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

   1 // Internal policy header for unordered_set and unordered_map -*- C++ -*-
   2
   3 // Copyright (C) 2010-2013 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/hashtable_policy.h
  26  *  This is an internal header file, included by other library headers.
  27  *  Do not attempt to use it directly.
  28  *  @headername{unordered_map,unordered_set}
  29  */
  30
  31 #ifndef _HASHTABLE_POLICY_H
  32 #define _HASHTABLE_POLICY_H 1
  33
  34 namespace std _GLIBCXX_VISIBILITY(default)
  35 {
  36 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  37
  38   template<typename _Key, typename _Value, typename _Alloc,
  39            typename _ExtractKey, typename _Equal,
  40            typename _H1, typename _H2, typename _Hash,
  41            typename _RehashPolicy, typename _Traits>
  42     class _Hashtable;
  43
  44 _GLIBCXX_END_NAMESPACE_VERSION
  45
  46 namespace __detail
  47 {
  48 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  49
  50   /**
  51    *  @defgroup hashtable-detail Base and Implementation Classes
  52    *  @ingroup unordered_associative_containers
  53    *  @{
  54    */
  55   template<typename _Key, typename _Value,
  56            typename _ExtractKey, typename _Equal,
  57            typename _H1, typename _H2, typename _Hash, typename _Traits>
  58     struct _Hashtable_base;
  59
  60   // Helper function: return distance(first, last) for forward
  61   // iterators, or 0 for input iterators.
  62   template<class _Iterator>
  63     inline typename std::iterator_traits<_Iterator>::difference_type
  64     __distance_fw(_Iterator __first, _Iterator __last,
  65                   std::input_iterator_tag)
  66     { return 0; }
  67
  68   template<class _Iterator>
  69     inline typename std::iterator_traits<_Iterator>::difference_type
  70     __distance_fw(_Iterator __first, _Iterator __last,
  71                   std::forward_iterator_tag)
  72     { return std::distance(__first, __last); }
  73
  74   template<class _Iterator>
  75     inline typename std::iterator_traits<_Iterator>::difference_type
  76     __distance_fw(_Iterator __first, _Iterator __last)
  77     {
  78       typedef typename std::iterator_traits<_Iterator>::iterator_category _Tag;
  79       return __distance_fw(__first, __last, _Tag());
  80     }
  81
  82   // Helper type used to detect whether the hash functor is noexcept.
  83   template <typename _Key, typename _Hash>
  84     struct __is_noexcept_hash : std::integral_constant<bool,
  85         noexcept(declval<const _Hash&>()(declval<const _Key&>()))>
  86     { };
  87
  88   struct _Identity
  89   {
  90     template<typename _Tp>
  91       _Tp&&
  92       operator()(_Tp&& __x) const
  93       { return std::forward<_Tp>(__x); }
  94   };
  95
  96   struct _Select1st
  97   {
  98     template<typename _Tp>
  99       auto
 100       operator()(_Tp&& __x) const
 101       -> decltype(std::get<0>(std::forward<_Tp>(__x)))
 102       { return std::get<0>(std::forward<_Tp>(__x)); }
 103   };
 104
 105   // Functor recycling a pool of nodes and using allocation once the pool is
 106   // empty.
 107   template<typename _Key, typename _Value, typename _Alloc,
 108            typename _ExtractKey, typename _Equal,
 109            typename _H1, typename _H2, typename _Hash,
 110            typename _RehashPolicy, typename _Traits>
 111     struct _ReuseOrAllocNode
 112     {
 113     private:
 114       using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey,
 115                                      _Equal, _H1, _H2, _Hash,
 116                                      _RehashPolicy, _Traits>;
 117       using __val_alloc_type = typename __hashtable::_Value_alloc_type;
 118       using __val_alloc_traits = typename __hashtable::_Value_alloc_traits;
 119       using __node_alloc_traits = typename __hashtable::_Node_alloc_traits;
 120       using __node_type = typename __hashtable::__node_type;
 121
 122     public:
 123       _ReuseOrAllocNode(__node_type* __nodes, __hashtable& __h)
 124         : _M_nodes(__nodes), _M_h(__h) { }
 125       _ReuseOrAllocNode(const _ReuseOrAllocNode&) = delete;
 126
 127       ~_ReuseOrAllocNode()
 128       { _M_h._M_deallocate_nodes(_M_nodes); }
 129
 130       template<typename _Arg>
 131         __node_type*
 132         operator()(_Arg&& __arg) const
 133         {
 134           if (_M_nodes)
 135             {
 136               __node_type* __node = _M_nodes;
 137               _M_nodes = _M_nodes->_M_next();
 138               __node->_M_nxt = nullptr;
 139               __val_alloc_type __a(_M_h._M_node_allocator());
 140               __val_alloc_traits::destroy(__a, __node->_M_valptr());
 141               __try
 142                 {
 143                   __val_alloc_traits::construct(__a, __node->_M_valptr(),
 144                                                 std::forward<_Arg>(__arg));
 145                 }
 146               __catch(...)
 147                 {
 148                   __node->~__node_type();
 149                   __node_alloc_traits::deallocate(_M_h._M_node_allocator(),
 150                                                   __node, 1);
 151                   __throw_exception_again;
 152                 }
 153               return __node;
 154             }
 155           return _M_h._M_allocate_node(std::forward<_Arg>(__arg));
 156         }
 157
 158     private:
 159       mutable __node_type* _M_nodes;
 160       __hashtable& _M_h;
 161     };
 162
 163   // Functor similar to the previous one but without any pool of node to recycle.
 164   template<typename _Key, typename _Value, typename _Alloc,
 165            typename _ExtractKey, typename _Equal,
 166            typename _H1, typename _H2, typename _Hash,
 167            typename _RehashPolicy, typename _Traits>
 168     struct _AllocNode
 169     {
 170     private:
 171       using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey,
 172                                      _Equal, _H1, _H2, _Hash,
 173                                      _RehashPolicy, _Traits>;
 174       using __node_type = typename __hashtable::__node_type;
 175
 176     public:
 177       _AllocNode(__hashtable& __h)
 178         : _M_h(__h) { }
 179
 180       template<typename _Arg>
 181         __node_type*
 182         operator()(_Arg&& __arg) const
 183         { return _M_h._M_allocate_node(std::forward<_Arg>(__arg)); }
 184
 185     private:
 186       __hashtable& _M_h;
 187     };
 188
 189   // Auxiliary types used for all instantiations of _Hashtable nodes
 190   // and iterators.
 191
 192   /**
 193    *  struct _Hashtable_traits
 194    *
 195    *  Important traits for hash tables.
 196    *
 197    *  @tparam _Cache_hash_code  Boolean value. True if the value of
 198    *  the hash function is stored along with the value. This is a
 199    *  time-space tradeoff.  Storing it may improve lookup speed by
 200    *  reducing the number of times we need to call the _Equal
 201    *  function.
 202    *
 203    *  @tparam _Constant_iterators  Boolean value. True if iterator and
 204    *  const_iterator are both constant iterator types. This is true
 205    *  for unordered_set and unordered_multiset, false for
 206    *  unordered_map and unordered_multimap.
 207    *
 208    *  @tparam _Unique_keys  Boolean value. True if the return value
 209    *  of _Hashtable::count(k) is always at most one, false if it may
 210    *  be an arbitrary number. This is true for unordered_set and
 211    *  unordered_map, false for unordered_multiset and
 212    *  unordered_multimap.
 213    */
 214   template<bool _Cache_hash_code, bool _Constant_iterators, bool _Unique_keys>
 215     struct _Hashtable_traits
 216     {
 217       template<bool _Cond>
 218         using __bool_constant = integral_constant<bool, _Cond>;
 219
 220       using __hash_cached = __bool_constant<_Cache_hash_code>;
 221       using __constant_iterators = __bool_constant<_Constant_iterators>;
 222       using __unique_keys = __bool_constant<_Unique_keys>;
 223     };
 224
 225   /**
 226    *  struct _Hash_node_base
 227    *
 228    *  Nodes, used to wrap elements stored in the hash table.  A policy
 229    *  template parameter of class template _Hashtable controls whether
 230    *  nodes also store a hash code. In some cases (e.g. strings) this
 231    *  may be a performance win.
 232    */
 233   struct _Hash_node_base
 234   {
 235     _Hash_node_base* _M_nxt;
 236
 237     _Hash_node_base() : _M_nxt() { }
 238
 239     _Hash_node_base(_Hash_node_base* __next) : _M_nxt(__next) { }
 240   };
 241
 242   /**
 243    *  struct _Hash_node_value_base
 244    *
 245    *  Node type with the value to store.
 246    */
 247   template<typename _Value>
 248     struct _Hash_node_value_base : _Hash_node_base
 249     {
 250       __gnu_cxx::__aligned_buffer<_Value> _M_storage;
 251
 252       _Value*
 253       _M_valptr() noexcept
 254       { return _M_storage._M_ptr(); }
 255
 256       const _Value*
 257       _M_valptr() const noexcept
 258       { return _M_storage._M_ptr(); }
 259
 260       _Value&
 261       _M_v() noexcept
 262       { return *_M_valptr(); }
 263
 264       const _Value&
 265       _M_v() const noexcept
 266       { return *_M_valptr(); }
 267     };
 268
 269   /**
 270    *  Primary template struct _Hash_node.
 271    */
 272   template<typename _Value, bool _Cache_hash_code>
 273     struct _Hash_node;
 274
 275   /**
 276    *  Specialization for nodes with caches, struct _Hash_node.
 277    *
 278    *  Base class is __detail::_Hash_node_value_base.
 279    */
 280   template<typename _Value>
 281     struct _Hash_node<_Value, true> : _Hash_node_value_base<_Value>
 282     {
 283       std::size_t  _M_hash_code;
 284
 285       _Hash_node*
 286       _M_next() const { return static_cast<_Hash_node*>(this->_M_nxt); }
 287     };
 288
 289   /**
 290    *  Specialization for nodes without caches, struct _Hash_node.
 291    *
 292    *  Base class is __detail::_Hash_node_value_base.
 293    */
 294   template<typename _Value>
 295     struct _Hash_node<_Value, false> : _Hash_node_value_base<_Value>
 296     {
 297       _Hash_node*
 298       _M_next() const { return static_cast<_Hash_node*>(this->_M_nxt); }
 299     };
 300
 301   /// Base class for node iterators.
 302   template<typename _Value, bool _Cache_hash_code>
 303     struct _Node_iterator_base
 304     {
 305       using __node_type = _Hash_node<_Value, _Cache_hash_code>;
 306
 307       __node_type*  _M_cur;
 308
 309       _Node_iterator_base(__node_type* __p)
 310       : _M_cur(__p) { }
 311
 312       void
 313       _M_incr()
 314       { _M_cur = _M_cur->_M_next(); }
 315     };
 316
 317   template<typename _Value, bool _Cache_hash_code>
 318     inline bool
 319     operator==(const _Node_iterator_base<_Value, _Cache_hash_code>& __x,
 320                const _Node_iterator_base<_Value, _Cache_hash_code >& __y)
 321     { return __x._M_cur == __y._M_cur; }
 322
 323   template<typename _Value, bool _Cache_hash_code>
 324     inline bool
 325     operator!=(const _Node_iterator_base<_Value, _Cache_hash_code>& __x,
 326                const _Node_iterator_base<_Value, _Cache_hash_code>& __y)
 327     { return __x._M_cur != __y._M_cur; }
 328
 329   /// Node iterators, used to iterate through all the hashtable.
 330   template<typename _Value, bool __constant_iterators, bool __cache>
 331     struct _Node_iterator
 332     : public _Node_iterator_base<_Value, __cache>
 333     {
 334     private:
 335       using __base_type = _Node_iterator_base<_Value, __cache>;
 336       using __node_type = typename __base_type::__node_type;
 337
 338     public:
 339       typedef _Value                                   value_type;
 340       typedef std::ptrdiff_t                           difference_type;
 341       typedef std::forward_iterator_tag                iterator_category;
 342
 343       using pointer = typename std::conditional<__constant_iterators,
 344                                                 const _Value*, _Value*>::type;
 345
 346       using reference = typename std::conditional<__constant_iterators,
 347                                                   const _Value&, _Value&>::type;
 348
 349       _Node_iterator()
 350       : __base_type(0) { }
 351
 352       explicit
 353       _Node_iterator(__node_type* __p)
 354       : __base_type(__p) { }
 355
 356       reference
 357       operator*() const
 358       { return this->_M_cur->_M_v(); }
 359
 360       pointer
 361       operator->() const
 362       { return this->_M_cur->_M_valptr(); }
 363
 364       _Node_iterator&
 365       operator++()
 366       {
 367         this->_M_incr();
 368         return *this;
 369       }
 370
 371       _Node_iterator
 372       operator++(int)
 373       {
 374         _Node_iterator __tmp(*this);
 375         this->_M_incr();
 376         return __tmp;
 377       }
 378     };
 379
 380   /// Node const_iterators, used to iterate through all the hashtable.
 381   template<typename _Value, bool __constant_iterators, bool __cache>
 382     struct _Node_const_iterator
 383     : public _Node_iterator_base<_Value, __cache>
 384     {
 385     private:
 386       using __base_type = _Node_iterator_base<_Value, __cache>;
 387       using __node_type = typename __base_type::__node_type;
 388
 389     public:
 390       typedef _Value                                   value_type;
 391       typedef std::ptrdiff_t                           difference_type;
 392       typedef std::forward_iterator_tag                iterator_category;
 393
 394       typedef const _Value*                            pointer;
 395       typedef const _Value&                            reference;
 396
 397       _Node_const_iterator()
 398       : __base_type(0) { }
 399
 400       explicit
 401       _Node_const_iterator(__node_type* __p)
 402       : __base_type(__p) { }
 403
 404       _Node_const_iterator(const _Node_iterator<_Value, __constant_iterators,
 405                            __cache>& __x)
 406       : __base_type(__x._M_cur) { }
 407
 408       reference
 409       operator*() const
 410       { return this->_M_cur->_M_v(); }
 411
 412       pointer
 413       operator->() const
 414       { return this->_M_cur->_M_valptr(); }
 415
 416       _Node_const_iterator&
 417       operator++()
 418       {
 419         this->_M_incr();
 420         return *this;
 421       }
 422
 423       _Node_const_iterator
 424       operator++(int)
 425       {
 426         _Node_const_iterator __tmp(*this);
 427         this->_M_incr();
 428         return __tmp;
 429       }
 430     };
 431
 432   // Many of class template _Hashtable's template parameters are policy
 433   // classes.  These are defaults for the policies.
 434
 435   /// Default range hashing function: use division to fold a large number
 436   /// into the range [0, N).
 437   struct _Mod_range_hashing
 438   {
 439     typedef std::size_t first_argument_type;
 440     typedef std::size_t second_argument_type;
 441     typedef std::size_t result_type;
 442
 443     result_type
 444     operator()(first_argument_type __num,
 445                second_argument_type __den) const noexcept
 446     { return __num % __den; }
 447   };
 448
 449   /// Default ranged hash function H.  In principle it should be a
 450   /// function object composed from objects of type H1 and H2 such that
 451   /// h(k, N) = h2(h1(k), N), but that would mean making extra copies of
 452   /// h1 and h2.  So instead we'll just use a tag to tell class template
 453   /// hashtable to do that composition.
 454   struct _Default_ranged_hash { };
 455
 456   /// Default value for rehash policy.  Bucket size is (usually) the
 457   /// smallest prime that keeps the load factor small enough.
 458   struct _Prime_rehash_policy
 459   {
 460     _Prime_rehash_policy(float __z = 1.0)
 461     : _M_max_load_factor(__z), _M_next_resize(0) { }
 462
 463     float
 464     max_load_factor() const noexcept
 465     { return _M_max_load_factor; }
 466
 467     // Return a bucket size no smaller than n.
 468     std::size_t
 469     _M_next_bkt(std::size_t __n) const;
 470
 471     // Return a bucket count appropriate for n elements
 472     std::size_t
 473     _M_bkt_for_elements(std::size_t __n) const
 474     { return __builtin_ceil(__n / (long double)_M_max_load_factor); }
 475
 476     // __n_bkt is current bucket count, __n_elt is current element count,
 477     // and __n_ins is number of elements to be inserted.  Do we need to
 478     // increase bucket count?  If so, return make_pair(true, n), where n
 479     // is the new bucket count.  If not, return make_pair(false, 0).
 480     std::pair<bool, std::size_t>
 481     _M_need_rehash(std::size_t __n_bkt, std::size_t __n_elt,
 482                    std::size_t __n_ins) const;
 483
 484     typedef std::size_t _State;
 485
 486     _State
 487     _M_state() const
 488     { return _M_next_resize; }
 489
 490     void
 491     _M_reset() noexcept
 492     { _M_next_resize = 0; }
 493
 494     void
 495     _M_reset(_State __state)
 496     { _M_next_resize = __state; }
 497
 498     enum { _S_n_primes = sizeof(unsigned long) != 8 ? 256 : 256 + 48 };
 499
 500     static const std::size_t _S_growth_factor = 2;
 501
 502     float                _M_max_load_factor;
 503     mutable std::size_t  _M_next_resize;
 504   };
 505
 506   // Base classes for std::_Hashtable.  We define these base classes
 507   // because in some cases we want to do different things depending on
 508   // the value of a policy class.  In some cases the policy class
 509   // affects which member functions and nested typedefs are defined;
 510   // we handle that by specializing base class templates.  Several of
 511   // the base class templates need to access other members of class
 512   // template _Hashtable, so we use a variant of the "Curiously
 513   // Recurring Template Pattern" (CRTP) technique.
 514
 515   /**
 516    *  Primary class template _Map_base.
 517    *
 518    *  If the hashtable has a value type of the form pair<T1, T2> and a
 519    *  key extraction policy (_ExtractKey) that returns the first part
 520    *  of the pair, the hashtable gets a mapped_type typedef.  If it
 521    *  satisfies those criteria and also has unique keys, then it also
 522    *  gets an operator[].
 523    */
 524   template<typename _Key, typename _Value, typename _Alloc,
 525            typename _ExtractKey, typename _Equal,
 526            typename _H1, typename _H2, typename _Hash,
 527            typename _RehashPolicy, typename _Traits,
 528            bool _Unique_keys = _Traits::__unique_keys::value>
 529     struct _Map_base { };
 530
 531   /// Partial specialization, __unique_keys set to false.
 532   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 533            typename _H1, typename _H2, typename _Hash,
 534            typename _RehashPolicy, typename _Traits>
 535     struct _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 536                      _H1, _H2, _Hash, _RehashPolicy, _Traits, false>
 537     {
 538       using mapped_type = typename std::tuple_element<1, _Pair>::type;
 539     };
 540
 541   /// Partial specialization, __unique_keys set to true.
 542   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 543            typename _H1, typename _H2, typename _Hash,
 544            typename _RehashPolicy, typename _Traits>
 545     struct _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 546                      _H1, _H2, _Hash, _RehashPolicy, _Traits, true>
 547     {
 548     private:
 549       using __hashtable_base = __detail::_Hashtable_base<_Key, _Pair,
 550                                                          _Select1st,
 551                                                         _Equal, _H1, _H2, _Hash,
 552                                                           _Traits>;
 553
 554       using __hashtable = _Hashtable<_Key, _Pair, _Alloc,
 555                                      _Select1st, _Equal,
 556                                      _H1, _H2, _Hash, _RehashPolicy, _Traits>;
 557
 558       using __hash_code = typename __hashtable_base::__hash_code;
 559       using __node_type = typename __hashtable_base::__node_type;
 560
 561     public:
 562       using key_type = typename __hashtable_base::key_type;
 563       using iterator = typename __hashtable_base::iterator;
 564       using mapped_type = typename std::tuple_element<1, _Pair>::type;
 565
 566       mapped_type&
 567       operator[](const key_type& __k);
 568
 569       mapped_type&
 570       operator[](key_type&& __k);
 571
 572       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 573       // DR 761. unordered_map needs an at() member function.
 574       mapped_type&
 575       at(const key_type& __k);
 576
 577       const mapped_type&
 578       at(const key_type& __k) const;
 579     };
 580
 581   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 582            typename _H1, typename _H2, typename _Hash,
 583            typename _RehashPolicy, typename _Traits>
 584     typename _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 585                        _H1, _H2, _Hash, _RehashPolicy, _Traits, true>
 586                        ::mapped_type&
 587     _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 588               _H1, _H2, _Hash, _RehashPolicy, _Traits, true>::
 589     operator[](const key_type& __k)
 590     {
 591       __hashtable* __h = static_cast<__hashtable*>(this);
 592       __hash_code __code = __h->_M_hash_code(__k);
 593       std::size_t __n = __h->_M_bucket_index(__k, __code);
 594       __node_type* __p = __h->_M_find_node(__n, __k, __code);
 595
 596       if (!__p)
 597         {
 598           __p = __h->_M_allocate_node(std::piecewise_construct,
 599                                       std::tuple<const key_type&>(__k),
 600                                       std::tuple<>());
 601           return __h->_M_insert_unique_node(__n, __code, __p)->second;
 602         }
 603
 604       return __p->_M_v().second;
 605     }
 606
 607   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 608            typename _H1, typename _H2, typename _Hash,
 609            typename _RehashPolicy, typename _Traits>
 610     typename _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 611                        _H1, _H2, _Hash, _RehashPolicy, _Traits, true>
 612                        ::mapped_type&
 613     _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 614               _H1, _H2, _Hash, _RehashPolicy, _Traits, true>::
 615     operator[](key_type&& __k)
 616     {
 617       __hashtable* __h = static_cast<__hashtable*>(this);
 618       __hash_code __code = __h->_M_hash_code(__k);
 619       std::size_t __n = __h->_M_bucket_index(__k, __code);
 620       __node_type* __p = __h->_M_find_node(__n, __k, __code);
 621
 622       if (!__p)
 623         {
 624           __p = __h->_M_allocate_node(std::piecewise_construct,
 625                                       std::forward_as_tuple(std::move(__k)),
 626                                       std::tuple<>());
 627           return __h->_M_insert_unique_node(__n, __code, __p)->second;
 628         }
 629
 630       return __p->_M_v().second;
 631     }
 632
 633   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 634            typename _H1, typename _H2, typename _Hash,
 635            typename _RehashPolicy, typename _Traits>
 636     typename _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 637                        _H1, _H2, _Hash, _RehashPolicy, _Traits, true>
 638                        ::mapped_type&
 639     _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 640               _H1, _H2, _Hash, _RehashPolicy, _Traits, true>::
 641     at(const key_type& __k)
 642     {
 643       __hashtable* __h = static_cast<__hashtable*>(this);
 644       __hash_code __code = __h->_M_hash_code(__k);
 645       std::size_t __n = __h->_M_bucket_index(__k, __code);
 646       __node_type* __p = __h->_M_find_node(__n, __k, __code);
 647
 648       if (!__p)
 649         __throw_out_of_range(__N("_Map_base::at"));
 650       return __p->_M_v().second;
 651     }
 652
 653   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 654            typename _H1, typename _H2, typename _Hash,
 655            typename _RehashPolicy, typename _Traits>
 656     const typename _Map_base<_Key, _Pair, _Alloc, _Select1st,
 657                              _Equal, _H1, _H2, _Hash, _RehashPolicy,
 658                              _Traits, true>::mapped_type&
 659     _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 660               _H1, _H2, _Hash, _RehashPolicy, _Traits, true>::
 661     at(const key_type& __k) const
 662     {
 663       const __hashtable* __h = static_cast<const __hashtable*>(this);
 664       __hash_code __code = __h->_M_hash_code(__k);
 665       std::size_t __n = __h->_M_bucket_index(__k, __code);
 666       __node_type* __p = __h->_M_find_node(__n, __k, __code);
 667
 668       if (!__p)
 669         __throw_out_of_range(__N("_Map_base::at"));
 670       return __p->_M_v().second;
 671     }
 672
 673   /**
 674    *  Primary class template _Insert_base.
 675    *
 676    *  insert member functions appropriate to all _Hashtables.
 677    */
 678   template<typename _Key, typename _Value, typename _Alloc,
 679            typename _ExtractKey, typename _Equal,
 680            typename _H1, typename _H2, typename _Hash,
 681            typename _RehashPolicy, typename _Traits>
 682     struct _Insert_base
 683     {
 684     protected:
 685       using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey,
 686                                      _Equal, _H1, _H2, _Hash,
 687                                      _RehashPolicy, _Traits>;
 688
 689       using __hashtable_base = _Hashtable_base<_Key, _Value, _ExtractKey,
 690                                                _Equal, _H1, _H2, _Hash,
 691                                                _Traits>;
 692
 693       using value_type = typename __hashtable_base::value_type;
 694       using iterator = typename __hashtable_base::iterator;
 695       using const_iterator =  typename __hashtable_base::const_iterator;
 696       using size_type = typename __hashtable_base::size_type;
 697
 698       using __unique_keys = typename __hashtable_base::__unique_keys;
 699       using __ireturn_type = typename __hashtable_base::__ireturn_type;
 700       using __node_gen_type = _AllocNode<_Key, _Value, _Alloc, _ExtractKey,
 701                                          _Equal, _H1, _H2, _Hash,
 702                                          _RehashPolicy, _Traits>;
 703
 704       __hashtable&
 705       _M_conjure_hashtable()
 706       { return *(static_cast<__hashtable*>(this)); }
 707
 708       template<typename _InputIterator, typename _NodeGetter>
 709         void
 710         _M_insert_range(_InputIterator __first, _InputIterator __last,
 711                         const _NodeGetter&);
 712
 713     public:
 714       __ireturn_type
 715       insert(const value_type& __v)
 716       {
 717         __hashtable& __h = _M_conjure_hashtable();
 718         __node_gen_type __node_gen(__h);
 719         return __h._M_insert(__v, __node_gen, __unique_keys());
 720       }
 721
 722       iterator
 723       insert(const_iterator __hint, const value_type& __v)
 724       {
 725         __hashtable& __h = _M_conjure_hashtable();
 726         __node_gen_type __node_gen(__h);
 727         return __h._M_insert(__hint, __v, __node_gen, __unique_keys());
 728       }
 729
 730       void
 731       insert(initializer_list<value_type> __l)
 732       { this->insert(__l.begin(), __l.end()); }
 733
 734       template<typename _InputIterator>
 735         void
 736         insert(_InputIterator __first, _InputIterator __last)
 737         {
 738           __hashtable& __h = _M_conjure_hashtable();
 739           __node_gen_type __node_gen(__h);
 740           return _M_insert_range(__first, __last, __node_gen);
 741         }
 742     };
 743
 744   template<typename _Key, typename _Value, typename _Alloc,
 745            typename _ExtractKey, typename _Equal,
 746            typename _H1, typename _H2, typename _Hash,
 747            typename _RehashPolicy, typename _Traits>
 748     template<typename _InputIterator, typename _NodeGetter>
 749       void
 750       _Insert_base<_Key, _Value, _Alloc, _ExtractKey, _Equal, _H1, _H2, _Hash,
 751                     _RehashPolicy, _Traits>::
 752       _M_insert_range(_InputIterator __first, _InputIterator __last,
 753                       const _NodeGetter& __node_gen)
 754       {
 755         using __rehash_type = typename __hashtable::__rehash_type;
 756         using __rehash_state = typename __hashtable::__rehash_state;
 757         using pair_type = std::pair<bool, std::size_t>;
 758
 759         size_type __n_elt = __detail::__distance_fw(__first, __last);
 760
 761         __hashtable& __h = _M_conjure_hashtable();
 762         __rehash_type& __rehash = __h._M_rehash_policy;
 763         const __rehash_state& __saved_state = __rehash._M_state();
 764         pair_type __do_rehash = __rehash._M_need_rehash(__h._M_bucket_count,
 765                                                         __h._M_element_count,
 766                                                         __n_elt);
 767
 768         if (__do_rehash.first)
 769           __h._M_rehash(__do_rehash.second, __saved_state);
 770
 771         for (; __first != __last; ++__first)
 772           __h._M_insert(*__first, __node_gen, __unique_keys());
 773       }
 774
 775   /**
 776    *  Primary class template _Insert.
 777    *
 778    *  Select insert member functions appropriate to _Hashtable policy choices.
 779    */
 780   template<typename _Key, typename _Value, typename _Alloc,
 781            typename _ExtractKey, typename _Equal,
 782            typename _H1, typename _H2, typename _Hash,
 783            typename _RehashPolicy, typename _Traits,
 784            bool _Constant_iterators = _Traits::__constant_iterators::value,
 785            bool _Unique_keys = _Traits::__unique_keys::value>
 786     struct _Insert;
 787
 788   /// Specialization.
 789   template<typename _Key, typename _Value, typename _Alloc,
 790            typename _ExtractKey, typename _Equal,
 791            typename _H1, typename _H2, typename _Hash,
 792            typename _RehashPolicy, typename _Traits>
 793     struct _Insert<_Key, _Value, _Alloc, _ExtractKey, _Equal, _H1, _H2, _Hash,
 794                    _RehashPolicy, _Traits, true, true>
 795     : public _Insert_base<_Key, _Value, _Alloc, _ExtractKey, _Equal,
 796                            _H1, _H2, _Hash, _RehashPolicy, _Traits>
 797     {
 798       using __base_type = _Insert_base<_Key, _Value, _Alloc, _ExtractKey,
 799                                         _Equal, _H1, _H2, _Hash,
 800                                         _RehashPolicy, _Traits>;
 801       using value_type = typename __base_type::value_type;
 802       using iterator = typename __base_type::iterator;
 803       using const_iterator =  typename __base_type::const_iterator;
 804
 805       using __unique_keys = typename __base_type::__unique_keys;
 806       using __hashtable = typename __base_type::__hashtable;
 807       using __node_gen_type = typename __base_type::__node_gen_type;
 808
 809       using __base_type::insert;
 810
 811       std::pair<iterator, bool>
 812       insert(value_type&& __v)
 813       {
 814         __hashtable& __h = this->_M_conjure_hashtable();
 815         __node_gen_type __node_gen(__h);
 816         return __h._M_insert(std::move(__v), __node_gen, __unique_keys());
 817       }
 818
 819       iterator
 820       insert(const_iterator __hint, value_type&& __v)
 821       {
 822         __hashtable& __h = this->_M_conjure_hashtable();
 823         __node_gen_type __node_gen(__h);
 824         return __h._M_insert(__hint, std::move(__v), __node_gen,
 825                              __unique_keys());
 826       }
 827     };
 828
 829   /// Specialization.
 830   template<typename _Key, typename _Value, typename _Alloc,
 831            typename _ExtractKey, typename _Equal,
 832            typename _H1, typename _H2, typename _Hash,
 833            typename _RehashPolicy, typename _Traits>
 834     struct _Insert<_Key, _Value, _Alloc, _ExtractKey, _Equal, _H1, _H2, _Hash,
 835                    _RehashPolicy, _Traits, true, false>
 836     : public _Insert_base<_Key, _Value, _Alloc, _ExtractKey, _Equal,
 837                            _H1, _H2, _Hash, _RehashPolicy, _Traits>
 838     {
 839       using __base_type = _Insert_base<_Key, _Value, _Alloc, _ExtractKey,
 840                                         _Equal, _H1, _H2, _Hash,
 841                                         _RehashPolicy, _Traits>;
 842       using value_type = typename __base_type::value_type;
 843       using iterator = typename __base_type::iterator;
 844       using const_iterator =  typename __base_type::const_iterator;
 845
 846       using __unique_keys = typename __base_type::__unique_keys;
 847       using __hashtable = typename __base_type::__hashtable;
 848       using __node_gen_type = typename __base_type::__node_gen_type;
 849
 850       using __base_type::insert;
 851
 852       iterator
 853       insert(value_type&& __v)
 854       {
 855         __hashtable& __h = this->_M_conjure_hashtable();
 856         __node_gen_type __node_gen(__h);
 857         return __h._M_insert(std::move(__v), __node_gen, __unique_keys());
 858       }
 859
 860       iterator
 861       insert(const_iterator __hint, value_type&& __v)
 862       {
 863         __hashtable& __h = this->_M_conjure_hashtable();
 864         __node_gen_type __node_gen(__h);
 865         return __h._M_insert(__hint, std::move(__v), __node_gen,
 866                              __unique_keys());
 867       }
 868     };
 869
 870   /// Specialization.
 871   template<typename _Key, typename _Value, typename _Alloc,
 872            typename _ExtractKey, typename _Equal,
 873            typename _H1, typename _H2, typename _Hash,
 874            typename _RehashPolicy, typename _Traits, bool _Unique_keys>
 875     struct _Insert<_Key, _Value, _Alloc, _ExtractKey, _Equal, _H1, _H2, _Hash,
 876                    _RehashPolicy, _Traits, false, _Unique_keys>
 877     : public _Insert_base<_Key, _Value, _Alloc, _ExtractKey, _Equal,
 878                            _H1, _H2, _Hash, _RehashPolicy, _Traits>
 879     {
 880       using __base_type = _Insert_base<_Key, _Value, _Alloc, _ExtractKey,
 881                                        _Equal, _H1, _H2, _Hash,
 882                                        _RehashPolicy, _Traits>;
 883       using value_type = typename __base_type::value_type;
 884       using iterator = typename __base_type::iterator;
 885       using const_iterator =  typename __base_type::const_iterator;
 886
 887       using __unique_keys = typename __base_type::__unique_keys;
 888       using __hashtable = typename __base_type::__hashtable;
 889       using __ireturn_type = typename __base_type::__ireturn_type;
 890
 891       using __base_type::insert;
 892
 893       template<typename _Pair>
 894         using __is_cons = std::is_constructible<value_type, _Pair&&>;
 895
 896       template<typename _Pair>
 897         using _IFcons = std::enable_if<__is_cons<_Pair>::value>;
 898
 899       template<typename _Pair>
 900         using _IFconsp = typename _IFcons<_Pair>::type;
 901
 902       template<typename _Pair, typename = _IFconsp<_Pair>>
 903         __ireturn_type
 904         insert(_Pair&& __v)
 905         {
 906           __hashtable& __h = this->_M_conjure_hashtable();
 907           return __h._M_emplace(__unique_keys(), std::forward<_Pair>(__v));
 908         }
 909
 910       template<typename _Pair, typename = _IFconsp<_Pair>>
 911         iterator
 912         insert(const_iterator __hint, _Pair&& __v)
 913         {
 914           __hashtable& __h = this->_M_conjure_hashtable();
 915           return __h._M_emplace(__hint, __unique_keys(),
 916                                 std::forward<_Pair>(__v));
 917         }
 918    };
 919
 920   /**
 921    *  Primary class template  _Rehash_base.
 922    *
 923    *  Give hashtable the max_load_factor functions and reserve iff the
 924    *  rehash policy is _Prime_rehash_policy.
 925   */
 926   template<typename _Key, typename _Value, typename _Alloc,
 927            typename _ExtractKey, typename _Equal,
 928            typename _H1, typename _H2, typename _Hash,
 929            typename _RehashPolicy, typename _Traits>
 930     struct _Rehash_base;
 931
 932   /// Specialization.
 933   template<typename _Key, typename _Value, typename _Alloc,
 934            typename _ExtractKey, typename _Equal,
 935            typename _H1, typename _H2, typename _Hash, typename _Traits>
 936     struct _Rehash_base<_Key, _Value, _Alloc, _ExtractKey, _Equal,
 937                         _H1, _H2, _Hash, _Prime_rehash_policy, _Traits>
 938     {
 939       using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey,
 940                                      _Equal, _H1, _H2, _Hash,
 941                                      _Prime_rehash_policy, _Traits>;
 942
 943       float
 944       max_load_factor() const noexcept
 945       {
 946         const __hashtable* __this = static_cast<const __hashtable*>(this);
 947         return __this->__rehash_policy().max_load_factor();
 948       }
 949
 950       void
 951       max_load_factor(float __z)
 952       {
 953         __hashtable* __this = static_cast<__hashtable*>(this);
 954         __this->__rehash_policy(_Prime_rehash_policy(__z));
 955       }
 956
 957       void
 958       reserve(std::size_t __n)
 959       {
 960         __hashtable* __this = static_cast<__hashtable*>(this);
 961         __this->rehash(__builtin_ceil(__n / max_load_factor()));
 962       }
 963     };
 964
 965   /**
 966    *  Primary class template _Hashtable_ebo_helper.
 967    *
 968    *  Helper class using EBO when it is not forbidden (the type is not
 969    *  final) and when it is worth it (the type is empty.)
 970    */
 971   template<int _Nm, typename _Tp,
 972            bool __use_ebo = !__is_final(_Tp) && __is_empty(_Tp)>
 973     struct _Hashtable_ebo_helper;
 974
 975   /// Specialization using EBO.
 976   template<int _Nm, typename _Tp>
 977     struct _Hashtable_ebo_helper<_Nm, _Tp, true>
 978     : private _Tp
 979     {
 980       _Hashtable_ebo_helper() = default;
 981
 982       _Hashtable_ebo_helper(const _Tp& __tp) : _Tp(__tp)
 983       { }
 984
 985       static const _Tp&
 986       _S_cget(const _Hashtable_ebo_helper& __eboh)
 987       { return static_cast<const _Tp&>(__eboh); }
 988
 989       static _Tp&
 990       _S_get(_Hashtable_ebo_helper& __eboh)
 991       { return static_cast<_Tp&>(__eboh); }
 992     };
 993
 994   /// Specialization not using EBO.
 995   template<int _Nm, typename _Tp>
 996     struct _Hashtable_ebo_helper<_Nm, _Tp, false>
 997     {
 998       _Hashtable_ebo_helper() = default;
 999
1000       _Hashtable_ebo_helper(const _Tp& __tp) : _M_tp(__tp)
1001       { }
1002
1003       static const _Tp&
1004       _S_cget(const _Hashtable_ebo_helper& __eboh)
1005       { return __eboh._M_tp; }
1006
1007       static _Tp&
1008       _S_get(_Hashtable_ebo_helper& __eboh)
1009       { return __eboh._M_tp; }
1010
1011     private:
1012       _Tp _M_tp;
1013     };
1014
1015   /**
1016    *  Primary class template _Local_iterator_base.
1017    *
1018    *  Base class for local iterators, used to iterate within a bucket
1019    *  but not between buckets.
1020    */
1021   template<typename _Key, typename _Value, typename _ExtractKey,
1022            typename _H1, typename _H2, typename _Hash,
1023            bool __cache_hash_code>
1024     struct _Local_iterator_base;
1025
1026   /**
1027    *  Primary class template _Hash_code_base.
1028    *
1029    *  Encapsulates two policy issues that aren't quite orthogonal.
1030    *   (1) the difference between using a ranged hash function and using
1031    *       the combination of a hash function and a range-hashing function.
1032    *       In the former case we don't have such things as hash codes, so
1033    *       we have a dummy type as placeholder.
1034    *   (2) Whether or not we cache hash codes.  Caching hash codes is
1035    *       meaningless if we have a ranged hash function.
1036    *
1037    *  We also put the key extraction objects here, for convenience.
1038    *  Each specialization derives from one or more of the template
1039    *  parameters to benefit from Ebo. This is important as this type
1040    *  is inherited in some cases by the _Local_iterator_base type used
1041    *  to implement local_iterator and const_local_iterator. As with
1042    *  any iterator type we prefer to make it as small as possible.
1043    *
1044    *  Primary template is unused except as a hook for specializations.
1045    */
1046   template<typename _Key, typename _Value, typename _ExtractKey,
1047            typename _H1, typename _H2, typename _Hash,
1048            bool __cache_hash_code>
1049     struct _Hash_code_base;
1050
1051   /// Specialization: ranged hash function, no caching hash codes.  H1
1052   /// and H2 are provided but ignored.  We define a dummy hash code type.
1053   template<typename _Key, typename _Value, typename _ExtractKey,
1054            typename _H1, typename _H2, typename _Hash>
1055     struct _Hash_code_base<_Key, _Value, _ExtractKey, _H1, _H2, _Hash, false>
1056     : private _Hashtable_ebo_helper<0, _ExtractKey>,
1057       private _Hashtable_ebo_helper<1, _Hash>
1058     {
1059     private:
1060       using __ebo_extract_key = _Hashtable_ebo_helper<0, _ExtractKey>;
1061       using __ebo_hash = _Hashtable_ebo_helper<1, _Hash>;
1062
1063     protected:
1064       typedef void*                                     __hash_code;
1065       typedef _Hash_node<_Value, false>                 __node_type;
1066
1067       // We need the default constructor for the local iterators.
1068       _Hash_code_base() = default;
1069
1070       _Hash_code_base(const _ExtractKey& __ex, const _H1&, const _H2&,
1071                       const _Hash& __h)
1072       : __ebo_extract_key(__ex), __ebo_hash(__h) { }
1073
1074       __hash_code
1075       _M_hash_code(const _Key& __key) const
1076       { return 0; }
1077
1078       std::size_t
1079       _M_bucket_index(const _Key& __k, __hash_code, std::size_t __n) const
1080       { return _M_ranged_hash()(__k, __n); }
1081
1082       std::size_t
1083       _M_bucket_index(const __node_type* __p, std::size_t __n) const
1084         noexcept( noexcept(declval<const _Hash&>()(declval<const _Key&>(), (std::size_t)0)) )
1085       { return _M_ranged_hash()(_M_extract()(__p->_M_v()), __n); }
1086
1087       void
1088       _M_store_code(__node_type*, __hash_code) const
1089       { }
1090
1091       void
1092       _M_copy_code(__node_type*, const __node_type*) const
1093       { }
1094
1095       void
1096       _M_swap(_Hash_code_base& __x)
1097       {
1098         std::swap(_M_extract(), __x._M_extract());
1099         std::swap(_M_ranged_hash(), __x._M_ranged_hash());
1100       }
1101
1102       const _ExtractKey&
1103       _M_extract() const { return __ebo_extract_key::_S_cget(*this); }
1104
1105       _ExtractKey&
1106       _M_extract() { return __ebo_extract_key::_S_get(*this); }
1107
1108       const _Hash&
1109       _M_ranged_hash() const { return __ebo_hash::_S_cget(*this); }
1110
1111       _Hash&
1112       _M_ranged_hash() { return __ebo_hash::_S_get(*this); }
1113     };
1114
1115   // No specialization for ranged hash function while caching hash codes.
1116   // That combination is meaningless, and trying to do it is an error.
1117
1118   /// Specialization: ranged hash function, cache hash codes.  This
1119   /// combination is meaningless, so we provide only a declaration
1120   /// and no definition.
1121   template<typename _Key, typename _Value, typename _ExtractKey,
1122            typename _H1, typename _H2, typename _Hash>
1123     struct _Hash_code_base<_Key, _Value, _ExtractKey, _H1, _H2, _Hash, true>;
1124
1125   /// Specialization: hash function and range-hashing function, no
1126   /// caching of hash codes.
1127   /// Provides typedef and accessor required by C++ 11.
1128   template<typename _Key, typename _Value, typename _ExtractKey,
1129            typename _H1, typename _H2>
1130     struct _Hash_code_base<_Key, _Value, _ExtractKey, _H1, _H2,
1131                            _Default_ranged_hash, false>
1132     : private _Hashtable_ebo_helper<0, _ExtractKey>,
1133       private _Hashtable_ebo_helper<1, _H1>,
1134       private _Hashtable_ebo_helper<2, _H2>
1135     {
1136     private:
1137       using __ebo_extract_key = _Hashtable_ebo_helper<0, _ExtractKey>;
1138       using __ebo_h1 = _Hashtable_ebo_helper<1, _H1>;
1139       using __ebo_h2 = _Hashtable_ebo_helper<2, _H2>;
1140
1141     public:
1142       typedef _H1                                       hasher;
1143
1144       hasher
1145       hash_function() const
1146       { return _M_h1(); }
1147
1148     protected:
1149       typedef std::size_t                               __hash_code;
1150       typedef _Hash_node<_Value, false>                 __node_type;
1151
1152       // We need the default constructor for the local iterators.
1153       _Hash_code_base() = default;
1154
1155       _Hash_code_base(const _ExtractKey& __ex,
1156                       const _H1& __h1, const _H2& __h2,
1157                       const _Default_ranged_hash&)
1158       : __ebo_extract_key(__ex), __ebo_h1(__h1), __ebo_h2(__h2) { }
1159
1160       __hash_code
1161       _M_hash_code(const _Key& __k) const
1162       { return _M_h1()(__k); }
1163
1164       std::size_t
1165       _M_bucket_index(const _Key&, __hash_code __c, std::size_t __n) const
1166       { return _M_h2()(__c, __n); }
1167
1168       std::size_t
1169       _M_bucket_index(const __node_type* __p, std::size_t __n) const
1170         noexcept( noexcept(declval<const _H1&>()(declval<const _Key&>()))
1171                   && noexcept(declval<const _H2&>()((__hash_code)0, (std::size_t)0)) )
1172       { return _M_h2()(_M_h1()(_M_extract()(__p->_M_v())), __n); }
1173
1174       void
1175       _M_store_code(__node_type*, __hash_code) const
1176       { }
1177
1178       void
1179       _M_copy_code(__node_type*, const __node_type*) const
1180       { }
1181
1182       void
1183       _M_swap(_Hash_code_base& __x)
1184       {
1185         std::swap(_M_extract(), __x._M_extract());
1186         std::swap(_M_h1(), __x._M_h1());
1187         std::swap(_M_h2(), __x._M_h2());
1188       }
1189
1190       const _ExtractKey&
1191       _M_extract() const { return __ebo_extract_key::_S_cget(*this); }
1192
1193       _ExtractKey&
1194       _M_extract() { return __ebo_extract_key::_S_get(*this); }
1195
1196       const _H1&
1197       _M_h1() const { return __ebo_h1::_S_cget(*this); }
1198
1199       _H1&
1200       _M_h1() { return __ebo_h1::_S_get(*this); }
1201
1202       const _H2&
1203       _M_h2() const { return __ebo_h2::_S_cget(*this); }
1204
1205       _H2&
1206       _M_h2() { return __ebo_h2::_S_get(*this); }
1207     };
1208
1209   /// Specialization: hash function and range-hashing function,
1210   /// caching hash codes.  H is provided but ignored.  Provides
1211   /// typedef and accessor required by C++ 11.
1212   template<typename _Key, typename _Value, typename _ExtractKey,
1213            typename _H1, typename _H2>
1214     struct _Hash_code_base<_Key, _Value, _ExtractKey, _H1, _H2,
1215                            _Default_ranged_hash, true>
1216     : private _Hashtable_ebo_helper<0, _ExtractKey>,
1217       private _Hashtable_ebo_helper<1, _H1>,
1218       private _Hashtable_ebo_helper<2, _H2>
1219     {
1220     private:
1221       // Gives access to _M_h2() to the local iterator implementation.
1222       friend struct _Local_iterator_base<_Key, _Value, _ExtractKey, _H1, _H2,
1223                                          _Default_ranged_hash, true>;
1224
1225       using __ebo_extract_key = _Hashtable_ebo_helper<0, _ExtractKey>;
1226       using __ebo_h1 = _Hashtable_ebo_helper<1, _H1>;
1227       using __ebo_h2 = _Hashtable_ebo_helper<2, _H2>;
1228
1229     public:
1230       typedef _H1                                       hasher;
1231
1232       hasher
1233       hash_function() const
1234       { return _M_h1(); }
1235
1236     protected:
1237       typedef std::size_t                               __hash_code;
1238       typedef _Hash_node<_Value, true>                  __node_type;
1239
1240       _Hash_code_base(const _ExtractKey& __ex,
1241                       const _H1& __h1, const _H2& __h2,
1242                       const _Default_ranged_hash&)
1243       : __ebo_extract_key(__ex), __ebo_h1(__h1), __ebo_h2(__h2) { }
1244
1245       __hash_code
1246       _M_hash_code(const _Key& __k) const
1247       { return _M_h1()(__k); }
1248
1249       std::size_t
1250       _M_bucket_index(const _Key&, __hash_code __c,
1251                       std::size_t __n) const
1252       { return _M_h2()(__c, __n); }
1253
1254       std::size_t
1255       _M_bucket_index(const __node_type* __p, std::size_t __n) const
1256         noexcept( noexcept(declval<const _H2&>()((__hash_code)0,
1257                                                  (std::size_t)0)) )
1258       { return _M_h2()(__p->_M_hash_code, __n); }
1259
1260       void
1261       _M_store_code(__node_type* __n, __hash_code __c) const
1262       { __n->_M_hash_code = __c; }
1263
1264       void
1265       _M_copy_code(__node_type* __to, const __node_type* __from) const
1266       { __to->_M_hash_code = __from->_M_hash_code; }
1267
1268       void
1269       _M_swap(_Hash_code_base& __x)
1270       {
1271         std::swap(_M_extract(), __x._M_extract());
1272         std::swap(_M_h1(), __x._M_h1());
1273         std::swap(_M_h2(), __x._M_h2());
1274       }
1275
1276       const _ExtractKey&
1277       _M_extract() const { return __ebo_extract_key::_S_cget(*this); }
1278
1279       _ExtractKey&
1280       _M_extract() { return __ebo_extract_key::_S_get(*this); }
1281
1282       const _H1&
1283       _M_h1() const { return __ebo_h1::_S_cget(*this); }
1284
1285       _H1&
1286       _M_h1() { return __ebo_h1::_S_get(*this); }
1287
1288       const _H2&
1289       _M_h2() const { return __ebo_h2::_S_cget(*this); }
1290
1291       _H2&
1292       _M_h2() { return __ebo_h2::_S_get(*this); }
1293     };
1294
1295   /**
1296    *  Primary class template _Equal_helper.
1297    *
1298    */
1299   template <typename _Key, typename _Value, typename _ExtractKey,
1300             typename _Equal, typename _HashCodeType,
1301             bool __cache_hash_code>
1302   struct _Equal_helper;
1303
1304   /// Specialization.
1305   template<typename _Key, typename _Value, typename _ExtractKey,
1306            typename _Equal, typename _HashCodeType>
1307   struct _Equal_helper<_Key, _Value, _ExtractKey, _Equal, _HashCodeType, true>
1308   {
1309     static bool
1310     _S_equals(const _Equal& __eq, const _ExtractKey& __extract,
1311               const _Key& __k, _HashCodeType __c, _Hash_node<_Value, true>* __n)
1312     { return __c == __n->_M_hash_code && __eq(__k, __extract(__n->_M_v())); }
1313   };
1314
1315   /// Specialization.
1316   template<typename _Key, typename _Value, typename _ExtractKey,
1317            typename _Equal, typename _HashCodeType>
1318   struct _Equal_helper<_Key, _Value, _ExtractKey, _Equal, _HashCodeType, false>
1319   {
1320     static bool
1321     _S_equals(const _Equal& __eq, const _ExtractKey& __extract,
1322               const _Key& __k, _HashCodeType, _Hash_node<_Value, false>* __n)
1323     { return __eq(__k, __extract(__n->_M_v())); }
1324   };
1325
1326
1327   /// Specialization.
1328   template<typename _Key, typename _Value, typename _ExtractKey,
1329            typename _H1, typename _H2, typename _Hash>
1330     struct _Local_iterator_base<_Key, _Value, _ExtractKey,
1331                                 _H1, _H2, _Hash, true>
1332     : private _Hashtable_ebo_helper<0, _H2>
1333     {
1334     protected:
1335       using __base_type = _Hashtable_ebo_helper<0, _H2>;
1336       using __hash_code_base = _Hash_code_base<_Key, _Value, _ExtractKey,
1337                                                _H1, _H2, _Hash, true>;
1338
1339     public:
1340       _Local_iterator_base() = default;
1341       _Local_iterator_base(const __hash_code_base& __base,
1342                            _Hash_node<_Value, true>* __p,
1343                            std::size_t __bkt, std::size_t __bkt_count)
1344       : __base_type(__base._M_h2()),
1345         _M_cur(__p), _M_bucket(__bkt), _M_bucket_count(__bkt_count) { }
1346
1347       void
1348       _M_incr()
1349       {
1350         _M_cur = _M_cur->_M_next();
1351         if (_M_cur)
1352           {
1353             std::size_t __bkt
1354               = __base_type::_S_get(*this)(_M_cur->_M_hash_code,
1355                                            _M_bucket_count);
1356             if (__bkt != _M_bucket)
1357               _M_cur = nullptr;
1358           }
1359       }
1360
1361       _Hash_node<_Value, true>*  _M_cur;
1362       std::size_t _M_bucket;
1363       std::size_t _M_bucket_count;
1364     };
1365
1366   /// Specialization.
1367   template<typename _Key, typename _Value, typename _ExtractKey,
1368            typename _H1, typename _H2, typename _Hash>
1369     struct _Local_iterator_base<_Key, _Value, _ExtractKey,
1370                                 _H1, _H2, _Hash, false>
1371     : private _Hash_code_base<_Key, _Value, _ExtractKey,
1372                               _H1, _H2, _Hash, false>
1373     {
1374     protected:
1375       using __hash_code_base = _Hash_code_base<_Key, _Value, _ExtractKey,
1376                                                _H1, _H2, _Hash, false>;
1377
1378     public:
1379       _Local_iterator_base() = default;
1380       _Local_iterator_base(const __hash_code_base& __base,
1381                            _Hash_node<_Value, false>* __p,
1382                            std::size_t __bkt, std::size_t __bkt_count)
1383         : __hash_code_base(__base),
1384           _M_cur(__p), _M_bucket(__bkt), _M_bucket_count(__bkt_count) { }
1385
1386       void
1387       _M_incr()
1388       {
1389         _M_cur = _M_cur->_M_next();
1390         if (_M_cur)
1391           {
1392             std::size_t __bkt = this->_M_bucket_index(_M_cur, _M_bucket_count);
1393             if (__bkt != _M_bucket)
1394               _M_cur = nullptr;
1395           }
1396       }
1397
1398       _Hash_node<_Value, false>*  _M_cur;
1399       std::size_t _M_bucket;
1400       std::size_t _M_bucket_count;
1401     };
1402
1403   template<typename _Key, typename _Value, typename _ExtractKey,
1404            typename _H1, typename _H2, typename _Hash, bool __cache>
1405     inline bool
1406     operator==(const _Local_iterator_base<_Key, _Value, _ExtractKey,
1407                                           _H1, _H2, _Hash, __cache>& __x,
1408                const _Local_iterator_base<_Key, _Value, _ExtractKey,
1409                                           _H1, _H2, _Hash, __cache>& __y)
1410     { return __x._M_cur == __y._M_cur; }
1411
1412   template<typename _Key, typename _Value, typename _ExtractKey,
1413            typename _H1, typename _H2, typename _Hash, bool __cache>
1414     inline bool
1415     operator!=(const _Local_iterator_base<_Key, _Value, _ExtractKey,
1416                                           _H1, _H2, _Hash, __cache>& __x,
1417                const _Local_iterator_base<_Key, _Value, _ExtractKey,
1418                                           _H1, _H2, _Hash, __cache>& __y)
1419     { return __x._M_cur != __y._M_cur; }
1420
1421   /// local iterators
1422   template<typename _Key, typename _Value, typename _ExtractKey,
1423            typename _H1, typename _H2, typename _Hash,
1424            bool __constant_iterators, bool __cache>
1425     struct _Local_iterator
1426     : public _Local_iterator_base<_Key, _Value, _ExtractKey,
1427                                   _H1, _H2, _Hash, __cache>
1428     {
1429     private:
1430       using __base_type = _Local_iterator_base<_Key, _Value, _ExtractKey,
1431                                                _H1, _H2, _Hash, __cache>;
1432       using __hash_code_base = typename __base_type::__hash_code_base;
1433     public:
1434       typedef _Value                                   value_type;
1435       typedef typename std::conditional<__constant_iterators,
1436                                         const _Value*, _Value*>::type
1437                                                        pointer;
1438       typedef typename std::conditional<__constant_iterators,
1439                                         const _Value&, _Value&>::type
1440                                                        reference;
1441       typedef std::ptrdiff_t                           difference_type;
1442       typedef std::forward_iterator_tag                iterator_category;
1443
1444       _Local_iterator() = default;
1445
1446       _Local_iterator(const __hash_code_base& __base,
1447                       _Hash_node<_Value, __cache>* __p,
1448                       std::size_t __bkt, std::size_t __bkt_count)
1449         : __base_type(__base, __p, __bkt, __bkt_count)
1450       { }
1451
1452       reference
1453       operator*() const
1454       { return this->_M_cur->_M_v(); }
1455
1456       pointer
1457       operator->() const
1458       { return this->_M_cur->_M_valptr(); }
1459
1460       _Local_iterator&
1461       operator++()
1462       {
1463         this->_M_incr();
1464         return *this;
1465       }
1466
1467       _Local_iterator
1468       operator++(int)
1469       {
1470         _Local_iterator __tmp(*this);
1471         this->_M_incr();
1472         return __tmp;
1473       }
1474     };
1475
1476   /// local const_iterators
1477   template<typename _Key, typename _Value, typename _ExtractKey,
1478            typename _H1, typename _H2, typename _Hash,
1479            bool __constant_iterators, bool __cache>
1480     struct _Local_const_iterator
1481     : public _Local_iterator_base<_Key, _Value, _ExtractKey,
1482                                   _H1, _H2, _Hash, __cache>
1483     {
1484     private:
1485       using __base_type = _Local_iterator_base<_Key, _Value, _ExtractKey,
1486                                                _H1, _H2, _Hash, __cache>;
1487       using __hash_code_base = typename __base_type::__hash_code_base;
1488
1489     public:
1490       typedef _Value                                   value_type;
1491       typedef const _Value*                            pointer;
1492       typedef const _Value&                            reference;
1493       typedef std::ptrdiff_t                           difference_type;
1494       typedef std::forward_iterator_tag                iterator_category;
1495
1496       _Local_const_iterator() = default;
1497
1498       _Local_const_iterator(const __hash_code_base& __base,
1499                             _Hash_node<_Value, __cache>* __p,
1500                             std::size_t __bkt, std::size_t __bkt_count)
1501         : __base_type(__base, __p, __bkt, __bkt_count)
1502       { }
1503
1504       _Local_const_iterator(const _Local_iterator<_Key, _Value, _ExtractKey,
1505                                                   _H1, _H2, _Hash,
1506                                                   __constant_iterators,
1507                                                   __cache>& __x)
1508         : __base_type(__x)
1509       { }
1510
1511       reference
1512       operator*() const
1513       { return this->_M_cur->_M_v(); }
1514
1515       pointer
1516       operator->() const
1517       { return this->_M_cur->_M_valptr(); }
1518
1519       _Local_const_iterator&
1520       operator++()
1521       {
1522         this->_M_incr();
1523         return *this;
1524       }
1525
1526       _Local_const_iterator
1527       operator++(int)
1528       {
1529         _Local_const_iterator __tmp(*this);
1530         this->_M_incr();
1531         return __tmp;
1532       }
1533     };
1534
1535   /**
1536    *  Primary class template _Hashtable_base.
1537    *
1538    *  Helper class adding management of _Equal functor to
1539    *  _Hash_code_base type.
1540    *
1541    *  Base class templates are:
1542    *    - __detail::_Hash_code_base
1543    *    - __detail::_Hashtable_ebo_helper
1544    */
1545   template<typename _Key, typename _Value,
1546            typename _ExtractKey, typename _Equal,
1547            typename _H1, typename _H2, typename _Hash, typename _Traits>
1548   struct _Hashtable_base
1549   : public _Hash_code_base<_Key, _Value, _ExtractKey, _H1, _H2, _Hash,
1550                            _Traits::__hash_cached::value>,
1551     private _Hashtable_ebo_helper<0, _Equal>
1552   {
1553   public:
1554     typedef _Key                                    key_type;
1555     typedef _Value                                  value_type;
1556     typedef _Equal                                  key_equal;
1557     typedef std::size_t                             size_type;
1558     typedef std::ptrdiff_t                          difference_type;
1559
1560     using __traits_type = _Traits;
1561     using __hash_cached = typename __traits_type::__hash_cached;
1562     using __constant_iterators = typename __traits_type::__constant_iterators;
1563     using __unique_keys = typename __traits_type::__unique_keys;
1564
1565     using __hash_code_base = _Hash_code_base<_Key, _Value, _ExtractKey,
1566                                              _H1, _H2, _Hash,
1567                                              __hash_cached::value>;
1568
1569     using __hash_code = typename __hash_code_base::__hash_code;
1570     using __node_type = typename __hash_code_base::__node_type;
1571
1572     using iterator = __detail::_Node_iterator<value_type,
1573                                               __constant_iterators::value,
1574                                               __hash_cached::value>;
1575
1576     using const_iterator = __detail::_Node_const_iterator<value_type,
1577                                                    __constant_iterators::value,
1578                                                    __hash_cached::value>;
1579
1580     using local_iterator = __detail::_Local_iterator<key_type, value_type,
1581                                                   _ExtractKey, _H1, _H2, _Hash,
1582                                                   __constant_iterators::value,
1583                                                      __hash_cached::value>;
1584
1585     using const_local_iterator = __detail::_Local_const_iterator<key_type,
1586                                                                  value_type,
1587                                         _ExtractKey, _H1, _H2, _Hash,
1588                                         __constant_iterators::value,
1589                                         __hash_cached::value>;
1590
1591     using __ireturn_type = typename std::conditional<__unique_keys::value,
1592                                                      std::pair<iterator, bool>,
1593                                                      iterator>::type;
1594   private:
1595     using _EqualEBO = _Hashtable_ebo_helper<0, _Equal>;
1596     using _EqualHelper =  _Equal_helper<_Key, _Value, _ExtractKey, _Equal,
1597                                         __hash_code, __hash_cached::value>;
1598
1599   protected:
1600     using __node_base = __detail::_Hash_node_base;
1601     using __bucket_type = __node_base*;
1602
1603     _Hashtable_base(const _ExtractKey& __ex, const _H1& __h1, const _H2& __h2,
1604                     const _Hash& __hash, const _Equal& __eq)
1605     : __hash_code_base(__ex, __h1, __h2, __hash), _EqualEBO(__eq)
1606     { }
1607
1608     bool
1609     _M_equals(const _Key& __k, __hash_code __c, __node_type* __n) const
1610     {
1611       return _EqualHelper::_S_equals(_M_eq(), this->_M_extract(),
1612                                      __k, __c, __n);
1613     }
1614
1615     void
1616     _M_swap(_Hashtable_base& __x)
1617     {
1618       __hash_code_base::_M_swap(__x);
1619       std::swap(_M_eq(), __x._M_eq());
1620     }
1621
1622     const _Equal&
1623     _M_eq() const { return _EqualEBO::_S_cget(*this); }
1624
1625     _Equal&
1626     _M_eq() { return _EqualEBO::_S_get(*this); }
1627   };
1628
1629   /**
1630    *  struct _Equality_base.
1631    *
1632    *  Common types and functions for class _Equality.
1633    */
1634   struct _Equality_base
1635   {
1636   protected:
1637     template<typename _Uiterator>
1638       static bool
1639       _S_is_permutation(_Uiterator, _Uiterator, _Uiterator);
1640   };
1641
1642   // See std::is_permutation in N3068.
1643   template<typename _Uiterator>
1644     bool
1645     _Equality_base::
1646     _S_is_permutation(_Uiterator __first1, _Uiterator __last1,
1647                       _Uiterator __first2)
1648     {
1649       for (; __first1 != __last1; ++__first1, ++__first2)
1650         if (!(*__first1 == *__first2))
1651           break;
1652
1653       if (__first1 == __last1)
1654         return true;
1655
1656       _Uiterator __last2 = __first2;
1657       std::advance(__last2, std::distance(__first1, __last1));
1658
1659       for (_Uiterator __it1 = __first1; __it1 != __last1; ++__it1)
1660         {
1661           _Uiterator __tmp =  __first1;
1662           while (__tmp != __it1 && !bool(*__tmp == *__it1))
1663             ++__tmp;
1664
1665           // We've seen this one before.
1666           if (__tmp != __it1)
1667             continue;
1668
1669           std::ptrdiff_t __n2 = 0;
1670           for (__tmp = __first2; __tmp != __last2; ++__tmp)
1671             if (*__tmp == *__it1)
1672               ++__n2;
1673
1674           if (!__n2)
1675             return false;
1676
1677           std::ptrdiff_t __n1 = 0;
1678           for (__tmp = __it1; __tmp != __last1; ++__tmp)
1679             if (*__tmp == *__it1)
1680               ++__n1;
1681
1682           if (__n1 != __n2)
1683             return false;
1684         }
1685       return true;
1686     }
1687
1688   /**
1689    *  Primary class template  _Equality.
1690    *
1691    *  This is for implementing equality comparison for unordered
1692    *  containers, per N3068, by John Lakos and Pablo Halpern.
1693    *  Algorithmically, we follow closely the reference implementations
1694    *  therein.
1695    */
1696   template<typename _Key, typename _Value, typename _Alloc,
1697            typename _ExtractKey, typename _Equal,
1698            typename _H1, typename _H2, typename _Hash,
1699            typename _RehashPolicy, typename _Traits,
1700            bool _Unique_keys = _Traits::__unique_keys::value>
1701     struct _Equality;
1702
1703   /// Specialization.
1704   template<typename _Key, typename _Value, typename _Alloc,
1705            typename _ExtractKey, typename _Equal,
1706            typename _H1, typename _H2, typename _Hash,
1707            typename _RehashPolicy, typename _Traits>
1708     struct _Equality<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1709                      _H1, _H2, _Hash, _RehashPolicy, _Traits, true>
1710     {
1711       using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1712                                      _H1, _H2, _Hash, _RehashPolicy, _Traits>;
1713
1714       bool
1715       _M_equal(const __hashtable&) const;
1716     };
1717
1718   template<typename _Key, typename _Value, typename _Alloc,
1719            typename _ExtractKey, typename _Equal,
1720            typename _H1, typename _H2, typename _Hash,
1721            typename _RehashPolicy, typename _Traits>
1722     bool
1723     _Equality<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1724               _H1, _H2, _Hash, _RehashPolicy, _Traits, true>::
1725     _M_equal(const __hashtable& __other) const
1726     {
1727       const __hashtable* __this = static_cast<const __hashtable*>(this);
1728
1729       if (__this->size() != __other.size())
1730         return false;
1731
1732       for (auto __itx = __this->begin(); __itx != __this->end(); ++__itx)
1733         {
1734           const auto __ity = __other.find(_ExtractKey()(*__itx));
1735           if (__ity == __other.end() || !bool(*__ity == *__itx))
1736             return false;
1737         }
1738       return true;
1739     }
1740
1741   /// Specialization.
1742   template<typename _Key, typename _Value, typename _Alloc,
1743            typename _ExtractKey, typename _Equal,
1744            typename _H1, typename _H2, typename _Hash,
1745            typename _RehashPolicy, typename _Traits>
1746     struct _Equality<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1747                      _H1, _H2, _Hash, _RehashPolicy, _Traits, false>
1748     : public _Equality_base
1749     {
1750       using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1751                                      _H1, _H2, _Hash, _RehashPolicy, _Traits>;
1752
1753       bool
1754       _M_equal(const __hashtable&) const;
1755     };
1756
1757   template<typename _Key, typename _Value, typename _Alloc,
1758            typename _ExtractKey, typename _Equal,
1759            typename _H1, typename _H2, typename _Hash,
1760            typename _RehashPolicy, typename _Traits>
1761     bool
1762     _Equality<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1763               _H1, _H2, _Hash, _RehashPolicy, _Traits, false>::
1764     _M_equal(const __hashtable& __other) const
1765     {
1766       const __hashtable* __this = static_cast<const __hashtable*>(this);
1767
1768       if (__this->size() != __other.size())
1769         return false;
1770
1771       for (auto __itx = __this->begin(); __itx != __this->end();)
1772         {
1773           const auto __xrange = __this->equal_range(_ExtractKey()(*__itx));
1774           const auto __yrange = __other.equal_range(_ExtractKey()(*__itx));
1775
1776           if (std::distance(__xrange.first, __xrange.second)
1777               != std::distance(__yrange.first, __yrange.second))
1778             return false;
1779
1780           if (!_S_is_permutation(__xrange.first, __xrange.second,
1781                                  __yrange.first))
1782             return false;
1783
1784           __itx = __xrange.second;
1785         }
1786       return true;
1787     }
1788
1789   /**
1790    * This type is to combine a _Hash_node_base instance with an allocator
1791    * instance through inheritance to benefit from EBO when possible.
1792    */
1793   template<typename _NodeAlloc>
1794     struct _Before_begin : public _NodeAlloc
1795     {
1796       _Hash_node_base _M_node;
1797
1798       _Before_begin(const _Before_begin&) = default;
1799       _Before_begin(_Before_begin&&) = default;
1800
1801       template<typename _Alloc>
1802         _Before_begin(_Alloc&& __a)
1803           : _NodeAlloc(std::forward<_Alloc>(__a))
1804         { }
1805     };
1806
1807  //@} hashtable-detail
1808 _GLIBCXX_END_NAMESPACE_VERSION
1809 } // namespace __detail
1810 } // namespace std
1811
1812 #endif // _HASHTABLE_POLICY_H