libcxx/include/__utility/in_place.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_IN_PLACE_H
  10 #define _LIBCPP___UTILITY_IN_PLACE_H
  11
  12 #include <__config>
  13 #include <__cstddef/size_t.h>
  14 #include <__type_traits/integral_constant.h>
  15 #include <__type_traits/remove_cvref.h>
  16
  17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  18 #  pragma GCC system_header
  19 #endif
  20
  21 _LIBCPP_BEGIN_NAMESPACE_STD
  22
  23 #if _LIBCPP_STD_VER >= 17
  24
  25 struct _LIBCPP_EXPORTED_FROM_ABI in_place_t {
  26   explicit in_place_t() = default;
  27 };
  28 inline constexpr in_place_t in_place{};
  29
  30 template <class _Tp>
  31 struct _LIBCPP_TEMPLATE_VIS in_place_type_t {
  32   _LIBCPP_HIDE_FROM_ABI explicit in_place_type_t() = default;
  33 };
  34 template <class _Tp>
  35 inline constexpr in_place_type_t<_Tp> in_place_type{};
  36
  37 template <size_t _Idx>
  38 struct _LIBCPP_TEMPLATE_VIS in_place_index_t {
  39   _LIBCPP_HIDE_FROM_ABI explicit in_place_index_t() = default;
  40 };
  41 template <size_t _Idx>
  42 inline constexpr in_place_index_t<_Idx> in_place_index{};
  43
  44 template <class _Tp>
  45 struct __is_inplace_type_imp : false_type {};
  46 template <class _Tp>
  47 struct __is_inplace_type_imp<in_place_type_t<_Tp>> : true_type {};
  48
  49 template <class _Tp>
  50 using __is_inplace_type = __is_inplace_type_imp<__remove_cvref_t<_Tp>>;
  51
  52 template <class _Tp>
  53 struct __is_inplace_index_imp : false_type {};
  54 template <size_t _Idx>
  55 struct __is_inplace_index_imp<in_place_index_t<_Idx>> : true_type {};
  56
  57 template <class _Tp>
  58 using __is_inplace_index = __is_inplace_index_imp<__remove_cvref_t<_Tp>>;
  59
  60 #endif // _LIBCPP_STD_VER >= 17
  61
  62 _LIBCPP_END_NAMESPACE_STD
  63
  64 #endif // _LIBCPP___UTILITY_IN_PLACE_H