libcxx/include/__utility/integer_sequence.h

   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___UTILITY_INTEGER_SEQUENCE_H
  10 #define _LIBCPP___UTILITY_INTEGER_SEQUENCE_H
  11
  12 #include <__config>
  13 #include <__type_traits/is_integral.h>
  14 #include <cstddef>
  15
  16 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  17 #  pragma GCC system_header
  18 #endif
  19
  20 _LIBCPP_BEGIN_NAMESPACE_STD
  21
  22 template <size_t...> struct __tuple_indices;
  23
  24 template <class _IdxType, _IdxType... _Values>
  25 struct __integer_sequence {
  26   template <template <class _OIdxType, _OIdxType...> class _ToIndexSeq, class _ToIndexType>
  27   using __convert = _ToIndexSeq<_ToIndexType, _Values...>;
  28
  29   template <size_t _Sp>
  30   using __to_tuple_indices = __tuple_indices<(_Values + _Sp)...>;
  31 };
  32
  33 #if !__has_builtin(__make_integer_seq) || defined(_LIBCPP_TESTING_FALLBACK_MAKE_INTEGER_SEQUENCE)
  34
  35 namespace __detail {
  36
  37 template<typename _Tp, size_t ..._Extra> struct __repeat;
  38 template<typename _Tp, _Tp ..._Np, size_t ..._Extra> struct __repeat<__integer_sequence<_Tp, _Np...>, _Extra...> {
  39   typedef _LIBCPP_NODEBUG __integer_sequence<_Tp,
  40                            _Np...,
  41                            sizeof...(_Np) + _Np...,
  42                            2 * sizeof...(_Np) + _Np...,
  43                            3 * sizeof...(_Np) + _Np...,
  44                            4 * sizeof...(_Np) + _Np...,
  45                            5 * sizeof...(_Np) + _Np...,
  46                            6 * sizeof...(_Np) + _Np...,
  47                            7 * sizeof...(_Np) + _Np...,
  48                            _Extra...> type;
  49 };
  50
  51 template<size_t _Np> struct __parity;
  52 template<size_t _Np> struct __make : __parity<_Np % 8>::template __pmake<_Np> {};
  53
  54 template<> struct __make<0> { typedef __integer_sequence<size_t> type; };
  55 template<> struct __make<1> { typedef __integer_sequence<size_t, 0> type; };
  56 template<> struct __make<2> { typedef __integer_sequence<size_t, 0, 1> type; };
  57 template<> struct __make<3> { typedef __integer_sequence<size_t, 0, 1, 2> type; };
  58 template<> struct __make<4> { typedef __integer_sequence<size_t, 0, 1, 2, 3> type; };
  59 template<> struct __make<5> { typedef __integer_sequence<size_t, 0, 1, 2, 3, 4> type; };
  60 template<> struct __make<6> { typedef __integer_sequence<size_t, 0, 1, 2, 3, 4, 5> type; };
  61 template<> struct __make<7> { typedef __integer_sequence<size_t, 0, 1, 2, 3, 4, 5, 6> type; };
  62
  63 template<> struct __parity<0> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type> {}; };
  64 template<> struct __parity<1> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 1> {}; };
  65 template<> struct __parity<2> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 2, _Np - 1> {}; };
  66 template<> struct __parity<3> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 3, _Np - 2, _Np - 1> {}; };
  67 template<> struct __parity<4> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
  68 template<> struct __parity<5> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 5, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
  69 template<> struct __parity<6> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 6, _Np - 5, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
  70 template<> struct __parity<7> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 7, _Np - 6, _Np - 5, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
  71
  72 } // namespace detail
  73
  74 #endif
  75
  76 #if __has_builtin(__make_integer_seq)
  77 template <size_t _Ep, size_t _Sp>
  78 using __make_indices_imp =
  79     typename __make_integer_seq<__integer_sequence, size_t, _Ep - _Sp>::template
  80     __to_tuple_indices<_Sp>;
  81 #else
  82 template <size_t _Ep, size_t _Sp>
  83 using __make_indices_imp =
  84     typename __detail::__make<_Ep - _Sp>::type::template __to_tuple_indices<_Sp>;
  85
  86 #endif
  87
  88 #if _LIBCPP_STD_VER >= 14
  89
  90 template<class _Tp, _Tp... _Ip>
  91 struct _LIBCPP_TEMPLATE_VIS integer_sequence
  92 {
  93     typedef _Tp value_type;
  94     static_assert( is_integral<_Tp>::value,
  95                   "std::integer_sequence can only be instantiated with an integral type" );
  96     static
  97     _LIBCPP_INLINE_VISIBILITY
  98     constexpr
  99     size_t
 100     size() noexcept { return sizeof...(_Ip); }
 101 };
 102
 103 template<size_t... _Ip>
 104     using index_sequence = integer_sequence<size_t, _Ip...>;
 105
 106 #if __has_builtin(__make_integer_seq) && !defined(_LIBCPP_TESTING_FALLBACK_MAKE_INTEGER_SEQUENCE)
 107
 108 template <class _Tp, _Tp _Ep>
 109 using __make_integer_sequence _LIBCPP_NODEBUG = __make_integer_seq<integer_sequence, _Tp, _Ep>;
 110
 111 #else
 112
 113 template<typename _Tp, _Tp _Np> using __make_integer_sequence_unchecked _LIBCPP_NODEBUG =
 114   typename __detail::__make<_Np>::type::template __convert<integer_sequence, _Tp>;
 115
 116 template <class _Tp, _Tp _Ep>
 117 struct __make_integer_sequence_checked
 118 {
 119     static_assert(is_integral<_Tp>::value,
 120                   "std::make_integer_sequence can only be instantiated with an integral type" );
 121     static_assert(0 <= _Ep, "std::make_integer_sequence must have a non-negative sequence length");
 122     // Workaround GCC bug by preventing bad installations when 0 <= _Ep
 123     // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68929
 124     typedef _LIBCPP_NODEBUG __make_integer_sequence_unchecked<_Tp, 0 <= _Ep ? _Ep : 0> type;
 125 };
 126
 127 template <class _Tp, _Tp _Ep>
 128 using __make_integer_sequence _LIBCPP_NODEBUG = typename __make_integer_sequence_checked<_Tp, _Ep>::type;
 129
 130 #endif
 131
 132 template<class _Tp, _Tp _Np>
 133     using make_integer_sequence = __make_integer_sequence<_Tp, _Np>;
 134
 135 template<size_t _Np>
 136     using make_index_sequence = make_integer_sequence<size_t, _Np>;
 137
 138 template<class... _Tp>
 139     using index_sequence_for = make_index_sequence<sizeof...(_Tp)>;
 140
 141 #  if _LIBCPP_STD_VER >= 20
 142 // Executes __func for every element in an index_sequence.
 143 template <size_t... _Index, class _Function>
 144 _LIBCPP_HIDE_FROM_ABI constexpr void __for_each_index_sequence(index_sequence<_Index...>, _Function __func) {
 145     (__func.template operator()<_Index>(), ...);
 146 }
 147 #  endif // _LIBCPP_STD_VER >= 20
 148
 149 #endif // _LIBCPP_STD_VER >= 14
 150
 151 _LIBCPP_END_NAMESPACE_STD
 152
 153 #endif // _LIBCPP___UTILITY_INTEGER_SEQUENCE_H