libcxx/include/__memory/uses_allocator.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___MEMORY_USES_ALLOCATOR_H
  11 #define _LIBCPP___MEMORY_USES_ALLOCATOR_H
  12
  13 #include <__config>
  14 #include <cstddef>
  15 #include <type_traits>
  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 template <class _Tp>
  24 struct __has_allocator_type
  25 {
  26 private:
  27     struct __two {char __lx; char __lxx;};
  28     template <class _Up> static __two __test(...);
  29     template <class _Up> static char __test(typename _Up::allocator_type* = 0);
  30 public:
  31     static const bool value = sizeof(__test<_Tp>(0)) == 1;
  32 };
  33
  34 template <class _Tp, class _Alloc, bool = __has_allocator_type<_Tp>::value>
  35 struct __uses_allocator
  36     : public integral_constant<bool,
  37         is_convertible<_Alloc, typename _Tp::allocator_type>::value>
  38 {
  39 };
  40
  41 template <class _Tp, class _Alloc>
  42 struct __uses_allocator<_Tp, _Alloc, false>
  43     : public false_type
  44 {
  45 };
  46
  47 template <class _Tp, class _Alloc>
  48 struct _LIBCPP_TEMPLATE_VIS uses_allocator
  49     : public __uses_allocator<_Tp, _Alloc>
  50 {
  51 };
  52
  53 #if _LIBCPP_STD_VER > 14
  54 template <class _Tp, class _Alloc>
  55 inline constexpr size_t uses_allocator_v = uses_allocator<_Tp, _Alloc>::value;
  56 #endif
  57
  58 _LIBCPP_END_NAMESPACE_STD
  59
  60 #endif // _LIBCPP___MEMORY_USES_ALLOCATOR_H