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

   1 // Internal policy header for unordered_set and unordered_map -*- C++ -*-
   2
   3 // Copyright (C) 2010-2015 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::__bool_constant<
  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   template<typename _NodeAlloc>
 106     struct _Hashtable_alloc;
 107
 108   // Functor recycling a pool of nodes and using allocation once the pool is
 109   // empty.
 110   template<typename _NodeAlloc>
 111     struct _ReuseOrAllocNode
 112     {
 113     private:
 114       using __node_alloc_type = _NodeAlloc;
 115       using __hashtable_alloc = _Hashtable_alloc<__node_alloc_type>;
 116       using __value_alloc_type = typename __hashtable_alloc::__value_alloc_type;
 117       using __value_alloc_traits =
 118         typename __hashtable_alloc::__value_alloc_traits;
 119       using __node_alloc_traits =
 120         typename __hashtable_alloc::__node_alloc_traits;
 121       using __node_type = typename __hashtable_alloc::__node_type;
 122
 123     public:
 124       _ReuseOrAllocNode(__node_type* __nodes, __hashtable_alloc& __h)
 125         : _M_nodes(__nodes), _M_h(__h) { }
 126       _ReuseOrAllocNode(const _ReuseOrAllocNode&) = delete;
 127
 128       ~_ReuseOrAllocNode()
 129       { _M_h._M_deallocate_nodes(_M_nodes); }
 130
 131       template<typename _Arg>
 132         __node_type*
 133         operator()(_Arg&& __arg) const
 134         {
 135           if (_M_nodes)
 136             {
 137               __node_type* __node = _M_nodes;
 138               _M_nodes = _M_nodes->_M_next();
 139               __node->_M_nxt = nullptr;
 140               __value_alloc_type __a(_M_h._M_node_allocator());
 141               __value_alloc_traits::destroy(__a, __node->_M_valptr());
 142               __try
 143                 {
 144                   __value_alloc_traits::construct(__a, __node->_M_valptr(),
 145                                                   std::forward<_Arg>(__arg));
 146                 }
 147               __catch(...)
 148                 {
 149                   __node->~__node_type();
 150                   __node_alloc_traits::deallocate(_M_h._M_node_allocator(),
 151                                                   __node, 1);
 152                   __throw_exception_again;
 153                 }
 154               return __node;
 155             }
 156           return _M_h._M_allocate_node(std::forward<_Arg>(__arg));
 157         }
 158
 159     private:
 160       mutable __node_type* _M_nodes;
 161       __hashtable_alloc& _M_h;
 162     };
 163
 164   // Functor similar to the previous one but without any pool of nodes to
 165   // recycle.
 166   template<typename _NodeAlloc>
 167     struct _AllocNode
 168     {
 169     private:
 170       using __hashtable_alloc = _Hashtable_alloc<_NodeAlloc>;
 171       using __node_type = typename __hashtable_alloc::__node_type;
 172
 173     public:
 174       _AllocNode(__hashtable_alloc& __h)
 175         : _M_h(__h) { }
 176
 177       template<typename _Arg>
 178         __node_type*
 179         operator()(_Arg&& __arg) const
 180         { return _M_h._M_allocate_node(std::forward<_Arg>(__arg)); }
 181
 182     private:
 183       __hashtable_alloc& _M_h;
 184     };
 185
 186   // Auxiliary types used for all instantiations of _Hashtable nodes
 187   // and iterators.
 188
 189   /**
 190    *  struct _Hashtable_traits
 191    *
 192    *  Important traits for hash tables.
 193    *
 194    *  @tparam _Cache_hash_code  Boolean value. True if the value of
 195    *  the hash function is stored along with the value. This is a
 196    *  time-space tradeoff.  Storing it may improve lookup speed by
 197    *  reducing the number of times we need to call the _Equal
 198    *  function.
 199    *
 200    *  @tparam _Constant_iterators  Boolean value. True if iterator and
 201    *  const_iterator are both constant iterator types. This is true
 202    *  for unordered_set and unordered_multiset, false for
 203    *  unordered_map and unordered_multimap.
 204    *
 205    *  @tparam _Unique_keys  Boolean value. True if the return value
 206    *  of _Hashtable::count(k) is always at most one, false if it may
 207    *  be an arbitrary number. This is true for unordered_set and
 208    *  unordered_map, false for unordered_multiset and
 209    *  unordered_multimap.
 210    */
 211   template<bool _Cache_hash_code, bool _Constant_iterators, bool _Unique_keys>
 212     struct _Hashtable_traits
 213     {
 214       using __hash_cached = __bool_constant<_Cache_hash_code>;
 215       using __constant_iterators = __bool_constant<_Constant_iterators>;
 216       using __unique_keys = __bool_constant<_Unique_keys>;
 217     };
 218
 219   /**
 220    *  struct _Hash_node_base
 221    *
 222    *  Nodes, used to wrap elements stored in the hash table.  A policy
 223    *  template parameter of class template _Hashtable controls whether
 224    *  nodes also store a hash code. In some cases (e.g. strings) this
 225    *  may be a performance win.
 226    */
 227   struct _Hash_node_base
 228   {
 229     _Hash_node_base* _M_nxt;
 230
 231     _Hash_node_base() noexcept : _M_nxt() { }
 232
 233     _Hash_node_base(_Hash_node_base* __next) noexcept : _M_nxt(__next) { }
 234   };
 235
 236   /**
 237    *  struct _Hash_node_value_base
 238    *
 239    *  Node type with the value to store.
 240    */
 241   template<typename _Value>
 242     struct _Hash_node_value_base : _Hash_node_base
 243     {
 244       typedef _Value value_type;
 245
 246       __gnu_cxx::__aligned_buffer<_Value> _M_storage;
 247
 248       _Value*
 249       _M_valptr() noexcept
 250       { return _M_storage._M_ptr(); }
 251
 252       const _Value*
 253       _M_valptr() const noexcept
 254       { return _M_storage._M_ptr(); }
 255
 256       _Value&
 257       _M_v() noexcept
 258       { return *_M_valptr(); }
 259
 260       const _Value&
 261       _M_v() const noexcept
 262       { return *_M_valptr(); }
 263     };
 264
 265   /**
 266    *  Primary template struct _Hash_node.
 267    */
 268   template<typename _Value, bool _Cache_hash_code>
 269     struct _Hash_node;
 270
 271   /**
 272    *  Specialization for nodes with caches, struct _Hash_node.
 273    *
 274    *  Base class is __detail::_Hash_node_value_base.
 275    */
 276   template<typename _Value>
 277     struct _Hash_node<_Value, true> : _Hash_node_value_base<_Value>
 278     {
 279       std::size_t  _M_hash_code;
 280
 281       _Hash_node*
 282       _M_next() const noexcept
 283       { return static_cast<_Hash_node*>(this->_M_nxt); }
 284     };
 285
 286   /**
 287    *  Specialization for nodes without caches, struct _Hash_node.
 288    *
 289    *  Base class is __detail::_Hash_node_value_base.
 290    */
 291   template<typename _Value>
 292     struct _Hash_node<_Value, false> : _Hash_node_value_base<_Value>
 293     {
 294       _Hash_node*
 295       _M_next() const noexcept
 296       { return static_cast<_Hash_node*>(this->_M_nxt); }
 297     };
 298
 299   /// Base class for node iterators.
 300   template<typename _Value, bool _Cache_hash_code>
 301     struct _Node_iterator_base
 302     {
 303       using __node_type = _Hash_node<_Value, _Cache_hash_code>;
 304
 305       __node_type*  _M_cur;
 306
 307       _Node_iterator_base(__node_type* __p) noexcept
 308       : _M_cur(__p) { }
 309
 310       void
 311       _M_incr() noexcept
 312       { _M_cur = _M_cur->_M_next(); }
 313     };
 314
 315   template<typename _Value, bool _Cache_hash_code>
 316     inline bool
 317     operator==(const _Node_iterator_base<_Value, _Cache_hash_code>& __x,
 318                const _Node_iterator_base<_Value, _Cache_hash_code >& __y)
 319     noexcept
 320     { return __x._M_cur == __y._M_cur; }
 321
 322   template<typename _Value, bool _Cache_hash_code>
 323     inline bool
 324     operator!=(const _Node_iterator_base<_Value, _Cache_hash_code>& __x,
 325                const _Node_iterator_base<_Value, _Cache_hash_code>& __y)
 326     noexcept
 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() noexcept
 350       : __base_type(0) { }
 351
 352       explicit
 353       _Node_iterator(__node_type* __p) noexcept
 354       : __base_type(__p) { }
 355
 356       reference
 357       operator*() const noexcept
 358       { return this->_M_cur->_M_v(); }
 359
 360       pointer
 361       operator->() const noexcept
 362       { return this->_M_cur->_M_valptr(); }
 363
 364       _Node_iterator&
 365       operator++() noexcept
 366       {
 367         this->_M_incr();
 368         return *this;
 369       }
 370
 371       _Node_iterator
 372       operator++(int) noexcept
 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() noexcept
 398       : __base_type(0) { }
 399
 400       explicit
 401       _Node_const_iterator(__node_type* __p) noexcept
 402       : __base_type(__p) { }
 403
 404       _Node_const_iterator(const _Node_iterator<_Value, __constant_iterators,
 405                            __cache>& __x) noexcept
 406       : __base_type(__x._M_cur) { }
 407
 408       reference
 409       operator*() const noexcept
 410       { return this->_M_cur->_M_v(); }
 411
 412       pointer
 413       operator->() const noexcept
 414       { return this->_M_cur->_M_valptr(); }
 415
 416       _Node_const_iterator&
 417       operator++() noexcept
 418       {
 419         this->_M_incr();
 420         return *this;
 421       }
 422
 423       _Node_const_iterator
 424       operator++(int) noexcept
 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) noexcept
 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     static const std::size_t _S_growth_factor = 2;
 499
 500     float               _M_max_load_factor;
 501     mutable std::size_t _M_next_resize;
 502   };
 503
 504   // Base classes for std::_Hashtable.  We define these base classes
 505   // because in some cases we want to do different things depending on
 506   // the value of a policy class.  In some cases the policy class
 507   // affects which member functions and nested typedefs are defined;
 508   // we handle that by specializing base class templates.  Several of
 509   // the base class templates need to access other members of class
 510   // template _Hashtable, so we use a variant of the "Curiously
 511   // Recurring Template Pattern" (CRTP) technique.
 512
 513   /**
 514    *  Primary class template _Map_base.
 515    *
 516    *  If the hashtable has a value type of the form pair<T1, T2> and a
 517    *  key extraction policy (_ExtractKey) that returns the first part
 518    *  of the pair, the hashtable gets a mapped_type typedef.  If it
 519    *  satisfies those criteria and also has unique keys, then it also
 520    *  gets an operator[].
 521    */
 522   template<typename _Key, typename _Value, typename _Alloc,
 523            typename _ExtractKey, typename _Equal,
 524            typename _H1, typename _H2, typename _Hash,
 525            typename _RehashPolicy, typename _Traits,
 526            bool _Unique_keys = _Traits::__unique_keys::value>
 527     struct _Map_base { };
 528
 529   /// Partial specialization, __unique_keys set to false.
 530   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 531            typename _H1, typename _H2, typename _Hash,
 532            typename _RehashPolicy, typename _Traits>
 533     struct _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 534                      _H1, _H2, _Hash, _RehashPolicy, _Traits, false>
 535     {
 536       using mapped_type = typename std::tuple_element<1, _Pair>::type;
 537     };
 538
 539   /// Partial specialization, __unique_keys set to true.
 540   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 541            typename _H1, typename _H2, typename _Hash,
 542            typename _RehashPolicy, typename _Traits>
 543     struct _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 544                      _H1, _H2, _Hash, _RehashPolicy, _Traits, true>
 545     {
 546     private:
 547       using __hashtable_base = __detail::_Hashtable_base<_Key, _Pair,
 548                                                          _Select1st,
 549                                                         _Equal, _H1, _H2, _Hash,
 550                                                           _Traits>;
 551
 552       using __hashtable = _Hashtable<_Key, _Pair, _Alloc,
 553                                      _Select1st, _Equal,
 554                                      _H1, _H2, _Hash, _RehashPolicy, _Traits>;
 555
 556       using __hash_code = typename __hashtable_base::__hash_code;
 557       using __node_type = typename __hashtable_base::__node_type;
 558
 559     public:
 560       using key_type = typename __hashtable_base::key_type;
 561       using iterator = typename __hashtable_base::iterator;
 562       using mapped_type = typename std::tuple_element<1, _Pair>::type;
 563
 564       mapped_type&
 565       operator[](const key_type& __k);
 566
 567       mapped_type&
 568       operator[](key_type&& __k);
 569
 570       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 571       // DR 761. unordered_map needs an at() member function.
 572       mapped_type&
 573       at(const key_type& __k);
 574
 575       const mapped_type&
 576       at(const key_type& __k) const;
 577     };
 578
 579   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 580            typename _H1, typename _H2, typename _Hash,
 581            typename _RehashPolicy, typename _Traits>
 582     auto
 583     _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 584               _H1, _H2, _Hash, _RehashPolicy, _Traits, true>::
 585     operator[](const key_type& __k)
 586     -> mapped_type&
 587     {
 588       __hashtable* __h = static_cast<__hashtable*>(this);
 589       __hash_code __code = __h->_M_hash_code(__k);
 590       std::size_t __n = __h->_M_bucket_index(__k, __code);
 591       __node_type* __p = __h->_M_find_node(__n, __k, __code);
 592
 593       if (!__p)
 594         {
 595           __p = __h->_M_allocate_node(std::piecewise_construct,
 596                                       std::tuple<const key_type&>(__k),
 597                                       std::tuple<>());
 598           return __h->_M_insert_unique_node(__n, __code, __p)->second;
 599         }
 600
 601       return __p->_M_v().second;
 602     }
 603
 604   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 605            typename _H1, typename _H2, typename _Hash,
 606            typename _RehashPolicy, typename _Traits>
 607     auto
 608     _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 609               _H1, _H2, _Hash, _RehashPolicy, _Traits, true>::
 610     operator[](key_type&& __k)
 611     -> mapped_type&
 612     {
 613       __hashtable* __h = static_cast<__hashtable*>(this);
 614       __hash_code __code = __h->_M_hash_code(__k);
 615       std::size_t __n = __h->_M_bucket_index(__k, __code);
 616       __node_type* __p = __h->_M_find_node(__n, __k, __code);
 617
 618       if (!__p)
 619         {
 620           __p = __h->_M_allocate_node(std::piecewise_construct,
 621                                       std::forward_as_tuple(std::move(__k)),
 622                                       std::tuple<>());
 623           return __h->_M_insert_unique_node(__n, __code, __p)->second;
 624         }
 625
 626       return __p->_M_v().second;
 627     }
 628
 629   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 630            typename _H1, typename _H2, typename _Hash,
 631            typename _RehashPolicy, typename _Traits>
 632     auto
 633     _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 634               _H1, _H2, _Hash, _RehashPolicy, _Traits, true>::
 635     at(const key_type& __k)
 636     -> mapped_type&
 637     {
 638       __hashtable* __h = static_cast<__hashtable*>(this);
 639       __hash_code __code = __h->_M_hash_code(__k);
 640       std::size_t __n = __h->_M_bucket_index(__k, __code);
 641       __node_type* __p = __h->_M_find_node(__n, __k, __code);
 642
 643       if (!__p)
 644         __throw_out_of_range(__N("_Map_base::at"));
 645       return __p->_M_v().second;
 646     }
 647
 648   template<typename _Key, typename _Pair, typename _Alloc, typename _Equal,
 649            typename _H1, typename _H2, typename _Hash,
 650            typename _RehashPolicy, typename _Traits>
 651     auto
 652     _Map_base<_Key, _Pair, _Alloc, _Select1st, _Equal,
 653               _H1, _H2, _Hash, _RehashPolicy, _Traits, true>::
 654     at(const key_type& __k) const
 655     -> const mapped_type&
 656     {
 657       const __hashtable* __h = static_cast<const __hashtable*>(this);
 658       __hash_code __code = __h->_M_hash_code(__k);
 659       std::size_t __n = __h->_M_bucket_index(__k, __code);
 660       __node_type* __p = __h->_M_find_node(__n, __k, __code);
 661
 662       if (!__p)
 663         __throw_out_of_range(__N("_Map_base::at"));
 664       return __p->_M_v().second;
 665     }
 666
 667   /**
 668    *  Primary class template _Insert_base.
 669    *
 670    *  insert member functions appropriate to all _Hashtables.
 671    */
 672   template<typename _Key, typename _Value, typename _Alloc,
 673            typename _ExtractKey, typename _Equal,
 674            typename _H1, typename _H2, typename _Hash,
 675            typename _RehashPolicy, typename _Traits>
 676     struct _Insert_base
 677     {
 678     protected:
 679       using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey,
 680                                      _Equal, _H1, _H2, _Hash,
 681                                      _RehashPolicy, _Traits>;
 682
 683       using __hashtable_base = _Hashtable_base<_Key, _Value, _ExtractKey,
 684                                                _Equal, _H1, _H2, _Hash,
 685                                                _Traits>;
 686
 687       using value_type = typename __hashtable_base::value_type;
 688       using iterator = typename __hashtable_base::iterator;
 689       using const_iterator =  typename __hashtable_base::const_iterator;
 690       using size_type = typename __hashtable_base::size_type;
 691
 692       using __unique_keys = typename __hashtable_base::__unique_keys;
 693       using __ireturn_type = typename __hashtable_base::__ireturn_type;
 694       using __node_type = _Hash_node<_Value, _Traits::__hash_cached::value>;
 695       using __node_alloc_type = __alloc_rebind<_Alloc, __node_type>;
 696       using __node_gen_type = _AllocNode<__node_alloc_type>;
 697
 698       __hashtable&
 699       _M_conjure_hashtable()
 700       { return *(static_cast<__hashtable*>(this)); }
 701
 702       template<typename _InputIterator, typename _NodeGetter>
 703         void
 704         _M_insert_range(_InputIterator __first, _InputIterator __last,
 705                         const _NodeGetter&);
 706
 707     public:
 708       __ireturn_type
 709       insert(const value_type& __v)
 710       {
 711         __hashtable& __h = _M_conjure_hashtable();
 712         __node_gen_type __node_gen(__h);
 713         return __h._M_insert(__v, __node_gen, __unique_keys());
 714       }
 715
 716       iterator
 717       insert(const_iterator __hint, const value_type& __v)
 718       {
 719         __hashtable& __h = _M_conjure_hashtable();
 720         __node_gen_type __node_gen(__h);
 721         return __h._M_insert(__hint, __v, __node_gen, __unique_keys());
 722       }
 723
 724       void
 725       insert(initializer_list<value_type> __l)
 726       { this->insert(__l.begin(), __l.end()); }
 727
 728       template<typename _InputIterator>
 729         void
 730         insert(_InputIterator __first, _InputIterator __last)
 731         {
 732           __hashtable& __h = _M_conjure_hashtable();
 733           __node_gen_type __node_gen(__h);
 734           return _M_insert_range(__first, __last, __node_gen);
 735         }
 736     };
 737
 738   template<typename _Key, typename _Value, typename _Alloc,
 739            typename _ExtractKey, typename _Equal,
 740            typename _H1, typename _H2, typename _Hash,
 741            typename _RehashPolicy, typename _Traits>
 742     template<typename _InputIterator, typename _NodeGetter>
 743       void
 744       _Insert_base<_Key, _Value, _Alloc, _ExtractKey, _Equal, _H1, _H2, _Hash,
 745                     _RehashPolicy, _Traits>::
 746       _M_insert_range(_InputIterator __first, _InputIterator __last,
 747                       const _NodeGetter& __node_gen)
 748       {
 749         using __rehash_type = typename __hashtable::__rehash_type;
 750         using __rehash_state = typename __hashtable::__rehash_state;
 751         using pair_type = std::pair<bool, std::size_t>;
 752
 753         size_type __n_elt = __detail::__distance_fw(__first, __last);
 754
 755         __hashtable& __h = _M_conjure_hashtable();
 756         __rehash_type& __rehash = __h._M_rehash_policy;
 757         const __rehash_state& __saved_state = __rehash._M_state();
 758         pair_type __do_rehash = __rehash._M_need_rehash(__h._M_bucket_count,
 759                                                         __h._M_element_count,
 760                                                         __n_elt);
 761
 762         if (__do_rehash.first)
 763           __h._M_rehash(__do_rehash.second, __saved_state);
 764
 765         for (; __first != __last; ++__first)
 766           __h._M_insert(*__first, __node_gen, __unique_keys());
 767       }
 768
 769   /**
 770    *  Primary class template _Insert.
 771    *
 772    *  Select insert member functions appropriate to _Hashtable policy choices.
 773    */
 774   template<typename _Key, typename _Value, typename _Alloc,
 775            typename _ExtractKey, typename _Equal,
 776            typename _H1, typename _H2, typename _Hash,
 777            typename _RehashPolicy, typename _Traits,
 778            bool _Constant_iterators = _Traits::__constant_iterators::value,
 779            bool _Unique_keys = _Traits::__unique_keys::value>
 780     struct _Insert;
 781
 782   /// Specialization.
 783   template<typename _Key, typename _Value, typename _Alloc,
 784            typename _ExtractKey, typename _Equal,
 785            typename _H1, typename _H2, typename _Hash,
 786            typename _RehashPolicy, typename _Traits>
 787     struct _Insert<_Key, _Value, _Alloc, _ExtractKey, _Equal, _H1, _H2, _Hash,
 788                    _RehashPolicy, _Traits, true, true>
 789     : public _Insert_base<_Key, _Value, _Alloc, _ExtractKey, _Equal,
 790                            _H1, _H2, _Hash, _RehashPolicy, _Traits>
 791     {
 792       using __base_type = _Insert_base<_Key, _Value, _Alloc, _ExtractKey,
 793                                         _Equal, _H1, _H2, _Hash,
 794                                         _RehashPolicy, _Traits>;
 795       using value_type = typename __base_type::value_type;
 796       using iterator = typename __base_type::iterator;
 797       using const_iterator =  typename __base_type::const_iterator;
 798
 799       using __unique_keys = typename __base_type::__unique_keys;
 800       using __hashtable = typename __base_type::__hashtable;
 801       using __node_gen_type = typename __base_type::__node_gen_type;
 802
 803       using __base_type::insert;
 804
 805       std::pair<iterator, bool>
 806       insert(value_type&& __v)
 807       {
 808         __hashtable& __h = this->_M_conjure_hashtable();
 809         __node_gen_type __node_gen(__h);
 810         return __h._M_insert(std::move(__v), __node_gen, __unique_keys());
 811       }
 812
 813       iterator
 814       insert(const_iterator __hint, value_type&& __v)
 815       {
 816         __hashtable& __h = this->_M_conjure_hashtable();
 817         __node_gen_type __node_gen(__h);
 818         return __h._M_insert(__hint, std::move(__v), __node_gen,
 819                              __unique_keys());
 820       }
 821     };
 822
 823   /// Specialization.
 824   template<typename _Key, typename _Value, typename _Alloc,
 825            typename _ExtractKey, typename _Equal,
 826            typename _H1, typename _H2, typename _Hash,
 827            typename _RehashPolicy, typename _Traits>
 828     struct _Insert<_Key, _Value, _Alloc, _ExtractKey, _Equal, _H1, _H2, _Hash,
 829                    _RehashPolicy, _Traits, true, false>
 830     : public _Insert_base<_Key, _Value, _Alloc, _ExtractKey, _Equal,
 831                            _H1, _H2, _Hash, _RehashPolicy, _Traits>
 832     {
 833       using __base_type = _Insert_base<_Key, _Value, _Alloc, _ExtractKey,
 834                                         _Equal, _H1, _H2, _Hash,
 835                                         _RehashPolicy, _Traits>;
 836       using value_type = typename __base_type::value_type;
 837       using iterator = typename __base_type::iterator;
 838       using const_iterator =  typename __base_type::const_iterator;
 839
 840       using __unique_keys = typename __base_type::__unique_keys;
 841       using __hashtable = typename __base_type::__hashtable;
 842       using __node_gen_type = typename __base_type::__node_gen_type;
 843
 844       using __base_type::insert;
 845
 846       iterator
 847       insert(value_type&& __v)
 848       {
 849         __hashtable& __h = this->_M_conjure_hashtable();
 850         __node_gen_type __node_gen(__h);
 851         return __h._M_insert(std::move(__v), __node_gen, __unique_keys());
 852       }
 853
 854       iterator
 855       insert(const_iterator __hint, value_type&& __v)
 856       {
 857         __hashtable& __h = this->_M_conjure_hashtable();
 858         __node_gen_type __node_gen(__h);
 859         return __h._M_insert(__hint, std::move(__v), __node_gen,
 860                              __unique_keys());
 861       }
 862     };
 863
 864   /// Specialization.
 865   template<typename _Key, typename _Value, typename _Alloc,
 866            typename _ExtractKey, typename _Equal,
 867            typename _H1, typename _H2, typename _Hash,
 868            typename _RehashPolicy, typename _Traits, bool _Unique_keys>
 869     struct _Insert<_Key, _Value, _Alloc, _ExtractKey, _Equal, _H1, _H2, _Hash,
 870                    _RehashPolicy, _Traits, false, _Unique_keys>
 871     : public _Insert_base<_Key, _Value, _Alloc, _ExtractKey, _Equal,
 872                            _H1, _H2, _Hash, _RehashPolicy, _Traits>
 873     {
 874       using __base_type = _Insert_base<_Key, _Value, _Alloc, _ExtractKey,
 875                                        _Equal, _H1, _H2, _Hash,
 876                                        _RehashPolicy, _Traits>;
 877       using value_type = typename __base_type::value_type;
 878       using iterator = typename __base_type::iterator;
 879       using const_iterator =  typename __base_type::const_iterator;
 880
 881       using __unique_keys = typename __base_type::__unique_keys;
 882       using __hashtable = typename __base_type::__hashtable;
 883       using __ireturn_type = typename __base_type::__ireturn_type;
 884
 885       using __base_type::insert;
 886
 887       template<typename _Pair>
 888         using __is_cons = std::is_constructible<value_type, _Pair&&>;
 889
 890       template<typename _Pair>
 891         using _IFcons = std::enable_if<__is_cons<_Pair>::value>;
 892
 893       template<typename _Pair>
 894         using _IFconsp = typename _IFcons<_Pair>::type;
 895
 896       template<typename _Pair, typename = _IFconsp<_Pair>>
 897         __ireturn_type
 898         insert(_Pair&& __v)
 899         {
 900           __hashtable& __h = this->_M_conjure_hashtable();
 901           return __h._M_emplace(__unique_keys(), std::forward<_Pair>(__v));
 902         }
 903
 904       template<typename _Pair, typename = _IFconsp<_Pair>>
 905         iterator
 906         insert(const_iterator __hint, _Pair&& __v)
 907         {
 908           __hashtable& __h = this->_M_conjure_hashtable();
 909           return __h._M_emplace(__hint, __unique_keys(),
 910                                 std::forward<_Pair>(__v));
 911         }
 912    };
 913
 914   /**
 915    *  Primary class template  _Rehash_base.
 916    *
 917    *  Give hashtable the max_load_factor functions and reserve iff the
 918    *  rehash policy is _Prime_rehash_policy.
 919   */
 920   template<typename _Key, typename _Value, typename _Alloc,
 921            typename _ExtractKey, typename _Equal,
 922            typename _H1, typename _H2, typename _Hash,
 923            typename _RehashPolicy, typename _Traits>
 924     struct _Rehash_base;
 925
 926   /// Specialization.
 927   template<typename _Key, typename _Value, typename _Alloc,
 928            typename _ExtractKey, typename _Equal,
 929            typename _H1, typename _H2, typename _Hash, typename _Traits>
 930     struct _Rehash_base<_Key, _Value, _Alloc, _ExtractKey, _Equal,
 931                         _H1, _H2, _Hash, _Prime_rehash_policy, _Traits>
 932     {
 933       using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey,
 934                                      _Equal, _H1, _H2, _Hash,
 935                                      _Prime_rehash_policy, _Traits>;
 936
 937       float
 938       max_load_factor() const noexcept
 939       {
 940         const __hashtable* __this = static_cast<const __hashtable*>(this);
 941         return __this->__rehash_policy().max_load_factor();
 942       }
 943
 944       void
 945       max_load_factor(float __z)
 946       {
 947         __hashtable* __this = static_cast<__hashtable*>(this);
 948         __this->__rehash_policy(_Prime_rehash_policy(__z));
 949       }
 950
 951       void
 952       reserve(std::size_t __n)
 953       {
 954         __hashtable* __this = static_cast<__hashtable*>(this);
 955         __this->rehash(__builtin_ceil(__n / max_load_factor()));
 956       }
 957     };
 958
 959   /**
 960    *  Primary class template _Hashtable_ebo_helper.
 961    *
 962    *  Helper class using EBO when it is not forbidden (the type is not
 963    *  final) and when it is worth it (the type is empty.)
 964    */
 965   template<int _Nm, typename _Tp,
 966            bool __use_ebo = !__is_final(_Tp) && __is_empty(_Tp)>
 967     struct _Hashtable_ebo_helper;
 968
 969   /// Specialization using EBO.
 970   template<int _Nm, typename _Tp>
 971     struct _Hashtable_ebo_helper<_Nm, _Tp, true>
 972     : private _Tp
 973     {
 974       _Hashtable_ebo_helper() = default;
 975
 976       template<typename _OtherTp>
 977         _Hashtable_ebo_helper(_OtherTp&& __tp)
 978           : _Tp(std::forward<_OtherTp>(__tp))
 979         { }
 980
 981       static const _Tp&
 982       _S_cget(const _Hashtable_ebo_helper& __eboh)
 983       { return static_cast<const _Tp&>(__eboh); }
 984
 985       static _Tp&
 986       _S_get(_Hashtable_ebo_helper& __eboh)
 987       { return static_cast<_Tp&>(__eboh); }
 988     };
 989
 990   /// Specialization not using EBO.
 991   template<int _Nm, typename _Tp>
 992     struct _Hashtable_ebo_helper<_Nm, _Tp, false>
 993     {
 994       _Hashtable_ebo_helper() = default;
 995
 996       template<typename _OtherTp>
 997         _Hashtable_ebo_helper(_OtherTp&& __tp)
 998           : _M_tp(std::forward<_OtherTp>(__tp))
 999         { }
1000
1001       static const _Tp&
1002       _S_cget(const _Hashtable_ebo_helper& __eboh)
1003       { return __eboh._M_tp; }
1004
1005       static _Tp&
1006       _S_get(_Hashtable_ebo_helper& __eboh)
1007       { return __eboh._M_tp; }
1008
1009     private:
1010       _Tp _M_tp;
1011     };
1012
1013   /**
1014    *  Primary class template _Local_iterator_base.
1015    *
1016    *  Base class for local iterators, used to iterate within a bucket
1017    *  but not between buckets.
1018    */
1019   template<typename _Key, typename _Value, typename _ExtractKey,
1020            typename _H1, typename _H2, typename _Hash,
1021            bool __cache_hash_code>
1022     struct _Local_iterator_base;
1023
1024   /**
1025    *  Primary class template _Hash_code_base.
1026    *
1027    *  Encapsulates two policy issues that aren't quite orthogonal.
1028    *   (1) the difference between using a ranged hash function and using
1029    *       the combination of a hash function and a range-hashing function.
1030    *       In the former case we don't have such things as hash codes, so
1031    *       we have a dummy type as placeholder.
1032    *   (2) Whether or not we cache hash codes.  Caching hash codes is
1033    *       meaningless if we have a ranged hash function.
1034    *
1035    *  We also put the key extraction objects here, for convenience.
1036    *  Each specialization derives from one or more of the template
1037    *  parameters to benefit from Ebo. This is important as this type
1038    *  is inherited in some cases by the _Local_iterator_base type used
1039    *  to implement local_iterator and const_local_iterator. As with
1040    *  any iterator type we prefer to make it as small as possible.
1041    *
1042    *  Primary template is unused except as a hook for specializations.
1043    */
1044   template<typename _Key, typename _Value, typename _ExtractKey,
1045            typename _H1, typename _H2, typename _Hash,
1046            bool __cache_hash_code>
1047     struct _Hash_code_base;
1048
1049   /// Specialization: ranged hash function, no caching hash codes.  H1
1050   /// and H2 are provided but ignored.  We define a dummy hash code type.
1051   template<typename _Key, typename _Value, typename _ExtractKey,
1052            typename _H1, typename _H2, typename _Hash>
1053     struct _Hash_code_base<_Key, _Value, _ExtractKey, _H1, _H2, _Hash, false>
1054     : private _Hashtable_ebo_helper<0, _ExtractKey>,
1055       private _Hashtable_ebo_helper<1, _Hash>
1056     {
1057     private:
1058       using __ebo_extract_key = _Hashtable_ebo_helper<0, _ExtractKey>;
1059       using __ebo_hash = _Hashtable_ebo_helper<1, _Hash>;
1060
1061     protected:
1062       typedef void*                                     __hash_code;
1063       typedef _Hash_node<_Value, false>                 __node_type;
1064
1065       // We need the default constructor for the local iterators and _Hashtable
1066       // default constructor.
1067       _Hash_code_base() = default;
1068
1069       _Hash_code_base(const _ExtractKey& __ex, const _H1&, const _H2&,
1070                       const _Hash& __h)
1071       : __ebo_extract_key(__ex), __ebo_hash(__h) { }
1072
1073       __hash_code
1074       _M_hash_code(const _Key& __key) const
1075       { return 0; }
1076
1077       std::size_t
1078       _M_bucket_index(const _Key& __k, __hash_code, std::size_t __n) const
1079       { return _M_ranged_hash()(__k, __n); }
1080
1081       std::size_t
1082       _M_bucket_index(const __node_type* __p, std::size_t __n) const
1083         noexcept( noexcept(declval<const _Hash&>()(declval<const _Key&>(),
1084                                                    (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       // Gives the local iterator implementation access to _M_bucket_index().
1142       friend struct _Local_iterator_base<_Key, _Value, _ExtractKey, _H1, _H2,
1143                                          _Default_ranged_hash, false>;
1144
1145     public:
1146       typedef _H1                                       hasher;
1147
1148       hasher
1149       hash_function() const
1150       { return _M_h1(); }
1151
1152     protected:
1153       typedef std::size_t                               __hash_code;
1154       typedef _Hash_node<_Value, false>                 __node_type;
1155
1156       // We need the default constructor for the local iterators and _Hashtable
1157       // default constructor.
1158       _Hash_code_base() = default;
1159
1160       _Hash_code_base(const _ExtractKey& __ex,
1161                       const _H1& __h1, const _H2& __h2,
1162                       const _Default_ranged_hash&)
1163       : __ebo_extract_key(__ex), __ebo_h1(__h1), __ebo_h2(__h2) { }
1164
1165       __hash_code
1166       _M_hash_code(const _Key& __k) const
1167       { return _M_h1()(__k); }
1168
1169       std::size_t
1170       _M_bucket_index(const _Key&, __hash_code __c, std::size_t __n) const
1171       { return _M_h2()(__c, __n); }
1172
1173       std::size_t
1174       _M_bucket_index(const __node_type* __p, std::size_t __n) const
1175         noexcept( noexcept(declval<const _H1&>()(declval<const _Key&>()))
1176                   && noexcept(declval<const _H2&>()((__hash_code)0,
1177                                                     (std::size_t)0)) )
1178       { return _M_h2()(_M_h1()(_M_extract()(__p->_M_v())), __n); }
1179
1180       void
1181       _M_store_code(__node_type*, __hash_code) const
1182       { }
1183
1184       void
1185       _M_copy_code(__node_type*, const __node_type*) const
1186       { }
1187
1188       void
1189       _M_swap(_Hash_code_base& __x)
1190       {
1191         std::swap(_M_extract(), __x._M_extract());
1192         std::swap(_M_h1(), __x._M_h1());
1193         std::swap(_M_h2(), __x._M_h2());
1194       }
1195
1196       const _ExtractKey&
1197       _M_extract() const { return __ebo_extract_key::_S_cget(*this); }
1198
1199       _ExtractKey&
1200       _M_extract() { return __ebo_extract_key::_S_get(*this); }
1201
1202       const _H1&
1203       _M_h1() const { return __ebo_h1::_S_cget(*this); }
1204
1205       _H1&
1206       _M_h1() { return __ebo_h1::_S_get(*this); }
1207
1208       const _H2&
1209       _M_h2() const { return __ebo_h2::_S_cget(*this); }
1210
1211       _H2&
1212       _M_h2() { return __ebo_h2::_S_get(*this); }
1213     };
1214
1215   /// Specialization: hash function and range-hashing function,
1216   /// caching hash codes.  H is provided but ignored.  Provides
1217   /// typedef and accessor required by C++ 11.
1218   template<typename _Key, typename _Value, typename _ExtractKey,
1219            typename _H1, typename _H2>
1220     struct _Hash_code_base<_Key, _Value, _ExtractKey, _H1, _H2,
1221                            _Default_ranged_hash, true>
1222     : private _Hashtable_ebo_helper<0, _ExtractKey>,
1223       private _Hashtable_ebo_helper<1, _H1>,
1224       private _Hashtable_ebo_helper<2, _H2>
1225     {
1226     private:
1227       // Gives the local iterator implementation access to _M_h2().
1228       friend struct _Local_iterator_base<_Key, _Value, _ExtractKey, _H1, _H2,
1229                                          _Default_ranged_hash, true>;
1230
1231       using __ebo_extract_key = _Hashtable_ebo_helper<0, _ExtractKey>;
1232       using __ebo_h1 = _Hashtable_ebo_helper<1, _H1>;
1233       using __ebo_h2 = _Hashtable_ebo_helper<2, _H2>;
1234
1235     public:
1236       typedef _H1                                       hasher;
1237
1238       hasher
1239       hash_function() const
1240       { return _M_h1(); }
1241
1242     protected:
1243       typedef std::size_t                               __hash_code;
1244       typedef _Hash_node<_Value, true>                  __node_type;
1245
1246       // We need the default constructor for _Hashtable default constructor.
1247       _Hash_code_base() = default;
1248       _Hash_code_base(const _ExtractKey& __ex,
1249                       const _H1& __h1, const _H2& __h2,
1250                       const _Default_ranged_hash&)
1251       : __ebo_extract_key(__ex), __ebo_h1(__h1), __ebo_h2(__h2) { }
1252
1253       __hash_code
1254       _M_hash_code(const _Key& __k) const
1255       { return _M_h1()(__k); }
1256
1257       std::size_t
1258       _M_bucket_index(const _Key&, __hash_code __c,
1259                       std::size_t __n) const
1260       { return _M_h2()(__c, __n); }
1261
1262       std::size_t
1263       _M_bucket_index(const __node_type* __p, std::size_t __n) const
1264         noexcept( noexcept(declval<const _H2&>()((__hash_code)0,
1265                                                  (std::size_t)0)) )
1266       { return _M_h2()(__p->_M_hash_code, __n); }
1267
1268       void
1269       _M_store_code(__node_type* __n, __hash_code __c) const
1270       { __n->_M_hash_code = __c; }
1271
1272       void
1273       _M_copy_code(__node_type* __to, const __node_type* __from) const
1274       { __to->_M_hash_code = __from->_M_hash_code; }
1275
1276       void
1277       _M_swap(_Hash_code_base& __x)
1278       {
1279         std::swap(_M_extract(), __x._M_extract());
1280         std::swap(_M_h1(), __x._M_h1());
1281         std::swap(_M_h2(), __x._M_h2());
1282       }
1283
1284       const _ExtractKey&
1285       _M_extract() const { return __ebo_extract_key::_S_cget(*this); }
1286
1287       _ExtractKey&
1288       _M_extract() { return __ebo_extract_key::_S_get(*this); }
1289
1290       const _H1&
1291       _M_h1() const { return __ebo_h1::_S_cget(*this); }
1292
1293       _H1&
1294       _M_h1() { return __ebo_h1::_S_get(*this); }
1295
1296       const _H2&
1297       _M_h2() const { return __ebo_h2::_S_cget(*this); }
1298
1299       _H2&
1300       _M_h2() { return __ebo_h2::_S_get(*this); }
1301     };
1302
1303   /**
1304    *  Primary class template _Equal_helper.
1305    *
1306    */
1307   template <typename _Key, typename _Value, typename _ExtractKey,
1308             typename _Equal, typename _HashCodeType,
1309             bool __cache_hash_code>
1310   struct _Equal_helper;
1311
1312   /// Specialization.
1313   template<typename _Key, typename _Value, typename _ExtractKey,
1314            typename _Equal, typename _HashCodeType>
1315   struct _Equal_helper<_Key, _Value, _ExtractKey, _Equal, _HashCodeType, true>
1316   {
1317     static bool
1318     _S_equals(const _Equal& __eq, const _ExtractKey& __extract,
1319               const _Key& __k, _HashCodeType __c, _Hash_node<_Value, true>* __n)
1320     { return __c == __n->_M_hash_code && __eq(__k, __extract(__n->_M_v())); }
1321   };
1322
1323   /// Specialization.
1324   template<typename _Key, typename _Value, typename _ExtractKey,
1325            typename _Equal, typename _HashCodeType>
1326   struct _Equal_helper<_Key, _Value, _ExtractKey, _Equal, _HashCodeType, false>
1327   {
1328     static bool
1329     _S_equals(const _Equal& __eq, const _ExtractKey& __extract,
1330               const _Key& __k, _HashCodeType, _Hash_node<_Value, false>* __n)
1331     { return __eq(__k, __extract(__n->_M_v())); }
1332   };
1333
1334
1335   /// Partial specialization used when nodes contain a cached hash code.
1336   template<typename _Key, typename _Value, typename _ExtractKey,
1337            typename _H1, typename _H2, typename _Hash>
1338     struct _Local_iterator_base<_Key, _Value, _ExtractKey,
1339                                 _H1, _H2, _Hash, true>
1340     : private _Hashtable_ebo_helper<0, _H2>
1341     {
1342     protected:
1343       using __base_type = _Hashtable_ebo_helper<0, _H2>;
1344       using __hash_code_base = _Hash_code_base<_Key, _Value, _ExtractKey,
1345                                                _H1, _H2, _Hash, true>;
1346
1347       _Local_iterator_base() = default;
1348       _Local_iterator_base(const __hash_code_base& __base,
1349                            _Hash_node<_Value, true>* __p,
1350                            std::size_t __bkt, std::size_t __bkt_count)
1351       : __base_type(__base._M_h2()),
1352         _M_cur(__p), _M_bucket(__bkt), _M_bucket_count(__bkt_count) { }
1353
1354       void
1355       _M_incr()
1356       {
1357         _M_cur = _M_cur->_M_next();
1358         if (_M_cur)
1359           {
1360             std::size_t __bkt
1361               = __base_type::_S_get(*this)(_M_cur->_M_hash_code,
1362                                            _M_bucket_count);
1363             if (__bkt != _M_bucket)
1364               _M_cur = nullptr;
1365           }
1366       }
1367
1368       _Hash_node<_Value, true>*  _M_cur;
1369       std::size_t _M_bucket;
1370       std::size_t _M_bucket_count;
1371
1372     public:
1373       const void*
1374       _M_curr() const { return _M_cur; }  // for equality ops
1375
1376       std::size_t
1377       _M_get_bucket() const { return _M_bucket; }  // for debug mode
1378     };
1379
1380   // Uninitialized storage for a _Hash_code_base.
1381   // This type is DefaultConstructible and Assignable even if the
1382   // _Hash_code_base type isn't, so that _Local_iterator_base<..., false>
1383   // can be DefaultConstructible and Assignable.
1384   template<typename _Tp, bool _IsEmpty = std::is_empty<_Tp>::value>
1385     struct _Hash_code_storage
1386     {
1387       __gnu_cxx::__aligned_buffer<_Tp> _M_storage;
1388
1389       _Tp*
1390       _M_h() { return _M_storage._M_ptr(); }
1391
1392       const _Tp*
1393       _M_h() const { return _M_storage._M_ptr(); }
1394     };
1395
1396   // Empty partial specialization for empty _Hash_code_base types.
1397   template<typename _Tp>
1398     struct _Hash_code_storage<_Tp, true>
1399     {
1400       static_assert( std::is_empty<_Tp>::value, "Type must be empty" );
1401
1402       // As _Tp is an empty type there will be no bytes written/read through
1403       // the cast pointer, so no strict-aliasing violation.
1404       _Tp*
1405       _M_h() { return reinterpret_cast<_Tp*>(this); }
1406
1407       const _Tp*
1408       _M_h() const { return reinterpret_cast<const _Tp*>(this); }
1409     };
1410
1411   template<typename _Key, typename _Value, typename _ExtractKey,
1412            typename _H1, typename _H2, typename _Hash>
1413     using __hash_code_for_local_iter
1414       = _Hash_code_storage<_Hash_code_base<_Key, _Value, _ExtractKey,
1415                                            _H1, _H2, _Hash, false>>;
1416
1417   // Partial specialization used when hash codes are not cached
1418   template<typename _Key, typename _Value, typename _ExtractKey,
1419            typename _H1, typename _H2, typename _Hash>
1420     struct _Local_iterator_base<_Key, _Value, _ExtractKey,
1421                                 _H1, _H2, _Hash, false>
1422     : __hash_code_for_local_iter<_Key, _Value, _ExtractKey, _H1, _H2, _Hash>
1423     {
1424     protected:
1425       using __hash_code_base = _Hash_code_base<_Key, _Value, _ExtractKey,
1426                                                _H1, _H2, _Hash, false>;
1427
1428       _Local_iterator_base() : _M_bucket_count(-1) { }
1429
1430       _Local_iterator_base(const __hash_code_base& __base,
1431                            _Hash_node<_Value, false>* __p,
1432                            std::size_t __bkt, std::size_t __bkt_count)
1433       : _M_cur(__p), _M_bucket(__bkt), _M_bucket_count(__bkt_count)
1434       { _M_init(__base); }
1435
1436       ~_Local_iterator_base()
1437       {
1438         if (_M_bucket_count != -1)
1439           _M_destroy();
1440       }
1441
1442       _Local_iterator_base(const _Local_iterator_base& __iter)
1443       : _M_cur(__iter._M_cur), _M_bucket(__iter._M_bucket),
1444         _M_bucket_count(__iter._M_bucket_count)
1445       {
1446         if (_M_bucket_count != -1)
1447           _M_init(*__iter._M_h());
1448       }
1449
1450       _Local_iterator_base&
1451       operator=(const _Local_iterator_base& __iter)
1452       {
1453         if (_M_bucket_count != -1)
1454           _M_destroy();
1455         _M_cur = __iter._M_cur;
1456         _M_bucket = __iter._M_bucket;
1457         _M_bucket_count = __iter._M_bucket_count;
1458         if (_M_bucket_count != -1)
1459           _M_init(*__iter._M_h());
1460         return *this;
1461       }
1462
1463       void
1464       _M_incr()
1465       {
1466         _M_cur = _M_cur->_M_next();
1467         if (_M_cur)
1468           {
1469             std::size_t __bkt = this->_M_h()->_M_bucket_index(_M_cur,
1470                                                               _M_bucket_count);
1471             if (__bkt != _M_bucket)
1472               _M_cur = nullptr;
1473           }
1474       }
1475
1476       _Hash_node<_Value, false>*  _M_cur;
1477       std::size_t _M_bucket;
1478       std::size_t _M_bucket_count;
1479
1480       void
1481       _M_init(const __hash_code_base& __base)
1482       { ::new(this->_M_h()) __hash_code_base(__base); }
1483
1484       void
1485       _M_destroy() { this->_M_h()->~__hash_code_base(); }
1486
1487     public:
1488       const void*
1489       _M_curr() const { return _M_cur; }  // for equality ops and debug mode
1490
1491       std::size_t
1492       _M_get_bucket() const { return _M_bucket; }  // for debug mode
1493     };
1494
1495   template<typename _Key, typename _Value, typename _ExtractKey,
1496            typename _H1, typename _H2, typename _Hash, bool __cache>
1497     inline bool
1498     operator==(const _Local_iterator_base<_Key, _Value, _ExtractKey,
1499                                           _H1, _H2, _Hash, __cache>& __x,
1500                const _Local_iterator_base<_Key, _Value, _ExtractKey,
1501                                           _H1, _H2, _Hash, __cache>& __y)
1502     { return __x._M_curr() == __y._M_curr(); }
1503
1504   template<typename _Key, typename _Value, typename _ExtractKey,
1505            typename _H1, typename _H2, typename _Hash, bool __cache>
1506     inline bool
1507     operator!=(const _Local_iterator_base<_Key, _Value, _ExtractKey,
1508                                           _H1, _H2, _Hash, __cache>& __x,
1509                const _Local_iterator_base<_Key, _Value, _ExtractKey,
1510                                           _H1, _H2, _Hash, __cache>& __y)
1511     { return __x._M_curr() != __y._M_curr(); }
1512
1513   /// local iterators
1514   template<typename _Key, typename _Value, typename _ExtractKey,
1515            typename _H1, typename _H2, typename _Hash,
1516            bool __constant_iterators, bool __cache>
1517     struct _Local_iterator
1518     : public _Local_iterator_base<_Key, _Value, _ExtractKey,
1519                                   _H1, _H2, _Hash, __cache>
1520     {
1521     private:
1522       using __base_type = _Local_iterator_base<_Key, _Value, _ExtractKey,
1523                                                _H1, _H2, _Hash, __cache>;
1524       using __hash_code_base = typename __base_type::__hash_code_base;
1525     public:
1526       typedef _Value                                    value_type;
1527       typedef typename std::conditional<__constant_iterators,
1528                                         const _Value*, _Value*>::type
1529                                                        pointer;
1530       typedef typename std::conditional<__constant_iterators,
1531                                         const _Value&, _Value&>::type
1532                                                        reference;
1533       typedef std::ptrdiff_t                            difference_type;
1534       typedef std::forward_iterator_tag                 iterator_category;
1535
1536       _Local_iterator() = default;
1537
1538       _Local_iterator(const __hash_code_base& __base,
1539                       _Hash_node<_Value, __cache>* __p,
1540                       std::size_t __bkt, std::size_t __bkt_count)
1541         : __base_type(__base, __p, __bkt, __bkt_count)
1542       { }
1543
1544       reference
1545       operator*() const
1546       { return this->_M_cur->_M_v(); }
1547
1548       pointer
1549       operator->() const
1550       { return this->_M_cur->_M_valptr(); }
1551
1552       _Local_iterator&
1553       operator++()
1554       {
1555         this->_M_incr();
1556         return *this;
1557       }
1558
1559       _Local_iterator
1560       operator++(int)
1561       {
1562         _Local_iterator __tmp(*this);
1563         this->_M_incr();
1564         return __tmp;
1565       }
1566     };
1567
1568   /// local const_iterators
1569   template<typename _Key, typename _Value, typename _ExtractKey,
1570            typename _H1, typename _H2, typename _Hash,
1571            bool __constant_iterators, bool __cache>
1572     struct _Local_const_iterator
1573     : public _Local_iterator_base<_Key, _Value, _ExtractKey,
1574                                   _H1, _H2, _Hash, __cache>
1575     {
1576     private:
1577       using __base_type = _Local_iterator_base<_Key, _Value, _ExtractKey,
1578                                                _H1, _H2, _Hash, __cache>;
1579       using __hash_code_base = typename __base_type::__hash_code_base;
1580
1581     public:
1582       typedef _Value                                    value_type;
1583       typedef const _Value*                             pointer;
1584       typedef const _Value&                             reference;
1585       typedef std::ptrdiff_t                            difference_type;
1586       typedef std::forward_iterator_tag                 iterator_category;
1587
1588       _Local_const_iterator() = default;
1589
1590       _Local_const_iterator(const __hash_code_base& __base,
1591                             _Hash_node<_Value, __cache>* __p,
1592                             std::size_t __bkt, std::size_t __bkt_count)
1593         : __base_type(__base, __p, __bkt, __bkt_count)
1594       { }
1595
1596       _Local_const_iterator(const _Local_iterator<_Key, _Value, _ExtractKey,
1597                                                   _H1, _H2, _Hash,
1598                                                   __constant_iterators,
1599                                                   __cache>& __x)
1600         : __base_type(__x)
1601       { }
1602
1603       reference
1604       operator*() const
1605       { return this->_M_cur->_M_v(); }
1606
1607       pointer
1608       operator->() const
1609       { return this->_M_cur->_M_valptr(); }
1610
1611       _Local_const_iterator&
1612       operator++()
1613       {
1614         this->_M_incr();
1615         return *this;
1616       }
1617
1618       _Local_const_iterator
1619       operator++(int)
1620       {
1621         _Local_const_iterator __tmp(*this);
1622         this->_M_incr();
1623         return __tmp;
1624       }
1625     };
1626
1627   /**
1628    *  Primary class template _Hashtable_base.
1629    *
1630    *  Helper class adding management of _Equal functor to
1631    *  _Hash_code_base type.
1632    *
1633    *  Base class templates are:
1634    *    - __detail::_Hash_code_base
1635    *    - __detail::_Hashtable_ebo_helper
1636    */
1637   template<typename _Key, typename _Value,
1638            typename _ExtractKey, typename _Equal,
1639            typename _H1, typename _H2, typename _Hash, typename _Traits>
1640   struct _Hashtable_base
1641   : public _Hash_code_base<_Key, _Value, _ExtractKey, _H1, _H2, _Hash,
1642                            _Traits::__hash_cached::value>,
1643     private _Hashtable_ebo_helper<0, _Equal>
1644   {
1645   public:
1646     typedef _Key                                        key_type;
1647     typedef _Value                                      value_type;
1648     typedef _Equal                                      key_equal;
1649     typedef std::size_t                                 size_type;
1650     typedef std::ptrdiff_t                              difference_type;
1651
1652     using __traits_type = _Traits;
1653     using __hash_cached = typename __traits_type::__hash_cached;
1654     using __constant_iterators = typename __traits_type::__constant_iterators;
1655     using __unique_keys = typename __traits_type::__unique_keys;
1656
1657     using __hash_code_base = _Hash_code_base<_Key, _Value, _ExtractKey,
1658                                              _H1, _H2, _Hash,
1659                                              __hash_cached::value>;
1660
1661     using __hash_code = typename __hash_code_base::__hash_code;
1662     using __node_type = typename __hash_code_base::__node_type;
1663
1664     using iterator = __detail::_Node_iterator<value_type,
1665                                               __constant_iterators::value,
1666                                               __hash_cached::value>;
1667
1668     using const_iterator = __detail::_Node_const_iterator<value_type,
1669                                                    __constant_iterators::value,
1670                                                    __hash_cached::value>;
1671
1672     using local_iterator = __detail::_Local_iterator<key_type, value_type,
1673                                                   _ExtractKey, _H1, _H2, _Hash,
1674                                                   __constant_iterators::value,
1675                                                      __hash_cached::value>;
1676
1677     using const_local_iterator = __detail::_Local_const_iterator<key_type,
1678                                                                  value_type,
1679                                         _ExtractKey, _H1, _H2, _Hash,
1680                                         __constant_iterators::value,
1681                                         __hash_cached::value>;
1682
1683     using __ireturn_type = typename std::conditional<__unique_keys::value,
1684                                                      std::pair<iterator, bool>,
1685                                                      iterator>::type;
1686   private:
1687     using _EqualEBO = _Hashtable_ebo_helper<0, _Equal>;
1688     using _EqualHelper =  _Equal_helper<_Key, _Value, _ExtractKey, _Equal,
1689                                         __hash_code, __hash_cached::value>;
1690
1691   protected:
1692     _Hashtable_base() = default;
1693     _Hashtable_base(const _ExtractKey& __ex, const _H1& __h1, const _H2& __h2,
1694                     const _Hash& __hash, const _Equal& __eq)
1695     : __hash_code_base(__ex, __h1, __h2, __hash), _EqualEBO(__eq)
1696     { }
1697
1698     bool
1699     _M_equals(const _Key& __k, __hash_code __c, __node_type* __n) const
1700     {
1701       return _EqualHelper::_S_equals(_M_eq(), this->_M_extract(),
1702                                      __k, __c, __n);
1703     }
1704
1705     void
1706     _M_swap(_Hashtable_base& __x)
1707     {
1708       __hash_code_base::_M_swap(__x);
1709       std::swap(_M_eq(), __x._M_eq());
1710     }
1711
1712     const _Equal&
1713     _M_eq() const { return _EqualEBO::_S_cget(*this); }
1714
1715     _Equal&
1716     _M_eq() { return _EqualEBO::_S_get(*this); }
1717   };
1718
1719   /**
1720    *  struct _Equality_base.
1721    *
1722    *  Common types and functions for class _Equality.
1723    */
1724   struct _Equality_base
1725   {
1726   protected:
1727     template<typename _Uiterator>
1728       static bool
1729       _S_is_permutation(_Uiterator, _Uiterator, _Uiterator);
1730   };
1731
1732   // See std::is_permutation in N3068.
1733   template<typename _Uiterator>
1734     bool
1735     _Equality_base::
1736     _S_is_permutation(_Uiterator __first1, _Uiterator __last1,
1737                       _Uiterator __first2)
1738     {
1739       for (; __first1 != __last1; ++__first1, ++__first2)
1740         if (!(*__first1 == *__first2))
1741           break;
1742
1743       if (__first1 == __last1)
1744         return true;
1745
1746       _Uiterator __last2 = __first2;
1747       std::advance(__last2, std::distance(__first1, __last1));
1748
1749       for (_Uiterator __it1 = __first1; __it1 != __last1; ++__it1)
1750         {
1751           _Uiterator __tmp =  __first1;
1752           while (__tmp != __it1 && !bool(*__tmp == *__it1))
1753             ++__tmp;
1754
1755           // We've seen this one before.
1756           if (__tmp != __it1)
1757             continue;
1758
1759           std::ptrdiff_t __n2 = 0;
1760           for (__tmp = __first2; __tmp != __last2; ++__tmp)
1761             if (*__tmp == *__it1)
1762               ++__n2;
1763
1764           if (!__n2)
1765             return false;
1766
1767           std::ptrdiff_t __n1 = 0;
1768           for (__tmp = __it1; __tmp != __last1; ++__tmp)
1769             if (*__tmp == *__it1)
1770               ++__n1;
1771
1772           if (__n1 != __n2)
1773             return false;
1774         }
1775       return true;
1776     }
1777
1778   /**
1779    *  Primary class template  _Equality.
1780    *
1781    *  This is for implementing equality comparison for unordered
1782    *  containers, per N3068, by John Lakos and Pablo Halpern.
1783    *  Algorithmically, we follow closely the reference implementations
1784    *  therein.
1785    */
1786   template<typename _Key, typename _Value, typename _Alloc,
1787            typename _ExtractKey, typename _Equal,
1788            typename _H1, typename _H2, typename _Hash,
1789            typename _RehashPolicy, typename _Traits,
1790            bool _Unique_keys = _Traits::__unique_keys::value>
1791     struct _Equality;
1792
1793   /// Specialization.
1794   template<typename _Key, typename _Value, typename _Alloc,
1795            typename _ExtractKey, typename _Equal,
1796            typename _H1, typename _H2, typename _Hash,
1797            typename _RehashPolicy, typename _Traits>
1798     struct _Equality<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1799                      _H1, _H2, _Hash, _RehashPolicy, _Traits, true>
1800     {
1801       using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1802                                      _H1, _H2, _Hash, _RehashPolicy, _Traits>;
1803
1804       bool
1805       _M_equal(const __hashtable&) const;
1806     };
1807
1808   template<typename _Key, typename _Value, typename _Alloc,
1809            typename _ExtractKey, typename _Equal,
1810            typename _H1, typename _H2, typename _Hash,
1811            typename _RehashPolicy, typename _Traits>
1812     bool
1813     _Equality<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1814               _H1, _H2, _Hash, _RehashPolicy, _Traits, true>::
1815     _M_equal(const __hashtable& __other) const
1816     {
1817       const __hashtable* __this = static_cast<const __hashtable*>(this);
1818
1819       if (__this->size() != __other.size())
1820         return false;
1821
1822       for (auto __itx = __this->begin(); __itx != __this->end(); ++__itx)
1823         {
1824           const auto __ity = __other.find(_ExtractKey()(*__itx));
1825           if (__ity == __other.end() || !bool(*__ity == *__itx))
1826             return false;
1827         }
1828       return true;
1829     }
1830
1831   /// Specialization.
1832   template<typename _Key, typename _Value, typename _Alloc,
1833            typename _ExtractKey, typename _Equal,
1834            typename _H1, typename _H2, typename _Hash,
1835            typename _RehashPolicy, typename _Traits>
1836     struct _Equality<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1837                      _H1, _H2, _Hash, _RehashPolicy, _Traits, false>
1838     : public _Equality_base
1839     {
1840       using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1841                                      _H1, _H2, _Hash, _RehashPolicy, _Traits>;
1842
1843       bool
1844       _M_equal(const __hashtable&) const;
1845     };
1846
1847   template<typename _Key, typename _Value, typename _Alloc,
1848            typename _ExtractKey, typename _Equal,
1849            typename _H1, typename _H2, typename _Hash,
1850            typename _RehashPolicy, typename _Traits>
1851     bool
1852     _Equality<_Key, _Value, _Alloc, _ExtractKey, _Equal,
1853               _H1, _H2, _Hash, _RehashPolicy, _Traits, false>::
1854     _M_equal(const __hashtable& __other) const
1855     {
1856       const __hashtable* __this = static_cast<const __hashtable*>(this);
1857
1858       if (__this->size() != __other.size())
1859         return false;
1860
1861       for (auto __itx = __this->begin(); __itx != __this->end();)
1862         {
1863           const auto __xrange = __this->equal_range(_ExtractKey()(*__itx));
1864           const auto __yrange = __other.equal_range(_ExtractKey()(*__itx));
1865
1866           if (std::distance(__xrange.first, __xrange.second)
1867               != std::distance(__yrange.first, __yrange.second))
1868             return false;
1869
1870           if (!_S_is_permutation(__xrange.first, __xrange.second,
1871                                  __yrange.first))
1872             return false;
1873
1874           __itx = __xrange.second;
1875         }
1876       return true;
1877     }
1878
1879   /**
1880    * This type deals with all allocation and keeps an allocator instance through
1881    * inheritance to benefit from EBO when possible.
1882    */
1883   template<typename _NodeAlloc>
1884     struct _Hashtable_alloc : private _Hashtable_ebo_helper<0, _NodeAlloc>
1885     {
1886     private:
1887       using __ebo_node_alloc = _Hashtable_ebo_helper<0, _NodeAlloc>;
1888     public:
1889       using __node_type = typename _NodeAlloc::value_type;
1890       using __node_alloc_type = _NodeAlloc;
1891       // Use __gnu_cxx to benefit from _S_always_equal and al.
1892       using __node_alloc_traits = __gnu_cxx::__alloc_traits<__node_alloc_type>;
1893
1894       using __value_type = typename __node_type::value_type;
1895       using __value_alloc_type =
1896         __alloc_rebind<__node_alloc_type, __value_type>;
1897       using __value_alloc_traits = std::allocator_traits<__value_alloc_type>;
1898
1899       using __node_base = __detail::_Hash_node_base;
1900       using __bucket_type = __node_base*;
1901       using __bucket_alloc_type =
1902         __alloc_rebind<__node_alloc_type, __bucket_type>;
1903       using __bucket_alloc_traits = std::allocator_traits<__bucket_alloc_type>;
1904
1905       _Hashtable_alloc() = default;
1906       _Hashtable_alloc(const _Hashtable_alloc&) = default;
1907       _Hashtable_alloc(_Hashtable_alloc&&) = default;
1908
1909       template<typename _Alloc>
1910         _Hashtable_alloc(_Alloc&& __a)
1911           : __ebo_node_alloc(std::forward<_Alloc>(__a))
1912         { }
1913
1914       __node_alloc_type&
1915       _M_node_allocator()
1916       { return __ebo_node_alloc::_S_get(*this); }
1917
1918       const __node_alloc_type&
1919       _M_node_allocator() const
1920       { return __ebo_node_alloc::_S_cget(*this); }
1921
1922       template<typename... _Args>
1923         __node_type*
1924         _M_allocate_node(_Args&&... __args);
1925
1926       void
1927       _M_deallocate_node(__node_type* __n);
1928
1929       // Deallocate the linked list of nodes pointed to by __n
1930       void
1931       _M_deallocate_nodes(__node_type* __n);
1932
1933       __bucket_type*
1934       _M_allocate_buckets(std::size_t __n);
1935
1936       void
1937       _M_deallocate_buckets(__bucket_type*, std::size_t __n);
1938     };
1939
1940   // Definitions of class template _Hashtable_alloc's out-of-line member
1941   // functions.
1942   template<typename _NodeAlloc>
1943     template<typename... _Args>
1944       typename _Hashtable_alloc<_NodeAlloc>::__node_type*
1945       _Hashtable_alloc<_NodeAlloc>::_M_allocate_node(_Args&&... __args)
1946       {
1947         auto __nptr = __node_alloc_traits::allocate(_M_node_allocator(), 1);
1948         __node_type* __n = std::__addressof(*__nptr);
1949         __try
1950           {
1951             __value_alloc_type __a(_M_node_allocator());
1952             ::new ((void*)__n) __node_type;
1953             __value_alloc_traits::construct(__a, __n->_M_valptr(),
1954                                             std::forward<_Args>(__args)...);
1955             return __n;
1956           }
1957         __catch(...)
1958           {
1959             __node_alloc_traits::deallocate(_M_node_allocator(), __nptr, 1);
1960             __throw_exception_again;
1961           }
1962       }
1963
1964   template<typename _NodeAlloc>
1965     void
1966     _Hashtable_alloc<_NodeAlloc>::_M_deallocate_node(__node_type* __n)
1967     {
1968       typedef typename __node_alloc_traits::pointer _Ptr;
1969       auto __ptr = std::pointer_traits<_Ptr>::pointer_to(*__n);
1970       __value_alloc_type __a(_M_node_allocator());
1971       __value_alloc_traits::destroy(__a, __n->_M_valptr());
1972       __n->~__node_type();
1973       __node_alloc_traits::deallocate(_M_node_allocator(), __ptr, 1);
1974     }
1975
1976   template<typename _NodeAlloc>
1977     void
1978     _Hashtable_alloc<_NodeAlloc>::_M_deallocate_nodes(__node_type* __n)
1979     {
1980       while (__n)
1981         {
1982           __node_type* __tmp = __n;
1983           __n = __n->_M_next();
1984           _M_deallocate_node(__tmp);
1985         }
1986     }
1987
1988   template<typename _NodeAlloc>
1989     typename _Hashtable_alloc<_NodeAlloc>::__bucket_type*
1990     _Hashtable_alloc<_NodeAlloc>::_M_allocate_buckets(std::size_t __n)
1991     {
1992       __bucket_alloc_type __alloc(_M_node_allocator());
1993
1994       auto __ptr = __bucket_alloc_traits::allocate(__alloc, __n);
1995       __bucket_type* __p = std::__addressof(*__ptr);
1996       __builtin_memset(__p, 0, __n * sizeof(__bucket_type));
1997       return __p;
1998     }
1999
2000   template<typename _NodeAlloc>
2001     void
2002     _Hashtable_alloc<_NodeAlloc>::_M_deallocate_buckets(__bucket_type* __bkts,
2003                                                         std::size_t __n)
2004     {
2005       typedef typename __bucket_alloc_traits::pointer _Ptr;
2006       auto __ptr = std::pointer_traits<_Ptr>::pointer_to(*__bkts);
2007       __bucket_alloc_type __alloc(_M_node_allocator());
2008       __bucket_alloc_traits::deallocate(__alloc, __ptr, __n);
2009     }
2010
2011  //@} hashtable-detail
2012 _GLIBCXX_END_NAMESPACE_VERSION
2013 } // namespace __detail
2014 } // namespace std
2015
2016 #endif // _HASHTABLE_POLICY_H