gcc/libstdc++-v3/include/tr1_impl/hashtable_policy.h

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

// Copyright (C) 2007 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 tr1_impl/hashtable_policy.h
 *  This is an internal header file, included by other library headers.
 *  You should not attempt to use it directly.
 */

namespace std
{ 
_GLIBCXX_BEGIN_NAMESPACE_TR1

namespace __detail
{
  // 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());
    }

  // 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 _Primes<> to exist at all.  
  struct _LessThan
  {
    template<typename _Tp, typename _Up>
      bool
      operator()(_Tp __x, _Up __y)
      { return __x < __y; }
  };

  template<int __ulongsize = sizeof(unsigned long)>
    struct _Primes
    {
      static const int __n_primes = __ulongsize != 8 ? 256 : 256 + 48;
      static const unsigned long __primes[256 + 48 + 1];
    };

  template<int __ulongsize>
    const int _Primes<__ulongsize>::__n_primes;

  template<int __ulongsize>
    const unsigned long _Primes<__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
    };

  // 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.
  template<typename _Value, bool __cache_hash_code>
    struct _Hash_node;

  template<typename _Value>
    struct _Hash_node<_Value, true>
    {
      _Value       _M_v;
      std::size_t  _M_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
      _M_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
      __gnu_cxx::__conditional_type<__constant_iterators,
				    const _Value*, _Value*>::__type
                                                       pointer;
      typedef typename
      __gnu_cxx::__conditional_type<__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->_M_incr();
	return *this; 
      }
  
      _Node_iterator
      operator++(int)
      { 
	_Node_iterator __tmp(*this);
	this->_M_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->_M_incr();
	return *this; 
      }
  
      _Node_const_iterator
      operator++(int)
      { 
	_Node_const_iterator __tmp(*this);
	this->_M_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
      _M_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
      __gnu_cxx::__conditional_type<__constant_iterators,
				    const _Value*, _Value*>::__type
                                                       pointer;
      typedef typename
      __gnu_cxx::__conditional_type<__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->_M_incr();
	return *this;
      }
  
      _Hashtable_iterator
      operator++(int)
      { 
	_Hashtable_iterator __tmp(*this);
	this->_M_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->_M_incr();
	return *this;
      }
  
      _Hashtable_const_iterator
      operator++(int)
      { 
	_Hashtable_const_iterator __tmp(*this);
	this->_M_incr();
	return __tmp;
      }
    };


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

  // 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 __num, second_argument_type __den) const
    { return __num % __den; }
  };

  // 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
    _M_next_bkt(std::size_t __n) const;
    
    // Return a bucket count appropriate for n elements
    std::size_t
    _M_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>
    _M_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;
  };

  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::
  _M_next_bkt(std::size_t __n) const
  {
    const unsigned long* const __last = (_Primes<>::__primes
					 + _Primes<>::__n_primes);
    const unsigned long* __p = std::lower_bound(_Primes<>::__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::
  _M_bkt_for_elements(std::size_t __n) const
  {
    const unsigned long* const __last = (_Primes<>::__primes
					 + _Primes<>::__n_primes);
    const float __min_bkts = __n / _M_max_load_factor;
    const unsigned long* __p = std::lower_bound(_Primes<>::__primes, __last,
						__min_bkts, _LessThan());
    _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 
  // _M_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::
  _M_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 = (_Primes<>::__primes
						 + _Primes<>::__n_primes);
	    const unsigned long* __p = std::lower_bound(_Primes<>::__primes,
							__last, __min_bkts,
							_LessThan());
	    _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);
  }

  // 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.

  // 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 _Key, typename _Value, typename _Ex, bool __unique,
	   typename _Hashtable>
    struct _Map_base { };
	  
  template<typename _Key, typename _Pair, typename _Hashtable>
    struct _Map_base<_Key, _Pair, std::_Select1st<_Pair>, false, _Hashtable>
    {
      typedef typename _Pair::second_type mapped_type;
    };

  template<typename _Key, typename _Pair, typename _Hashtable>
  struct _Map_base<_Key, _Pair, std::_Select1st<_Pair>, true, _Hashtable>
    {
      typedef typename _Pair::second_type mapped_type;
      
      mapped_type&
      operator[](const _Key& __k);
    };

  template<typename _Key, typename _Pair, typename _Hashtable>
    typename _Map_base<_Key, _Pair, std::_Select1st<_Pair>,
		       true, _Hashtable>::mapped_type&
    _Map_base<_Key, _Pair, std::_Select1st<_Pair>, true, _Hashtable>::
    operator[](const _Key& __k)
    {
      _Hashtable* __h = static_cast<_Hashtable*>(this);
      typename _Hashtable::_Hash_code_type __code = __h->_M_hash_code(__k);
      std::size_t __n = __h->_M_bucket_index(__k, __code,
					     __h->_M_bucket_count);

      typename _Hashtable::_Node* __p =
	__h->_M_find_node(__h->_M_buckets[__n], __k, __code);
      if (!__p)
	return __h->_M_insert_bucket(std::make_pair(__k, mapped_type()),
				     __n, __code)->second;
      return (__p->_M_v).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 _Hash,
	   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 _Hash>
    struct _Hash_code_base<_Key, _Value, _ExtractKey, _Equal, _H1, _H2,
			   _Hash, false>
    {
    protected:
      _Hash_code_base(const _ExtractKey& __ex, const _Equal& __eq,
		      const _H1&, const _H2&, const _Hash& __h)
      : _M_extract(__ex), _M_eq(__eq), _M_ranged_hash(__h) { }

      typedef void* _Hash_code_type;
  
      _Hash_code_type
      _M_hash_code(const _Key& __key) const
      { return 0; }
  
      std::size_t
      _M_bucket_index(const _Key& __k, _Hash_code_type,
		      std::size_t __n) const
      { return _M_ranged_hash(__k, __n); }

      std::size_t
      _M_bucket_index(const _Hash_node<_Value, false>* __p,
		      std::size_t __n) const
      { return _M_ranged_hash(_M_extract(__p->_M_v), __n); }
  
      bool
      _M_compare(const _Key& __k, _Hash_code_type,
		 _Hash_node<_Value, false>* __n) const
      { return _M_eq(__k, _M_extract(__n->_M_v)); }

      void
      _M_store_code(_Hash_node<_Value, false>*, _Hash_code_type) const
      { }

      void
      _M_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;
      _Hash        _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 _Hash>
    struct _Hash_code_base<_Key, _Value, _ExtractKey, _Equal, _H1, _H2,
			   _Hash, 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_type;

      _Hash_code_type
      _M_hash_code(const _Key& __k) const
      { return _M_h1(__k); }
      
      std::size_t
      _M_bucket_index(const _Key&, _Hash_code_type __c,
		      std::size_t __n) const
      { return _M_h2(__c, __n); }

      std::size_t
      _M_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
      _M_compare(const _Key& __k, _Hash_code_type,
		 _Hash_node<_Value, false>* __n) const
      { return _M_eq(__k, _M_extract(__n->_M_v)); }

      void
      _M_store_code(_Hash_node<_Value, false>*, _Hash_code_type) const
      { }

      void
      _M_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_type;
  
      _Hash_code_type
      _M_hash_code(const _Key& __k) const
      { return _M_h1(__k); }
  
      std::size_t
      _M_bucket_index(const _Key&, _Hash_code_type __c,
		      std::size_t __n) const
      { return _M_h2(__c, __n); }

      std::size_t
      _M_bucket_index(const _Hash_node<_Value, true>* __p,
		      std::size_t __n) const
      { return _M_h2(__p->_M_hash_code, __n); }

      bool
      _M_compare(const _Key& __k, _Hash_code_type __c,
		 _Hash_node<_Value, true>* __n) const
      { return __c == __n->_M_hash_code && _M_eq(__k, _M_extract(__n->_M_v)); }

      void
      _M_store_code(_Hash_node<_Value, true>* __n, _Hash_code_type __c) const
      { __n->_M_hash_code = __c; }

      void
      _M_copy_code(_Hash_node<_Value, true>* __to,
		   const _Hash_node<_Value, true>* __from) const
      { __to->_M_hash_code = __from->_M_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 __detail

_GLIBCXX_END_NAMESPACE_TR1
}