bits/hashtable.h

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// hashtable.h header -*- C++ -*-

// Copyright (C) 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/** @file bits/hashtable.h
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{unordered_map, unordered_set}
 */

#ifndef _HASHTABLE_H
#define _HASHTABLE_H 1

#pragma GCC system_header

#include <bits/hashtable_policy.h>

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  // Class template _Hashtable, class definition.

  // Meaning of class template _Hashtable's template parameters

  // _Key and _Value: arbitrary CopyConstructible types.

  // _Allocator: an allocator type ([lib.allocator.requirements]) whose
  // value type is Value.  As a conforming extension, we allow for
  // value type != Value.

  // _ExtractKey: function object that takes an object of type Value
  // and returns a value of type _Key.

  // _Equal: function object that takes two objects of type k and returns
  // a bool-like value that is true if the two objects are considered equal.

  // _H1: the hash function.  A unary function object with argument type
  // Key and result type size_t.  Return values should be distributed
  // over the entire range [0, numeric_limits<size_t>:::max()].

  // _H2: the range-hashing function (in the terminology of Tavori and
  // Dreizin).  A binary function object whose argument types and result
  // type are all size_t.  Given arguments r and N, the return value is
  // in the range [0, N).

  // _Hash: the ranged hash function (Tavori and Dreizin). A binary function
  // whose argument types are _Key and size_t and whose result type is
  // size_t.  Given arguments k and N, the return value is in the range
  // [0, N).  Default: hash(k, N) = h2(h1(k), N).  If _Hash is anything other
  // than the default, _H1 and _H2 are ignored.

  // _RehashPolicy: Policy class with three members, all of which govern
  // the bucket count. _M_next_bkt(n) returns a bucket count no smaller
  // than n.  _M_bkt_for_elements(n) returns a bucket count appropriate
  // for an element count of n.  _M_need_rehash(n_bkt, n_elt, n_ins)
  // determines whether, if the current bucket count is n_bkt and the
  // current element count is n_elt, we need to increase the bucket
  // count.  If so, returns make_pair(true, n), where n is the new
  // bucket count.  If not, returns make_pair(false, <anything>).

  // __cache_hash_code: bool.  true if we store the value of the hash
  // function along with the value.  This is a time-space tradeoff.
  // Storing it may improve lookup speed by reducing the number of times
  // we need to call the Equal function.

  // __constant_iterators: bool.  true if iterator and const_iterator are
  // both constant iterator types.  This is true for unordered_set and
  // unordered_multiset, false for unordered_map and unordered_multimap.

  // __unique_keys: bool.  true if the return value of _Hashtable::count(k)
  // is always at most one, false if it may be an arbitrary number.  This
  // true for unordered_set and unordered_map, false for unordered_multiset
  // and unordered_multimap.
  /**
   * Here's _Hashtable data structure, each _Hashtable has:
   * - _Bucket[]       _M_buckets
   * - _Hash_node_base _M_before_begin
   * - size_type       _M_bucket_count
   * - size_type       _M_element_count
   *
   * with _Bucket being _Hash_node* and _Hash_node constaining:
   * - _Hash_node*   _M_next
   * - Tp            _M_value
   * - size_t        _M_code if cache_hash_code is true
   *
   * In terms of Standard containers the hastable is like the aggregation of:
   * - std::forward_list<_Node> containing the elements
   * - std::vector<std::forward_list<_Node>::iterator> representing the buckets
   *
   * The non-empty buckets contain the node before the first bucket node. This
   * design allow to implement something like a std::forward_list::insert_after
   * on container insertion and std::forward_list::erase_after on container
   * erase calls. _M_before_begin is equivalent to
   * std::foward_list::before_begin. Empty buckets are containing nullptr.
   * Note that one of the non-empty bucket contains &_M_before_begin which is
   * not a derefenrenceable node so the node pointers in buckets shall never be
   * derefenrenced, only its next node can be.
   * 
   * Walk through a bucket nodes require a check on the hash code to see if the
   * node is still in the bucket. Such a design impose a quite efficient hash
   * functor and is one of the reasons it is highly advise to set
   * __cache_hash_code to true.
   *
   * The container iterators are simply built from nodes. This way incrementing
   * the iterator is perfectly efficient independent of how many empty buckets
   * there are in the container.
   *
   * On insert we compute element hash code and thanks to it find the bucket
   * index. If the element must be inserted on an empty bucket we add it at the
   * beginning of the singly linked list and make the bucket point to
   * _M_before_begin. The bucket that used to point to _M_before_begin, if any,
   * is updated to point to its new before begin node.
   *
   * On erase, the simple iterator design impose to use the hash functor to get
   * the index of the bucket to update. For this reason, when __cache_hash_code
   * is set to false, there is a static assertion that the hash functor cannot
   * throw.
   */

  template<typename _Key, typename _Value, typename _Allocator,
       typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash,
       typename _RehashPolicy,
       bool __cache_hash_code,
       bool __constant_iterators,
       bool __unique_keys>
    class _Hashtable
    : public __detail::_Rehash_base<_RehashPolicy,
                    _Hashtable<_Key, _Value, _Allocator,
                           _ExtractKey,
                           _Equal, _H1, _H2, _Hash,
                           _RehashPolicy,
                           __cache_hash_code,
                           __constant_iterators,
                           __unique_keys> >,
      public __detail::_Hashtable_base<_Key, _Value, _ExtractKey, _Equal,
                       _H1, _H2, _Hash, __cache_hash_code>,
      public __detail::_Map_base<_Key, _Value, _ExtractKey, __unique_keys,
                 _Hashtable<_Key, _Value, _Allocator,
                        _ExtractKey,
                        _Equal, _H1, _H2, _Hash,
                        _RehashPolicy,
                        __cache_hash_code,
                        __constant_iterators,
                        __unique_keys> >,
      public __detail::_Equality_base<_ExtractKey, __unique_keys,
                      _Hashtable<_Key, _Value, _Allocator,
                         _ExtractKey,
                         _Equal, _H1, _H2, _Hash,
                         _RehashPolicy,
                         __cache_hash_code,
                         __constant_iterators,
                         __unique_keys> >
    {
      template<typename _Cond>
    using __if_hash_code_cached
      = __or_<__not_<integral_constant<bool, __cache_hash_code>>, _Cond>;

      template<typename _Cond>
    using __if_hash_code_not_cached
      = __or_<integral_constant<bool, __cache_hash_code>, _Cond>;

      // When hash codes are not cached the hash functor shall not throw
      // because it is used in methods (erase, swap...) that shall not throw.
      static_assert(__if_hash_code_not_cached<__detail::__is_noexcept_hash<_Key,
                                _H1>>::value,
            "Cache the hash code or qualify your hash functor with noexcept");

      // Following two static assertions are necessary to guarantee that
      // swapping two hashtable instances won't invalidate associated local
      // iterators.

      // When hash codes are cached local iterator only uses H2 which must then
      // be empty.
      static_assert(__if_hash_code_cached<is_empty<_H2>>::value,
        "Functor used to map hash code to bucket index must be empty");

      typedef __detail::_Hash_code_base<_Key, _Value, _ExtractKey,
                    _H1, _H2, _Hash,
                        __cache_hash_code> _HCBase;

      // When hash codes are not cached local iterator is going to use _HCBase
      // above to compute node bucket index so it has to be empty.
      static_assert(__if_hash_code_not_cached<is_empty<_HCBase>>::value,
        "Cache the hash code or make functors involved in hash code"
        " and bucket index computation empty");

    public:
      typedef _Allocator                                  allocator_type;
      typedef _Value                                      value_type;
      typedef _Key                                        key_type;
      typedef _Equal                                      key_equal;
      // mapped_type, if present, comes from _Map_base.
      // hasher, if present, comes from _Hash_code_base.
      typedef typename _Allocator::pointer                pointer;
      typedef typename _Allocator::const_pointer          const_pointer;
      typedef typename _Allocator::reference              reference;
      typedef typename _Allocator::const_reference        const_reference;

      typedef std::size_t                                 size_type;
      typedef std::ptrdiff_t                              difference_type;
      typedef __detail::_Local_iterator<key_type, value_type, _ExtractKey,
                    _H1, _H2, _Hash,
                    __constant_iterators,
                    __cache_hash_code>
                              local_iterator;
      typedef __detail::_Local_const_iterator<key_type, value_type, _ExtractKey,
                          _H1, _H2, _Hash,
                          __constant_iterators,
                          __cache_hash_code>
                              const_local_iterator;
      typedef __detail::_Node_iterator<value_type, __constant_iterators,
                       __cache_hash_code>
                              iterator;
      typedef __detail::_Node_const_iterator<value_type,
                         __constant_iterators,
                         __cache_hash_code>
                              const_iterator;

      template<typename _Key2, typename _Value2, typename _Ex2, bool __unique2,
           typename _Hashtable2>
    friend struct __detail::_Map_base;

    private:
      typedef typename _RehashPolicy::_State _RehashPolicyState;
      typedef __detail::_Hash_node<_Value, __cache_hash_code> _Node;
      typedef typename _Allocator::template rebind<_Node>::other
                            _Node_allocator_type;
      typedef __detail::_Hash_node_base _BaseNode;
      typedef _BaseNode* _Bucket;
      typedef typename _Allocator::template rebind<_Bucket>::other
                            _Bucket_allocator_type;

      typedef typename _Allocator::template rebind<_Value>::other
                            _Value_allocator_type;

      _Node_allocator_type  _M_node_allocator;
      _Bucket*          _M_buckets;
      size_type         _M_bucket_count;
      _BaseNode         _M_before_begin;
      size_type         _M_element_count;
      _RehashPolicy     _M_rehash_policy;

      template<typename... _Args>
    _Node*
    _M_allocate_node(_Args&&... __args);

      void
      _M_deallocate_node(_Node* __n);

      // Deallocate the linked list of nodes pointed to by __n
      void
      _M_deallocate_nodes(_Node* __n);

      _Bucket*
      _M_allocate_buckets(size_type __n);

      void
      _M_deallocate_buckets(_Bucket*, size_type __n);

      // Gets bucket begin, deals with the fact that non-empty buckets contain
      // their before begin node.
      _Node*
      _M_bucket_begin(size_type __bkt) const;

      _Node*
      _M_begin() const
      { return static_cast<_Node*>(_M_before_begin._M_nxt); }

    public:
      // Constructor, destructor, assignment, swap
      _Hashtable(size_type __bucket_hint,
         const _H1&, const _H2&, const _Hash&,
         const _Equal&, const _ExtractKey&,
         const allocator_type&);

      template<typename _InputIterator>
    _Hashtable(_InputIterator __first, _InputIterator __last,
           size_type __bucket_hint,
           const _H1&, const _H2&, const _Hash&,
           const _Equal&, const _ExtractKey&,
           const allocator_type&);

      _Hashtable(const _Hashtable&);

      _Hashtable(_Hashtable&&);

      _Hashtable&
      operator=(const _Hashtable& __ht)
      {
    _Hashtable __tmp(__ht);
    this->swap(__tmp);
    return *this;
      }

      _Hashtable&
      operator=(_Hashtable&& __ht)
      {
    // NB: DR 1204.
    // NB: DR 675.
    this->clear();
    this->swap(__ht);
    return *this;
      }

      ~_Hashtable() noexcept;

      void swap(_Hashtable&);

      // Basic container operations
      iterator
      begin() noexcept
      { return iterator(_M_begin()); }

      const_iterator
      begin() const noexcept
      { return const_iterator(_M_begin()); }

      iterator
      end() noexcept
      { return iterator(nullptr); }

      const_iterator
      end() const noexcept
      { return const_iterator(nullptr); }

      const_iterator
      cbegin() const noexcept
      { return const_iterator(_M_begin()); }

      const_iterator
      cend() const noexcept
      { return const_iterator(nullptr); }

      size_type
      size() const noexcept
      { return _M_element_count; }

      bool
      empty() const noexcept
      { return size() == 0; }

      allocator_type
      get_allocator() const noexcept
      { return allocator_type(_M_node_allocator); }

      size_type
      max_size() const noexcept
      { return _M_node_allocator.max_size(); }

      // Observers
      key_equal
      key_eq() const
      { return this->_M_eq(); }

      // hash_function, if present, comes from _Hash_code_base.

      // Bucket operations
      size_type
      bucket_count() const noexcept
      { return _M_bucket_count; }

      size_type
      max_bucket_count() const noexcept
      { return max_size(); }

      size_type
      bucket_size(size_type __n) const
      { return std::distance(begin(__n), end(__n)); }

      size_type
      bucket(const key_type& __k) const
      { return _M_bucket_index(__k, this->_M_hash_code(__k)); }

      local_iterator
      begin(size_type __n)
      { return local_iterator(_M_bucket_begin(__n), __n,
                  _M_bucket_count); }

      local_iterator
      end(size_type __n)
      { return local_iterator(nullptr, __n, _M_bucket_count); }

      const_local_iterator
      begin(size_type __n) const
      { return const_local_iterator(_M_bucket_begin(__n), __n,
                    _M_bucket_count); }

      const_local_iterator
      end(size_type __n) const
      { return const_local_iterator(nullptr, __n, _M_bucket_count); }

      // DR 691.
      const_local_iterator
      cbegin(size_type __n) const
      { return const_local_iterator(_M_bucket_begin(__n), __n,
                    _M_bucket_count); }

      const_local_iterator
      cend(size_type __n) const
      { return const_local_iterator(nullptr, __n, _M_bucket_count); }

      float
      load_factor() const noexcept
      {
    return static_cast<float>(size()) / static_cast<float>(bucket_count());
      }

      // max_load_factor, if present, comes from _Rehash_base.

      // Generalization of max_load_factor.  Extension, not found in TR1.  Only
      // useful if _RehashPolicy is something other than the default.
      const _RehashPolicy&
      __rehash_policy() const
      { return _M_rehash_policy; }

      void
      __rehash_policy(const _RehashPolicy&);

      // Lookup.
      iterator
      find(const key_type& __k);

      const_iterator
      find(const key_type& __k) const;

      size_type
      count(const key_type& __k) const;

      std::pair<iterator, iterator>
      equal_range(const key_type& __k);

      std::pair<const_iterator, const_iterator>
      equal_range(const key_type& __k) const;

    private:
      // Bucket index computation helpers.
      size_type
      _M_bucket_index(_Node* __n) const
      { return _HCBase::_M_bucket_index(__n, _M_bucket_count); }

      size_type
      _M_bucket_index(const key_type& __k,
              typename _Hashtable::_Hash_code_type __c) const
      { return _HCBase::_M_bucket_index(__k, __c, _M_bucket_count); }

      // Find and insert helper functions and types
      // Find the node before the one matching the criteria.
      _BaseNode*
      _M_find_before_node(size_type, const key_type&,
              typename _Hashtable::_Hash_code_type) const;

      _Node*
      _M_find_node(size_type __bkt, const key_type& __key,
           typename _Hashtable::_Hash_code_type __c) const
      {
    _BaseNode* __before_n = _M_find_before_node(__bkt, __key, __c);
    if (__before_n)
      return static_cast<_Node*>(__before_n->_M_nxt);
    return nullptr;
      }

      // Insert a node at the beginning of a bucket.
      void
      _M_insert_bucket_begin(size_type, _Node*);

      // Remove the bucket first node
      void
      _M_remove_bucket_begin(size_type __bkt, _Node* __next_n,
                 size_type __next_bkt);

      // Get the node before __n in the bucket __bkt
      _BaseNode*
      _M_get_previous_node(size_type __bkt, _BaseNode* __n);

      template<typename _Arg>
    iterator
    _M_insert_bucket(_Arg&&, size_type,
             typename _Hashtable::_Hash_code_type);

      typedef typename std::conditional<__unique_keys,
                    std::pair<iterator, bool>,
                    iterator>::type
    _Insert_Return_Type;

      typedef typename std::conditional<__unique_keys,
                    std::_Select1st<_Insert_Return_Type>,
                    std::_Identity<_Insert_Return_Type>
                   >::type
    _Insert_Conv_Type;

    protected:
      template<typename... _Args>
    std::pair<iterator, bool>
    _M_emplace(std::true_type, _Args&&... __args);

      template<typename... _Args>
    iterator
    _M_emplace(std::false_type, _Args&&... __args);

      template<typename _Arg>
    std::pair<iterator, bool>
    _M_insert(_Arg&&, std::true_type);

      template<typename _Arg>
    iterator
    _M_insert(_Arg&&, std::false_type);

    public:
      // Emplace, insert and erase
      template<typename... _Args>
    _Insert_Return_Type
    emplace(_Args&&... __args)
    { return _M_emplace(integral_constant<bool, __unique_keys>(),
                std::forward<_Args>(__args)...); }

      template<typename... _Args>
    iterator
    emplace_hint(const_iterator, _Args&&... __args)
    { return _Insert_Conv_Type()(emplace(std::forward<_Args>(__args)...)); }

      _Insert_Return_Type
      insert(const value_type& __v)
      { return _M_insert(__v, integral_constant<bool, __unique_keys>()); }

      iterator
      insert(const_iterator, const value_type& __v)
      { return _Insert_Conv_Type()(insert(__v)); }

      template<typename _Pair, typename = typename
    std::enable_if<__and_<integral_constant<bool, !__constant_iterators>,
                  std::is_convertible<_Pair,
                          value_type>>::value>::type>
    _Insert_Return_Type
    insert(_Pair&& __v)
    { return _M_insert(std::forward<_Pair>(__v),
               integral_constant<bool, __unique_keys>()); }

      template<typename _Pair, typename = typename
        std::enable_if<__and_<integral_constant<bool, !__constant_iterators>,
                  std::is_convertible<_Pair,
                          value_type>>::value>::type>
    iterator
    insert(const_iterator, _Pair&& __v)
    { return _Insert_Conv_Type()(insert(std::forward<_Pair>(__v))); }

      template<typename _InputIterator>
    void
    insert(_InputIterator __first, _InputIterator __last);

      void
      insert(initializer_list<value_type> __l)
      { this->insert(__l.begin(), __l.end()); }

      iterator
      erase(const_iterator);

      // LWG 2059.
      iterator
      erase(iterator __it)
      { return erase(const_iterator(__it)); }

      size_type
      erase(const key_type&);

      iterator
      erase(const_iterator, const_iterator);

      void
      clear() noexcept;

      // Set number of buckets to be appropriate for container of n element.
      void rehash(size_type __n);

      // DR 1189.
      // reserve, if present, comes from _Rehash_base.

    private:
      // Unconditionally change size of bucket array to n, restore hash policy
      // state to __state on exception.
      void _M_rehash(size_type __n, const _RehashPolicyState& __state);
    };


  // Definitions of class template _Hashtable's out-of-line member functions.
  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    template<typename... _Args>
      typename _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
              _H1, _H2, _Hash, _RehashPolicy,
              __chc, __cit, __uk>::_Node*
      _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
         _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
      _M_allocate_node(_Args&&... __args)
      {
    _Node* __n = _M_node_allocator.allocate(1);
    __try
      {
        _M_node_allocator.construct(__n, std::forward<_Args>(__args)...);
        return __n;
      }
    __catch(...)
      {
        _M_node_allocator.deallocate(__n, 1);
        __throw_exception_again;
      }
      }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    void
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    _M_deallocate_node(_Node* __n)
    {
      _M_node_allocator.destroy(__n);
      _M_node_allocator.deallocate(__n, 1);
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    void
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    _M_deallocate_nodes(_Node* __n)
    {
      while (__n)
    {
      _Node* __tmp = __n;
      __n = __n->_M_next();
      _M_deallocate_node(__tmp);
    }
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    typename _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
            _H1, _H2, _Hash, _RehashPolicy,
            __chc, __cit, __uk>::_Bucket*
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    _M_allocate_buckets(size_type __n)
    {
      _Bucket_allocator_type __alloc(_M_node_allocator);

      _Bucket* __p = __alloc.allocate(__n);
      __builtin_memset(__p, 0, __n * sizeof(_Bucket));
      return __p;
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    void
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    _M_deallocate_buckets(_Bucket* __p, size_type __n)
    {
      _Bucket_allocator_type __alloc(_M_node_allocator);
      __alloc.deallocate(__p, __n);
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    typename _Hashtable<_Key, _Value, _Allocator, _ExtractKey,
            _Equal, _H1, _H2, _Hash, _RehashPolicy,
            __chc, __cit, __uk>::_Node*
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    _M_bucket_begin(size_type __bkt) const
    {
      _BaseNode* __n = _M_buckets[__bkt];
      return __n ? static_cast<_Node*>(__n->_M_nxt) : nullptr;
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    _Hashtable(size_type __bucket_hint,
           const _H1& __h1, const _H2& __h2, const _Hash& __h,
           const _Equal& __eq, const _ExtractKey& __exk,
           const allocator_type& __a)
    : __detail::_Rehash_base<_RehashPolicy, _Hashtable>(),
      __detail::_Hashtable_base<_Key, _Value, _ExtractKey, _Equal,
                _H1, _H2, _Hash, __chc>(__exk, __h1, __h2, __h,
                            __eq),
      __detail::_Map_base<_Key, _Value, _ExtractKey, __uk, _Hashtable>(),
      _M_node_allocator(__a),
      _M_bucket_count(0),
      _M_element_count(0),
      _M_rehash_policy()
    {
      _M_bucket_count = _M_rehash_policy._M_next_bkt(__bucket_hint);
      // We don't want the rehash policy to ask for the hashtable to shrink
      // on the first insertion so we need to reset its previous resize level.
      _M_rehash_policy._M_prev_resize = 0;
      _M_buckets = _M_allocate_buckets(_M_bucket_count);
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    template<typename _InputIterator>
      _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
         _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
      _Hashtable(_InputIterator __f, _InputIterator __l,
         size_type __bucket_hint,
         const _H1& __h1, const _H2& __h2, const _Hash& __h,
         const _Equal& __eq, const _ExtractKey& __exk,
         const allocator_type& __a)
      : __detail::_Rehash_base<_RehashPolicy, _Hashtable>(),
    __detail::_Hashtable_base<_Key, _Value, _ExtractKey, _Equal,
                  _H1, _H2, _Hash, __chc>(__exk, __h1, __h2, __h,
                              __eq),
    __detail::_Map_base<_Key, _Value, _ExtractKey, __uk, _Hashtable>(),
    _M_node_allocator(__a),
    _M_bucket_count(0),
    _M_element_count(0),
    _M_rehash_policy()
      {
    _M_bucket_count = std::max(_M_rehash_policy._M_next_bkt(__bucket_hint),
                   _M_rehash_policy.
                   _M_bkt_for_elements(__detail::
                               __distance_fw(__f,
                                     __l)));
        // We don't want the rehash policy to ask for the hashtable to shrink
        // on the first insertion so we need to reset its previous resize
    // level.
    _M_rehash_policy._M_prev_resize = 0;
    _M_buckets = _M_allocate_buckets(_M_bucket_count);
    __try
      {
        for (; __f != __l; ++__f)
          this->insert(*__f);
      }
    __catch(...)
      {
        clear();
        _M_deallocate_buckets(_M_buckets, _M_bucket_count);
        __throw_exception_again;
      }
      }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    _Hashtable(const _Hashtable& __ht)
    : __detail::_Rehash_base<_RehashPolicy, _Hashtable>(__ht),
      __detail::_Hashtable_base<_Key, _Value, _ExtractKey, _Equal,
                _H1, _H2, _Hash, __chc>(__ht),
      __detail::_Map_base<_Key, _Value, _ExtractKey, __uk, _Hashtable>(__ht),
      _M_node_allocator(__ht._M_node_allocator),
      _M_bucket_count(__ht._M_bucket_count),
      _M_element_count(__ht._M_element_count),
      _M_rehash_policy(__ht._M_rehash_policy)
    {
      _M_buckets = _M_allocate_buckets(_M_bucket_count);
      __try
    {
      if (!__ht._M_before_begin._M_nxt)
        return;

      // First deal with the special first node pointed to by
      // _M_before_begin.
      const _Node* __ht_n = __ht._M_begin();
      _Node* __this_n = _M_allocate_node(__ht_n->_M_v);
      this->_M_copy_code(__this_n, __ht_n);
      _M_before_begin._M_nxt = __this_n;
      _M_buckets[_M_bucket_index(__this_n)] = &_M_before_begin;

      // Then deal with other nodes.
      _BaseNode* __prev_n = __this_n;
      for (__ht_n = __ht_n->_M_next(); __ht_n; __ht_n = __ht_n->_M_next())
        {
          __this_n = _M_allocate_node(__ht_n->_M_v);
          __prev_n->_M_nxt = __this_n;
          this->_M_copy_code(__this_n, __ht_n);
          size_type __bkt = _M_bucket_index(__this_n);
          if (!_M_buckets[__bkt])
        _M_buckets[__bkt] = __prev_n;
          __prev_n = __this_n;
        }
    }
      __catch(...)
    {
      clear();
      _M_deallocate_buckets(_M_buckets, _M_bucket_count);
      __throw_exception_again;
    }
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    _Hashtable(_Hashtable&& __ht)
    : __detail::_Rehash_base<_RehashPolicy, _Hashtable>(__ht),
      __detail::_Hashtable_base<_Key, _Value, _ExtractKey, _Equal,
                _H1, _H2, _Hash, __chc>(__ht),
      __detail::_Map_base<_Key, _Value, _ExtractKey, __uk, _Hashtable>(__ht),
      _M_node_allocator(std::move(__ht._M_node_allocator)),
      _M_buckets(__ht._M_buckets),
      _M_bucket_count(__ht._M_bucket_count),
      _M_before_begin(__ht._M_before_begin._M_nxt),
      _M_element_count(__ht._M_element_count),
      _M_rehash_policy(__ht._M_rehash_policy)
    {
      // Update, if necessary, bucket pointing to before begin that hasn't move.
      if (_M_begin())
    _M_buckets[_M_bucket_index(_M_begin())] = &_M_before_begin;
      __ht._M_rehash_policy = _RehashPolicy();
      __ht._M_bucket_count = __ht._M_rehash_policy._M_next_bkt(0);
      __ht._M_buckets = __ht._M_allocate_buckets(__ht._M_bucket_count);
      __ht._M_before_begin._M_nxt = nullptr;
      __ht._M_element_count = 0;
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    ~_Hashtable() noexcept
    {
      clear();
      _M_deallocate_buckets(_M_buckets, _M_bucket_count);
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    void
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    swap(_Hashtable& __x)
    {
      // The only base class with member variables is hash_code_base.  We
      // define _Hash_code_base::_M_swap because different specializations
      // have different members.
      this->_M_swap(__x);

      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 431. Swapping containers with unequal allocators.
      std::__alloc_swap<_Node_allocator_type>::_S_do_it(_M_node_allocator,
                            __x._M_node_allocator);

      std::swap(_M_rehash_policy, __x._M_rehash_policy);
      std::swap(_M_buckets, __x._M_buckets);
      std::swap(_M_bucket_count, __x._M_bucket_count);
      std::swap(_M_before_begin._M_nxt, __x._M_before_begin._M_nxt);
      std::swap(_M_element_count, __x._M_element_count);
      // Fix buckets containing the _M_before_begin pointers that can't be
      // swapped.
      if (_M_begin())
    _M_buckets[_M_bucket_index(_M_begin())] = &_M_before_begin;
      if (__x._M_begin())
    __x._M_buckets[__x._M_bucket_index(__x._M_begin())]
      = &(__x._M_before_begin);
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    void
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    __rehash_policy(const _RehashPolicy& __pol)
    {
      size_type __n_bkt = __pol._M_bkt_for_elements(_M_element_count);
      if (__n_bkt != _M_bucket_count)
    _M_rehash(__n_bkt, _M_rehash_policy._M_state());
      _M_rehash_policy = __pol;
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    typename _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
            _H1, _H2, _Hash, _RehashPolicy,
            __chc, __cit, __uk>::iterator
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    find(const key_type& __k)
    {
      typename _Hashtable::_Hash_code_type __code = this->_M_hash_code(__k);
      std::size_t __n = _M_bucket_index(__k, __code);
      _Node* __p = _M_find_node(__n, __k, __code);
      return __p ? iterator(__p) : this->end();
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    typename _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
            _H1, _H2, _Hash, _RehashPolicy,
            __chc, __cit, __uk>::const_iterator
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    find(const key_type& __k) const
    {
      typename _Hashtable::_Hash_code_type __code = this->_M_hash_code(__k);
      std::size_t __n = _M_bucket_index(__k, __code);
      _Node* __p = _M_find_node(__n, __k, __code);
      return __p ? const_iterator(__p) : this->end();
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    typename _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
            _H1, _H2, _Hash, _RehashPolicy,
            __chc, __cit, __uk>::size_type
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    count(const key_type& __k) const
    {
      typename _Hashtable::_Hash_code_type __code = this->_M_hash_code(__k);
      std::size_t __n = _M_bucket_index(__k, __code);
      _Node* __p = _M_bucket_begin(__n);
      if (!__p)
    return 0;

      std::size_t __result = 0;
      for (;; __p = __p->_M_next())
    {
      if (this->_M_equals(__k, __code, __p))
        ++__result;
      else if (__result)
        // All equivalent values are next to each other, if we found a not
        // equivalent value after an equivalent one it means that we won't
        // find anymore an equivalent value.
        break;
      if (!__p->_M_nxt || _M_bucket_index(__p->_M_next()) != __n)
        break;
    }
      return __result;
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    std::pair<typename _Hashtable<_Key, _Value, _Allocator,
                  _ExtractKey, _Equal, _H1,
                  _H2, _Hash, _RehashPolicy,
                  __chc, __cit, __uk>::iterator,
          typename _Hashtable<_Key, _Value, _Allocator,
                  _ExtractKey, _Equal, _H1,
                  _H2, _Hash, _RehashPolicy,
                  __chc, __cit, __uk>::iterator>
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    equal_range(const key_type& __k)
    {
      typename _Hashtable::_Hash_code_type __code = this->_M_hash_code(__k);
      std::size_t __n = _M_bucket_index(__k, __code);
      _Node* __p = _M_find_node(__n, __k, __code);

      if (__p)
    {
      _Node* __p1 = __p->_M_next();
      while (__p1 && _M_bucket_index(__p1) == __n
         && this->_M_equals(__k, __code, __p1))
        __p1 = __p1->_M_next();

      return std::make_pair(iterator(__p), iterator(__p1));
    }
      else
    return std::make_pair(this->end(), this->end());
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    std::pair<typename _Hashtable<_Key, _Value, _Allocator,
                  _ExtractKey, _Equal, _H1,
                  _H2, _Hash, _RehashPolicy,
                  __chc, __cit, __uk>::const_iterator,
          typename _Hashtable<_Key, _Value, _Allocator,
                  _ExtractKey, _Equal, _H1,
                  _H2, _Hash, _RehashPolicy,
                  __chc, __cit, __uk>::const_iterator>
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    equal_range(const key_type& __k) const
    {
      typename _Hashtable::_Hash_code_type __code = this->_M_hash_code(__k);
      std::size_t __n = _M_bucket_index(__k, __code);
      _Node* __p = _M_find_node(__n, __k, __code);

      if (__p)
    {
      _Node* __p1 = __p->_M_next();
      while (__p1 && _M_bucket_index(__p1) == __n
         && this->_M_equals(__k, __code, __p1))
        __p1 = __p1->_M_next();

      return std::make_pair(const_iterator(__p), const_iterator(__p1));
    }
      else
    return std::make_pair(this->end(), this->end());
    }

  // Find the node whose key compares equal to k in the bucket n. Return nullptr
  // if no node is found.
  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    typename _Hashtable<_Key, _Value, _Allocator, _ExtractKey,
            _Equal, _H1, _H2, _Hash, _RehashPolicy,
            __chc, __cit, __uk>::_BaseNode*
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    _M_find_before_node(size_type __n, const key_type& __k,
            typename _Hashtable::_Hash_code_type __code) const
    {
      _BaseNode* __prev_p = _M_buckets[__n];
      if (!__prev_p)
    return nullptr;
      _Node* __p = static_cast<_Node*>(__prev_p->_M_nxt);
      for (;; __p = __p->_M_next())
    {
      if (this->_M_equals(__k, __code, __p))
        return __prev_p;
      if (!(__p->_M_nxt) || _M_bucket_index(__p->_M_next()) != __n)
        break;
      __prev_p = __p;
    }
      return nullptr;
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    void
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    _M_insert_bucket_begin(size_type __bkt, _Node* __new_node)
    {
      if (_M_buckets[__bkt])
    {
      // Bucket is not empty, we just need to insert the new node after the
      // bucket before begin.
      __new_node->_M_nxt = _M_buckets[__bkt]->_M_nxt;
      _M_buckets[__bkt]->_M_nxt = __new_node;
    }
      else
    {
      // The bucket is empty, the new node is inserted at the beginning of
      // the singly linked list and the bucket will contain _M_before_begin
      // pointer.
      __new_node->_M_nxt = _M_before_begin._M_nxt;
      _M_before_begin._M_nxt = __new_node;
      if (__new_node->_M_nxt)
        // We must update former begin bucket that is pointing to
        // _M_before_begin.
        _M_buckets[_M_bucket_index(__new_node->_M_next())] = __new_node;
      _M_buckets[__bkt] = &_M_before_begin;
    }
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    void
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    _M_remove_bucket_begin(size_type __bkt, _Node* __next, size_type __next_bkt)
    {
      if (!__next || __next_bkt != __bkt)
    {
      // Bucket is now empty
      // First update next bucket if any
      if (__next)
        _M_buckets[__next_bkt] = _M_buckets[__bkt];
      // Second update before begin node if necessary
      if (&_M_before_begin == _M_buckets[__bkt])
        _M_before_begin._M_nxt = __next;
      _M_buckets[__bkt] = nullptr;
    }
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    typename _Hashtable<_Key, _Value, _Allocator, _ExtractKey,
            _Equal, _H1, _H2, _Hash, _RehashPolicy,
            __chc, __cit, __uk>::_BaseNode*
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    _M_get_previous_node(size_type __bkt, _BaseNode* __n)
    {
      _BaseNode* __prev_n = _M_buckets[__bkt];
      while (__prev_n->_M_nxt != __n)
    __prev_n = __prev_n->_M_nxt;
      return __prev_n;
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    template<typename... _Args>
      std::pair<typename _Hashtable<_Key, _Value, _Allocator,
                    _ExtractKey, _Equal, _H1,
                    _H2, _Hash, _RehashPolicy,
                    __chc, __cit, __uk>::iterator, bool>
      _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
         _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
      _M_emplace(std::true_type, _Args&&... __args)
      {
    // First build the node to get access to the hash code
    _Node* __new_node = _M_allocate_node(std::forward<_Args>(__args)...);
    __try
      {
        const key_type& __k = this->_M_extract()(__new_node->_M_v);
        typename _Hashtable::_Hash_code_type __code
          = this->_M_hash_code(__k);
        size_type __bkt = _M_bucket_index(__k, __code);

        if (_Node* __p = _M_find_node(__bkt, __k, __code))
          {
        // There is already an equivalent node, no insertion
        _M_deallocate_node(__new_node);
        return std::make_pair(iterator(__p), false);
          }

        // We are going to insert this node
        this->_M_store_code(__new_node, __code);
        const _RehashPolicyState& __saved_state
          = _M_rehash_policy._M_state();
        std::pair<bool, std::size_t> __do_rehash
          = _M_rehash_policy._M_need_rehash(_M_bucket_count,
                        _M_element_count, 1);

        if (__do_rehash.first)
          {
        _M_rehash(__do_rehash.second, __saved_state);
        __bkt = _M_bucket_index(__k, __code);
          }

        _M_insert_bucket_begin(__bkt, __new_node);
        ++_M_element_count;
        return std::make_pair(iterator(__new_node), true);
      }
    __catch(...)
      {
        _M_deallocate_node(__new_node);
        __throw_exception_again;
      }
      }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    template<typename... _Args>
      typename _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
              _H1, _H2, _Hash, _RehashPolicy,
              __chc, __cit, __uk>::iterator
      _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
         _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
      _M_emplace(std::false_type, _Args&&... __args)
      {
    const _RehashPolicyState& __saved_state = _M_rehash_policy._M_state();
    std::pair<bool, std::size_t> __do_rehash
      = _M_rehash_policy._M_need_rehash(_M_bucket_count,
                        _M_element_count, 1);

    // First build the node to get its hash code.
    _Node* __new_node = _M_allocate_node(std::forward<_Args>(__args)...);
    __try
      {
        const key_type& __k = this->_M_extract()(__new_node->_M_v);
        typename _Hashtable::_Hash_code_type __code
          = this->_M_hash_code(__k);
        this->_M_store_code(__new_node, __code);

        // Second, do rehash if necessary.
        if (__do_rehash.first)
        _M_rehash(__do_rehash.second, __saved_state);

        // Third, find the node before an equivalent one.
        size_type __bkt = _M_bucket_index(__k, __code);
        _BaseNode* __prev = _M_find_before_node(__bkt, __k, __code);
        
        if (__prev)
          {
        // Insert after the node before the equivalent one.
        __new_node->_M_nxt = __prev->_M_nxt;
        __prev->_M_nxt = __new_node;
          }
        else
          // The inserted node has no equivalent in the hashtable. We must
          // insert the new node at the beginning of the bucket to preserve
          // equivalent elements relative positions.
          _M_insert_bucket_begin(__bkt, __new_node);
        ++_M_element_count;
        return iterator(__new_node);
      }
    __catch(...)
      {
        _M_deallocate_node(__new_node);
        __throw_exception_again;
      }
      }

  // Insert v in bucket n (assumes no element with its key already present).
  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    template<typename _Arg>
      typename _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
              _H1, _H2, _Hash, _RehashPolicy,
              __chc, __cit, __uk>::iterator
      _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
         _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
      _M_insert_bucket(_Arg&& __v, size_type __n,
               typename _Hashtable::_Hash_code_type __code)
      {
    const _RehashPolicyState& __saved_state = _M_rehash_policy._M_state();
    std::pair<bool, std::size_t> __do_rehash
      = _M_rehash_policy._M_need_rehash(_M_bucket_count,
                        _M_element_count, 1);

    if (__do_rehash.first)
      {
        const key_type& __k = this->_M_extract()(__v);
        __n = _HCBase::_M_bucket_index(__k, __code, __do_rehash.second);
      }

    _Node* __new_node = nullptr;
    __try
      {
        // Allocate the new node before doing the rehash so that we
        // don't do a rehash if the allocation throws.
        __new_node = _M_allocate_node(std::forward<_Arg>(__v));
        this->_M_store_code(__new_node, __code);
        if (__do_rehash.first)
          _M_rehash(__do_rehash.second, __saved_state);

        _M_insert_bucket_begin(__n, __new_node);
        ++_M_element_count;
        return iterator(__new_node);
      }
    __catch(...)
      {
        if (!__new_node)
          _M_rehash_policy._M_reset(__saved_state);
        else
          _M_deallocate_node(__new_node);
        __throw_exception_again;
      }
      }

  // Insert v if no element with its key is already present.
  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    template<typename _Arg>
      std::pair<typename _Hashtable<_Key, _Value, _Allocator,
                    _ExtractKey, _Equal, _H1,
                    _H2, _Hash, _RehashPolicy,
                    __chc, __cit, __uk>::iterator, bool>
      _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
         _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
      _M_insert(_Arg&& __v, std::true_type)
      {
    const key_type& __k = this->_M_extract()(__v);
    typename _Hashtable::_Hash_code_type __code = this->_M_hash_code(__k);
    size_type __n = _M_bucket_index(__k, __code);

    if (_Node* __p = _M_find_node(__n, __k, __code))
      return std::make_pair(iterator(__p), false);
    return std::make_pair(_M_insert_bucket(std::forward<_Arg>(__v),
                  __n, __code), true);
      }

  // Insert v unconditionally.
  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    template<typename _Arg>
      typename _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
              _H1, _H2, _Hash, _RehashPolicy,
              __chc, __cit, __uk>::iterator
      _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
         _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
      _M_insert(_Arg&& __v, std::false_type)
      {
    const _RehashPolicyState& __saved_state = _M_rehash_policy._M_state();
    std::pair<bool, std::size_t> __do_rehash
      = _M_rehash_policy._M_need_rehash(_M_bucket_count,
                        _M_element_count, 1);

    // First compute the hash code so that we don't do anything if it throws.
    typename _Hashtable::_Hash_code_type __code
      = this->_M_hash_code(this->_M_extract()(__v));

    _Node* __new_node = nullptr;
    __try
      {
        // Second allocate new node so that we don't rehash if it throws.
        __new_node = _M_allocate_node(std::forward<_Arg>(__v));
        this->_M_store_code(__new_node, __code);
        if (__do_rehash.first)
        _M_rehash(__do_rehash.second, __saved_state);

        // Third, find the node before an equivalent one.
        size_type __bkt = _M_bucket_index(__new_node);
        _BaseNode* __prev
          = _M_find_before_node(__bkt, this->_M_extract()(__new_node->_M_v),
                    __code);
        if (__prev)
          {
        // Insert after the node before the equivalent one.
        __new_node->_M_nxt = __prev->_M_nxt;
        __prev->_M_nxt = __new_node;
          }
        else
          // The inserted node has no equivalent in the hashtable. We must
          // insert the new node at the beginning of the bucket to preserve
          // equivalent elements relative positions.
          _M_insert_bucket_begin(__bkt, __new_node);
        ++_M_element_count;
        return iterator(__new_node);
      }
    __catch(...)
      {
        if (!__new_node)
          _M_rehash_policy._M_reset(__saved_state);
        else
          _M_deallocate_node(__new_node);
        __throw_exception_again;
      }
      }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    template<typename _InputIterator>
      void
      _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
         _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
      insert(_InputIterator __first, _InputIterator __last)
      {
    size_type __n_elt = __detail::__distance_fw(__first, __last);
    const _RehashPolicyState& __saved_state = _M_rehash_policy._M_state();
    std::pair<bool, std::size_t> __do_rehash
      = _M_rehash_policy._M_need_rehash(_M_bucket_count,
                        _M_element_count, __n_elt);
    if (__do_rehash.first)
      _M_rehash(__do_rehash.second, __saved_state);

    for (; __first != __last; ++__first)
      this->insert(*__first);
      }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    typename _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
            _H1, _H2, _Hash, _RehashPolicy,
            __chc, __cit, __uk>::iterator
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    erase(const_iterator __it)
    {
      _Node* __n = __it._M_cur;
      std::size_t __bkt = _M_bucket_index(__n);

      // Look for previous node to unlink it from the erased one, this is why
      // we need buckets to contain the before begin to make this research fast.
      _BaseNode* __prev_n = _M_get_previous_node(__bkt, __n);
      if (__n == _M_bucket_begin(__bkt))
    _M_remove_bucket_begin(__bkt, __n->_M_next(),
       __n->_M_nxt ? _M_bucket_index(__n->_M_next()) : 0);
      else if (__n->_M_nxt)
    {
      size_type __next_bkt = _M_bucket_index(__n->_M_next());
      if (__next_bkt != __bkt)
        _M_buckets[__next_bkt] = __prev_n;
    }

      __prev_n->_M_nxt = __n->_M_nxt;
      iterator __result(__n->_M_next());
      _M_deallocate_node(__n);
      --_M_element_count;

      return __result;
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    typename _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
            _H1, _H2, _Hash, _RehashPolicy,
            __chc, __cit, __uk>::size_type
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    erase(const key_type& __k)
    {
      typename _Hashtable::_Hash_code_type __code = this->_M_hash_code(__k);
      std::size_t __bkt = _M_bucket_index(__k, __code);
      // Look for the node before the first matching node.
      _BaseNode* __prev_n = _M_find_before_node(__bkt, __k, __code);
      if (!__prev_n)
    return 0;
      _Node* __n = static_cast<_Node*>(__prev_n->_M_nxt);
      bool __is_bucket_begin = _M_buckets[__bkt] == __prev_n;

      // We found a matching node, start deallocation loop from it
      std::size_t __next_bkt = __bkt;
      _Node* __next_n = __n;
      size_type __result = 0;
      _Node* __saved_n = nullptr;
      do
    {
      _Node* __p = __next_n;
      __next_n = __p->_M_next();
      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 526. Is it undefined if a function in the standard changes
      // in parameters?
      if (std::__addressof(this->_M_extract()(__p->_M_v))
          != std::__addressof(__k))
        _M_deallocate_node(__p);
      else
        __saved_n = __p;
      --_M_element_count;
      ++__result;
      if (!__next_n)
        break;
      __next_bkt = _M_bucket_index(__next_n);
    }
      while (__next_bkt == __bkt && this->_M_equals(__k, __code, __next_n));

      if (__saved_n)
    _M_deallocate_node(__saved_n);
      if (__is_bucket_begin)
    _M_remove_bucket_begin(__bkt, __next_n, __next_bkt);
      else if (__next_n && __next_bkt != __bkt)
    _M_buckets[__next_bkt] = __prev_n;
      if (__prev_n)
    __prev_n->_M_nxt = __next_n;
      return __result;
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    typename _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
            _H1, _H2, _Hash, _RehashPolicy,
            __chc, __cit, __uk>::iterator
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    erase(const_iterator __first, const_iterator __last)
    {
      _Node* __n = __first._M_cur;
      _Node* __last_n = __last._M_cur;
      if (__n == __last_n)
    return iterator(__n);

      std::size_t __bkt = _M_bucket_index(__n);

      _BaseNode* __prev_n = _M_get_previous_node(__bkt, __n);
      bool __is_bucket_begin = __n == _M_bucket_begin(__bkt);
      std::size_t __n_bkt = __bkt;
      for (;;)
    {
      do
        {
          _Node* __tmp = __n;
          __n = __n->_M_next();
          _M_deallocate_node(__tmp);
          --_M_element_count;
          if (!__n)
        break;
          __n_bkt = _M_bucket_index(__n);
        }
      while (__n != __last_n && __n_bkt == __bkt);
      if (__is_bucket_begin)
        _M_remove_bucket_begin(__bkt, __n, __n_bkt);
      if (__n == __last_n)
        break;
      __is_bucket_begin = true;
      __bkt = __n_bkt;
    }

      if (__n && (__n_bkt != __bkt || __is_bucket_begin))
    _M_buckets[__n_bkt] = __prev_n;
      __prev_n->_M_nxt = __n;
      return iterator(__n);
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    void
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    clear() noexcept
    {
      _M_deallocate_nodes(_M_begin());
      __builtin_memset(_M_buckets, 0, _M_bucket_count * sizeof(_Bucket));
      _M_element_count = 0;
      _M_before_begin._M_nxt = nullptr;
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    void
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    rehash(size_type __n)
    {
      const _RehashPolicyState& __saved_state = _M_rehash_policy._M_state();
      _M_rehash(std::max(_M_rehash_policy._M_next_bkt(__n),
             _M_rehash_policy._M_bkt_for_elements(_M_element_count
                                  + 1)),
        __saved_state);
    }

  template<typename _Key, typename _Value,
       typename _Allocator, typename _ExtractKey, typename _Equal,
       typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
       bool __chc, bool __cit, bool __uk>
    void
    _Hashtable<_Key, _Value, _Allocator, _ExtractKey, _Equal,
           _H1, _H2, _Hash, _RehashPolicy, __chc, __cit, __uk>::
    _M_rehash(size_type __n, const _RehashPolicyState& __state)
    {
      __try
    {
      _Bucket* __new_buckets = _M_allocate_buckets(__n);
      _Node* __p = _M_begin();
      _M_before_begin._M_nxt = nullptr;
      std::size_t __cur_bbegin_bkt;
      while (__p)
        {
          _Node* __next = __p->_M_next();
          std::size_t __new_index = _HCBase::_M_bucket_index(__p, __n);
          if (!__new_buckets[__new_index])
        {
          __p->_M_nxt = _M_before_begin._M_nxt;
          _M_before_begin._M_nxt = __p;
          __new_buckets[__new_index] = &_M_before_begin;
          if (__p->_M_nxt)
            __new_buckets[__cur_bbegin_bkt] = __p;
          __cur_bbegin_bkt = __new_index;
        }
          else
        {
          __p->_M_nxt = __new_buckets[__new_index]->_M_nxt;
          __new_buckets[__new_index]->_M_nxt = __p;
        }
          __p = __next;
        }
      _M_deallocate_buckets(_M_buckets, _M_bucket_count);
      _M_bucket_count = __n;
      _M_buckets = __new_buckets;
    }
      __catch(...)
    {
      // A failure here means that buckets allocation failed.  We only
      // have to restore hash policy previous state.
      _M_rehash_policy._M_reset(__state);
      __throw_exception_again;
    }
    }

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std

#endif // _HASHTABLE_H