text: // Allocator traits -*- C++ -*-
  
  // Copyright (C) 2011-2019 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 bits/alloc_traits.h
   *  This is an internal header file, included by other library headers.
   *  Do not attempt to use it directly. @headername{memory}
   */
  
  #ifndef _ALLOC_TRAITS_H
  #define _ALLOC_TRAITS_H 1
  
  #if __cplusplus >= 201103L
  
  #include <bits/memoryfwd.h>
  #include <bits/ptr_traits.h>
  #include <ext/numeric_traits.h>
  
  #define __cpp_lib_allocator_traits_is_always_equal 201411
  
  namespace std _GLIBCXX_VISIBILITY(default)
  {
  _GLIBCXX_BEGIN_NAMESPACE_VERSION
  
    struct __allocator_traits_base
    {
      template<typename _Tp, typename _Up, typename = void>
        struct __rebind : __replace_first_arg<_Tp, _Up> { };
  
      template<typename _Tp, typename _Up>
        struct __rebind<_Tp, _Up,
  		      __void_t<typename _Tp::template rebind<_Up>::other>>
        { using type = typename _Tp::template rebind<_Up>::other; };
  
    protected:
      template<typename _Tp>
        using __pointer = typename _Tp::pointer;
      template<typename _Tp>
        using __c_pointer = typename _Tp::const_pointer;
      template<typename _Tp>
        using __v_pointer = typename _Tp::void_pointer;
      template<typename _Tp>
        using __cv_pointer = typename _Tp::const_void_pointer;
      template<typename _Tp>
        using __pocca = typename _Tp::propagate_on_container_copy_assignment;
      template<typename _Tp>
        using __pocma = typename _Tp::propagate_on_container_move_assignment;
      template<typename _Tp>
        using __pocs = typename _Tp::propagate_on_container_swap;
      template<typename _Tp>
        using __equal = typename _Tp::is_always_equal;
    };
  
    template<typename _Alloc, typename _Up>
      using __alloc_rebind
        = typename __allocator_traits_base::template __rebind<_Alloc, _Up>::type;
  
    /**
     * @brief  Uniform interface to all allocator types.
     * @ingroup allocators
    */
    template<typename _Alloc>
      struct allocator_traits : __allocator_traits_base
      {
        /// The allocator type
        typedef _Alloc allocator_type;
        /// The allocated type
        typedef typename _Alloc::value_type value_type;
  
        /**
         * @brief   The allocator's pointer type.
         *
         * @c Alloc::pointer if that type exists, otherwise @c value_type*
        */
        using pointer = __detected_or_t<value_type*, __pointer, _Alloc>;
  
      private:
        // Select _Func<_Alloc> or pointer_traits<pointer>::rebind<_Tp>
        template<template<typename> class _Func, typename _Tp, typename = void>
  	struct _Ptr
  	{
  	  using type = typename pointer_traits<pointer>::template rebind<_Tp>;
  	};
  
        template<template<typename> class _Func, typename _Tp>
  	struct _Ptr<_Func, _Tp, __void_t<_Func<_Alloc>>>
  	{
  	  using type = _Func<_Alloc>;
  	};
  
        // Select _A2::difference_type or pointer_traits<_Ptr>::difference_type
        template<typename _A2, typename _PtrT, typename = void>
  	struct _Diff
  	{ using type = typename pointer_traits<_PtrT>::difference_type; };
  
        template<typename _A2, typename _PtrT>
  	struct _Diff<_A2, _PtrT, __void_t<typename _A2::difference_type>>
  	{ using type = typename _A2::difference_type; };
  
        // Select _A2::size_type or make_unsigned<_DiffT>::type
        template<typename _A2, typename _DiffT, typename = void>
  	struct _Size : make_unsigned<_DiffT> { };
  
        template<typename _A2, typename _DiffT>
  	struct _Size<_A2, _DiffT, __void_t<typename _A2::size_type>>
  	{ using type = typename _A2::size_type; };
  
      public:
        /**
         * @brief   The allocator's const pointer type.
         *
         * @c Alloc::const_pointer if that type exists, otherwise
         * <tt> pointer_traits<pointer>::rebind<const value_type> </tt>
        */
        using const_pointer = typename _Ptr<__c_pointer, const value_type>::type;
  
        /**
         * @brief   The allocator's void pointer type.
         *
         * @c Alloc::void_pointer if that type exists, otherwise
         * <tt> pointer_traits<pointer>::rebind<void> </tt>
        */
        using void_pointer = typename _Ptr<__v_pointer, void>::type;
  
        /**
         * @brief   The allocator's const void pointer type.
         *
         * @c Alloc::const_void_pointer if that type exists, otherwise
         * <tt> pointer_traits<pointer>::rebind<const void> </tt>
        */
        using const_void_pointer = typename _Ptr<__cv_pointer, const void>::type;
  
        /**
         * @brief   The allocator's difference type
         *
         * @c Alloc::difference_type if that type exists, otherwise
         * <tt> pointer_traits<pointer>::difference_type </tt>
        */
        using difference_type = typename _Diff<_Alloc, pointer>::type;
  
        /**
         * @brief   The allocator's size type
         *
         * @c Alloc::size_type if that type exists, otherwise
         * <tt> make_unsigned<difference_type>::type </tt>
        */
        using size_type = typename _Size<_Alloc, difference_type>::type;
  
        /**
         * @brief   How the allocator is propagated on copy assignment
         *
         * @c Alloc::propagate_on_container_copy_assignment if that type exists,
         * otherwise @c false_type
        */
        using propagate_on_container_copy_assignment
  	= __detected_or_t<false_type, __pocca, _Alloc>;
  
        /**
         * @brief   How the allocator is propagated on move assignment
         *
         * @c Alloc::propagate_on_container_move_assignment if that type exists,
         * otherwise @c false_type
        */
        using propagate_on_container_move_assignment
  	= __detected_or_t<false_type, __pocma, _Alloc>;
  
        /**
         * @brief   How the allocator is propagated on swap
         *
         * @c Alloc::propagate_on_container_swap if that type exists,
         * otherwise @c false_type
        */
        using propagate_on_container_swap
  	= __detected_or_t<false_type, __pocs, _Alloc>;
  
        /**
         * @brief   Whether all instances of the allocator type compare equal.
         *
         * @c Alloc::is_always_equal if that type exists,
         * otherwise @c is_empty<Alloc>::type
        */
        using is_always_equal
  	= __detected_or_t<typename is_empty<_Alloc>::type, __equal, _Alloc>;
  
        template<typename _Tp>
  	using rebind_alloc = __alloc_rebind<_Alloc, _Tp>;
        template<typename _Tp>
  	using rebind_traits = allocator_traits<rebind_alloc<_Tp>>;
  
      private:
        template<typename _Alloc2>
  	static auto
  	_S_allocate(_Alloc2& __a, size_type __n, const_void_pointer __hint, int)
  	-> decltype(__a.allocate(__n, __hint))
  	{ return __a.allocate(__n, __hint); }
  
        template<typename _Alloc2>
  	static pointer
  	_S_allocate(_Alloc2& __a, size_type __n, const_void_pointer, ...)
  	{ return __a.allocate(__n); }
  
        template<typename _Tp, typename... _Args>
  	struct __construct_helper
  	{
  	  template<typename _Alloc2,
  	    typename = decltype(std::declval<_Alloc2*>()->construct(
  		  std::declval<_Tp*>(), std::declval<_Args>()...))>
  	    static true_type __test(int);
  
  	  template<typename>
  	    static false_type __test(...);
  
  	  using type = decltype(__test<_Alloc>(0));
  	};
  
        template<typename _Tp, typename... _Args>
  	using __has_construct
  	  = typename __construct_helper<_Tp, _Args...>::type;
  
        template<typename _Tp, typename... _Args>
  	static _Require<__has_construct<_Tp, _Args...>>
  	_S_construct(_Alloc& __a, _Tp* __p, _Args&&... __args)
  	noexcept(noexcept(__a.construct(__p, std::forward<_Args>(__args)...)))
  	{ __a.construct(__p, std::forward<_Args>(__args)...); }
  
        template<typename _Tp, typename... _Args>
  	static
  	_Require<__and_<__not_<__has_construct<_Tp, _Args...>>,
  			       is_constructible<_Tp, _Args...>>>
  	_S_construct(_Alloc&, _Tp* __p, _Args&&... __args)
  	noexcept(std::is_nothrow_constructible<_Tp, _Args...>::value)
  	{ ::new((void*)__p) _Tp(std::forward<_Args>(__args)...); }
  
        template<typename _Alloc2, typename _Tp>
  	static auto
  	_S_destroy(_Alloc2& __a, _Tp* __p, int)
  	noexcept(noexcept(__a.destroy(__p)))
  	-> decltype(__a.destroy(__p))
  	{ __a.destroy(__p); }
  
        template<typename _Alloc2, typename _Tp>
  	static void
  	_S_destroy(_Alloc2&, _Tp* __p, ...)
  	noexcept(std::is_nothrow_destructible<_Tp>::value)
  	{ __p->~_Tp(); }
  
        template<typename _Alloc2>
  	static auto
  	_S_max_size(_Alloc2& __a, int)
  	-> decltype(__a.max_size())
  	{ return __a.max_size(); }
  
        template<typename _Alloc2>
  	static size_type
  	_S_max_size(_Alloc2&, ...)
  	{
  	  // _GLIBCXX_RESOLVE_LIB_DEFECTS
  	  // 2466. allocator_traits::max_size() default behavior is incorrect
  	  return __gnu_cxx::__numeric_traits<size_type>::__max
  	    / sizeof(value_type);
  	}
  
        template<typename _Alloc2>
  	static auto
  	_S_select(_Alloc2& __a, int)
  	-> decltype(__a.select_on_container_copy_construction())
  	{ return __a.select_on_container_copy_construction(); }
  
        template<typename _Alloc2>
  	static _Alloc2
  	_S_select(_Alloc2& __a, ...)
  	{ return __a; }
  
      public:
  
        /**
         *  @brief  Allocate memory.
         *  @param  __a  An allocator.
         *  @param  __n  The number of objects to allocate space for.
         *
         *  Calls @c a.allocate(n)
        */
        _GLIBCXX_NODISCARD static pointer
        allocate(_Alloc& __a, size_type __n)
        { return __a.allocate(__n); }
  
        /**
         *  @brief  Allocate memory.
         *  @param  __a  An allocator.
         *  @param  __n  The number of objects to allocate space for.
         *  @param  __hint Aid to locality.
         *  @return Memory of suitable size and alignment for @a n objects
         *          of type @c value_type
         *
         *  Returns <tt> a.allocate(n, hint) </tt> if that expression is
         *  well-formed, otherwise returns @c a.allocate(n)
        */
        _GLIBCXX_NODISCARD static pointer
        allocate(_Alloc& __a, size_type __n, const_void_pointer __hint)
        { return _S_allocate(__a, __n, __hint, 0); }
  
        /**
         *  @brief  Deallocate memory.
         *  @param  __a  An allocator.
         *  @param  __p  Pointer to the memory to deallocate.
         *  @param  __n  The number of objects space was allocated for.
         *
         *  Calls <tt> a.deallocate(p, n) </tt>
        */
        static void
        deallocate(_Alloc& __a, pointer __p, size_type __n)
        { __a.deallocate(__p, __n); }
  
        /**
         *  @brief  Construct an object of type `_Tp`
         *  @param  __a  An allocator.
         *  @param  __p  Pointer to memory of suitable size and alignment for Tp
         *  @param  __args Constructor arguments.
         *
         *  Calls <tt> __a.construct(__p, std::forward<Args>(__args)...) </tt>
         *  if that expression is well-formed, otherwise uses placement-new
         *  to construct an object of type @a _Tp at location @a __p from the
         *  arguments @a __args...
        */
        template<typename _Tp, typename... _Args>
  	static auto construct(_Alloc& __a, _Tp* __p, _Args&&... __args)
  	noexcept(noexcept(_S_construct(__a, __p,
  				       std::forward<_Args>(__args)...)))
  	-> decltype(_S_construct(__a, __p, std::forward<_Args>(__args)...))
  	{ _S_construct(__a, __p, std::forward<_Args>(__args)...); }
  
        /**
         *  @brief  Destroy an object of type @a _Tp
         *  @param  __a  An allocator.
         *  @param  __p  Pointer to the object to destroy
         *
         *  Calls @c __a.destroy(__p) if that expression is well-formed,
         *  otherwise calls @c __p->~_Tp()
        */
        template<typename _Tp>
  	static void destroy(_Alloc& __a, _Tp* __p)
  	noexcept(noexcept(_S_destroy(__a, __p, 0)))
  	{ _S_destroy(__a, __p, 0); }
  
        /**
         *  @brief  The maximum supported allocation size
         *  @param  __a  An allocator.
         *  @return @c __a.max_size() or @c numeric_limits<size_type>::max()
         *
         *  Returns @c __a.max_size() if that expression is well-formed,
         *  otherwise returns @c numeric_limits<size_type>::max()
        */
        static size_type max_size(const _Alloc& __a) noexcept
        { return _S_max_size(__a, 0); }
  
        /**
         *  @brief  Obtain an allocator to use when copying a container.
         *  @param  __rhs  An allocator.
         *  @return @c __rhs.select_on_container_copy_construction() or @a __rhs
         *
         *  Returns @c __rhs.select_on_container_copy_construction() if that
         *  expression is well-formed, otherwise returns @a __rhs
        */
        static _Alloc
        select_on_container_copy_construction(const _Alloc& __rhs)
        { return _S_select(__rhs, 0); }
      };
  
    /// Partial specialization for std::allocator.
    template<typename _Tp>
      struct allocator_traits<allocator<_Tp>>
      {
        /// The allocator type
        using allocator_type = allocator<_Tp>;
        /// The allocated type
        using value_type = _Tp;
  
        /// The allocator's pointer type.
        using pointer = _Tp*;
  
        /// The allocator's const pointer type.
        using const_pointer = const _Tp*;
  
        /// The allocator's void pointer type.
        using void_pointer = void*;
  
        /// The allocator's const void pointer type.
        using const_void_pointer = const void*;
  
        /// The allocator's difference type
        using difference_type = std::ptrdiff_t;
  
        /// The allocator's size type
        using size_type = std::size_t;
  
        /// How the allocator is propagated on copy assignment
        using propagate_on_container_copy_assignment = false_type;
  
        /// How the allocator is propagated on move assignment
        using propagate_on_container_move_assignment = true_type;
  
        /// How the allocator is propagated on swap
        using propagate_on_container_swap = false_type;
  
        /// Whether all instances of the allocator type compare equal.
        using is_always_equal = true_type;
  
        template<typename _Up>
  	using rebind_alloc = allocator<_Up>;
  
        template<typename _Up>
  	using rebind_traits = allocator_traits<allocator<_Up>>;
  
        /**
         *  @brief  Allocate memory.
         *  @param  __a  An allocator.
         *  @param  __n  The number of objects to allocate space for.
         *
         *  Calls @c a.allocate(n)
        */
        _GLIBCXX_NODISCARD static pointer
        allocate(allocator_type& __a, size_type __n)
        { return __a.allocate(__n); }
  
        /**
         *  @brief  Allocate memory.
         *  @param  __a  An allocator.
         *  @param  __n  The number of objects to allocate space for.
         *  @param  __hint Aid to locality.
         *  @return Memory of suitable size and alignment for @a n objects
         *          of type @c value_type
         *
         *  Returns <tt> a.allocate(n, hint) </tt>
        */
        _GLIBCXX_NODISCARD static pointer
        allocate(allocator_type& __a, size_type __n, const_void_pointer __hint)
        { return __a.allocate(__n, __hint); }
  
        /**
         *  @brief  Deallocate memory.
         *  @param  __a  An allocator.
         *  @param  __p  Pointer to the memory to deallocate.
         *  @param  __n  The number of objects space was allocated for.
         *
         *  Calls <tt> a.deallocate(p, n) </tt>
        */
        static void
        deallocate(allocator_type& __a, pointer __p, size_type __n)
        { __a.deallocate(__p, __n); }
  
        /**
         *  @brief  Construct an object of type @a _Up
         *  @param  __a  An allocator.
         *  @param  __p  Pointer to memory of suitable size and alignment for Tp
         *  @param  __args Constructor arguments.
         *
         *  Calls <tt> __a.construct(__p, std::forward<Args>(__args)...) </tt>
        */
        template<typename _Up, typename... _Args>
  	static void
  	construct(allocator_type& __a, _Up* __p, _Args&&... __args)
  	noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
  	{ __a.construct(__p, std::forward<_Args>(__args)...); }
  
        /**
         *  @brief  Destroy an object of type @a _Up
         *  @param  __a  An allocator.
         *  @param  __p  Pointer to the object to destroy
         *
         *  Calls @c __a.destroy(__p).
        */
        template<typename _Up>
  	static void
  	destroy(allocator_type& __a, _Up* __p)
  	noexcept(noexcept(__a.destroy(__p)))
  	{ __a.destroy(__p); }
  
        /**
         *  @brief  The maximum supported allocation size
         *  @param  __a  An allocator.
         *  @return @c __a.max_size()
        */
        static size_type
        max_size(const allocator_type& __a) noexcept
        { return __a.max_size(); }
  
        /**
         *  @brief  Obtain an allocator to use when copying a container.
         *  @param  __rhs  An allocator.
         *  @return @c __rhs
        */
        static allocator_type
        select_on_container_copy_construction(const allocator_type& __rhs)
        { return __rhs; }
      };
  
  
    template<typename _Alloc>
      inline void
      __do_alloc_on_copy(_Alloc& __one, const _Alloc& __two, true_type)
      { __one = __two; }
  
    template<typename _Alloc>
      inline void
      __do_alloc_on_copy(_Alloc&, const _Alloc&, false_type)
      { }
  
    template<typename _Alloc>
      inline void __alloc_on_copy(_Alloc& __one, const _Alloc& __two)
      {
        typedef allocator_traits<_Alloc> __traits;
        typedef typename __traits::propagate_on_container_copy_assignment __pocca;
        __do_alloc_on_copy(__one, __two, __pocca());
      }
  
    template<typename _Alloc>
      inline _Alloc __alloc_on_copy(const _Alloc& __a)
      {
        typedef allocator_traits<_Alloc> __traits;
        return __traits::select_on_container_copy_construction(__a);
      }
  
    template<typename _Alloc>
      inline void __do_alloc_on_move(_Alloc& __one, _Alloc& __two, true_type)
      { __one = std::move(__two); }
  
    template<typename _Alloc>
      inline void __do_alloc_on_move(_Alloc&, _Alloc&, false_type)
      { }
  
    template<typename _Alloc>
      inline void __alloc_on_move(_Alloc& __one, _Alloc& __two)
      {
        typedef allocator_traits<_Alloc> __traits;
        typedef typename __traits::propagate_on_container_move_assignment __pocma;
        __do_alloc_on_move(__one, __two, __pocma());
      }
  
    template<typename _Alloc>
      inline void __do_alloc_on_swap(_Alloc& __one, _Alloc& __two, true_type)
      {
        using std::swap;
        swap(__one, __two);
      }
  
    template<typename _Alloc>
      inline void __do_alloc_on_swap(_Alloc&, _Alloc&, false_type)
      { }
  
    template<typename _Alloc>
      inline void __alloc_on_swap(_Alloc& __one, _Alloc& __two)
      {
        typedef allocator_traits<_Alloc> __traits;
        typedef typename __traits::propagate_on_container_swap __pocs;
        __do_alloc_on_swap(__one, __two, __pocs());
      }
  
    template<typename _Alloc, typename _Tp,
  	   typename _ValueT = __remove_cvref_t<typename _Alloc::value_type>,
  	   typename = void>
      struct __is_alloc_insertable_impl
      : false_type
      { };
  
    template<typename _Alloc, typename _Tp, typename _ValueT>
      struct __is_alloc_insertable_impl<_Alloc, _Tp, _ValueT,
        __void_t<decltype(allocator_traits<_Alloc>::construct(
  		   std::declval<_Alloc&>(), std::declval<_ValueT*>(),
  		   std::declval<_Tp>()))>>
      : true_type
      { };
  
    // true if _Alloc::value_type is CopyInsertable into containers using _Alloc
    // (might be wrong if _Alloc::construct exists but is not constrained,
    // i.e. actually trying to use it would still be invalid. Use with caution.)
    template<typename _Alloc>
      struct __is_copy_insertable
      : __is_alloc_insertable_impl<_Alloc,
  				 typename _Alloc::value_type const&>::type
      { };
  
    // std::allocator<_Tp> just requires CopyConstructible
    template<typename _Tp>
      struct __is_copy_insertable<allocator<_Tp>>
      : is_copy_constructible<_Tp>
      { };
  
    // true if _Alloc::value_type is MoveInsertable into containers using _Alloc
    // (might be wrong if _Alloc::construct exists but is not constrained,
    // i.e. actually trying to use it would still be invalid. Use with caution.)
    template<typename _Alloc>
      struct __is_move_insertable
      : __is_alloc_insertable_impl<_Alloc, typename _Alloc::value_type>::type
      { };
  
    // std::allocator<_Tp> just requires MoveConstructible
    template<typename _Tp>
      struct __is_move_insertable<allocator<_Tp>>
      : is_move_constructible<_Tp>
      { };
  
    // Trait to detect Allocator-like types.
    template<typename _Alloc, typename = void>
      struct __is_allocator : false_type { };
  
    template<typename _Alloc>
      struct __is_allocator<_Alloc,
        __void_t<typename _Alloc::value_type,
  	       decltype(std::declval<_Alloc&>().allocate(size_t{}))>>
      : true_type { };
  
    template<typename _Alloc>
      using _RequireAllocator
        = typename enable_if<__is_allocator<_Alloc>::value, _Alloc>::type;
  
    template<typename _Alloc>
      using _RequireNotAllocator
        = typename enable_if<!__is_allocator<_Alloc>::value, _Alloc>::type;
  
  _GLIBCXX_END_NAMESPACE_VERSION
  } // namespace std
  #endif // C++11
  #endif // _ALLOC_TRAITS_H
  