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/usr/include/c++/11/bits/node_handle.h


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     1	// Node handles for containers -*- C++ -*-
     2	
     3	// Copyright (C) 2016-2021 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	/** @file bits/node_handle.h
    26	 *  This is an internal header file, included by other library headers.
    27	 *  Do not attempt to use it directly.
    28	 *  @headername{map,set,unordered_map,unordered_set}
    29	 */
    30	
    31	#ifndef _NODE_HANDLE
    32	#define _NODE_HANDLE 1
    33	
    34	#pragma GCC system_header
    35	
    36	#if __cplusplus >= 201703L
    37	# define __cpp_lib_node_extract 201606
    38	
    39	#include <new>
    40	#include <bits/alloc_traits.h>
    41	#include <bits/ptr_traits.h>
    42	
    43	namespace std _GLIBCXX_VISIBILITY(default)
    44	{
    45	_GLIBCXX_BEGIN_NAMESPACE_VERSION
    46	
    47	  /**
    48	   * @defgroup node_handles Node handles
    49	   * @ingroup associative_containers
    50	   * @since C++17
    51	   *
    52	   * The associative containers (`map`, `set`, `multimap` and `multiset`)
    53	   * support extracting and re-inserting nodes from the container. Those
    54	   * operations use the container's `node_handle` type, which is an alias
    55	   * for a `_Node_handle<...>` type. You should always use the container's
    56	   * `node_handle` type (e.g. `std::set<int>::node_handle`) to refer to
    57	   * these types, not the non-standard internal `_Node_handle` names.
    58	   *
    59	   * @{
    60	   */
    61	
    62	  /// Base class for node handle types of maps and sets.
    63	  template<typename _Val, typename _NodeAlloc>
    64	    class _Node_handle_common
    65	    {
    66	      using _AllocTraits = allocator_traits<_NodeAlloc>;
    67	
    68	    public:
    69	      using allocator_type = __alloc_rebind<_NodeAlloc, _Val>;
    70	
    71	      allocator_type
    72	      get_allocator() const noexcept
    73	      {
    74		__glibcxx_assert(!this->empty());
    75		return allocator_type(_M_alloc._M_alloc);
    76	      }
    77	
    78	      explicit operator bool() const noexcept { return _M_ptr != nullptr; }
    79	
    80	      [[nodiscard]] bool empty() const noexcept { return _M_ptr == nullptr; }
    81	
    82	    /// @cond undocumented
    83	    protected:
    84	      constexpr _Node_handle_common() noexcept : _M_ptr() { }
    85	
    86	      ~_Node_handle_common()
    87	      {
    88		if (!empty())
    89		  _M_reset();
    90	      }
    91	
    92	      _Node_handle_common(_Node_handle_common&& __nh) noexcept
    93	      : _M_ptr(__nh._M_ptr)
    94	      {
    95		if (_M_ptr)
    96		  _M_move(std::move(__nh));
    97	      }
    98	
    99	      _Node_handle_common&
   100	      operator=(_Node_handle_common&& __nh) noexcept
   101	      {
   102		if (empty())
   103		  {
   104		    if (!__nh.empty())
   105		      _M_move(std::move(__nh));
   106		  }
   107		else if (__nh.empty())
   108		  _M_reset();
   109		else
   110		  {
   111		    // Free the current node before replacing the allocator.
   112		    _AllocTraits::destroy(*_M_alloc, _M_ptr->_M_valptr());
   113		    _AllocTraits::deallocate(*_M_alloc, _M_ptr, 1);
   114	
   115		    _M_alloc = __nh._M_alloc.release(); // assigns if POCMA
   116		    _M_ptr = __nh._M_ptr;
   117		    __nh._M_ptr = nullptr;
   118		  }
   119		return *this;
   120	      }
   121	
   122	      _Node_handle_common(typename _AllocTraits::pointer __ptr,
   123				  const _NodeAlloc& __alloc)
   124	      : _M_ptr(__ptr), _M_alloc(__alloc)
   125	      {
   126		__glibcxx_assert(__ptr != nullptr);
   127	      }
   128	
   129	      void
   130	      _M_swap(_Node_handle_common& __nh) noexcept
   131	      {
   132		if (empty())
   133		  {
   134		    if (!__nh.empty())
   135		      _M_move(std::move(__nh));
   136		  }
   137		else if (__nh.empty())
   138		  __nh._M_move(std::move(*this));
   139		else
   140		  {
   141		    using std::swap;
   142		    swap(_M_ptr, __nh._M_ptr);
   143		    _M_alloc.swap(__nh._M_alloc); // swaps if POCS
   144		  }
   145	      }
   146	
   147	    private:
   148	      // Moves the pointer and allocator from __nh to *this.
   149	      // Precondition: empty() && !__nh.empty()
   150	      // Postcondition: !empty() && __nh.empty()
   151	      void
   152	      _M_move(_Node_handle_common&& __nh) noexcept
   153	      {
   154		::new (std::__addressof(_M_alloc)) _NodeAlloc(__nh._M_alloc.release());
   155		_M_ptr = __nh._M_ptr;
   156		__nh._M_ptr = nullptr;
   157	      }
   158	
   159	      // Deallocates the node, destroys the allocator.
   160	      // Precondition: !empty()
   161	      // Postcondition: empty()
   162	      void
   163	      _M_reset() noexcept
   164	      {
   165		_NodeAlloc __alloc = _M_alloc.release();
   166		_AllocTraits::destroy(__alloc, _M_ptr->_M_valptr());
   167		_AllocTraits::deallocate(__alloc, _M_ptr, 1);
   168		_M_ptr = nullptr;
   169	      }
   170	
   171	    protected:
   172	      typename _AllocTraits::pointer _M_ptr;
   173	
   174	    private:
   175	      // A simplified, non-copyable std::optional<_NodeAlloc>.
   176	      // Call release() before destruction iff the allocator member is active.
   177	      union _Optional_alloc
   178	      {
   179		_Optional_alloc() { }
   180		~_Optional_alloc() { }
   181	
   182		_Optional_alloc(_Optional_alloc&&) = delete;
   183		_Optional_alloc& operator=(_Optional_alloc&&) = delete;
   184	
   185		_Optional_alloc(const _NodeAlloc& __alloc) noexcept
   186		: _M_alloc(__alloc)
   187		{ }
   188	
   189		// Precondition: _M_alloc is the active member of the union.
   190		void
   191		operator=(_NodeAlloc&& __alloc) noexcept
   192		{
   193		  using _ATr = _AllocTraits;
   194		  if constexpr (_ATr::propagate_on_container_move_assignment::value)
   195		    _M_alloc = std::move(__alloc);
   196		  else if constexpr (!_AllocTraits::is_always_equal::value)
   197		    __glibcxx_assert(_M_alloc == __alloc);
   198		}
   199	
   200		// Precondition: _M_alloc is the active member of both unions.
   201		void
   202		swap(_Optional_alloc& __other) noexcept
   203		{
   204		  using std::swap;
   205		  if constexpr (_AllocTraits::propagate_on_container_swap::value)
   206		    swap(_M_alloc, __other._M_alloc);
   207		  else if constexpr (!_AllocTraits::is_always_equal::value)
   208		    __glibcxx_assert(_M_alloc == __other._M_alloc);
   209		}
   210	
   211		// Precondition: _M_alloc is the active member of the union.
   212		_NodeAlloc& operator*() noexcept { return _M_alloc; }
   213	
   214		// Precondition: _M_alloc is the active member of the union.
   215		_NodeAlloc release() noexcept
   216		{
   217		  _NodeAlloc __tmp = std::move(_M_alloc);
   218		  _M_alloc.~_NodeAlloc();
   219		  return __tmp;
   220		}
   221	
   222		struct _Empty { };
   223	
   224		[[__no_unique_address__]] _Empty     _M_empty;
   225		[[__no_unique_address__]] _NodeAlloc _M_alloc;
   226	      };
   227	
   228	      [[__no_unique_address__]] _Optional_alloc _M_alloc;
   229	
   230	      template<typename _Key2, typename _Value2, typename _KeyOfValue,
   231		       typename _Compare, typename _ValueAlloc>
   232		friend class _Rb_tree;
   233	
   234	      /// @endcond
   235	    };
   236	
   237	  /// Node handle type for maps.
   238	  template<typename _Key, typename _Value, typename _NodeAlloc>
   239	    class _Node_handle : public _Node_handle_common<_Value, _NodeAlloc>
   240	    {
   241	    public:
   242	      constexpr _Node_handle() noexcept = default;
   243	      ~_Node_handle() = default;
   244	      _Node_handle(_Node_handle&&) noexcept = default;
   245	
   246	      _Node_handle&
   247	      operator=(_Node_handle&&) noexcept = default;
   248	
   249	      using key_type = _Key;
   250	      using mapped_type = typename _Value::second_type;
   251	
   252	      key_type&
   253	      key() const noexcept
   254	      {
   255		__glibcxx_assert(!this->empty());
   256		return *_M_pkey;
   257	      }
   258	
   259	      mapped_type&
   260	      mapped() const noexcept
   261	      {
   262		__glibcxx_assert(!this->empty());
   263		return *_M_pmapped;
   264	      }
   265	
   266	      void
   267	      swap(_Node_handle& __nh) noexcept
   268	      {
   269		this->_M_swap(__nh);
   270		using std::swap;
   271		swap(_M_pkey, __nh._M_pkey);
   272		swap(_M_pmapped, __nh._M_pmapped);
   273	      }
   274	
   275	      friend void
   276	      swap(_Node_handle& __x, _Node_handle& __y)
   277	      noexcept(noexcept(__x.swap(__y)))
   278	      { __x.swap(__y); }
   279	
   280	    private:
   281	      using _AllocTraits = allocator_traits<_NodeAlloc>;
   282	
   283	      _Node_handle(typename _AllocTraits::pointer __ptr,
   284			   const _NodeAlloc& __alloc)
   285	      : _Node_handle_common<_Value, _NodeAlloc>(__ptr, __alloc)
   286	      {
   287		if (__ptr)
   288		  {
   289		    auto& __key = const_cast<_Key&>(__ptr->_M_valptr()->first);
   290		    _M_pkey = _S_pointer_to(__key);
   291		    _M_pmapped = _S_pointer_to(__ptr->_M_valptr()->second);
   292		  }
   293		else
   294		  {
   295		    _M_pkey = nullptr;
   296		    _M_pmapped = nullptr;
   297		  }
   298	      }
   299	
   300	      template<typename _Tp>
   301		using __pointer
   302		  = __ptr_rebind<typename _AllocTraits::pointer,
   303				 remove_reference_t<_Tp>>;
   304	
   305	      __pointer<_Key>				_M_pkey = nullptr;
   306	      __pointer<typename _Value::second_type>	_M_pmapped = nullptr;
   307	
   308	      template<typename _Tp>
   309		__pointer<_Tp>
   310		_S_pointer_to(_Tp& __obj)
   311		{ return pointer_traits<__pointer<_Tp>>::pointer_to(__obj); }
   312	
   313	      const key_type&
   314	      _M_key() const noexcept { return key(); }
   315	
   316	      template<typename _Key2, typename _Value2, typename _KeyOfValue,
   317		       typename _Compare, typename _ValueAlloc>
   318		friend class _Rb_tree;
   319	
   320	      template<typename _Key2, typename _Value2, typename _ValueAlloc,
   321		       typename _ExtractKey, typename _Equal,
   322		       typename _Hash, typename _RangeHash, typename _Unused,
   323		       typename _RehashPolicy, typename _Traits>
   324		friend class _Hashtable;
   325	    };
   326	
   327	  /// Node handle type for sets.
   328	  template<typename _Value, typename _NodeAlloc>
   329	    class _Node_handle<_Value, _Value, _NodeAlloc>
   330	    : public _Node_handle_common<_Value, _NodeAlloc>
   331	    {
   332	    public:
   333	      constexpr _Node_handle() noexcept = default;
   334	      ~_Node_handle() = default;
   335	      _Node_handle(_Node_handle&&) noexcept = default;
   336	
   337	      _Node_handle&
   338	      operator=(_Node_handle&&) noexcept = default;
   339	
   340	      using value_type = _Value;
   341	
   342	      value_type&
   343	      value() const noexcept
   344	      {
   345		__glibcxx_assert(!this->empty());
   346		return *this->_M_ptr->_M_valptr();
   347	      }
   348	
   349	      void
   350	      swap(_Node_handle& __nh) noexcept
   351	      { this->_M_swap(__nh); }
   352	
   353	      friend void
   354	      swap(_Node_handle& __x, _Node_handle& __y)
   355	      noexcept(noexcept(__x.swap(__y)))
   356	      { __x.swap(__y); }
   357	
   358	    private:
   359	      using _AllocTraits = allocator_traits<_NodeAlloc>;
   360	
   361	      _Node_handle(typename _AllocTraits::pointer __ptr,
   362			   const _NodeAlloc& __alloc)
   363	      : _Node_handle_common<_Value, _NodeAlloc>(__ptr, __alloc) { }
   364	
   365	      const value_type&
   366	      _M_key() const noexcept { return value(); }
   367	
   368	      template<typename _Key, typename _Val, typename _KeyOfValue,
   369		       typename _Compare, typename _Alloc>
   370		friend class _Rb_tree;
   371	
   372	      template<typename _Key2, typename _Value2, typename _ValueAlloc,
   373		       typename _ExtractKey, typename _Equal,
   374		       typename _Hash, typename _RangeHash, typename _Unused,
   375		       typename _RehashPolicy, typename _Traits>
   376		friend class _Hashtable;
   377	    };
   378	
   379	  /// Return type of insert(node_handle&&) on unique maps/sets.
   380	  template<typename _Iterator, typename _NodeHandle>
   381	    struct _Node_insert_return
   382	    {
   383	      _Iterator		position = _Iterator();
   384	      bool		inserted = false;
   385	      _NodeHandle	node;
   386	    };
   387	
   388	  /// @}
   389	
   390	_GLIBCXX_END_NAMESPACE_VERSION
   391	} // namespace std
   392	
   393	#endif // C++17
   394	#endif