libcxx/include/__memory/allocator_arg_t.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP___FUNCTIONAL_ALLOCATOR_ARG_T_H
  11 #define _LIBCPP___FUNCTIONAL_ALLOCATOR_ARG_T_H
  12
  13 #include <__config>
  14 #include <__memory/uses_allocator.h>
  15 #include <__type_traits/integral_constant.h>
  16 #include <__type_traits/is_constructible.h>
  17 #include <__type_traits/remove_cvref.h>
  18 #include <__utility/forward.h>
  19
  20 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  21 #  pragma GCC system_header
  22 #endif
  23
  24 _LIBCPP_BEGIN_NAMESPACE_STD
  25
  26 struct _LIBCPP_TEMPLATE_VIS allocator_arg_t { explicit allocator_arg_t() = default; };
  27
  28 #if _LIBCPP_STD_VER >= 17
  29 inline constexpr allocator_arg_t allocator_arg = allocator_arg_t();
  30 #elif !defined(_LIBCPP_CXX03_LANG)
  31 constexpr allocator_arg_t allocator_arg = allocator_arg_t();
  32 #endif
  33
  34 #ifndef _LIBCPP_CXX03_LANG
  35
  36 // allocator construction
  37
  38 template <class _Tp, class _Alloc, class ..._Args>
  39 struct __uses_alloc_ctor_imp
  40 {
  41     typedef _LIBCPP_NODEBUG __remove_cvref_t<_Alloc> _RawAlloc;
  42     static const bool __ua = uses_allocator<_Tp, _RawAlloc>::value;
  43     static const bool __ic =
  44         is_constructible<_Tp, allocator_arg_t, _Alloc, _Args...>::value;
  45     static const int value = __ua ? 2 - __ic : 0;
  46 };
  47
  48 template <class _Tp, class _Alloc, class ..._Args>
  49 struct __uses_alloc_ctor
  50     : integral_constant<int, __uses_alloc_ctor_imp<_Tp, _Alloc, _Args...>::value>
  51     {};
  52
  53 template <class _Tp, class _Allocator, class... _Args>
  54 inline _LIBCPP_INLINE_VISIBILITY
  55 void __user_alloc_construct_impl (integral_constant<int, 0>, _Tp *__storage, const _Allocator &, _Args &&... __args )
  56 {
  57     new (__storage) _Tp (_VSTD::forward<_Args>(__args)...);
  58 }
  59
  60 // FIXME: This should have a version which takes a non-const alloc.
  61 template <class _Tp, class _Allocator, class... _Args>
  62 inline _LIBCPP_INLINE_VISIBILITY
  63 void __user_alloc_construct_impl (integral_constant<int, 1>, _Tp *__storage, const _Allocator &__a, _Args &&... __args )
  64 {
  65     new (__storage) _Tp (allocator_arg, __a, _VSTD::forward<_Args>(__args)...);
  66 }
  67
  68 // FIXME: This should have a version which takes a non-const alloc.
  69 template <class _Tp, class _Allocator, class... _Args>
  70 inline _LIBCPP_INLINE_VISIBILITY
  71 void __user_alloc_construct_impl (integral_constant<int, 2>, _Tp *__storage, const _Allocator &__a, _Args &&... __args )
  72 {
  73     new (__storage) _Tp (_VSTD::forward<_Args>(__args)..., __a);
  74 }
  75
  76 #endif // _LIBCPP_CXX03_LANG
  77
  78 _LIBCPP_END_NAMESPACE_STD
  79
  80 #endif // _LIBCPP___FUNCTIONAL_ALLOCATOR_ARG_T_H