libstdc++-v3/include/bits/uses_allocator.h

   1 // Uses-allocator Construction -*- C++ -*-
   2
   3 // Copyright (C) 2010-2016 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 #ifndef _USES_ALLOCATOR_H
  26 #define _USES_ALLOCATOR_H 1
  27
  28 #if __cplusplus < 201103L
  29 # include <bits/c++0x_warning.h>
  30 #else
  31
  32 #include <type_traits>
  33 #include <bits/move.h>
  34
  35 namespace std _GLIBCXX_VISIBILITY(default)
  36 {
  37 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  38
  39   struct __erased_type { };
  40
  41   template<typename _Alloc, typename _Tp>
  42     using __is_erased_or_convertible
  43       = __or_<is_same<_Tp, __erased_type>, is_convertible<_Alloc, _Tp>>;
  44
  45   /// [allocator.tag]
  46   struct allocator_arg_t { explicit allocator_arg_t() = default; };
  47
  48   constexpr allocator_arg_t allocator_arg = allocator_arg_t();
  49
  50   template<typename _Tp, typename _Alloc, typename = __void_t<>>
  51     struct __uses_allocator_helper
  52     : false_type { };
  53
  54   template<typename _Tp, typename _Alloc>
  55     struct __uses_allocator_helper<_Tp, _Alloc,
  56                                    __void_t<typename _Tp::allocator_type>>
  57     : __is_erased_or_convertible<_Alloc, typename _Tp::allocator_type>::type
  58     { };
  59
  60   /// [allocator.uses.trait]
  61   template<typename _Tp, typename _Alloc>
  62     struct uses_allocator
  63     : __uses_allocator_helper<_Tp, _Alloc>::type
  64     { };
  65
  66   struct __uses_alloc_base { };
  67
  68   struct __uses_alloc0 : __uses_alloc_base
  69   {
  70     struct _Sink { void operator=(const void*) { } } _M_a;
  71   };
  72
  73   template<typename _Alloc>
  74     struct __uses_alloc1 : __uses_alloc_base { const _Alloc* _M_a; };
  75
  76   template<typename _Alloc>
  77     struct __uses_alloc2 : __uses_alloc_base { const _Alloc* _M_a; };
  78
  79   template<bool, typename _Tp, typename _Alloc, typename... _Args>
  80     struct __uses_alloc;
  81
  82   template<typename _Tp, typename _Alloc, typename... _Args>
  83     struct __uses_alloc<true, _Tp, _Alloc, _Args...>
  84     : conditional<
  85         is_constructible<_Tp, allocator_arg_t, _Alloc, _Args...>::value,
  86         __uses_alloc1<_Alloc>,
  87         __uses_alloc2<_Alloc>>::type
  88     {
  89       static_assert(__or_<
  90           is_constructible<_Tp, allocator_arg_t, _Alloc, _Args...>,
  91           is_constructible<_Tp, _Args..., _Alloc>>::value, "construction with"
  92           " an allocator must be possible if uses_allocator is true");
  93     };
  94
  95   template<typename _Tp, typename _Alloc, typename... _Args>
  96     struct __uses_alloc<false, _Tp, _Alloc, _Args...>
  97     : __uses_alloc0 { };
  98
  99   template<typename _Tp, typename _Alloc, typename... _Args>
 100     using __uses_alloc_t =
 101       __uses_alloc<uses_allocator<_Tp, _Alloc>::value, _Tp, _Alloc, _Args...>;
 102
 103   template<typename _Tp, typename _Alloc, typename... _Args>
 104     inline __uses_alloc_t<_Tp, _Alloc, _Args...>
 105     __use_alloc(const _Alloc& __a)
 106     {
 107       __uses_alloc_t<_Tp, _Alloc, _Args...> __ret;
 108       __ret._M_a = std::__addressof(__a);
 109       return __ret;
 110     }
 111
 112 _GLIBCXX_END_NAMESPACE_VERSION
 113 } // namespace std
 114
 115 #endif
 116 #endif