Retro68/gcc/libstdc++-v3/include/bits/hashtable.h

// 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