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20effc67 | 1 | // Copyright (c) 2018 Sergei Fedorov |
1e59de90 | 2 | // Copyright (c) 2019-2022 Antony Polukhin |
20effc67 TL |
3 | // |
4 | // Distributed under the Boost Software License, Version 1.0. (See accompanying | |
5 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
6 | ||
7 | #ifndef BOOST_PFR_DETAIL_MAKE_INTEGER_SEQUENCE_HPP | |
8 | #define BOOST_PFR_DETAIL_MAKE_INTEGER_SEQUENCE_HPP | |
9 | #pragma once | |
10 | ||
11 | #include <boost/pfr/detail/config.hpp> | |
12 | ||
13 | #include <type_traits> | |
14 | #include <utility> | |
15 | #include <cstddef> | |
16 | ||
17 | namespace boost { namespace pfr { namespace detail { | |
18 | ||
19 | #if BOOST_PFR_USE_STD_MAKE_INTEGRAL_SEQUENCE == 0 | |
20 | ||
21 | #ifdef __has_builtin | |
22 | # if __has_builtin(__make_integer_seq) | |
23 | # define BOOST_PFR_USE_MAKE_INTEGER_SEQ_BUILTIN | |
24 | # endif | |
25 | #endif | |
26 | ||
27 | #ifdef BOOST_PFR_USE_MAKE_INTEGER_SEQ_BUILTIN | |
28 | ||
29 | using std::integer_sequence; | |
30 | ||
31 | // Clang unable to use namespace qualified std::integer_sequence in __make_integer_seq. | |
32 | template <typename T, T N> | |
33 | using make_integer_sequence = __make_integer_seq<integer_sequence, T, N>; | |
34 | ||
35 | #undef BOOST_PFR_USE_MAKE_INTEGER_SEQ_BUILTIN | |
36 | ||
37 | #else | |
38 | ||
39 | template <typename T, typename U> | |
40 | struct join_sequences; | |
41 | ||
42 | template <typename T, T... A, T... B> | |
43 | struct join_sequences<std::integer_sequence<T, A...>, std::integer_sequence<T, B...>> { | |
44 | using type = std::integer_sequence<T, A..., B...>; | |
45 | }; | |
46 | ||
47 | template <typename T, T Min, T Max> | |
48 | struct build_sequence_impl { | |
49 | static_assert(Min < Max, "Start of range must be less than its end"); | |
50 | static constexpr T size = Max - Min; | |
51 | using type = typename join_sequences< | |
52 | typename build_sequence_impl<T, Min, Min + size / 2>::type, | |
53 | typename build_sequence_impl<T, Min + size / 2 + 1, Max>::type | |
54 | >::type; | |
55 | }; | |
56 | ||
57 | template <typename T, T V> | |
58 | struct build_sequence_impl<T, V, V> { | |
59 | using type = std::integer_sequence<T, V>; | |
60 | }; | |
61 | ||
62 | template <typename T, std::size_t N> | |
63 | struct make_integer_sequence_impl : build_sequence_impl<T, 0, N - 1> {}; | |
64 | ||
65 | template <typename T> | |
66 | struct make_integer_sequence_impl<T, 0> { | |
67 | using type = std::integer_sequence<T>; | |
68 | }; | |
69 | ||
70 | template <typename T, T N> | |
71 | using make_integer_sequence = typename make_integer_sequence_impl<T, N>::type; | |
72 | ||
73 | #endif // !defined BOOST_PFR_USE_MAKE_INTEGER_SEQ_BUILTIN | |
74 | #else // BOOST_PFR_USE_STD_MAKE_INTEGRAL_SEQUENCE == 1 | |
75 | ||
76 | template <typename T, T N> | |
77 | using make_integer_sequence = std::make_integer_sequence<T, N>; | |
78 | ||
79 | #endif // BOOST_PFR_USE_STD_MAKE_INTEGRAL_SEQUENCE == 1 | |
80 | ||
81 | template <std::size_t N> | |
82 | using make_index_sequence = make_integer_sequence<std::size_t, N>; | |
83 | ||
84 | template <typename... T> | |
85 | using index_sequence_for = make_index_sequence<sizeof...(T)>; | |
86 | ||
87 | }}} // namespace boost::pfr::detail | |
88 | ||
89 | #endif | |
90 |