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// Internal header for TR1 unordered_set and unordered_map -*- C++ -*-

// Copyright (C) 2005, 2006 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 2, 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.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

/** @file 
 *  This is a TR1 C++ Library header. 
 */

// This header file defines std::tr1::hashtable, which is used to
// implement std::tr1::unordered_set, std::tr1::unordered_map, 
// std::tr1::unordered_multiset, and std::tr1::unordered_multimap.
// hashtable has many template parameters, partly to accommodate
// the differences between those four classes and partly to 
// accommodate policy choices that go beyond what TR1 calls for.

// ??? Arguably this should be Internal::hashtable, not std::tr1::hashtable.

// Class template hashtable attempts to encapsulate all reasonable
// variation among hash tables that use chaining.  It does not handle
// open addressing.

// References: 
// M. Austern, "A Proposal to Add Hash Tables to the Standard
//    Library (revision 4)," WG21 Document N1456=03-0039, 2003.
// D. E. Knuth, The Art of Computer Programming, v. 3, Sorting and Searching.
// A. Tavori and V. Dreizin, "Generic Associative Containers", 2004.
//    ??? Full citation?

#ifndef GNU_LIBSTDCXX_TR1_HASHTABLE_
#define GNU_LIBSTDCXX_TR1_HASHTABLE_

#include <utility>              // For std::pair
#include <iterator>
#include <cstddef>
#include <cstdlib>
#include <cmath>
#include <bits/functexcept.h>
#include <tr1/type_traits>      // For true_type and false_type

//----------------------------------------------------------------------
// General utilities

namespace Internal
{
  template<bool Flag, typename IfTrue, typename IfFalse>
    struct IF;

  template<typename IfTrue, typename IfFalse>
    struct IF<true, IfTrue, IfFalse>
    { typedef IfTrue type; };
 
  template <typename IfTrue, typename IfFalse>
    struct IF<false, IfTrue, IfFalse>
    { typedef IfFalse type; };

  // Helper function: return distance(first, last) for forward
  // iterators, or 0 for input iterators.
  template<class Iterator>
    inline typename std::iterator_traits<Iterator>::difference_type
    distance_fw(Iterator first, Iterator last, std::input_iterator_tag)
    { return 0; }

  template<class Iterator>
    inline typename std::iterator_traits<Iterator>::difference_type
    distance_fw(Iterator first, Iterator last, std::forward_iterator_tag)
    { return std::distance(first, last); }

  template<class Iterator>
    inline typename std::iterator_traits<Iterator>::difference_type
    distance_fw(Iterator first, Iterator last)
    {
      typedef typename std::iterator_traits<Iterator>::iterator_category tag;
      return distance_fw(first, last, tag());
    }
  
} // namespace Internal

//----------------------------------------------------------------------
// Auxiliary types used for all instantiations of hashtable: nodes
// and iterators.

// Nodes, used to wrap elements stored in the hash table.  A policy
// template parameter of class template hashtable controls whether
// nodes also store a hash code. In some cases (e.g. strings) this may
// be a performance win.

namespace Internal
{
  template<typename Value, bool cache_hash_code>
    struct hash_node;

  template<typename Value>
    struct hash_node<Value, true>
    {
      Value m_v;
      std::size_t hash_code;
      hash_node* m_next;
    };

  template<typename Value>
    struct hash_node<Value, false>
    {
      Value m_v;
      hash_node* m_next;
    };

  // Local iterators, used to iterate within a bucket but not between
  // buckets.

  template<typename Value, bool cache>
    struct node_iterator_base
    {
      node_iterator_base(hash_node<Value, cache>* p)
      : m_cur(p) { }
      
      void
      incr()
      { m_cur = m_cur->m_next; }

      hash_node<Value, cache>* m_cur;
    };

  template<typename Value, bool cache>
    inline bool
    operator==(const node_iterator_base<Value, cache>& x,
               const node_iterator_base<Value, cache>& y)
    { return x.m_cur == y.m_cur; }

  template<typename Value, bool cache>
    inline bool
    operator!=(const node_iterator_base<Value, cache>& x,
               const node_iterator_base<Value, cache>& y)
    { return x.m_cur != y.m_cur; }

  template<typename Value, bool constant_iterators, bool cache>
    struct node_iterator
    : public node_iterator_base<Value, cache>
    {
      typedef Value                                    value_type;
      typedef typename IF<constant_iterators, const Value*, Value*>::type
                                                       pointer;
      typedef typename IF<constant_iterators, const Value&, Value&>::type
                                                       reference;
      typedef std::ptrdiff_t                           difference_type;
      typedef std::forward_iterator_tag                iterator_category;

      node_iterator()
      : node_iterator_base<Value, cache>(0) { }

      explicit
      node_iterator(hash_node<Value, cache>* p)
      : node_iterator_base<Value, cache>(p) { }

      reference
      operator*() const
      { return this->m_cur->m_v; }
  
      pointer
      operator->() const
      { return &this->m_cur->m_v; }

      node_iterator&
      operator++()
      { 
        this->incr(); 
        return *this; 
      }
  
      node_iterator
      operator++(int)
      { 
        node_iterator tmp(*this);
        this->incr();
        return tmp;
      }
    };

  template<typename Value, bool constant_iterators, bool cache>
    struct node_const_iterator
    : public node_iterator_base<Value, cache>
    {
      typedef Value                                    value_type;
      typedef const Value*                             pointer;
      typedef const Value&                             reference;
      typedef std::ptrdiff_t                           difference_type;
      typedef std::forward_iterator_tag                iterator_category;

      node_const_iterator()
      : node_iterator_base<Value, cache>(0) { }

      explicit
      node_const_iterator(hash_node<Value, cache>* p)
      : node_iterator_base<Value, cache>(p) { }

      node_const_iterator(const node_iterator<Value, constant_iterators,
                          cache>& x)
      : node_iterator_base<Value, cache>(x.m_cur) { }

      reference
      operator*() const
      { return this->m_cur->m_v; }
  
      pointer
      operator->() const
      { return &this->m_cur->m_v; }

      node_const_iterator&
      operator++()
      { 
        this->incr(); 
        return *this; 
      }
  
      node_const_iterator
      operator++(int)
      { 
        node_const_iterator tmp(*this);
        this->incr();
        return tmp;
      }
    };

  template<typename Value, bool cache>
    struct hashtable_iterator_base
    {
      hashtable_iterator_base(hash_node<Value, cache>* node,
                              hash_node<Value, cache>** bucket)
      : m_cur_node(node), m_cur_bucket(bucket) { }

      void
      incr()
      {
        m_cur_node = m_cur_node->m_next;
        if (!m_cur_node)
          m_incr_bucket();
      }

      void
      m_incr_bucket();

      hash_node<Value, cache>* m_cur_node;
      hash_node<Value, cache>** m_cur_bucket;
    };

  // Global iterators, used for arbitrary iteration within a hash
  // table.  Larger and more expensive than local iterators.
  template<typename Value, bool cache>
    void
    hashtable_iterator_base<Value, cache>::
    m_incr_bucket()
    {
      ++m_cur_bucket;

      // This loop requires the bucket array to have a non-null sentinel.
      while (!*m_cur_bucket)
        ++m_cur_bucket;
      m_cur_node = *m_cur_bucket;
    }

  template<typename Value, bool cache>
    inline bool
    operator==(const hashtable_iterator_base<Value, cache>& x,
               const hashtable_iterator_base<Value, cache>& y)
    { return x.m_cur_node == y.m_cur_node; }

  template<typename Value, bool cache>
    inline bool
    operator!=(const hashtable_iterator_base<Value, cache>& x,
               const hashtable_iterator_base<Value, cache>& y)
    { return x.m_cur_node != y.m_cur_node; }

  template<typename Value, bool constant_iterators, bool cache>
    struct hashtable_iterator
    : public hashtable_iterator_base<Value, cache>
    {
      typedef Value                                    value_type;
      typedef typename IF<constant_iterators, const Value*, Value*>::type
                                                       pointer;
      typedef typename IF<constant_iterators, const Value&, Value&>::type
                                                       reference;
      typedef std::ptrdiff_t                           difference_type;
      typedef std::forward_iterator_tag                iterator_category;

      hashtable_iterator()
      : hashtable_iterator_base<Value, cache>(0, 0) { }

      hashtable_iterator(hash_node<Value, cache>* p,
                         hash_node<Value, cache>** b)
      : hashtable_iterator_base<Value, cache>(p, b) { }

      explicit
      hashtable_iterator(hash_node<Value, cache>** b)
      : hashtable_iterator_base<Value, cache>(*b, b) { }

      reference
      operator*() const
      { return this->m_cur_node->m_v; }
  
      pointer
      operator->() const
      { return &this->m_cur_node->m_v; }

      hashtable_iterator&
      operator++()
      { 
        this->incr();
        return *this;
      }
  
      hashtable_iterator
      operator++(int)
      { 
        hashtable_iterator tmp(*this);
        this->incr();
        return tmp;
      }
    };

  template<typename Value, bool constant_iterators, bool cache>
    struct hashtable_const_iterator
    : public hashtable_iterator_base<Value, cache>
    {
      typedef Value                                    value_type;
      typedef const Value*                             pointer;
      typedef const Value&                             reference;
      typedef std::ptrdiff_t                           difference_type;
      typedef std::forward_iterator_tag                iterator_category;

      hashtable_const_iterator()
      : hashtable_iterator_base<Value, cache>(0, 0) { }

      hashtable_const_iterator(hash_node<Value, cache>* p,
                               hash_node<Value, cache>** b)
      : hashtable_iterator_base<Value, cache>(p, b) { }

      explicit
      hashtable_const_iterator(hash_node<Value, cache>** b)
      : hashtable_iterator_base<Value, cache>(*b, b) { }

      hashtable_const_iterator(const hashtable_iterator<Value,
                               constant_iterators, cache>& x)
      : hashtable_iterator_base<Value, cache>(x.m_cur_node, x.m_cur_bucket) { }

      reference
      operator*() const
      { return this->m_cur_node->m_v; }
  
      pointer
      operator->() const
      { return &this->m_cur_node->m_v; }

      hashtable_const_iterator&
      operator++()
      { 
        this->incr();
        return *this;
      }
  
      hashtable_const_iterator
      operator++(int)
      { 
        hashtable_const_iterator tmp(*this);
        this->incr();
        return tmp;
      }
    };
} // namespace Internal

// ----------------------------------------------------------------------
// Many of class template hashtable's template parameters are policy
// classes.  These are defaults for the policies.

namespace Internal
{
  // The two key extraction policies used by the *set and *map variants.
  template<typename T>
    struct identity
    {
      const T&
      operator()(const T& t) const
      { return t; }
    };

  template<typename Pair>
    struct extract1st
    {
      const typename Pair::first_type&
      operator()(const Pair& p) const
      { return p.first; }
    };

  // Default range hashing function: use division to fold a large number
  // into the range [0, N).
  struct mod_range_hashing
  {
    typedef std::size_t first_argument_type;
    typedef std::size_t second_argument_type;
    typedef std::size_t result_type;

    result_type
    operator() (first_argument_type r, second_argument_type N) const
    { return r % N; }
  };

  // Default ranged hash function H.  In principle it should be a
  // function object composed from objects of type H1 and H2 such that
  // h(k, N) = h2(h1(k), N), but that would mean making extra copies of
  // h1 and h2.  So instead we'll just use a tag to tell class template
  // hashtable to do that composition.
  struct default_ranged_hash { };

  // Default value for rehash policy.  Bucket size is (usually) the
  // smallest prime that keeps the load factor small enough.
  struct prime_rehash_policy
  {
    prime_rehash_policy(float z = 1.0);
    
    float
    max_load_factor() const;

    // Return a bucket size no smaller than n.
    std::size_t
    next_bkt(std::size_t n) const;
    
    // Return a bucket count appropriate for n elements
    std::size_t
    bkt_for_elements(std::size_t n) const;
    
    // n_bkt is current bucket count, n_elt is current element count,
    // and n_ins is number of elements to be inserted.  Do we need to
    // increase bucket count?  If so, return make_pair(true, n), where n
    // is the new bucket count.  If not, return make_pair(false, 0).
    std::pair<bool, std::size_t>
    need_rehash(std::size_t n_bkt, std::size_t n_elt, std::size_t n_ins) const;
    
    float m_max_load_factor;
    float m_growth_factor;
    mutable std::size_t m_next_resize;
  };

  // XXX This is a hack.  prime_rehash_policy's member functions, and
  // certainly the list of primes, should be defined in a .cc file.
  // We're temporarily putting them in a header because we don't have a
  // place to put TR1 .cc files yet.  There's no good reason for any of
  // prime_rehash_policy's member functions to be inline, and there's
  // certainly no good reason for X<> to exist at all.
  
  struct lt
  {
    template<typename X, typename Y>
      bool
      operator()(X x, Y y)
      { return x < y; }
  };

  template<int ulongsize = sizeof(unsigned long)>
    struct X
    {
      static const int n_primes = ulongsize != 8 ? 256 : 256 + 48;
      static const unsigned long primes[256 + 48 + 1];
    };

  template<int ulongsize>
    const int X<ulongsize>::n_primes;

  template<int ulongsize>
    const unsigned long X<ulongsize>::primes[256 + 48 + 1] =
    {
      2ul, 3ul, 5ul, 7ul, 11ul, 13ul, 17ul, 19ul, 23ul, 29ul, 31ul,
      37ul, 41ul, 43ul, 47ul, 53ul, 59ul, 61ul, 67ul, 71ul, 73ul, 79ul,
      83ul, 89ul, 97ul, 103ul, 109ul, 113ul, 127ul, 137ul, 139ul, 149ul,
      157ul, 167ul, 179ul, 193ul, 199ul, 211ul, 227ul, 241ul, 257ul,
      277ul, 293ul, 313ul, 337ul, 359ul, 383ul, 409ul, 439ul, 467ul,
      503ul, 541ul, 577ul, 619ul, 661ul, 709ul, 761ul, 823ul, 887ul,
      953ul, 1031ul, 1109ul, 1193ul, 1289ul, 1381ul, 1493ul, 1613ul,
      1741ul, 1879ul, 2029ul, 2179ul, 2357ul, 2549ul, 2753ul, 2971ul,
      3209ul, 3469ul, 3739ul, 4027ul, 4349ul, 4703ul, 5087ul, 5503ul,
      5953ul, 6427ul, 6949ul, 7517ul, 8123ul, 8783ul, 9497ul, 10273ul,
      11113ul, 12011ul, 12983ul, 14033ul, 15173ul, 16411ul, 17749ul,
      19183ul, 20753ul, 22447ul, 24281ul, 26267ul, 28411ul, 30727ul,
      33223ul, 35933ul, 38873ul, 42043ul, 45481ul, 49201ul, 53201ul,
      57557ul, 62233ul, 67307ul, 72817ul, 78779ul, 85229ul, 92203ul,
      99733ul, 107897ul, 116731ul, 126271ul, 136607ul, 147793ul,
      159871ul, 172933ul, 187091ul, 202409ul, 218971ul, 236897ul,
      256279ul, 277261ul, 299951ul, 324503ul, 351061ul, 379787ul,
      410857ul, 444487ul, 480881ul, 520241ul, 562841ul, 608903ul,
      658753ul, 712697ul, 771049ul, 834181ul, 902483ul, 976369ul,
      1056323ul, 1142821ul, 1236397ul, 1337629ul, 1447153ul, 1565659ul,
      1693859ul, 1832561ul, 1982627ul, 2144977ul, 2320627ul, 2510653ul,
      2716249ul, 2938679ul, 3179303ul, 3439651ul, 3721303ul, 4026031ul,
      4355707ul, 4712381ul, 5098259ul, 5515729ul, 5967347ul, 6456007ul,
      6984629ul, 7556579ul, 8175383ul, 8844859ul, 9569143ul, 10352717ul,
      11200489ul, 12117689ul, 13109983ul, 14183539ul, 15345007ul,
      16601593ul, 17961079ul, 19431899ul, 21023161ul, 22744717ul,
      24607243ul, 26622317ul, 28802401ul, 31160981ul, 33712729ul,
      36473443ul, 39460231ul, 42691603ul, 46187573ul, 49969847ul,
      54061849ul, 58488943ul, 63278561ul, 68460391ul, 74066549ul,
      80131819ul, 86693767ul, 93793069ul, 101473717ul, 109783337ul,
      118773397ul, 128499677ul, 139022417ul, 150406843ul, 162723577ul,
      176048909ul, 190465427ul, 206062531ul, 222936881ul, 241193053ul,
      260944219ul, 282312799ul, 305431229ul, 330442829ul, 357502601ul,
      386778277ul, 418451333ul, 452718089ul, 489790921ul, 529899637ul,
      573292817ul, 620239453ul, 671030513ul, 725980837ul, 785430967ul,
      849749479ul, 919334987ul, 994618837ul, 1076067617ul, 1164186217ul,
      1259520799ul, 1362662261ul, 1474249943ul, 1594975441ul,
      1725587117ul, 1866894511ul, 2019773507ul, 2185171673ul,
      2364114217ul, 2557710269ul, 2767159799ul, 2993761039ul,
      3238918481ul, 3504151727ul, 3791104843ul, 4101556399ul,
      4294967291ul,
      // Sentinel, so we don't have to test the result of lower_bound,
      // or, on 64-bit machines, rest of the table.
      ulongsize != 8 ? 4294967291ul : (unsigned long)6442450933ull,
      (unsigned long)8589934583ull,
      (unsigned long)12884901857ull, (unsigned long)17179869143ull,
      (unsigned long)25769803693ull, (unsigned long)34359738337ull,
      (unsigned long)51539607367ull, (unsigned long)68719476731ull,
      (unsigned long)103079215087ull, (unsigned long)137438953447ull,
      (unsigned long)206158430123ull, (unsigned long)274877906899ull,
      (unsigned long)412316860387ull, (unsigned long)549755813881ull,
      (unsigned long)824633720731ull, (unsigned long)1099511627689ull,
      (unsigned long)1649267441579ull, (unsigned long)2199023255531ull,
      (unsigned long)3298534883309ull, (unsigned long)4398046511093ull,
      (unsigned long)6597069766607ull, (unsigned long)8796093022151ull,
      (unsigned long)13194139533241ull, (unsigned long)17592186044399ull,
      (unsigned long)26388279066581ull, (unsigned long)35184372088777ull,
      (unsigned long)52776558133177ull, (unsigned long)70368744177643ull,
      (unsigned long)105553116266399ull, (unsigned long)140737488355213ull,
      (unsigned long)211106232532861ull, (unsigned long)281474976710597ull,
      (unsigned long)562949953421231ull, (unsigned long)1125899906842597ull,
      (unsigned long)2251799813685119ull, (unsigned long)4503599627370449ull,
      (unsigned long)9007199254740881ull, (unsigned long)18014398509481951ull,
      (unsigned long)36028797018963913ull, (unsigned long)72057594037927931ull,
      (unsigned long)144115188075855859ull,
      (unsigned long)288230376151711717ull,
      (unsigned long)576460752303423433ull,
      (unsigned long)1152921504606846883ull,
      (unsigned long)2305843009213693951ull,
      (unsigned long)4611686018427387847ull,
      (unsigned long)9223372036854775783ull,
      (unsigned long)18446744073709551557ull,
      (unsigned long)18446744073709551557ull
    };

  inline
  prime_rehash_policy::
  prime_rehash_policy(float z)
  : m_max_load_factor(z), m_growth_factor(2.f), m_next_resize(0)
  { }

  inline float
  prime_rehash_policy::
  max_load_factor() const
  { return m_max_load_factor; }

  // Return a prime no smaller than n.
  inline std::size_t
  prime_rehash_policy::
  next_bkt(std::size_t n) const
  {
    const unsigned long* const last = X<>::primes + X<>::n_primes;
    const unsigned long* p = std::lower_bound (X<>::primes, last, n);
    m_next_resize = static_cast<std::size_t>(std::ceil(*p * m_max_load_factor));
    return *p;
  }

  // Return the smallest prime p such that alpha p >= n, where alpha
  // is the load factor.
  inline std::size_t
  prime_rehash_policy::
  bkt_for_elements(std::size_t n) const
  {
    const unsigned long* const last = X<>::primes + X<>::n_primes;
    const float min_bkts = n / m_max_load_factor;
    const unsigned long* p = std::lower_bound (X<>::primes, last,
                                               min_bkts, lt());
    m_next_resize = static_cast<std::size_t>(std::ceil(*p * m_max_load_factor));
    return *p;
  }

  // Finds the smallest prime p such that alpha p > n_elt + n_ins.
  // If p > n_bkt, return make_pair(true, p); otherwise return
  // make_pair(false, 0).  In principle this isn't very different from 
  // bkt_for_elements.
  
  // The only tricky part is that we're caching the element count at
  // which we need to rehash, so we don't have to do a floating-point
  // multiply for every insertion.
  
  inline std::pair<bool, std::size_t>
  prime_rehash_policy::
  need_rehash(std::size_t n_bkt, std::size_t n_elt, std::size_t n_ins) const
  {
    if (n_elt + n_ins > m_next_resize)
      {
        float min_bkts = (float(n_ins) + float(n_elt)) / m_max_load_factor;
        if (min_bkts > n_bkt)
          {
            min_bkts = std::max (min_bkts, m_growth_factor * n_bkt);
            const unsigned long* const last = X<>::primes + X<>::n_primes;
            const unsigned long* p = std::lower_bound (X<>::primes, last,
                                                       min_bkts, lt());
            m_next_resize = 
              static_cast<std::size_t>(std::ceil(*p * m_max_load_factor));
            return std::make_pair(true, *p);
          }
        else 
          {
            m_next_resize = 
              static_cast<std::size_t>(std::ceil(n_bkt * m_max_load_factor));
            return std::make_pair(false, 0);
          }
      }
    else
      return std::make_pair(false, 0);
  }

} // namespace Internal

//----------------------------------------------------------------------
// Base classes for std::tr1::hashtable.  We define these base classes
// because in some cases we want to do different things depending on
// the value of a policy class.  In some cases the policy class affects
// which member functions and nested typedefs are defined; we handle that
// by specializing base class templates.  Several of the base class templates
// need to access other members of class template hashtable, so we use
// the "curiously recurring template pattern" for them.

namespace Internal
{
  // class template map_base.  If the hashtable has a value type of the
  // form pair<T1, T2> and a key extraction policy that returns the
  // first part of the pair, the hashtable gets a mapped_type typedef.
  // If it satisfies those criteria and also has unique keys, then it
  // also gets an operator[].
  
  template<typename K, typename V, typename Ex, bool unique, typename Hashtable>
    struct map_base { };
          
  template<typename K, typename Pair, typename Hashtable>
    struct map_base<K, Pair, extract1st<Pair>, false, Hashtable>
    {
      typedef typename Pair::second_type mapped_type;
    };

  template<typename K, typename Pair, typename Hashtable>
    struct map_base<K, Pair, extract1st<Pair>, true, Hashtable>
    {
      typedef typename Pair::second_type mapped_type;
      
      mapped_type&
      operator[](const K& k)
      {
        Hashtable* h = static_cast<Hashtable*>(this);
        typename Hashtable::iterator it = 
          h->insert(std::make_pair(k, mapped_type())).first;
        return it->second;
      }
    };

  // class template rehash_base.  Give hashtable the max_load_factor
  // functions iff the rehash policy is prime_rehash_policy.
  template<typename RehashPolicy, typename Hashtable>
    struct rehash_base { };

  template<typename Hashtable>
    struct rehash_base<prime_rehash_policy, Hashtable>
    {
      float
      max_load_factor() const
      {
        const Hashtable* This = static_cast<const Hashtable*>(this);
        return This->rehash_policy().max_load_factor();
      }

      void
      max_load_factor(float z)
      {
        Hashtable* This = static_cast<Hashtable*>(this);
        This->rehash_policy(prime_rehash_policy(z));    
      }
    };

  // Class template hash_code_base.  Encapsulates two policy issues that
  // aren't quite orthogonal.
  //   (1) the difference between using a ranged hash function and using
  //       the combination of a hash function and a range-hashing function.
  //       In the former case we don't have such things as hash codes, so
  //       we have a dummy type as placeholder.
  //   (2) Whether or not we cache hash codes.  Caching hash codes is
  //       meaningless if we have a ranged hash function.
  // We also put the key extraction and equality comparison function 
  // objects here, for convenience.
  
  // Primary template: unused except as a hook for specializations.
  
  template<typename Key, typename Value,
           typename ExtractKey, typename Equal,
           typename H1, typename H2, typename H,
           bool cache_hash_code>
    struct hash_code_base;

  // Specialization: ranged hash function, no caching hash codes.  H1
  // and H2 are provided but ignored.  We define a dummy hash code type.
  template<typename Key, typename Value,
           typename ExtractKey, typename Equal,
           typename H1, typename H2, typename H>
    struct hash_code_base<Key, Value, ExtractKey, Equal, H1, H2, H, false>
    {
    protected:
      hash_code_base(const ExtractKey& ex, const Equal& eq,
                     const H1&, const H2&, const H& h)
      : m_extract(ex), m_eq(eq), m_ranged_hash(h) { }

      typedef void* hash_code_t;
  
      hash_code_t
      m_hash_code(const Key& k) const
      { return 0; }
  
      std::size_t
      bucket_index(const Key& k, hash_code_t, std::size_t N) const
      { return m_ranged_hash (k, N); }

      std::size_t
      bucket_index(const hash_node<Value, false>* p, std::size_t N) const
      { return m_ranged_hash (m_extract (p->m_v), N); }
  
      bool
      compare(const Key& k, hash_code_t, hash_node<Value, false>* n) const
      { return m_eq (k, m_extract(n->m_v)); }

      void
      store_code(hash_node<Value, false>*, hash_code_t) const
      { }

      void
      copy_code(hash_node<Value, false>*, const hash_node<Value, false>*) const
      { }
      
      void
      m_swap(hash_code_base& x)
      {
        std::swap(m_extract, x.m_extract);
        std::swap(m_eq, x.m_eq);
        std::swap(m_ranged_hash, x.m_ranged_hash);
      }

    protected:
      ExtractKey m_extract;
      Equal m_eq;
      H m_ranged_hash;
    };


  // No specialization for ranged hash function while caching hash codes.
  // That combination is meaningless, and trying to do it is an error.
  
  
  // Specialization: ranged hash function, cache hash codes.  This
  // combination is meaningless, so we provide only a declaration
  // and no definition.
  
  template<typename Key, typename Value,
            typename ExtractKey, typename Equal,
            typename H1, typename H2, typename H>
    struct hash_code_base<Key, Value, ExtractKey, Equal, H1, H2, H, true>;


  // Specialization: hash function and range-hashing function, no
  // caching of hash codes.  H is provided but ignored.  Provides
  // typedef and accessor required by TR1.
  
  template<typename Key, typename Value,
           typename ExtractKey, typename Equal,
           typename H1, typename H2>
    struct hash_code_base<Key, Value, ExtractKey, Equal, H1, H2,
                          default_ranged_hash, false>
    {
      typedef H1 hasher;
      
      hasher
      hash_function() const
      { return m_h1; }

    protected:
      hash_code_base(const ExtractKey& ex, const Equal& eq,
                     const H1& h1, const H2& h2, const default_ranged_hash&)
      : m_extract(ex), m_eq(eq), m_h1(h1), m_h2(h2) { }

      typedef std::size_t hash_code_t;
      
      hash_code_t
      m_hash_code(const Key& k) const
      { return m_h1(k); }
      
      std::size_t
      bucket_index(const Key&, hash_code_t c, std::size_t N) const
      { return m_h2 (c, N); }

      std::size_t
      bucket_index(const hash_node<Value, false>* p, std::size_t N) const
      { return m_h2 (m_h1 (m_extract (p->m_v)), N); }

      bool
      compare(const Key& k, hash_code_t, hash_node<Value, false>* n) const
      { return m_eq (k, m_extract(n->m_v)); }

      void
      store_code(hash_node<Value, false>*, hash_code_t) const
      { }

      void
      copy_code(hash_node<Value, false>*, const hash_node<Value, false>*) const
      { }

      void
      m_swap(hash_code_base& x)
      {
        std::swap(m_extract, x.m_extract);
        std::swap(m_eq, x.m_eq);
        std::swap(m_h1, x.m_h1);
        std::swap(m_h2, x.m_h2);
      }

    protected:
      ExtractKey m_extract;
      Equal m_eq;
      H1 m_h1;
      H2 m_h2;
    };

  // Specialization: hash function and range-hashing function, 
  // caching hash codes.  H is provided but ignored.  Provides
  // typedef and accessor required by TR1.
  template<typename Key, typename Value,
           typename ExtractKey, typename Equal,
           typename H1, typename H2>
    struct hash_code_base<Key, Value, ExtractKey, Equal, H1, H2,
                          default_ranged_hash, true>
    {
      typedef H1 hasher;
      
      hasher
      hash_function() const
      { return m_h1; }

    protected:
      hash_code_base(const ExtractKey& ex, const Equal& eq,
                     const H1& h1, const H2& h2, const default_ranged_hash&)
      : m_extract(ex), m_eq(eq), m_h1(h1), m_h2(h2) { }

      typedef std::size_t hash_code_t;
  
      hash_code_t
      m_hash_code(const Key& k) const
      { return m_h1(k); }
  
      std::size_t
      bucket_index(const Key&, hash_code_t c, std::size_t N) const
      { return m_h2 (c, N); }

      std::size_t
      bucket_index(const hash_node<Value, true>* p, std::size_t N) const
      { return m_h2 (p->hash_code, N); }

      bool
      compare(const Key& k, hash_code_t c, hash_node<Value, true>* n) const
      { return c == n->hash_code && m_eq(k, m_extract(n->m_v)); }

      void
      store_code(hash_node<Value, true>* n, hash_code_t c) const
      { n->hash_code = c; }

      void
      copy_code(hash_node<Value, true>* to,
                const hash_node<Value, true>* from) const
      { to->hash_code = from->hash_code; }

      void
      m_swap(hash_code_base& x)
      {
        std::swap(m_extract, x.m_extract);
        std::swap(m_eq, x.m_eq);
        std::swap(m_h1, x.m_h1);
        std::swap(m_h2, x.m_h2);
      }
      
    protected:
      ExtractKey m_extract;
      Equal m_eq;
      H1 m_h1;
      H2 m_h2;
    };

} // namespace internal

namespace std
{ 
namespace tr1
{
  //----------------------------------------------------------------------
  // 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.
  
  // ExtractKey: function object that takes a 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).
  
  // H: 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: h(k, N) = h2(h1(k), N).  If H is anything other
  // than the default, H1 and H2 are ignored.
  
  // RehashPolicy: Policy class with three members, all of which govern
  // the bucket count. n_bkt(n) returns a bucket count no smaller
  // than n.  bkt_for_elements(n) returns a bucket count appropriate
  // for an element count of n.  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>).
  
  // ??? Right now it is hard-wired that the number of buckets never
  // shrinks.  Should we allow RehashPolicy to change that?
  
  // 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.
  
  template<typename Key, typename Value, 
           typename Allocator,
           typename ExtractKey, typename Equal,
           typename H1, typename H2,
           typename H, typename RehashPolicy,
           bool cache_hash_code,
           bool constant_iterators,
           bool unique_keys>
    class hashtable
    : public Internal::rehash_base<RehashPolicy,
                                   hashtable<Key, Value, Allocator, ExtractKey,
                                             Equal, H1, H2, H, RehashPolicy,
                                             cache_hash_code, constant_iterators,
                                             unique_keys> >,
      public Internal::hash_code_base<Key, Value, ExtractKey, Equal, H1, H2, H,
                                      cache_hash_code>,
      public Internal::map_base<Key, Value, ExtractKey, unique_keys,
                                hashtable<Key, Value, Allocator, ExtractKey,
                                          Equal, H1, H2, H, RehashPolicy,
                                          cache_hash_code, constant_iterators,
                                          unique_keys> >
    {
    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::difference_type            difference_type;
      typedef typename Allocator::size_type                  size_type;
      typedef typename Allocator::reference                  reference;
      typedef typename Allocator::const_reference            const_reference;
      
      typedef Internal::node_iterator<value_type, constant_iterators,
                                      cache_hash_code>
        local_iterator;
      typedef Internal::node_const_iterator<value_type, constant_iterators,
                                            cache_hash_code>
        const_local_iterator;

      typedef Internal::hashtable_iterator<value_type, constant_iterators,
                                           cache_hash_code>
        iterator;
      typedef Internal::hashtable_const_iterator<value_type, constant_iterators,
                                                 cache_hash_code>
        const_iterator;

    private:
      typedef Internal::hash_node<Value, cache_hash_code>    node;
      typedef typename Allocator::template rebind<node>::other
        node_allocator_t;
      typedef typename Allocator::template rebind<node*>::other
        bucket_allocator_t;

    private:
      node_allocator_t m_node_allocator;
      node** m_buckets;
      size_type m_bucket_count;
      size_type m_element_count;
      RehashPolicy m_rehash_policy;
      
      node*
      m_allocate_node(const value_type& v);
  
      void
      m_deallocate_node(node* n);
  
      void
      m_deallocate_nodes(node**, size_type);

      node**
      m_allocate_buckets(size_type n);
  
      void
      m_deallocate_buckets(node**, size_type n);

    public:                         // Constructor, destructor, assignment, swap
      hashtable(size_type bucket_hint,
                const H1&, const H2&, const H&,
                const Equal&, const ExtractKey&,
                const allocator_type&);
  
      template<typename InIter>
        hashtable(InIter first, InIter last,
                  size_type bucket_hint,
                  const H1&, const H2&, const H&,
                  const Equal&, const ExtractKey&,
                  const allocator_type&);
  
      hashtable(const hashtable&);
      
      hashtable&
      operator=(const hashtable&);
  
      ~hashtable();

      void swap(hashtable&);

    public:                             // Basic container operations
      iterator
      begin()
      {
        iterator i(m_buckets);
        if (!i.m_cur_node)
          i.m_incr_bucket();
        return i;
      }

      const_iterator
      begin() const
      {
        const_iterator i(m_buckets);
        if (!i.m_cur_node)
          i.m_incr_bucket();
        return i;
      }

      iterator
      end()
      { return iterator(m_buckets + m_bucket_count); }

      const_iterator
      end() const
      { return const_iterator(m_buckets + m_bucket_count); }

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

      allocator_type
      get_allocator() const
      { return m_node_allocator; }
  
      size_type
      max_size() const
      { return m_node_allocator.max_size(); }

    public:                             // Observers
      key_equal
      key_eq() const
      { return this->m_eq; }

      // hash_function, if present, comes from hash_code_base.

    public:                             // Bucket operations
      size_type
      bucket_count() const
      { return m_bucket_count; }
  
      size_type
      max_bucket_count() const
      { 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 this->bucket_index(k, this->m_hash_code(k),
                                  this->m_bucket_count);
      }

      local_iterator
      begin(size_type n)
      { return local_iterator(m_buckets[n]); }
  
      local_iterator
      end(size_type)
      { return local_iterator(0); }
  
      const_local_iterator
      begin(size_type n) const
      { return const_local_iterator(m_buckets[n]); }
  
      const_local_iterator
      end(size_type) const
      { return const_local_iterator(0); }

      float
      load_factor() const
      { 
        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&);

    public:                             // lookup
      iterator
      find(const key_type&);

      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:                    // Insert and erase helper functions
      // ??? This dispatching is a workaround for the fact that we don't
      // have partial specialization of member templates; it would be
      // better to just specialize insert on unique_keys.  There may be a
      // cleaner workaround.
      typedef typename Internal::IF<unique_keys,
                                    std::pair<iterator, bool>, iterator>::type
        Insert_Return_Type;

      typedef typename Internal::IF<unique_keys,
                                    Internal::extract1st<Insert_Return_Type>,
                                    Internal::identity<Insert_Return_Type>
                                   >::type
        Insert_Conv_Type;

      node*
      find_node(node* p, const key_type& k,
                typename hashtable::hash_code_t c) const;

      std::pair<iterator, bool>
      insert(const value_type&, std::tr1::true_type);
  
      iterator
      insert(const value_type&, std::tr1::false_type);

      void
      erase_node(node*, node**);

    public:                             // Insert and erase
      Insert_Return_Type
      insert(const value_type& v) 
      { 
        return this->insert(v, std::tr1::integral_constant<bool,
                            unique_keys>());
      }

      iterator
      insert(iterator, const value_type& v)
      { return iterator(Insert_Conv_Type()(this->insert(v))); }
      
      const_iterator
      insert(const_iterator, const value_type& v)
      { return const_iterator(Insert_Conv_Type()(this->insert(v))); }

      template<typename InIter>
        void
        insert(InIter first, InIter last);

      iterator
      erase(iterator);

      const_iterator
      erase(const_iterator);

      size_type
      erase(const key_type&);

      iterator
      erase(iterator, iterator);

      const_iterator
      erase(const_iterator, const_iterator);

      void
      clear();

    public:
      // Set number of buckets to be appropriate for container of n element.
      void rehash(size_type n);
      
    private:
      // Unconditionally change size of bucket array to n.
      void m_rehash(size_type n);
    };

  //----------------------------------------------------------------------
  // Definitions of class template hashtable's out-of-line member functions.
  
  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    typename hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::node*
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    m_allocate_node(const value_type& v)
    {
      node* n = m_node_allocator.allocate(1);
      try
        {
          get_allocator().construct(&n->m_v, v);
          n->m_next = 0;
          return n;
        }
      catch(...)
        {
          m_node_allocator.deallocate(n, 1);
          __throw_exception_again;
        }
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    void
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    m_deallocate_node(node* n)
    {
      get_allocator().destroy(&n->m_v);
      m_node_allocator.deallocate(n, 1);
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    void
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    m_deallocate_nodes(node** array, size_type n)
    {
      for (size_type i = 0; i < n; ++i)
        {
          node* p = array[i];
          while (p)
            {
              node* tmp = p;
              p = p->m_next;
              m_deallocate_node (tmp);
            }
          array[i] = 0;
        }
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    typename hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::node**
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    m_allocate_buckets(size_type n)
    {
      bucket_allocator_t alloc(m_node_allocator);

      // We allocate one extra bucket to hold a sentinel, an arbitrary
      // non-null pointer.  Iterator increment relies on this.
      node** p = alloc.allocate(n+1);
      std::fill(p, p+n, (node*) 0);
      p[n] = reinterpret_cast<node*>(0x1000);
      return p;
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    void
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    m_deallocate_buckets(node** p, size_type n)
    {
      bucket_allocator_t alloc(m_node_allocator);
      alloc.deallocate(p, n+1);
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    hashtable(size_type bucket_hint,
              const H1& h1, const H2& h2, const H& h,
              const Eq& eq, const Ex& exk,
              const allocator_type& a)
    : Internal::rehash_base<RP,hashtable>(),
      Internal::hash_code_base<K, V, Ex, Eq, H1, H2, H, c>(exk, eq, h1, h2, h),
      Internal::map_base<K, V, Ex, u, hashtable>(),
      m_node_allocator(a),
      m_bucket_count(0),
      m_element_count(0),
      m_rehash_policy()
    {
      m_bucket_count = m_rehash_policy.next_bkt(bucket_hint);
      m_buckets = m_allocate_buckets(m_bucket_count);
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    template<typename InIter>
      hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
      hashtable(InIter f, InIter l,
                size_type bucket_hint,
                const H1& h1, const H2& h2, const H& h,
                const Eq& eq, const Ex& exk,
                const allocator_type& a)
      : Internal::rehash_base<RP,hashtable>(),
        Internal::hash_code_base<K, V, Ex, Eq, H1, H2, H, c> (exk, eq,
                                                              h1, h2, h),
        Internal::map_base<K,V,Ex,u,hashtable>(),
        m_node_allocator(a),
        m_bucket_count (0),
        m_element_count(0),
        m_rehash_policy()
      {
        m_bucket_count = std::max(m_rehash_policy.next_bkt(bucket_hint),
                                  m_rehash_policy.
                                  bkt_for_elements(Internal::
                                                   distance_fw(f, l)));
        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 K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    hashtable(const hashtable& ht)
    : Internal::rehash_base<RP, hashtable>(ht),
      Internal::hash_code_base<K, V, Ex, Eq, H1, H2, H, c>(ht),
      Internal::map_base<K, V, Ex, u, hashtable>(ht),
      m_node_allocator(ht.get_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
        {
          for (size_t i = 0; i < ht.m_bucket_count; ++i)
            {
              node* n = ht.m_buckets[i];
              node** tail = m_buckets + i;
              while (n)
                {
                  *tail = m_allocate_node(n->m_v);
                  this->copy_code(*tail, n);
                  tail = &((*tail)->m_next);
                  n = n->m_next;
                }
            }
        }
      catch (...)
        {
          clear();
          m_deallocate_buckets (m_buckets, m_bucket_count);
          __throw_exception_again;
        }
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>&
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    operator=(const hashtable& ht)
    {
      hashtable tmp(ht);
      this->swap(tmp);
      return *this;
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    ~hashtable()
    {
      clear();
      m_deallocate_buckets(m_buckets, m_bucket_count);
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    void
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    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.
      Internal::hash_code_base<K, V, Ex, Eq, H1, H2, H, c>::m_swap(x);

      // open LWG issue 431
      // std::swap(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_element_count, x.m_element_count);
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    void
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    rehash_policy(const RP& pol)
    {
      m_rehash_policy = pol;
      size_type n_bkt = pol.bkt_for_elements(m_element_count);
      if (n_bkt > m_bucket_count)
        m_rehash (n_bkt);
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    typename hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::iterator
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    find(const key_type& k)
    {
      typename hashtable::hash_code_t code = this->m_hash_code(k);
      std::size_t n = this->bucket_index(k, code, this->bucket_count());
      node* p = find_node(m_buckets[n], k, code);
      return p ? iterator(p, m_buckets + n) : this->end();
    }
  
  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    typename hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::const_iterator
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    find(const key_type& k) const
    {
      typename hashtable::hash_code_t code = this->m_hash_code(k);
      std::size_t n = this->bucket_index(k, code, this->bucket_count());
      node* p = find_node(m_buckets[n], k, code);
      return p ? const_iterator(p, m_buckets + n) : this->end();
    }
  
  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    typename hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::size_type
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    count(const key_type& k) const
    {
      typename hashtable::hash_code_t code = this->m_hash_code(k);
      std::size_t n = this->bucket_index(k, code, this->bucket_count());
      size_t result = 0;
      for (node* p = m_buckets[n]; p ; p = p->m_next)
        if (this->compare(k, code, p))
          ++result;
      return result;
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    std::pair<typename hashtable<K, V, A, Ex, Eq, H1,
                                 H2, H, RP, c, ci, u>::iterator,
              typename hashtable<K, V, A, Ex, Eq, H1,
                                 H2, H, RP, c, ci, u>::iterator>
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    equal_range(const key_type& k)
    {
      typename hashtable::hash_code_t code = this->m_hash_code(k);
      std::size_t n = this->bucket_index(k, code, this->bucket_count());
      node** head = m_buckets + n;
      node* p = find_node (*head, k, code);
      
      if (p)
        {
          node* p1 = p->m_next;
          for (; p1 ; p1 = p1->m_next)
            if (!this->compare (k, code, p1))
              break;

          iterator first(p, head);
          iterator last(p1, head);
          if (!p1)
            last.m_incr_bucket();
          return std::make_pair(first, last);
        }
      else
        return std::make_pair(this->end(), this->end());
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    std::pair<typename hashtable<K, V, A, Ex, Eq, H1,
                                 H2, H, RP, c, ci, u>::const_iterator,
              typename hashtable<K, V, A, Ex, Eq, H1,
                                 H2, H, RP, c, ci, u>::const_iterator>
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    equal_range(const key_type& k) const
    {
      typename hashtable::hash_code_t code = this->m_hash_code(k);
      std::size_t n = this->bucket_index(k, code, this->bucket_count());
      node** head = m_buckets + n;
      node* p = find_node(*head, k, code);

      if (p)
        {
          node* p1 = p->m_next;
          for (; p1 ; p1 = p1->m_next)
            if (!this->compare(k, code, p1))
              break;

          const_iterator first(p, head);
          const_iterator last(p1, head);
          if (!p1)
            last.m_incr_bucket();
          return std::make_pair(first, last);
        }
      else
        return std::make_pair(this->end(), this->end());
    }

  // Find the node whose key compares equal to k, beginning the search
  // at p (usually the head of a bucket).  Return nil if no node is found.
  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    typename hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::node* 
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    find_node(node* p, const key_type& k,
              typename hashtable::hash_code_t code) const
    {
      for ( ; p ; p = p->m_next)
        if (this->compare (k, code, p))
          return p;
      return false;
    }

  // Insert v if no element with its key is already present.
  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    std::pair<typename hashtable<K, V, A, Ex, Eq, H1,
                                 H2, H, RP, c, ci, u>::iterator, bool>
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    insert(const value_type& v, std::tr1::true_type)
    {
      const key_type& k = this->m_extract(v);
      typename hashtable::hash_code_t code = this->m_hash_code(k);
      size_type n = this->bucket_index(k, code, m_bucket_count);
      
      if (node* p = find_node(m_buckets[n], k, code))
        return std::make_pair(iterator(p, m_buckets + n), false);

      std::pair<bool, size_t> do_rehash
        = m_rehash_policy.need_rehash(m_bucket_count, m_element_count, 1);

      // Allocate the new node before doing the rehash so that we don't
      // do a rehash if the allocation throws.
      node* new_node = m_allocate_node (v);
      
      try
        {
          if (do_rehash.first)
            {
              n = this->bucket_index(k, code, do_rehash.second);
              m_rehash(do_rehash.second);
            }

          new_node->m_next = m_buckets[n];
          this->store_code(new_node, code);
          m_buckets[n] = new_node;
          ++m_element_count;
          return std::make_pair(iterator(new_node, m_buckets + n), true);
        }
      catch (...)
        {
          m_deallocate_node (new_node);
          __throw_exception_again;
        }
    }
  
  // Insert v unconditionally.
  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    typename hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::iterator
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    insert(const value_type& v, std::tr1::false_type)
    {
      std::pair<bool, std::size_t> do_rehash
        = m_rehash_policy.need_rehash(m_bucket_count, m_element_count, 1);
      if (do_rehash.first)
        m_rehash(do_rehash.second);

      const key_type& k = this->m_extract(v);
      typename hashtable::hash_code_t code = this->m_hash_code(k);
      size_type n = this->bucket_index(k, code, m_bucket_count);
      
      node* new_node = m_allocate_node (v);
      node* prev = find_node(m_buckets[n], k, code);
      if (prev)
        {
          new_node->m_next = prev->m_next;
          prev->m_next = new_node;
        }
      else
        {
          new_node->m_next = m_buckets[n];
          m_buckets[n] = new_node;
        }
      this->store_code(new_node, code);

      ++m_element_count;
      return iterator(new_node, m_buckets + n);
    }

  // For erase(iterator) and erase(const_iterator).
  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    void
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    erase_node(node* p, node** b)
    {
      node* cur = *b;
      if (cur == p)
        *b = cur->m_next;
      else
        {
          node* next = cur->m_next;
          while (next != p)
            {
              cur = next;
              next = cur->m_next;
            }
          cur->m_next = next->m_next;
        }

      m_deallocate_node (p);
      --m_element_count;
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    template<typename InIter>
      void 
      hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
      insert(InIter first, InIter last)
      {
        size_type n_elt = Internal::distance_fw (first, last);
        std::pair<bool, std::size_t> do_rehash
          = m_rehash_policy.need_rehash(m_bucket_count, m_element_count, n_elt);
        if (do_rehash.first)
          m_rehash(do_rehash.second);

        for (; first != last; ++first)
          this->insert (*first);
      }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    typename hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::iterator
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    erase(iterator i)
    {
      iterator result = i;
      ++result;
      erase_node(i.m_cur_node, i.m_cur_bucket);
      return result;
    }
  
  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    typename hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::const_iterator
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    erase(const_iterator i)
    {
      const_iterator result = i;
      ++result;
      erase_node(i.m_cur_node, i.m_cur_bucket);
      return result;
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    typename hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::size_type
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    erase(const key_type& k)
    {
      typename hashtable::hash_code_t code = this->m_hash_code(k);
      size_type n = this->bucket_index(k, code, m_bucket_count);
      size_type result = 0;
      
      node** slot = m_buckets + n;
      while (*slot && ! this->compare(k, code, *slot))
        slot = &((*slot)->m_next);

      while (*slot && this->compare(k, code, *slot))
        {
          node* n = *slot;
          *slot = n->m_next;
          m_deallocate_node (n);
          --m_element_count;
          ++result;
        }

      return result;
    }

  // ??? This could be optimized by taking advantage of the bucket
  // structure, but it's not clear that it's worth doing.  It probably
  // wouldn't even be an optimization unless the load factor is large.
  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    typename hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::iterator
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    erase(iterator first, iterator last)
    {
      while (first != last)
        first = this->erase(first);
      return last;
    }
  
  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    typename hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::const_iterator
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    erase(const_iterator first, const_iterator last)
    {
      while (first != last)
        first = this->erase(first);
      return last;
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    void
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    clear()
    {
      m_deallocate_nodes(m_buckets, m_bucket_count);
      m_element_count = 0;
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    void
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    rehash(size_type n)
    {
      m_rehash(std::max(m_rehash_policy.next_bkt(n),
                        m_rehash_policy.bkt_for_elements(m_element_count
                                                         + 1)));
    }

  template<typename K, typename V, 
           typename A, typename Ex, typename Eq,
           typename H1, typename H2, typename H, typename RP,
           bool c, bool ci, bool u>
    void
    hashtable<K, V, A, Ex, Eq, H1, H2, H, RP, c, ci, u>::
    m_rehash(size_type N)
    {
      node** new_array = m_allocate_buckets (N);
      try
        {
          for (size_type i = 0; i < m_bucket_count; ++i)
            while (node* p = m_buckets[i])
              {
                size_type new_index = this->bucket_index (p, N);
                m_buckets[i] = p->m_next;
                p->m_next = new_array[new_index];
                new_array[new_index] = p;
              }
          m_deallocate_buckets(m_buckets, m_bucket_count);
          m_bucket_count = N;
          m_buckets = new_array;
        }
      catch (...)
        {
          // A failure here means that a hash function threw an exception.
          // We can't restore the previous state without calling the hash
          // function again, so the only sensible recovery is to delete
          // everything.
          m_deallocate_nodes(new_array, N);
          m_deallocate_buckets(new_array, N);
          m_deallocate_nodes(m_buckets, m_bucket_count);
          m_element_count = 0;
          __throw_exception_again;
        }
    }
}
}                               // Namespace std::tr1

#endif /* GNU_LIBSTDCXX_TR1_HASHTABLE_ */