scoped_allocator

Go to the documentation of this file.

// <scoped_allocator> -*- C++ -*-
 
// Copyright (C) 2011-2025 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
 
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
 
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.
 
/** @file include/scoped_allocator
 *  This is a Standard C++ Library header.
 */
 
#ifndef _SCOPED_ALLOCATOR
#define _SCOPED_ALLOCATOR 1
 
#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif
 
#if __cplusplus < 201103L
# include <bits/c++0x_warning.h>
#else
 
#include <tuple>
#include <bits/alloc_traits.h>
#include <bits/stl_pair.h>
#include <bits/uses_allocator.h>
#if __cplusplus > 201703L
# include <bits/uses_allocator_args.h>
#endif
 
#define __glibcxx_want_allocator_traits_is_always_equal
#include <bits/version.h>
 
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
 
  /**
   * @addtogroup allocators
   * @{
   */
 
  template<typename _OuterAlloc, typename... _InnerAllocs>
    class scoped_allocator_adaptor;
 
  /// @cond undocumented
 
  template<typename _Alloc>
    using __outer_allocator_t
      = decltype(std::declval<_Alloc>().outer_allocator());
 
  template<typename _Alloc, typename = void>
    struct __outermost_type
    {
      using type = _Alloc;
      static type& _S_outermost(_Alloc& __a) noexcept { return __a; }
    };
 
  template<typename _Alloc>
    struct __outermost_type<_Alloc, __void_t<__outer_allocator_t<_Alloc>>>
    : __outermost_type<
      typename remove_reference<__outer_allocator_t<_Alloc>>::type
    >
    {
      using __base = __outermost_type<
        typename remove_reference<__outer_allocator_t<_Alloc>>::type
      >;
 
      static typename __base::type&
      _S_outermost(_Alloc& __a) noexcept
      { return __base::_S_outermost(__a.outer_allocator()); }
    };
 
  // Implementation of the OUTERMOST pseudofunction
  template<typename _Alloc>
    inline typename __outermost_type<_Alloc>::type&
    __outermost(_Alloc& __a)
    { return __outermost_type<_Alloc>::_S_outermost(__a); }
 
  template<typename...>
    struct __inner_type_impl;
 
  template<typename _Outer>
    struct __inner_type_impl<_Outer>
    {
      typedef scoped_allocator_adaptor<_Outer> __type;
 
      __inner_type_impl() = default;
      __inner_type_impl(const __inner_type_impl&) = default;
      __inner_type_impl(__inner_type_impl&&) = default;
      __inner_type_impl& operator=(const __inner_type_impl&) = default;
      __inner_type_impl& operator=(__inner_type_impl&&) = default;
 
      template<typename _Alloc>
      __inner_type_impl(const __inner_type_impl<_Alloc>&) noexcept
      { }
 
      template<typename _Alloc>
      __inner_type_impl(__inner_type_impl<_Alloc>&&) noexcept
      { }
 
      __type&
      _M_get(__type* __p) noexcept { return *__p; }
 
      const __type&
      _M_get(const __type* __p) const noexcept { return *__p; }
 
      tuple<>
      _M_tie() const noexcept { return tuple<>(); }
 
      bool
      operator==(const __inner_type_impl&) const noexcept
      { return true; }
    };
 
  template<typename _Outer, typename _InnerHead, typename... _InnerTail>
    struct __inner_type_impl<_Outer, _InnerHead, _InnerTail...>
    {
      typedef scoped_allocator_adaptor<_InnerHead, _InnerTail...> __type;
 
      __inner_type_impl() = default;
      __inner_type_impl(const __inner_type_impl&) = default;
      __inner_type_impl(__inner_type_impl&&) = default;
      __inner_type_impl& operator=(const __inner_type_impl&) = default;
      __inner_type_impl& operator=(__inner_type_impl&&) = default;
 
      template<typename... _Allocs>
      __inner_type_impl(const __inner_type_impl<_Allocs...>& __other) noexcept
      : _M_inner(__other._M_inner) { }
 
      template<typename... _Allocs>
      __inner_type_impl(__inner_type_impl<_Allocs...>&& __other) noexcept
      : _M_inner(std::move(__other._M_inner)) { }
 
    template<typename... _Args>
      explicit
      __inner_type_impl(_Args&&... __args) noexcept
      : _M_inner(std::forward<_Args>(__args)...) { }
 
      __type&
      _M_get(void*) noexcept { return _M_inner; }
 
      const __type&
      _M_get(const void*) const noexcept { return _M_inner; }
 
      tuple<const _InnerHead&, const _InnerTail&...>
      _M_tie() const noexcept
      { return _M_inner._M_tie(); }
 
      bool
      operator==(const __inner_type_impl& __other) const noexcept
      { return _M_inner == __other._M_inner; }
 
    private:
      template<typename...> friend struct __inner_type_impl;
      template<typename, typename...> friend class scoped_allocator_adaptor;
 
      __type _M_inner;
    };
 
  /// @endcond
 
  /// An adaptor to recursively pass an allocator to the objects it constructs
  template<typename _OuterAlloc, typename... _InnerAllocs>
    class scoped_allocator_adaptor
    : public _OuterAlloc
    {
      typedef allocator_traits<_OuterAlloc> __traits;
 
      typedef __inner_type_impl<_OuterAlloc, _InnerAllocs...> __inner_type;
      __inner_type _M_inner;
 
      template<typename _Outer, typename... _Inner>
        friend class scoped_allocator_adaptor;
 
      template<typename...>
        friend struct __inner_type_impl;
 
      tuple<const _OuterAlloc&, const _InnerAllocs&...>
      _M_tie() const noexcept
      { return std::tuple_cat(std::tie(outer_allocator()), _M_inner._M_tie()); }
 
      template<typename _Alloc>
        using __outermost_alloc_traits
          = allocator_traits<typename __outermost_type<_Alloc>::type>;
 
#if ! __glibcxx_make_obj_using_allocator
      template<typename _Tp, typename... _Args>
        void
        _M_construct(__uses_alloc0, _Tp* __p, _Args&&... __args)
        {
          typedef __outermost_alloc_traits<scoped_allocator_adaptor> _O_traits;
          _O_traits::construct(__outermost(*this), __p,
                               std::forward<_Args>(__args)...);
        }
 
      typedef __uses_alloc1<typename __inner_type::__type> __uses_alloc1_;
      typedef __uses_alloc2<typename __inner_type::__type> __uses_alloc2_;
 
      template<typename _Tp, typename... _Args>
        void
        _M_construct(__uses_alloc1_, _Tp* __p, _Args&&... __args)
        {
          typedef __outermost_alloc_traits<scoped_allocator_adaptor> _O_traits;
          _O_traits::construct(__outermost(*this), __p,
                               allocator_arg, inner_allocator(),
                               std::forward<_Args>(__args)...);
        }
 
      template<typename _Tp, typename... _Args>
        void
        _M_construct(__uses_alloc2_, _Tp* __p, _Args&&... __args)
        {
          typedef __outermost_alloc_traits<scoped_allocator_adaptor> _O_traits;
          _O_traits::construct(__outermost(*this), __p,
                               std::forward<_Args>(__args)...,
                               inner_allocator());
        }
#endif // ! make_obj_using_allocator
 
      template<typename _Alloc>
        static _Alloc
        _S_select_on_copy(const _Alloc& __a)
        {
          typedef allocator_traits<_Alloc> __a_traits;
          return __a_traits::select_on_container_copy_construction(__a);
        }
 
      template<std::size_t... _Indices>
        scoped_allocator_adaptor(tuple<const _OuterAlloc&,
                                       const _InnerAllocs&...> __refs,
                                 _Index_tuple<_Indices...>)
        : _OuterAlloc(_S_select_on_copy(std::get<0>(__refs))),
          _M_inner(_S_select_on_copy(std::get<_Indices+1>(__refs))...)
        { }
 
      // Used to constrain constructors to disallow invalid conversions.
      template<typename _Alloc>
        using _Constructible = typename enable_if<
            is_constructible<_OuterAlloc, _Alloc>::value
          >::type;
 
      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 2975. Missing case for pair construction in scoped [...] allocators
      template<typename _Tp>
        struct __not_pair { using type = void; };
 
      template<typename _Tp, typename _Up>
        struct __not_pair<pair<_Tp, _Up>> { };
 
    public:
      typedef _OuterAlloc                       outer_allocator_type;
      typedef typename __inner_type::__type     inner_allocator_type;
 
      typedef typename __traits::value_type             value_type;
      typedef typename __traits::size_type              size_type;
      typedef typename __traits::difference_type        difference_type;
      typedef typename __traits::pointer                pointer;
      typedef typename __traits::const_pointer          const_pointer;
      typedef typename __traits::void_pointer           void_pointer;
      typedef typename __traits::const_void_pointer     const_void_pointer;
 
      typedef typename __or_<
        typename __traits::propagate_on_container_copy_assignment,
        typename allocator_traits<_InnerAllocs>::
          propagate_on_container_copy_assignment...>::type
          propagate_on_container_copy_assignment;
 
      typedef typename __or_<
        typename __traits::propagate_on_container_move_assignment,
        typename allocator_traits<_InnerAllocs>::
          propagate_on_container_move_assignment...>::type
          propagate_on_container_move_assignment;
 
      typedef typename __or_<
        typename __traits::propagate_on_container_swap,
        typename allocator_traits<_InnerAllocs>::
          propagate_on_container_swap...>::type
          propagate_on_container_swap;
 
      typedef typename __and_<
        typename __traits::is_always_equal,
        typename allocator_traits<_InnerAllocs>::is_always_equal...>::type
          is_always_equal;
 
      template <class _Tp>
        struct rebind
        {
          typedef scoped_allocator_adaptor<
            typename __traits::template rebind_alloc<_Tp>,
            _InnerAllocs...> other;
        };
 
      scoped_allocator_adaptor() : _OuterAlloc(), _M_inner() { }
 
      template<typename _Outer2, typename = _Constructible<_Outer2>>
        scoped_allocator_adaptor(_Outer2&& __outer,
                                 const _InnerAllocs&... __inner) noexcept
        : _OuterAlloc(std::forward<_Outer2>(__outer)),
          _M_inner(__inner...)
        { }
 
      scoped_allocator_adaptor(const scoped_allocator_adaptor& __other) noexcept
      : _OuterAlloc(__other.outer_allocator()),
        _M_inner(__other._M_inner)
      { }
 
      scoped_allocator_adaptor(scoped_allocator_adaptor&& __other) noexcept
      : _OuterAlloc(std::move(__other.outer_allocator())),
        _M_inner(std::move(__other._M_inner))
      { }
 
      template<typename _Outer2, typename = _Constructible<const _Outer2&>>
        scoped_allocator_adaptor(
          const scoped_allocator_adaptor<_Outer2, _InnerAllocs...>& __other
        ) noexcept
        : _OuterAlloc(__other.outer_allocator()),
          _M_inner(__other._M_inner)
        { }
 
      template<typename _Outer2, typename = _Constructible<_Outer2>>
        scoped_allocator_adaptor(
          scoped_allocator_adaptor<_Outer2, _InnerAllocs...>&& __other) noexcept
        : _OuterAlloc(std::move(__other.outer_allocator())),
          _M_inner(std::move(__other._M_inner))
        { }
 
      scoped_allocator_adaptor&
      operator=(const scoped_allocator_adaptor&) = default;
 
      scoped_allocator_adaptor&
      operator=(scoped_allocator_adaptor&&) = default;
 
      inner_allocator_type&
      inner_allocator() noexcept
      { return _M_inner._M_get(this); }
 
      const inner_allocator_type&
      inner_allocator() const noexcept
      { return _M_inner._M_get(this); }
 
      outer_allocator_type&
      outer_allocator() noexcept
      { return static_cast<_OuterAlloc&>(*this); }
 
      const outer_allocator_type&
      outer_allocator() const noexcept
      { return static_cast<const _OuterAlloc&>(*this); }
 
      _GLIBCXX_NODISCARD pointer
      allocate(size_type __n)
      { return __traits::allocate(outer_allocator(), __n); }
 
      _GLIBCXX_NODISCARD pointer
      allocate(size_type __n, const_void_pointer __hint)
      { return __traits::allocate(outer_allocator(), __n, __hint); }
 
      void deallocate(pointer __p, size_type __n) noexcept
      { return __traits::deallocate(outer_allocator(), __p, __n); }
 
      size_type max_size() const
      { return __traits::max_size(outer_allocator()); }
 
#if ! __glibcxx_make_obj_using_allocator
      template<typename _Tp, typename... _Args>
        typename __not_pair<_Tp>::type
        construct(_Tp* __p, _Args&&... __args)
        {
          auto& __inner = inner_allocator();
          auto __use_tag
            = std::__use_alloc<_Tp, inner_allocator_type, _Args...>(__inner);
          _M_construct(__use_tag, __p, std::forward<_Args>(__args)...);
        }
 
      template<typename _T1, typename _T2, typename... _Args1,
               typename... _Args2>
        void
        construct(pair<_T1, _T2>* __p, piecewise_construct_t,
                  tuple<_Args1...> __x, tuple<_Args2...> __y)
        {
          // _GLIBCXX_RESOLVE_LIB_DEFECTS
          // 2203.  wrong argument types for piecewise construction
          auto& __inner = inner_allocator();
          auto __x_use_tag
            = std::__use_alloc<_T1, inner_allocator_type, _Args1...>(__inner);
          auto __y_use_tag
            = std::__use_alloc<_T2, inner_allocator_type, _Args2...>(__inner);
          typename _Build_index_tuple<sizeof...(_Args1)>::__type __x_indices;
          typename _Build_index_tuple<sizeof...(_Args2)>::__type __y_indices;
          typedef __outermost_alloc_traits<scoped_allocator_adaptor> _O_traits;
          _O_traits::construct(__outermost(*this), __p, piecewise_construct,
                               _M_construct_p(__x_use_tag, __x_indices, __x),
                               _M_construct_p(__y_use_tag, __y_indices, __y));
        }
 
      template<typename _T1, typename _T2>
        void
        construct(pair<_T1, _T2>* __p)
        { construct(__p, piecewise_construct, tuple<>(), tuple<>()); }
 
      template<typename _T1, typename _T2, typename _Up, typename _Vp>
        void
        construct(pair<_T1, _T2>* __p, _Up&& __u, _Vp&& __v)
        {
          construct(__p, piecewise_construct,
                    std::forward_as_tuple(std::forward<_Up>(__u)),
                    std::forward_as_tuple(std::forward<_Vp>(__v)));
        }
 
      template<typename _T1, typename _T2, typename _Up, typename _Vp>
        void
        construct(pair<_T1, _T2>* __p, const pair<_Up, _Vp>& __x)
        {
          construct(__p, piecewise_construct,
                    std::forward_as_tuple(__x.first),
                    std::forward_as_tuple(__x.second));
        }
 
      template<typename _T1, typename _T2, typename _Up, typename _Vp>
        void
        construct(pair<_T1, _T2>* __p, pair<_Up, _Vp>&& __x)
        {
          construct(__p, piecewise_construct,
                    std::forward_as_tuple(std::forward<_Up>(__x.first)),
                    std::forward_as_tuple(std::forward<_Vp>(__x.second)));
        }
#else // make_obj_using_allocator
      template<typename _Tp, typename... _Args>
        __attribute__((__nonnull__))
        void
        construct(_Tp* __p, _Args&&... __args)
        {
          typedef __outermost_alloc_traits<scoped_allocator_adaptor> _O_traits;
          std::apply([__p, this](auto&&... __newargs) {
              _O_traits::construct(__outermost(*this), __p,
                  std::forward<decltype(__newargs)>(__newargs)...);
          },
          uses_allocator_construction_args<_Tp>(inner_allocator(),
            std::forward<_Args>(__args)...));
        }
#endif
 
      template<typename _Tp>
        void destroy(_Tp* __p)
        {
          typedef __outermost_alloc_traits<scoped_allocator_adaptor> _O_traits;
          _O_traits::destroy(__outermost(*this), __p);
        }
 
      scoped_allocator_adaptor
      select_on_container_copy_construction() const
      {
        typedef typename _Build_index_tuple<sizeof...(_InnerAllocs)>::__type
            _Indices;
        return scoped_allocator_adaptor(_M_tie(), _Indices());
      }
 
      template <typename _OutA1, typename _OutA2, typename... _InA>
      friend bool
      operator==(const scoped_allocator_adaptor<_OutA1, _InA...>& __a,
                 const scoped_allocator_adaptor<_OutA2, _InA...>& __b) noexcept;
 
    private:
#if ! __glibcxx_make_obj_using_allocator
      template<typename _Ind, typename... _Args>
        tuple<_Args&&...>
        _M_construct_p(__uses_alloc0, _Ind, tuple<_Args...>& __t)
        { return std::move(__t); }
 
      template<size_t... _Ind, typename... _Args>
        tuple<allocator_arg_t, inner_allocator_type&, _Args&&...>
        _M_construct_p(__uses_alloc1_, _Index_tuple<_Ind...>,
                       tuple<_Args...>& __t)
        {
          return { allocator_arg, inner_allocator(),
              std::get<_Ind>(std::move(__t))...
          };
        }
 
      template<size_t... _Ind, typename... _Args>
        tuple<_Args&&..., inner_allocator_type&>
        _M_construct_p(__uses_alloc2_, _Index_tuple<_Ind...>,
                       tuple<_Args...>& __t)
        {
          return { std::get<_Ind>(std::move(__t))..., inner_allocator() };
        }
#endif // ! make_obj_using_allocator
    };
 
  /// @related std::scoped_allocator_adaptor
  template <typename _OutA1, typename _OutA2, typename... _InA>
    inline bool
    operator==(const scoped_allocator_adaptor<_OutA1, _InA...>& __a,
               const scoped_allocator_adaptor<_OutA2, _InA...>& __b) noexcept
    {
      return __a.outer_allocator() == __b.outer_allocator()
          && __a._M_inner == __b._M_inner;
    }
 
#if __cpp_impl_three_way_comparison < 201907L
  /// @related std::scoped_allocator_adaptor
  template <typename _OutA1, typename _OutA2, typename... _InA>
    inline bool
    operator!=(const scoped_allocator_adaptor<_OutA1, _InA...>& __a,
               const scoped_allocator_adaptor<_OutA2, _InA...>& __b) noexcept
    { return !(__a == __b); }
#endif
 
  /// @}
 
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
 
#endif // C++11
 
#endif // _SCOPED_ALLOCATOR