hashtable   [plain text]

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

// Copyright (C) 2005 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, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// 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 <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 is_const, bool cache>
struct node_iterator : public node_iterator_base<Value, cache> {
  typedef Value                                             value_type;
  typedef typename IF<is_const, const Value*, Value*>::type pointer;
  typedef typename IF<is_const, const Value&, Value&>::type reference;
  typedef std::ptrdiff_t                                    difference_type;
  typedef std::forward_iterator_tag                         iterator_category;

  explicit node_iterator (hash_node<Value, cache>* p = 0)
    : node_iterator_base<Value, cache>(p) { }
  node_iterator (const node_iterator<Value, true, 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_iterator& operator++() { this->incr(); return *this; }
  node_iterator operator++(int)
  { node_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 is_const, bool cache>
struct hashtable_iterator : public hashtable_iterator_base<Value, cache>
{
  typedef Value                                             value_type;
  typedef typename IF<is_const, const Value*, Value*>::type pointer;
  typedef typename IF<is_const, const Value&, Value&>::type reference;
  typedef std::ptrdiff_t                                    difference_type;
  typedef std::forward_iterator_tag                         iterator_category;

  hashtable_iterator (hash_node<Value, cache>* p, hash_node<Value, cache>** b)
    : hashtable_iterator_base<Value, cache>(p, b) { }
  hashtable_iterator (hash_node<Value, cache>** b)
    : hashtable_iterator_base<Value, cache>(*b, b) { }
  hashtable_iterator (const hashtable_iterator<Value, true, 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_iterator& operator++() { this->incr(); return *this; }
  hashtable_iterator operator++(int)
  { hashtable_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 {
  T operator()(const T& t) const { return t; }
};

template <typename Pair>
struct extract1st {
  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 dummy>
struct X {
  static const int n_primes = 256;
  static const unsigned long primes[n_primes + 1];
};

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

template <int dummy>
const unsigned long X<dummy>::primes[n_primes + 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,
    4294967291ul // sentinel so we don't have to test result of lower_bound
  };

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<0>::primes + X<0>::n_primes;
  const unsigned long* p = std::lower_bound (X<0>::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<0>::primes + X<0>::n_primes;
  const float min_bkts = n / m_max_load_factor;
  const unsigned long* p = std::lower_bound (X<0>::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<0>::primes + X<0>::n_primes;
      const unsigned long* p = std::lower_bound (X<0>::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 copy_code (hash_node<Value, false>*, const hash_node<Value, false>*) const { }

  void m_swap(hash_code_base& x) {
    m_extract.m_swap(x);
    m_eq.m_swap(x);
    m_ranged_hash.m_swap(x);
  }

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

  void m_swap(hash_code_base& x) {
    m_extract.m_swap(x);
    m_eq.m_swap(x);
    m_h1.m_swap(x);
    m_h2.m_swap(x);
  }

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 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) {
    m_extract.m_swap(x);
    m_eq.m_swap(x);
    m_h1.m_swap(x);
    m_h2.m_swap(x);
  }

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.

// mutable_iterators: bool.  true if hashtable::iterator is a mutable
// iterator, false if iterator and const_iterator are both const 
// iterators.  This is true for unordered_map and unordered_multimap,
// false for unordered_set and unordered_multiset.

// 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 mutable_iterators,
	  bool unique_keys>
class hashtable
  : public Internal::rehash_base<RehashPolicy, hashtable<Key, Value, Allocator, ExtractKey, Equal, H1, H2, H, RehashPolicy, cache_hash_code, mutable_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, mutable_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, !mutable_iterators, cache_hash_code>
          local_iterator;
  typedef Internal::node_iterator<value_type, false,              cache_hash_code>
          const_local_iterator;

  typedef Internal::hashtable_iterator<value_type, !mutable_iterators, cache_hash_code>
          iterator;
  typedef Internal::hashtable_iterator<value_type, false,              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:				// 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, this->m_bucket_count); }

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

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

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

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

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

  void erase(const_iterator);
  size_type erase(const key_type&);
  void erase(const_iterator, const_iterator);
  void clear();

public:
  // Set number of buckets to be apropriate 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 m, bool u>
typename hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,u>::node*
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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;
  }
}

template <typename K, typename V, 
	  typename A, typename Ex, typename Eq,
	  typename H1, typename H2, typename H, typename RP,
	  bool c, bool m, bool u>
void
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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 m, bool u>
void
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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 m, bool u>
typename hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,u>::node**
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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 m, bool u>
void
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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 m, bool u>
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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 m, bool u>
template <typename InIter>
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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;
  }
}

template <typename K, typename V, 
	  typename A, typename Ex, typename Eq,
	  typename H1, typename H2, typename H, typename RP,
	  bool c, bool m, bool u>
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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);
	(*tail).copy_code_from (n);
	tail = &((*tail)->m_next);
	n = n->m_next;
      }
    }
  }
  catch (...) {
    clear();
    m_deallocate_buckets (m_buckets, m_bucket_count);
    throw;
  }
}

template <typename K, typename V, 
	  typename A, typename Ex, typename Eq,
	  typename H1, typename H2, typename H, typename RP,
	  bool c, bool m, bool u>
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,u>&
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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 m, bool u>
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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 m, bool u>
void hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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 m, bool u>
void
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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 m, bool u>
typename hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,u>::iterator
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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 m, bool u>
typename hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,u>::const_iterator
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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 m, bool u>
typename hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,u>::size_type
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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 m, bool u>
std::pair<typename hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,u>::iterator,
	  typename hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,u>::iterator>
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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 m, bool u>
std::pair<typename hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,u>::const_iterator,
	  typename hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,u>::const_iterator>
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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 m, bool u>
typename hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,u>::node* 
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,u>
::find_node (node* p, const key_type& k, typename hashtable::hash_code_t code)
{
  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 m, bool u>
std::pair<typename hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,u>::iterator, bool>
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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];
    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;
  }
}

// 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 m, bool u>
typename hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,u>::iterator
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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;
  }

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

template <typename K, typename V, 
	  typename A, typename Ex, typename Eq,
	  typename H1, typename H2, typename H, typename RP,
	  bool c, bool m, bool u>
template <typename InIter>
void 
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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);
}

// XXX We're following the TR in giving this a return type of void,
// but that ought to change.  The return type should be const_iterator,
// and it should return the iterator following the one we've erased.
// That would simplify range erase.
template <typename K, typename V, 
	  typename A, typename Ex, typename Eq,
	  typename H1, typename H2, typename H, typename RP,
	  bool c, bool m, bool u>
void hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,u>::erase (const_iterator i)
{
  node* p = i.m_cur_node;
  node* cur = *i.m_cur_bucket;
  if (cur == p)
    *i.m_cur_bucket = 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 m, bool u>
typename hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,u>::size_type 
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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);

  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;
  }
}

// ??? 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 m, bool u>
void hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,u>
::erase(const_iterator first, const_iterator last)
{
  while (first != last) {
    const_iterator next = first;
    ++next;
    this->erase(first);
    first = next;
  }
}

template <typename K, typename V, 
	  typename A, typename Ex, typename Eq,
	  typename H1, typename H2, typename H, typename RP,
	  bool c, bool m, bool u>
void hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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 m, bool u>
void
hashtable<K,V,A,Ex,Eq,H1,H2,H,RP,c,m,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;
  }
}

} }				// Namespace std::tr1

#endif /* GNU_LIBSTDCXX_TR1_HASHTABLE_ */