__first1), std::move(__last1), std::move(__result));
70   auto __ret2 = ranges::copy(std::move(__first2), std::move(__last2), std::move(__ret1.out));
71   return {std::move(__ret1.in), std::move(__ret2.in), std::move(__ret2.out)};
72 }
73 
74 struct __fn {
75   template <input_iterator _InIter1,
76             sentinel_for<_InIter1> _Sent1,
77             input_iterator _InIter2,
78             sentinel_for<_InIter2> _Sent2,
79             weakly_incrementable _OutIter,
80             class _Comp  = less,
81             class _Proj1 = identity,
82             class _Proj2 = identity>
83     requires mergeable<_InIter1, _InIter2, _OutIter, _Comp, _Proj1, _Proj2>
84   _LIBCPP_HIDE_FROM_ABI constexpr merge_result<_InIter1, _InIter2, _OutIter> operator()(
85       _InIter1 __first1,
86       _Sent1 __last1,
87       _InIter2 __first2,
88       _Sent2 __last2,
89       _OutIter __result,
90       _Comp __comp   = {},
91       _Proj1 __proj1 = {},
92       _Proj2 __proj2 = {}) const {
93     return __merge::__merge_impl(__first1, __last1, __first2, __last2, __result, __comp, __proj1, __proj2);
94   }
95 
96   template <input_range _Range1,
97             input_range _Range2,
98             weakly_incrementable _OutIter,
99             class _Comp  = less,
100             class _Proj1 = identity,
101             class _Proj2 = identity>
102     requires mergeable<iterator_t<_Range1>, iterator_t<_Range2>, _OutIter, _Comp, _Proj1, _Proj2>
103   _LIBCPP_HIDE_FROM_ABI constexpr merge_result<borrowed_iterator_t<_Range1>, borrowed_iterator_t<_Range2>, _OutIter>
104   operator()(_Range1&& __range1,
105              _Range2&& __range2,
106              _OutIter __result,
107              _Comp __comp   = {},
108              _Proj1 __proj1 = {},
109              _Proj2 __proj2 = {}) const {
110     return __merge::__merge_impl(
111         ranges::begin(__range1),
112         ranges::end(__range1),
113         ranges::begin(__range2),
114         ranges::end(__range2),
115         __result,
116         __comp,
117         __proj1,
118         __proj2);
119   }
120 };
121 
122 } // namespace __merge
123 
124 inline namespace __cpo {
125 inline constexpr auto merge = __merge::__fn{};
126 } // namespace __cpo
127 } // namespace ranges
128 
129 _LIBCPP_END_NAMESPACE_STD
130 
131 #endif // _LIBCPP_STD_VER >= 20
132 
133 #endif // _LIBCPP___ALGORITHM_RANGES_MERGE_H
134