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
  34 namespace std _GLIBCXX_VISIBILITY(default)
  35 {
  36 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  37
  38   struct __erased_type { };
  39
  40   template<typename _Alloc, typename _Tp>
  41     using __is_erased_or_convertible
  42       = __or_<is_same<_Tp, __erased_type>, is_convertible<_Alloc, _Tp>>;
  43
  44   /// [allocator.tag]
  45   struct allocator_arg_t { explicit allocator_arg_t() = default; };
  46
  47   constexpr allocator_arg_t allocator_arg = allocator_arg_t();
  48
  49   template<typename _Tp, typename _Alloc, typename = __void_t<>>
  50     struct __uses_allocator_helper
  51     : false_type { };
  52
  53   template<typename _Tp, typename _Alloc>
  54     struct __uses_allocator_helper<_Tp, _Alloc,
  55                                    __void_t<typename _Tp::allocator_type>>
  56     : __is_erased_or_convertible<_Alloc, typename _Tp::allocator_type>::type
  57     { };
  58
  59   /// [allocator.uses.trait]
  60   template<typename _Tp, typename _Alloc>
  61     struct uses_allocator
  62     : __uses_allocator_helper<_Tp, _Alloc>::type
  63     { };
  64
  65   struct __uses_alloc_base { };
  66
  67   struct __uses_alloc0 : __uses_alloc_base
  68   {
  69     struct _Sink { void operator=(const void*) { } } _M_a;
  70   };
  71
  72   template<typename _Alloc>
  73     struct __uses_alloc1 : __uses_alloc_base { const _Alloc* _M_a; };
  74
  75   template<typename _Alloc>
  76     struct __uses_alloc2 : __uses_alloc_base { const _Alloc* _M_a; };
  77
  78   template<bool, typename _Tp, typename _Alloc, typename... _Args>
  79     struct __uses_alloc;
  80
  81   template<typename _Tp, typename _Alloc, typename... _Args>
  82     struct __uses_alloc<true, _Tp, _Alloc, _Args...>
  83     : conditional<
  84         is_constructible<_Tp, allocator_arg_t, _Alloc, _Args...>::value,
  85         __uses_alloc1<_Alloc>,
  86         __uses_alloc2<_Alloc>>::type
  87     { };
  88
  89   template<typename _Tp, typename _Alloc, typename... _Args>
  90     struct __uses_alloc<false, _Tp, _Alloc, _Args...>
  91     : __uses_alloc0 { };
  92
  93   template<typename _Tp, typename _Alloc, typename... _Args>
  94     using __uses_alloc_t =
  95       __uses_alloc<uses_allocator<_Tp, _Alloc>::value, _Tp, _Alloc, _Args...>;
  96
  97   template<typename _Tp, typename _Alloc, typename... _Args>
  98     inline __uses_alloc_t<_Tp, _Alloc, _Args...>
  99     __use_alloc(const _Alloc& __a)
 100     {
 101       __uses_alloc_t<_Tp, _Alloc, _Args...> __ret;
 102       __ret._M_a = &__a;
 103       return __ret;
 104     }
 105
 106 _GLIBCXX_END_NAMESPACE_VERSION
 107 } // namespace std
 108
 109 #endif
 110 #endif