Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

boost/intrusive/hashtable.hpp

/////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Ion Gaztanaga  2006-2009
//
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file LICENSE_1_0.txt or copy at
//          http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/libs/intrusive for documentation.
//
/////////////////////////////////////////////////////////////////////////////
#ifndef BOOST_INTRUSIVE_HASHTABLE_HPP
#define BOOST_INTRUSIVE_HASHTABLE_HPP

#include <boost/intrusive/detail/config_begin.hpp>
//std C++
#include <functional>   //std::equal_to
#include <utility>      //std::pair
#include <algorithm>    //std::swap, std::lower_bound, std::upper_bound
#include <cstddef>      //std::size_t
#include <iterator>     //std::iterator_traits
//boost
#include <boost/intrusive/detail/assert.hpp>
#include <boost/static_assert.hpp>
#include <boost/functional/hash.hpp>
//General intrusive utilities
#include <boost/intrusive/intrusive_fwd.hpp>
#include <boost/intrusive/detail/pointer_to_other.hpp>
#include <boost/intrusive/detail/hashtable_node.hpp>
#include <boost/intrusive/detail/transform_iterator.hpp>
#include <boost/intrusive/link_mode.hpp>
#include <boost/intrusive/detail/ebo_functor_holder.hpp>
#include <boost/intrusive/detail/clear_on_destructor_base.hpp>
//Implementation utilities
#include <boost/intrusive/trivial_value_traits.hpp>
#include <boost/intrusive/unordered_set_hook.hpp>
#include <boost/intrusive/slist.hpp>
#include <boost/intrusive/detail/mpl.hpp>

namespace boost {
namespace intrusive {

/// @cond

namespace detail {

struct hash_bool_flags
{
   static const std::size_t unique_keys_pos        = 1u;
   static const std::size_t constant_time_size_pos = 2u;
   static const std::size_t power_2_buckets_pos    = 4u;
   static const std::size_t cache_begin_pos        = 8u;
   static const std::size_t compare_hash_pos       = 16u;
   static const std::size_t incremental_pos        = 32u;
};

template 
   < class  ValueTraits
   , class  Hash
   , class  Equal
   , class  SizeType
   , class  BucketTraits
   , std::size_t BoolFlags
   >
struct usetopt
{
   typedef ValueTraits  value_traits;
   typedef Hash         hash;
   typedef Equal        equal;
   typedef SizeType     size_type;
   typedef BucketTraits bucket_traits;
   static const std::size_t bool_flags = BoolFlags;
};

template
   < class UsetOpt
   , std::size_t BoolMask
   >
struct usetopt_mask
{
   typedef usetopt
      <typename UsetOpt::value_traits
      ,typename UsetOpt::hash
      ,typename UsetOpt::equal
      ,typename UsetOpt::size_type
      ,typename UsetOpt::bucket_traits
      ,UsetOpt::bool_flags & BoolMask
      > type;
};

template <class NodeTraits>
struct hash_reduced_slist_node_traits
{
   template <class U> static detail::one test(...);
   template <class U> static detail::two test(typename U::reduced_slist_node_traits* = 0);
   static const bool value = sizeof(test<NodeTraits>(0)) == sizeof(detail::two);
};

template <class NodeTraits>
struct apply_reduced_slist_node_traits
{
   typedef typename NodeTraits::reduced_slist_node_traits type;
};

template <class NodeTraits>
struct reduced_slist_node_traits
{
   typedef typename detail::eval_if_c
      < hash_reduced_slist_node_traits<NodeTraits>::value
      , apply_reduced_slist_node_traits<NodeTraits>
      , detail::identity<NodeTraits>
      >::type type;
};

template<class NodeTraits>
struct get_slist_impl
{
   typedef trivial_value_traits<NodeTraits, normal_link> trivial_traits;

   //Reducing symbol length
   struct type : make_slist
      < typename NodeTraits::node
      , boost::intrusive::value_traits<trivial_traits>
      , boost::intrusive::constant_time_size<false>
      , boost::intrusive::size_type<std::size_t>
      >::type
   {};
};

template<class SupposedValueTraits>
struct real_from_supposed_value_traits
{
   typedef typename detail::eval_if_c
      < detail::external_value_traits_is_true
         <SupposedValueTraits>::value
      , detail::eval_value_traits
         <SupposedValueTraits>
      , detail::identity
         <SupposedValueTraits>
      >::type  type;
};

template<class SupposedValueTraits>
struct get_slist_impl_from_supposed_value_traits
{
   typedef typename
      real_from_supposed_value_traits
         < SupposedValueTraits>::type           real_value_traits;
   typedef typename detail::get_node_traits
      <real_value_traits>::type                 node_traits;
   typedef typename get_slist_impl
      <typename reduced_slist_node_traits
         <node_traits>::type
      >::type                                   type;
};

template<class SupposedValueTraits>
struct unordered_bucket_impl
{
   /// @cond
   typedef typename 
      get_slist_impl_from_supposed_value_traits
         <SupposedValueTraits>::type            slist_impl;
   typedef detail::bucket_impl<slist_impl>      implementation_defined;
   /// @endcond
   typedef implementation_defined               type;
};

template<class SupposedValueTraits>
struct unordered_bucket_ptr_impl
{
   /// @cond
   typedef typename detail::get_node_traits
      <SupposedValueTraits>::type::node_ptr     node_ptr;
   typedef typename unordered_bucket_impl
      <SupposedValueTraits>::type               bucket_type;
   typedef typename boost::pointer_to_other
      <node_ptr, bucket_type>::type             implementation_defined;
   /// @endcond
   typedef implementation_defined               type;
};

template <class T>
struct store_hash_bool
{
   template<bool Add>
   struct two_or_three {one _[2 + Add];};
   template <class U> static one test(...);
   template <class U> static two_or_three<U::store_hash> test (int);
   static const std::size_t value = sizeof(test<T>(0));
};

template <class T>
struct store_hash_is_true
{
   static const bool value = store_hash_bool<T>::value > sizeof(one)*2;
};

template <class T>
struct optimize_multikey_bool
{
   template<bool Add>
   struct two_or_three {one _[2 + Add];};
   template <class U> static one test(...);
   template <class U> static two_or_three<U::optimize_multikey> test (int);
   static const std::size_t value = sizeof(test<T>(0));
};

template <class T>
struct optimize_multikey_is_true
{
   static const bool value = optimize_multikey_bool<T>::value > sizeof(one)*2;
};

template<class Config>
struct bucket_plus_size
   : public detail::size_holder
      < 0 != (Config::bool_flags & hash_bool_flags::constant_time_size_pos)
      , typename Config::size_type>
{
   typedef detail::size_holder
      < 0 != (Config::bool_flags & hash_bool_flags::constant_time_size_pos)
      , typename Config::size_type>       size_traits;
   typedef typename Config::bucket_traits bucket_traits;

   bucket_plus_size(const bucket_traits &b_traits)
      :  bucket_traits_(b_traits)
   {}
   bucket_traits bucket_traits_;
};

template<class Config>
struct bucket_hash_t
   : public detail::ebo_functor_holder<typename Config::hash>
{
   typedef typename Config::hash          hasher;
   typedef detail::size_holder
      < 0 != (Config::bool_flags & hash_bool_flags::constant_time_size_pos)
      , typename Config::size_type>       size_traits;
   typedef typename Config::bucket_traits bucket_traits;

   bucket_hash_t(const bucket_traits &b_traits, const hasher & h)
      :  detail::ebo_functor_holder<hasher>(h), bucket_plus_size_(b_traits)
   {}

   bucket_plus_size<Config> bucket_plus_size_;
};

template<class Config, bool>
struct bucket_hash_equal_t : public detail::ebo_functor_holder<typename Config::equal>
{
   typedef typename Config::equal         equal;
   typedef typename Config::hash          hasher;
   typedef typename Config::bucket_traits bucket_traits;

   bucket_hash_equal_t(const bucket_traits &b_traits, const hasher & h, const equal &e)
      :  detail::ebo_functor_holder<typename Config::equal>(e), bucket_hash(b_traits, h)
   {}
   bucket_hash_t<Config> bucket_hash;
};

template<class Config>  //cache_begin == true version
struct bucket_hash_equal_t<Config, true>
   : public detail::ebo_functor_holder<typename Config::equal>
{
   typedef typename Config::equal               equal;
   typedef typename Config::hash                hasher;
   typedef typename Config::bucket_traits       bucket_traits;
   typedef typename unordered_bucket_ptr_impl
      <typename Config::value_traits>::type     bucket_ptr;

   bucket_hash_equal_t(const bucket_traits &b_traits, const hasher & h, const equal &e)
      :  detail::ebo_functor_holder<typename Config::equal>(e), bucket_hash(b_traits, h)
   {}
   bucket_hash_t<Config> bucket_hash;
   bucket_ptr cached_begin_;
};

template<class Config>
struct hashtable_data_t : public Config::value_traits
{
   static const std::size_t bool_flags       = Config::bool_flags;
   typedef typename Config::value_traits  value_traits;
   typedef typename Config::equal         equal;
   typedef typename Config::hash          hasher;
   typedef typename Config::bucket_traits bucket_traits;

   hashtable_data_t( const bucket_traits &b_traits, const hasher & h
                   , const equal &e, const value_traits &val_traits)
      :  Config::value_traits(val_traits), internal_(b_traits, h, e)
   {}
   typedef typename detail::usetopt_mask
      < Config
      , detail::hash_bool_flags::constant_time_size_pos
      | detail::hash_bool_flags::incremental_pos
      >::type masked_config_t;
   struct internal
      :  public detail::size_holder
         < 0 != (Config::bool_flags & hash_bool_flags::incremental_pos)
         , typename Config::size_type>
   {
      internal(const bucket_traits &b_traits, const hasher & h, const equal &e)
         :  bucket_hash_equal_(b_traits, h, e)
      {}

      bucket_hash_equal_t
         < masked_config_t
         , 0 != (bool_flags & hash_bool_flags::cache_begin_pos)
         > bucket_hash_equal_;
   } internal_;
};

struct insert_commit_data_impl
{
   std::size_t hash;
};

template<class NodeTraits>
struct group_functions
{
   typedef NodeTraits                                             node_traits;
   typedef unordered_group_adapter<node_traits>                   group_traits;
   typedef typename node_traits::node_ptr                         node_ptr;
   typedef typename node_traits::node                             node;
   typedef typename reduced_slist_node_traits
      <node_traits>::type                                         reduced_node_traits;
   typedef typename reduced_node_traits::node_ptr                 slist_node_ptr;
   typedef typename reduced_node_traits::node                     slist_node;
   typedef circular_slist_algorithms<group_traits>                group_algorithms;

   static node_ptr dcast_bucket_ptr(slist_node_ptr p)
   {  return node_ptr(&static_cast<node&>(*p));   }

   static slist_node_ptr priv_get_bucket_before_begin
      (slist_node_ptr bucket_beg, slist_node_ptr bucket_end, node_ptr p)
   {
      //First find the last node of p's group.
      //This requires checking the first node of the next group or
      //the bucket node.
      node_ptr prev_node = p;
      node_ptr nxt(node_traits::get_next(p));
      while(!(bucket_beg <= nxt && nxt <= bucket_end) &&
             (group_traits::get_next(nxt) == prev_node)){
         prev_node = nxt;
         nxt = node_traits::get_next(nxt);
      }

      //If we've reached the bucket node just return it.
      if(bucket_beg <= nxt && nxt <= bucket_end){
         return nxt;
      }

      //Otherwise, iterate using group links until the bucket node
      node_ptr first_node_of_group  = nxt;
      node_ptr last_node_group      = group_traits::get_next(first_node_of_group);
      slist_node_ptr possible_end   = node_traits::get_next(last_node_group);

      while(!(bucket_beg <= possible_end && possible_end <= bucket_end)){
         first_node_of_group = dcast_bucket_ptr(possible_end);
         last_node_group   = group_traits::get_next(first_node_of_group);
         possible_end      = node_traits::get_next(last_node_group);
      }
      return possible_end;
   }

   static node_ptr priv_get_prev_to_first_in_group(slist_node_ptr bucket_node, node_ptr first_in_group)
   {
      //Just iterate using group links and obtain the node
      //before "first_in_group)"
      node_ptr prev_node = dcast_bucket_ptr(bucket_node);
      node_ptr nxt(node_traits::get_next(prev_node));
      while(nxt != first_in_group){
         prev_node = group_traits::get_next(nxt);
         nxt = node_traits::get_next(prev_node);
      }
      return prev_node;
   }

   static node_ptr priv_get_first_in_group_of_last_in_group(node_ptr last_in_group)
   {
      //Just iterate using group links and obtain the node
      //before "last_in_group"
      node_ptr possible_first = group_traits::get_next(last_in_group);
      node_ptr possible_first_prev = group_traits::get_next(possible_first);
      // The deleted node is at the end of the group, so the
      // node in the group pointing to it is at the beginning
      // of the group. Find that to change its pointer.
      while(possible_first_prev != last_in_group){
         possible_first = possible_first_prev;
         possible_first_prev = group_traits::get_next(possible_first);
      }
      return possible_first;
   }


   static void priv_erase_from_group(slist_node_ptr end_ptr, node_ptr to_erase_ptr, detail::true_)
   {
      node_ptr nxt_ptr(node_traits::get_next(to_erase_ptr));
      node_ptr prev_in_group_ptr(group_traits::get_next(to_erase_ptr));
      bool last_in_group = (end_ptr == nxt_ptr) ||
         (group_traits::get_next(nxt_ptr) != to_erase_ptr);
      bool first_in_group = node_traits::get_next(prev_in_group_ptr) != to_erase_ptr;

      if(first_in_group && last_in_group){
         group_algorithms::init(to_erase_ptr);
      }
      else if(first_in_group){
         group_algorithms::unlink_after(nxt_ptr);
      }
      else if(last_in_group){
         node_ptr first_in_group =
            priv_get_first_in_group_of_last_in_group(to_erase_ptr);
         group_algorithms::unlink_after(first_in_group);
      }
      else{
         group_algorithms::unlink_after(nxt_ptr);
      }
   }

   static void priv_erase_from_group(slist_node_ptr, node_ptr, detail::false_)
   {}

   static node_ptr priv_get_last_in_group(node_ptr first_in_group, detail::true_)
   {  return group_traits::get_next(first_in_group);  }

   static node_ptr priv_get_last_in_group(node_ptr n, detail::false_)
   {  return n;  }
};

template<class BucketType, class SplitTraits>
class incremental_rehash_rollback
{
   private:
   typedef BucketType   bucket_type;
   typedef SplitTraits  split_traits;

   incremental_rehash_rollback();
   incremental_rehash_rollback & operator=(const incremental_rehash_rollback &);
   incremental_rehash_rollback (const incremental_rehash_rollback &);

   public:
   incremental_rehash_rollback
      (bucket_type &source_bucket, bucket_type &destiny_bucket, split_traits &split_traits)
      :  source_bucket_(source_bucket),  destiny_bucket_(destiny_bucket)
      ,  split_traits_(split_traits),  released_(false)
   {}

   void release()
   {  released_ = true; }

   ~incremental_rehash_rollback()
   {
      if(!released_){
         //If an exception is thrown, just put all moved nodes back in the old bucket
         //and move back the split mark.
         destiny_bucket_.splice_after(destiny_bucket_.before_begin(), source_bucket_);
         split_traits_.decrement();
      }
   }

   private:
   bucket_type &source_bucket_;
   bucket_type &destiny_bucket_;
   split_traits &split_traits_;
   bool released_;
};

}  //namespace detail {

//!This metafunction will obtain the type of a bucket
//!from the value_traits or hook option to be used with
//!a hash container.
template<class ValueTraitsOrHookOption>
struct unordered_bucket
   : public detail::unordered_bucket_impl
      <typename ValueTraitsOrHookOption::
         template pack<none>::value_traits
      >
{};

//!This metafunction will obtain the type of a bucket pointer
//!from the value_traits or hook option to be used with
//!a hash container.
template<class ValueTraitsOrHookOption>
struct unordered_bucket_ptr
   :  public detail::unordered_bucket_ptr_impl
         <typename ValueTraitsOrHookOption::
          template pack<none>::value_traits
         >
{};

//!This metafunction will obtain the type of the default bucket traits
//!(when the user does not specify the bucket_traits<> option) from the
//!value_traits or hook option to be used with
//!a hash container.
template<class ValueTraitsOrHookOption>
struct unordered_default_bucket_traits
{
   /// @cond
   typedef typename ValueTraitsOrHookOption::
      template pack<none>::value_traits         supposed_value_traits;
   typedef typename detail::
      get_slist_impl_from_supposed_value_traits
         <supposed_value_traits>::type          slist_impl;
   typedef detail::bucket_traits_impl
      <slist_impl>                              implementation_defined;
   /// @endcond
   typedef implementation_defined               type;
};

struct default_bucket_traits;

template <class T>
struct uset_defaults
   :  pack_options
      < none
      , base_hook<detail::default_uset_hook>
      , constant_time_size<true>
      , size_type<std::size_t>
      , equal<std::equal_to<T> >
      , hash<boost::hash<T> >
      , bucket_traits<default_bucket_traits>
      , power_2_buckets<false>
      , cache_begin<false>
      , compare_hash<false>
      , incremental<false>
      >::type
{};

/// @endcond

//! The class template hashtable is an intrusive hash table container, that
//! is used to construct intrusive unordered_set and unordered_multiset containers. The
//! no-throw guarantee holds only, if the Equal object and Hasher don't throw.
//!
//! hashtable is a semi-intrusive container: each object to be stored in the
//! container must contain a proper hook, but the container also needs
//! additional auxiliary memory to work: hashtable needs a pointer to an array
//! of type `bucket_type` to be passed in the constructor. This bucket array must
//! have at least the same lifetime as the container. This makes the use of
//! hashtable more complicated than purely intrusive containers.
//! `bucket_type` is default-constructible, copyable and assignable
//!
//! The template parameter \c T is the type to be managed by the container.
//! The user can specify additional options and if no options are provided
//! default options are used.
//!
//! The container supports the following options:
//! \c base_hook<>/member_hook<>/value_traits<>,
//! \c constant_time_size<>, \c size_type<>, \c hash<> and \c equal<>
//! \c bucket_traits<>, power_2_buckets<>, cache_begin<> and incremental<>.
//!
//! hashtable only provides forward iterators but it provides 4 iterator types:
//! iterator and const_iterator to navigate through the whole container and
//! local_iterator and const_local_iterator to navigate through the values
//! stored in a single bucket. Local iterators are faster and smaller.
//!
//! It's not recommended to use non constant-time size hashtables because several
//! key functions, like "empty()", become non-constant time functions. Non
//! constant_time size hashtables are mainly provided to support auto-unlink hooks.
//!
//! hashtables, does not make automatic rehashings nor
//! offers functions related to a load factor. Rehashing can be explicitly requested
//! and the user must provide a new bucket array that will be used from that moment.
//!
//! Since no automatic rehashing is done, iterators are never invalidated when
//! inserting or erasing elements. Iterators are only invalidated when rehashing.
#if defined(BOOST_INTRUSIVE_DOXYGEN_INVOKED)
template<class T, class ...Options>
#else
template<class Config>
#endif
class hashtable_impl
   :  private detail::clear_on_destructor_base<hashtable_impl<Config> >
{
   template<class C> friend class detail::clear_on_destructor_base;
   public:
   typedef typename Config::value_traits                             value_traits;

   /// @cond
   static const bool external_value_traits =
      detail::external_value_traits_is_true<value_traits>::value;
   typedef typename detail::eval_if_c
      < external_value_traits
      , detail::eval_value_traits<value_traits>
      , detail::identity<value_traits>
      >::type                                                        real_value_traits;
   typedef typename Config::bucket_traits                            bucket_traits;
   static const bool external_bucket_traits =
      detail::external_bucket_traits_is_true<bucket_traits>::value;
   typedef typename detail::eval_if_c
      < external_bucket_traits
      , detail::eval_bucket_traits<bucket_traits>
      , detail::identity<bucket_traits>
      >::type                                                        real_bucket_traits;
   typedef typename detail::get_slist_impl
      <typename detail::reduced_slist_node_traits
         <typename real_value_traits::node_traits>::type
      >::type                                                        slist_impl;
   /// @endcond

   typedef typename real_value_traits::pointer                       pointer;
   typedef typename real_value_traits::const_pointer                 const_pointer;
   typedef typename real_value_traits::value_type                                                value_type;
   typedef typename std::iterator_traits<pointer>::reference         reference;
   typedef typename std::iterator_traits<const_pointer>::reference   const_reference;
   typedef typename std::iterator_traits<pointer>::difference_type   difference_type;
   typedef typename Config::size_type                                size_type;
   typedef value_type                                                key_type;
   typedef typename Config::equal                                    key_equal;
   typedef typename Config::hash                                     hasher;
   typedef detail::bucket_impl<slist_impl>                           bucket_type;
   typedef typename boost::pointer_to_other
      <pointer, bucket_type>::type                                   bucket_ptr;
   typedef typename slist_impl::iterator                             siterator;
   typedef typename slist_impl::const_iterator                       const_siterator;
   typedef detail::hashtable_iterator<hashtable_impl, false>         iterator;
   typedef detail::hashtable_iterator<hashtable_impl, true>          const_iterator;
   typedef typename real_value_traits::node_traits                   node_traits;
   typedef typename node_traits::node                                node;
   typedef typename boost::pointer_to_other
      <pointer, node>::type                                          node_ptr;
   typedef typename boost::pointer_to_other
      <node_ptr, const node>::type                                   const_node_ptr;
   typedef typename slist_impl::node_algorithms                      node_algorithms;

   static const bool stateful_value_traits = detail::is_stateful_value_traits<real_value_traits>::value;
   static const bool store_hash = detail::store_hash_is_true<node_traits>::value;

   static const bool unique_keys          = 0 != (Config::bool_flags  & detail::hash_bool_flags::unique_keys_pos);
   static const bool constant_time_size   = 0 != (Config::bool_flags  & detail::hash_bool_flags::constant_time_size_pos);
   static const bool cache_begin          = 0 != (Config::bool_flags  & detail::hash_bool_flags::cache_begin_pos);
   static const bool compare_hash         = 0 != (Config::bool_flags  & detail::hash_bool_flags::compare_hash_pos);
   static const bool incremental          = 0 != (Config::bool_flags  & detail::hash_bool_flags::incremental_pos);
   static const bool power_2_buckets      = incremental || (0 != (Config::bool_flags  & detail::hash_bool_flags::power_2_buckets_pos));

   static const bool optimize_multikey
      = detail::optimize_multikey_is_true<node_traits>::value && !unique_keys;

   /// @cond
   private:

   //Configuration error: compare_hash<> can't be specified without store_hash<>
   //See documentation for more explanations
   BOOST_STATIC_ASSERT((!compare_hash || store_hash));

   typedef typename slist_impl::node_ptr                             slist_node_ptr;
   typedef typename boost::pointer_to_other
         <slist_node_ptr, void>::type                                void_pointer;
   //We'll define group traits, but these won't be instantiated if
   //optimize_multikey is not true
   typedef unordered_group_adapter<node_traits>                      group_traits;
   typedef circular_slist_algorithms<group_traits>                   group_algorithms;
   typedef detail::bool_<store_hash>                                 store_hash_t;
   typedef detail::bool_<optimize_multikey>                          optimize_multikey_t;
   typedef detail::bool_<cache_begin>                                cache_begin_t;
   typedef detail::bool_<power_2_buckets>                            power_2_buckets_t;
   typedef detail::size_holder<constant_time_size, size_type>        size_traits;
   typedef detail::size_holder<incremental, size_type>               split_traits;
   typedef detail::group_functions<node_traits>                      group_functions_t;

   static const std::size_t hashtable_data_bool_flags_mask  =
      ( detail::hash_bool_flags::cache_begin_pos
      | detail::hash_bool_flags::constant_time_size_pos
      | detail::hash_bool_flags::incremental_pos
      );
   typedef typename detail::usetopt_mask
      <Config, hashtable_data_bool_flags_mask>::type masked_config_t;
   detail::hashtable_data_t<masked_config_t>   data_;

   template<bool IsConst>
   struct downcast_node_to_value
      :  public detail::node_to_value<hashtable_impl, IsConst>
   {
      typedef detail::node_to_value<hashtable_impl, IsConst> base_t;
      typedef typename base_t::result_type               result_type;
      typedef typename detail::add_const_if_c
            <typename slist_impl::node, IsConst>::type  &first_argument_type;
      typedef typename detail::add_const_if_c
            <node, IsConst>::type                       &intermediate_argument_type;

      downcast_node_to_value(const hashtable_impl *cont)
         :  base_t(cont)
      {}

      result_type operator()(first_argument_type arg) const
      {  return this->base_t::operator()(static_cast<intermediate_argument_type>(arg)); }
   };

   template<class F>
   struct node_cast_adaptor
      :  private detail::ebo_functor_holder<F>
   {
      typedef detail::ebo_functor_holder<F> base_t;

      template<class ConvertibleToF>
      node_cast_adaptor(const ConvertibleToF &c2f, const hashtable_impl *cont)
         :  base_t(base_t(c2f, cont))
      {}
      
      typename base_t::node_ptr operator()(const typename slist_impl::node &to_clone)
      {  return base_t::operator()(static_cast<const node &>(to_clone));   }

      void operator()(typename slist_impl::node_ptr to_clone)
      {  base_t::operator()(node_ptr(&static_cast<node &>(*to_clone)));   }
   };

   private:
   //noncopyable
   hashtable_impl (const hashtable_impl&);
   hashtable_impl operator =(const hashtable_impl&);

   enum { safemode_or_autounlink  = 
            (int)real_value_traits::link_mode == (int)auto_unlink   ||
            (int)real_value_traits::link_mode == (int)safe_link     };

   //Constant-time size is incompatible with auto-unlink hooks!
   BOOST_STATIC_ASSERT(!(constant_time_size && ((int)real_value_traits::link_mode == (int)auto_unlink)));
   //Cache begin is incompatible with auto-unlink hooks!
   BOOST_STATIC_ASSERT(!(cache_begin && ((int)real_value_traits::link_mode == (int)auto_unlink)));

   template<class Disposer>
   node_cast_adaptor<detail::node_disposer<Disposer, hashtable_impl> >
      make_node_disposer(const Disposer &disposer) const
   {  return node_cast_adaptor<detail::node_disposer<Disposer, hashtable_impl> >(disposer, this);   }

   /// @endcond

   public:
   typedef detail::insert_commit_data_impl insert_commit_data;

   typedef detail::transform_iterator
      < typename slist_impl::iterator
      , downcast_node_to_value<false> >                              local_iterator;

   typedef detail::transform_iterator
      < typename slist_impl::iterator
      , downcast_node_to_value<true> >                               const_local_iterator;

   /// @cond

   const real_value_traits &get_real_value_traits(detail::bool_<false>) const
   {  return this->data_;  }

   const real_value_traits &get_real_value_traits(detail::bool_<true>) const
   {  return data_.get_value_traits(*this);  }

   real_value_traits &get_real_value_traits(detail::bool_<false>)
   {  return this->data_;  }

   real_value_traits &get_real_value_traits(detail::bool_<true>)
   {  return data_.get_value_traits(*this);  }

   /// @endcond

   public:

   const real_value_traits &get_real_value_traits() const
   {  return this->get_real_value_traits(detail::bool_<external_value_traits>());  }

   real_value_traits &get_real_value_traits()
   {  return this->get_real_value_traits(detail::bool_<external_value_traits>());  }

   //! <b>Requires</b>: buckets must not be being used by any other resource.
   //!
   //! <b>Effects</b>: Constructs an empty unordered_set, storing a reference
   //!   to the bucket array and copies of the key_hasher and equal_func functors.
   //!   
   //! <b>Complexity</b>: Constant. 
   //! 
   //! <b>Throws</b>: If value_traits::node_traits::node
   //!   constructor throws (this does not happen with predefined Boost.Intrusive hooks)
   //!   or the copy constructor or invocation of hash_func or equal_func throws. 
   //!
   //! <b>Notes</b>: buckets array must be disposed only after
   //!   *this is disposed.
   hashtable_impl ( const bucket_traits &b_traits
                  , const hasher & hash_func = hasher()
                  , const key_equal &equal_func = key_equal()
                  , const value_traits &v_traits = value_traits()) 
      :  data_(b_traits, hash_func, equal_func, v_traits)
   {
      priv_initialize_buckets();
      this->priv_size_traits().set_size(size_type(0));
      size_type bucket_size = this->priv_buckets_len();
      BOOST_INTRUSIVE_INVARIANT_ASSERT(bucket_size != 0);
      //Check power of two bucket array if the option is activated
      BOOST_INTRUSIVE_INVARIANT_ASSERT
         (!power_2_buckets || (0 == (bucket_size & (bucket_size-1))));
      priv_split_traits().set_size(bucket_size>>1);
   }

   //! <b>Effects</b>: Detaches all elements from this. The objects in the unordered_set 
   //!   are not deleted (i.e. no destructors are called).
   //! 
   //! <b>Complexity</b>: Linear to the number of elements in the unordered_set, if 
   //!   it's a safe-mode or auto-unlink value. Otherwise constant.
   //! 
   //! <b>Throws</b>: Nothing.
   ~hashtable_impl() 
   {}

   //! <b>Effects</b>: Returns an iterator pointing to the beginning of the unordered_set.
   //! 
   //! <b>Complexity</b>: Amortized constant time.
   //!   Worst case (empty unordered_set): O(this->bucket_count())
   //! 
   //! <b>Throws</b>: Nothing.
   iterator begin()
   {  return iterator(this->priv_begin(), this);   }

   //! <b>Effects</b>: Returns a const_iterator pointing to the beginning
   //!   of the unordered_set.
   //!
   //! <b>Complexity</b>: Amortized constant time.
   //!   Worst case (empty unordered_set): O(this->bucket_count())
   //! 
   //! <b>Throws</b>: Nothing.
   const_iterator begin() const
   {  return this->cbegin();  }

   //! <b>Effects</b>: Returns a const_iterator pointing to the beginning
   //!   of the unordered_set.
   //!
   //! <b>Complexity</b>: Amortized constant time.
   //!   Worst case (empty unordered_set): O(this->bucket_count())
   //! 
   //! <b>Throws</b>: Nothing.
   const_iterator cbegin() const
   {  return const_iterator(this->priv_begin(), this);   }

   //! <b>Effects</b>: Returns an iterator pointing to the end of the unordered_set.
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: Nothing.
   iterator end()
   {  return iterator(priv_invalid_local_it(), 0);   }

   //! <b>Effects</b>: Returns a const_iterator pointing to the end of the unordered_set.
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: Nothing.
   const_iterator end() const
   {  return this->cend(); }

   //! <b>Effects</b>: Returns a const_iterator pointing to the end of the unordered_set.
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: Nothing.
   const_iterator cend() const
   {  return const_iterator(priv_invalid_local_it(), 0);  }

   //! <b>Effects</b>: Returns the hasher object used by the unordered_set.
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: If hasher copy-constructor throws.
   hasher hash_function() const
   {  return this->priv_hasher();  }

   //! <b>Effects</b>: Returns the key_equal object used by the unordered_set.
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: If key_equal copy-constructor throws.
   key_equal key_eq() const
   {  return this->priv_equal();   }

   //! <b>Effects</b>: Returns true if the container is empty.
   //! 
   //! <b>Complexity</b>: if constant-time size and cache_begin options are disabled,
   //!   average constant time (worst case, with empty() == true: O(this->bucket_count()).
   //!   Otherwise constant.
   //! 
   //! <b>Throws</b>: Nothing.
   bool empty() const
   {
      if(constant_time_size){
         return !this->size();
      }
      else if(cache_begin){
         return this->begin() == this->end();
      }
      else{
         size_type buckets_len = this->priv_buckets_len();
         const bucket_type *b = detail::get_pointer(this->priv_buckets());
         for (size_type n = 0; n < buckets_len; ++n, ++b){
            if(!b->empty()){
               return false;
            }
         }
         return true;
      }
   }

   //! <b>Effects</b>: Returns the number of elements stored in the unordered_set.
   //! 
   //! <b>Complexity</b>: Linear to elements contained in *this if
   //!   constant_time_size is false. Constant-time otherwise.
   //! 
   //! <b>Throws</b>: Nothing.
   size_type size() const
   {
      if(constant_time_size)
         return this->priv_size_traits().get_size();
      else{
         size_type len = 0;
         size_type buckets_len = this->priv_buckets_len();
         const bucket_type *b = detail::get_pointer(this->priv_buckets());
         for (size_type n = 0; n < buckets_len; ++n, ++b){
            len += b->size();
         }
         return len;
      }
   }

   //! <b>Requires</b>: the hasher and the equality function unqualified swap
   //!   call should not throw.
   //! 
   //! <b>Effects</b>: Swaps the contents of two unordered_sets.
   //!   Swaps also the contained bucket array and equality and hasher functors.
   //! 
   //! <b>Complexity</b>: Constant.
   //!
   //! <b>Throws</b>: If the swap() call for the comparison or hash functors
   //!   found using ADL throw. Basic guarantee.
   void swap(hashtable_impl& other)
   {
      using std::swap;
      //These can throw
      swap(this->priv_equal(), other.priv_equal());
      swap(this->priv_hasher(), other.priv_hasher());
      //These can't throw
      swap(this->priv_real_bucket_traits(), other.priv_real_bucket_traits());
      priv_swap_cache(cache_begin_t(), other);
      if(constant_time_size){
         size_type backup = this->priv_size_traits().get_size();
         this->priv_size_traits().set_size(other.priv_size_traits().get_size());
         other.priv_size_traits().set_size(backup);
      }
      else if(incremental){
         size_type backup = this->priv_split_traits().get_size();
         this->priv_split_traits().set_size(other.priv_split_traits().get_size());
         other.priv_split_traits().set_size(backup);
      }
   }

   //! <b>Requires</b>: Disposer::operator()(pointer) shouldn't throw
   //!   Cloner should yield to nodes that compare equal and produce the same
   //!   hash than the original node.
   //!
   //! <b>Effects</b>: Erases all the elements from *this
   //!   calling Disposer::operator()(pointer), clones all the 
   //!   elements from src calling Cloner::operator()(const_reference )
   //!   and inserts them on *this. The hash function and the equality
   //!   predicate are copied from the source.
   //!
   //!   If store_hash option is true, this method does not use the hash function.
   //!
   //!   If any operation throws, all cloned elements are unlinked and disposed
   //!   calling Disposer::operator()(pointer).
   //!
   //! <b>Complexity</b>: Linear to erased plus inserted elements.
   //! 
   //! <b>Throws</b>: If cloner or hasher throw or hash or equality predicate copying
   //!   throws. Basic guarantee.
   template <class Cloner, class Disposer>
   void clone_from(const hashtable_impl &src, Cloner cloner, Disposer disposer)
   {
      this->clear_and_dispose(disposer);
      if(!constant_time_size || !src.empty()){
         const size_type src_bucket_count = src.bucket_count();
         const size_type dst_bucket_count = this->bucket_count();
         //Check power of two bucket array if the option is activated
         BOOST_INTRUSIVE_INVARIANT_ASSERT
         (!power_2_buckets || (0 == (src_bucket_count & (src_bucket_count-1))));
         BOOST_INTRUSIVE_INVARIANT_ASSERT
         (!power_2_buckets || (0 == (dst_bucket_count & (dst_bucket_count-1))));

         //If src bucket count is bigger or equal, structural copy is possible
         if(!incremental && (src_bucket_count >= dst_bucket_count)){
            //First clone the first ones
            const bucket_ptr src_buckets = src.priv_buckets();
            const bucket_ptr dst_buckets = this->priv_buckets();
            size_type constructed;
            typedef node_cast_adaptor<detail::node_disposer<Disposer, hashtable_impl> > NodeDisposer;
            typedef node_cast_adaptor<detail::node_cloner<Cloner, hashtable_impl> > NodeCloner;
            NodeDisposer node_disp(disposer, this);
   
            detail::exception_array_disposer<bucket_type, NodeDisposer>
               rollback(dst_buckets[0], node_disp, constructed);
            for( constructed = 0
               ; constructed < dst_bucket_count
               ; ++constructed){
               dst_buckets[constructed].clone_from
                  ( src_buckets[constructed]
                  , NodeCloner(cloner, this), node_disp);
            }
            if(src_bucket_count != dst_bucket_count){
               //Now insert the remaining ones using the modulo trick
               for(//"constructed" comes from the previous loop
                  ; constructed < src_bucket_count
                  ; ++constructed){
                  bucket_type &dst_b =
                     dst_buckets[priv_hash_to_bucket(constructed, dst_bucket_count, dst_bucket_count)];
                  bucket_type &src_b = src_buckets[constructed];
                  for( siterator b(src_b.begin()), e(src_b.end())
                     ; b != e
                     ; ++b){
                     dst_b.push_front(*(NodeCloner(cloner, this)(*b.pointed_node())));
                  }
               }
            }
            this->priv_hasher() = src.priv_hasher();
            this->priv_equal()  = src.priv_equal();
            rollback.release();
            this->priv_size_traits().set_size(src.priv_size_traits().get_size());
            this->priv_split_traits().set_size(dst_bucket_count);
            priv_insertion_update_cache(0u);
            priv_erasure_update_cache();
         }
         else if(store_hash){
            //Unlike previous cloning algorithm, this can throw
            //if cloner, hasher or comparison functor throw
            const_iterator b(src.begin()), e(src.end());
            detail::exception_disposer<hashtable_impl, Disposer>
               rollback(*this, disposer);
            for(; b != e; ++b){
               std::size_t hash_value = this->priv_stored_or_compute_hash(*b, store_hash_t());;
               this->priv_insert_equal_with_hash(*cloner(*b), hash_value);
            }
            rollback.release();
         }
         else{
            //Unlike previous cloning algorithm, this can throw
            //if cloner, hasher or comparison functor throw
            const_iterator b(src.begin()), e(src.end());
            detail::exception_disposer<hashtable_impl, Disposer>
               rollback(*this, disposer);
            for(; b != e; ++b){
               this->insert_equal(*cloner(*b));
            }
            rollback.release();
         }
      }
   }

   //! <b>Requires</b>: value must be an lvalue
   //! 
   //! <b>Effects</b>: Inserts the value into the unordered_set.
   //!
   //! <b>Returns</b>: An iterator to the inserted value.
   //! 
   //! <b>Complexity</b>: Average case O(1), worst case O(this->size()).
   //! 
   //! <b>Throws</b>: If the internal hasher or the equality functor throws. Strong guarantee.
   //! 
   //! <b>Note</b>: Does not affect the validity of iterators and references.
   //!   No copy-constructors are called.
   iterator insert_equal(reference value)
   {
      size_type bucket_num;
      std::size_t hash_value;
      siterator prev;
      siterator it = this->priv_find
         (value, this->priv_hasher(), this->priv_equal(), bucket_num, hash_value, prev);
      return priv_insert_equal_find(value, bucket_num, hash_value, it);
   }

   //! <b>Requires</b>: Dereferencing iterator must yield an lvalue 
   //!   of type value_type.
   //! 
   //! <b>Effects</b>: Equivalent to this->insert_equal(t) for each element in [b, e).
   //! 
   //! <b>Complexity</b>: Average case O(N), where N is std::distance(b, e).
   //!   Worst case O(N*this->size()).
   //! 
   //! <b>Throws</b>: If the internal hasher or the equality functor throws. Basic guarantee.
   //! 
   //! <b>Note</b>: Does not affect the validity of iterators and references.
   //!   No copy-constructors are called.
   template<class Iterator>
   void insert_equal(Iterator b, Iterator e)
   {
      for (; b != e; ++b)
         this->insert_equal(*b);
   }

   //! <b>Requires</b>: value must be an lvalue
   //! 
   //! <b>Effects</b>: Tries to inserts value into the unordered_set.
   //!
   //! <b>Returns</b>: If the value
   //!   is not already present inserts it and returns a pair containing the
   //!   iterator to the new value and true. If there is an equivalent value
   //!   returns a pair containing an iterator to the already present value
   //!   and false.
   //! 
   //! <b>Complexity</b>: Average case O(1), worst case O(this->size()).
   //! 
   //! <b>Throws</b>: If the internal hasher or the equality functor throws. Strong guarantee.
   //! 
   //! <b>Note</b>: Does not affect the validity of iterators and references.
   //!   No copy-constructors are called.
   std::pair<iterator, bool> insert_unique(reference value)
   {
      insert_commit_data commit_data;
      std::pair<iterator, bool> ret = this->insert_unique_check
         (value, this->priv_hasher(), this->priv_equal(), commit_data);
      if(!ret.second)
         return ret;
      return std::pair<iterator, bool> 
         (this->insert_unique_commit(value, commit_data), true);
   }

   //! <b>Requires</b>: Dereferencing iterator must yield an lvalue 
   //!   of type value_type.
   //! 
   //! <b>Effects</b>: Equivalent to this->insert_unique(t) for each element in [b, e).
   //! 
   //! <b>Complexity</b>: Average case O(N), where N is std::distance(b, e).
   //!   Worst case O(N*this->size()).
   //! 
   //! <b>Throws</b>: If the internal hasher or the equality functor throws. Basic guarantee.
   //! 
   //! <b>Note</b>: Does not affect the validity of iterators and references.
   //!   No copy-constructors are called.
   template<class Iterator>
   void insert_unique(Iterator b, Iterator e)
   {
      for (; b != e; ++b)
         this->insert_unique(*b);
   }

   //! <b>Requires</b>: "hash_func" must be a hash function that induces 
   //!   the same hash values as the stored hasher. The difference is that
   //!   "hash_func" hashes the given key instead of the value_type.
   //!
   //!   "equal_func" must be a equality function that induces 
   //!   the same equality as key_equal. The difference is that
   //!   "equal_func" compares an arbitrary key with the contained values.
   //! 
   //! <b>Effects</b>: Checks if a value can be inserted in the unordered_set, using
   //!   a user provided key instead of the value itself.
   //!
   //! <b>Returns</b>: If there is an equivalent value
   //!   returns a pair containing an iterator to the already present value
   //!   and false. If the value can be inserted returns true in the returned
   //!   pair boolean and fills "commit_data" that is meant to be used with
   //!   the "insert_commit" function.
   //! 
   //! <b>Complexity</b>: Average case O(1), worst case O(this->size()).
   //!
   //! <b>Throws</b>: If hash_func or equal_func throw. Strong guarantee.
   //! 
   //! <b>Notes</b>: This function is used to improve performance when constructing
   //!   a value_type is expensive: if there is an equivalent value
   //!   the constructed object must be discarded. Many times, the part of the
   //!   node that is used to impose the hash or the equality is much cheaper to
   //!   construct than the value_type and this function offers the possibility to
   //!   use that the part to check if the insertion will be successful.
   //!
   //!   If the check is successful, the user can construct the value_type and use
   //!   "insert_commit" to insert the object in constant-time.
   //!
   //!   "commit_data" remains valid for a subsequent "insert_commit" only if no more
   //!   objects are inserted or erased from the unordered_set.
   //!
   //!   After a successful rehashing insert_commit_data remains valid.
   template<class KeyType, class KeyHasher, class KeyValueEqual>
   std::pair<iterator, bool> insert_unique_check
      ( const KeyType &key
      , KeyHasher hash_func
      , KeyValueEqual equal_func
      , insert_commit_data &commit_data)
   {
      size_type bucket_num;
      siterator prev;
      siterator prev_pos =
         this->priv_find(key, hash_func, equal_func, bucket_num, commit_data.hash, prev);
      bool success = prev_pos == priv_invalid_local_it();
      if(success){
         prev_pos = prev;
      }
      return std::pair<iterator, bool>(iterator(prev_pos, this),success);
   }

   //! <b>Requires</b>: value must be an lvalue of type value_type. commit_data
   //!   must have been obtained from a previous call to "insert_check".
   //!   No objects should have been inserted or erased from the unordered_set between
   //!   the "insert_check" that filled "commit_data" and the call to "insert_commit".
   //! 
   //! <b>Effects</b>: Inserts the value in the unordered_set using the information obtained
   //!   from the "commit_data" that a previous "insert_check" filled.
   //!
   //! <b>Returns</b>: An iterator to the newly inserted object.
   //! 
   //! <b>Complexity</b>: Constant time.
   //!
   //! <b>Throws</b>: Nothing.
   //! 
   //! <b>Notes</b>: This function has only sense if a "insert_check" has been
   //!   previously executed to fill "commit_data". No value should be inserted or
   //!   erased between the "insert_check" and "insert_commit" calls.
   //!
   //!   After a successful rehashing insert_commit_data remains valid.
   iterator insert_unique_commit(reference value, const insert_commit_data &commit_data)
   {
      size_type bucket_num = priv_hash_to_bucket(commit_data.hash);
      bucket_type &b = this->priv_buckets()[bucket_num];
      this->priv_size_traits().increment();
      node_ptr n = node_ptr(&priv_value_to_node(value));
      this->priv_store_hash(n, commit_data.hash, store_hash_t());
      if(safemode_or_autounlink)
         BOOST_INTRUSIVE_SAFE_HOOK_DEFAULT_ASSERT(node_algorithms::unique(n));
      priv_insertion_update_cache(bucket_num);
      this->priv_insert_in_group(node_ptr(0), n, optimize_multikey_t());
      return iterator(b.insert_after(b.before_begin(), *n), this);
   }

   //! <b>Effects</b>: Erases the element pointed to by i. 
   //! 
   //! <b>Complexity</b>: Average case O(1), worst case O(this->size()).
   //! 
   //! <b>Throws</b>: Nothing.
   //! 
   //! <b>Note</b>: Invalidates the iterators (but not the references)
   //!    to the erased element. No destructors are called.
   iterator erase(const_iterator i)
   {  return this->erase_and_dispose(i, detail::null_disposer());  }

   //! <b>Effects</b>: Erases the range pointed to by b end e. 
   //! 
   //! <b>Complexity</b>: Average case O(std::distance(b, e)),
   //!   worst case O(this->size()).
   //! 
   //! <b>Throws</b>: Nothing.
   //! 
   //! <b>Note</b>: Invalidates the iterators (but not the references)
   //!    to the erased elements. No destructors are called.
   iterator erase(const_iterator b, const_iterator e)
   {  return this->erase_and_dispose(b, e, detail::null_disposer());  }

   //! <b>Effects</b>: Erases all the elements with the given value.
   //! 
   //! <b>Returns</b>: The number of erased elements.
   //! 
   //! <b>Complexity</b>: Average case O(this->count(value)).
   //!   Worst case O(this->size()).
   //! 
   //! <b>Throws</b>: If the internal hasher or the equality functor throws. 
   //!   Basic guarantee.
   //! 
   //! <b>Note</b>: Invalidates the iterators (but not the references)
   //!    to the erased elements. No destructors are called.
   size_type erase(const_reference value)
   {  return this->erase(value, this->priv_hasher(), this->priv_equal());  }

   //! <b>Requires</b>: "hash_func" must be a hash function that induces 
   //!   the same hash values as the stored hasher. The difference is that
   //!   "hash_func" hashes the given key instead of the value_type.
   //!
   //!   "equal_func" must be a equality function that induces 
   //!   the same equality as key_equal. The difference is that
   //!   "equal_func" compares an arbitrary key with the contained values.
   //!
   //! <b>Effects</b>: Erases all the elements that have the same hash and
   //!   compare equal with the given key.
   //! 
   //! <b>Returns</b>: The number of erased elements.
   //! 
   //! <b>Complexity</b>: Average case O(this->count(value)).
   //!   Worst case O(this->size()).
   //! 
   //! <b>Throws</b>: If hash_func or equal_func throw. Basic guarantee.
   //! 
   //! <b>Note</b>: Invalidates the iterators (but not the references)
   //!    to the erased elements. No destructors are called.
   template<class KeyType, class KeyHasher, class KeyValueEqual>
   size_type erase(const KeyType& key, KeyHasher hash_func, KeyValueEqual equal_func)
   {  return this->erase_and_dispose(key, hash_func, equal_func, detail::null_disposer()); }

   //! <b>Requires</b>: Disposer::operator()(pointer) shouldn't throw.
   //!
   //! <b>Effects</b>: Erases the element pointed to by i. 
   //!   Disposer::operator()(pointer) is called for the removed element.
   //! 
   //! <b>Complexity</b>: Average case O(1), worst case O(this->size()).
   //! 
   //! <b>Throws</b>: Nothing.
   //! 
   //! <b>Note</b>: Invalidates the iterators 
   //!    to the erased elements.
   template<class Disposer>
   iterator erase_and_dispose(const_iterator i, Disposer disposer
                              /// @cond
                              , typename detail::enable_if_c<!detail::is_convertible<Disposer, const_iterator>::value >::type * = 0
                              /// @endcond
                              )
   {
      iterator ret(i.unconst());
      ++ret;
      priv_erase(i, disposer, optimize_multikey_t());
      this->priv_size_traits().decrement();
      priv_erasure_update_cache();
      return ret;
   }

   //! <b>Requires</b>: Disposer::operator()(pointer) shouldn't throw.
   //!
   //! <b>Effects</b>: Erases the range pointed to by b end e.
   //!   Disposer::operator()(pointer) is called for the removed elements.
   //! 
   //! <b>Complexity</b>: Average case O(std::distance(b, e)),
   //!   worst case O(this->size()).
   //! 
   //! <b>Throws</b>: Nothing.
   //! 
   //! <b>Note</b>: Invalidates the iterators
   //!    to the erased elements.
   template<class Disposer>
   iterator erase_and_dispose(const_iterator b, const_iterator e, Disposer disposer)
   {
      if(b != e){
         //Get the bucket number and local iterator for both iterators
         siterator first_local_it(b.slist_it());
         size_type first_bucket_num = this->priv_get_bucket_num(first_local_it);

         siterator before_first_local_it
            = priv_get_previous(priv_buckets()[first_bucket_num], first_local_it);
         size_type last_bucket_num;
         siterator last_local_it;

         //For the end iterator, we will assign the end iterator
         //of the last bucket
         if(e == this->end()){
            last_bucket_num   = this->bucket_count() - 1;
            last_local_it     = priv_buckets()[last_bucket_num].end();
         }
         else{
            last_local_it     = e.slist_it();
            last_bucket_num = this->priv_get_bucket_num(last_local_it);
         }
         priv_erase_range(before_first_local_it, first_bucket_num, last_local_it, last_bucket_num, disposer);
         priv_erasure_update_cache(first_bucket_num, last_bucket_num);
      }
      return e.unconst();
   }

   //! <b>Requires</b>: Disposer::operator()(pointer) shouldn't throw.
   //!
   //! <b>Effects</b>: Erases all the elements with the given value.
   //!   Disposer::operator()(pointer) is called for the removed elements.
   //! 
   //! <b>Returns</b>: The number of erased elements.
   //! 
   //! <b>Complexity</b>: Average case O(this->count(value)).
   //!   Worst case O(this->size()).
   //! 
   //! <b>Throws</b>: If the internal hasher or the equality functor throws.
   //!   Basic guarantee.
   //! 
   //! <b>Note</b>: Invalidates the iterators (but not the references)
   //!    to the erased elements. No destructors are called.
   template<class Disposer>
   size_type erase_and_dispose(const_reference value, Disposer disposer)
   {  return this->erase_and_dispose(value, priv_hasher(), priv_equal(), disposer);   }

   //! <b>Requires</b>: Disposer::operator()(pointer) shouldn't throw.
   //!
   //! <b>Effects</b>: Erases all the elements with the given key.
   //!   according to the comparison functor "equal_func".
   //!   Disposer::operator()(pointer) is called for the removed elements.
   //!
   //! <b>Returns</b>: The number of erased elements.
   //! 
   //! <b>Complexity</b>: Average case O(this->count(value)).
   //!   Worst case O(this->size()).
   //! 
   //! <b>Throws</b>: If hash_func or equal_func throw. Basic guarantee.
   //! 
   //! <b>Note</b>: Invalidates the iterators
   //!    to the erased elements.
   template<class KeyType, class KeyHasher, class KeyValueEqual, class Disposer>
   size_type erase_and_dispose(const KeyType& key, KeyHasher hash_func
                              ,KeyValueEqual equal_func, Disposer disposer)
   {
      size_type bucket_num;
      std::size_t h;
      siterator prev;
      siterator it =
         this->priv_find(key, hash_func, equal_func, bucket_num, h, prev);
      bool success = it != priv_invalid_local_it();
      size_type count(0);
      if(!success){
         return 0;
      }
      else if(optimize_multikey){
         siterator last = bucket_type::s_iterator_to
            (*node_traits::get_next(group_functions_t::priv_get_last_in_group
               (dcast_bucket_ptr(it.pointed_node()), optimize_multikey_t())));
         this->priv_erase_range_impl(bucket_num, prev, last, disposer, count);
      }
      else{
         //If found erase all equal values
         bucket_type &b = this->priv_buckets()[bucket_num];
         for(siterator end = b.end(); it != end; ++count, ++it){
            slist_node_ptr n(it.pointed_node());
            const value_type &v = priv_value_from_slist_node(n);
            if(compare_hash){
               std::size_t vh = this->priv_stored_or_compute_hash(v, store_hash_t());
               if(h != vh || !equal_func(key, v)){
                  break;
               }
            }
            else if(!equal_func(key, v)){
               break;
            }
            this->priv_size_traits().decrement();
         }
         b.erase_after_and_dispose(prev, it, make_node_disposer(disposer));
      }
      priv_erasure_update_cache();
      return count;
   }

   //! <b>Effects</b>: Erases all of the elements. 
   //! 
   //! <b>Complexity</b>: Linear to the number of elements on the container.
   //!   if it's a safe-mode or auto-unlink value_type. Constant time otherwise.
   //! 
   //! <b>Throws</b>: Nothing.
   //! 
   //! <b>Note</b>: Invalidates the iterators (but not the references)
   //!    to the erased elements. No destructors are called.
   void clear()
   {
      priv_clear_buckets();
      this->priv_size_traits().set_size(size_type(0));
   }

   //! <b>Requires</b>: Disposer::operator()(pointer) shouldn't throw.
   //! 
   //! <b>Effects</b>: Erases all of the elements. 
   //! 
   //! <b>Complexity</b>: Linear to the number of elements on the container.
   //!   Disposer::operator()(pointer) is called for the removed elements.
   //! 
   //! <b>Throws</b>: Nothing.
   //! 
   //! <b>Note</b>: Invalidates the iterators (but not the references)
   //!    to the erased elements. No destructors are called.
   template<class Disposer>
   void clear_and_dispose(Disposer disposer)
   {
      if(!constant_time_size || !this->empty()){
         size_type num_buckets = this->bucket_count();
         bucket_ptr b = this->priv_buckets();
         for(; num_buckets--; ++b){
            b->clear_and_dispose(make_node_disposer(disposer));
         }
         this->priv_size_traits().set_size(size_type(0));
      }
      priv_initialize_cache();
   }

   //! <b>Effects</b>: Returns the number of contained elements with the given value
   //! 
   //! <b>Complexity</b>: Average case O(1), worst case O(this->size()).
   //! 
   //! <b>Throws</b>: If the internal hasher or the equality functor throws.
   size_type count(const_reference value) const
   {  return this->count(value, this->priv_hasher(), this->priv_equal());  }

   //! <b>Requires</b>: "hash_func" must be a hash function that induces 
   //!   the same hash values as the stored hasher. The difference is that
   //!   "hash_func" hashes the given key instead of the value_type.
   //!
   //!   "equal_func" must be a equality function that induces 
   //!   the same equality as key_equal. The difference is that
   //!   "equal_func" compares an arbitrary key with the contained values.
   //!
   //! <b>Effects</b>: Returns the number of contained elements with the given key
   //!
   //! <b>Complexity</b>: Average case O(1), worst case O(this->size()).
   //! 
   //! <b>Throws</b>: If hash_func or equal throw.
   template<class KeyType, class KeyHasher, class KeyValueEqual>
   size_type count(const KeyType &key, const KeyHasher &hash_func, const KeyValueEqual &equal_func) const
   {
      size_type bucket_n1, bucket_n2, count;
      this->priv_equal_range(key, hash_func, equal_func, bucket_n1, bucket_n2, count);
      return count;
   }

   //! <b>Effects</b>: Finds an iterator to the first element is equal to
   //!   "value" or end() if that element does not exist.
   //!
   //! <b>Complexity</b>: Average case O(1), worst case O(this->size()).
   //! 
   //! <b>Throws</b>: If the internal hasher or the equality functor throws.
   iterator find(const_reference value)
   {  return this->find(value, this->priv_hasher(), this->priv_equal());   }

   //! <b>Requires</b>: "hash_func" must be a hash function that induces 
   //!   the same hash values as the stored hasher. The difference is that
   //!   "hash_func" hashes the given key instead of the value_type.
   //!
   //!   "equal_func" must be a equality function that induces 
   //!   the same equality as key_equal. The difference is that
   //!   "equal_func" compares an arbitrary key with the contained values.
   //!
   //! <b>Effects</b>: Finds an iterator to the first element whose key is 
   //!   "key" according to the given hash and equality functor or end() if
   //!   that element does not exist.
   //!
   //! <b>Complexity</b>: Average case O(1), worst case O(this->size()).
   //! 
   //! <b>Throws</b>: If hash_func or equal_func throw.
   //!
   //! <b>Note</b>: This function is used when constructing a value_type
   //!   is expensive and the value_type can be compared with a cheaper
   //!   key type. Usually this key is part of the value_type.
   template<class KeyType, class KeyHasher, class KeyValueEqual>
   iterator find(const KeyType &key, KeyHasher hash_func, KeyValueEqual equal_func)
   {
      size_type bucket_n;
      std::size_t hash;
      siterator prev;
      siterator local_it = this->priv_find(key, hash_func, equal_func, bucket_n, hash, prev);
      return iterator(local_it, this);
   }

   //! <b>Effects</b>: Finds a const_iterator to the first element whose key is 
   //!   "key" or end() if that element does not exist.
   //! 
   //! <b>Complexity</b>: Average case O(1), worst case O(this->size()).
   //! 
   //! <b>Throws</b>: If the internal hasher or the equality functor throws.
   const_iterator find(const_reference value) const
   {  return this->find(value, this->priv_hasher(), this->priv_equal());   }

   //! <b>Requires</b>: "hash_func" must be a hash function that induces 
   //!   the same hash values as the stored hasher. The difference is that
   //!   "hash_func" hashes the given key instead of the value_type.
   //!
   //!   "equal_func" must be a equality function that induces 
   //!   the same equality as key_equal. The difference is that
   //!   "equal_func" compares an arbitrary key with the contained values.
   //!
   //! <b>Effects</b>: Finds an iterator to the first element whose key is 
   //!   "key" according to the given hasher and equality functor or end() if
   //!   that element does not exist.
   //! 
   //! <b>Complexity</b>: Average case O(1), worst case O(this->size()).
   //! 
   //! <b>Throws</b>: If hash_func or equal_func throw.
   //!
   //! <b>Note</b>: This function is used when constructing a value_type
   //!   is expensive and the value_type can be compared with a cheaper
   //!   key type. Usually this key is part of the value_type.
   template<class KeyType, class KeyHasher, class KeyValueEqual>
   const_iterator find
      (const KeyType &key, KeyHasher hash_func, KeyValueEqual equal_func) const
   {
      size_type bucket_n;
      std::size_t hash_value;
      siterator prev;
      siterator sit = this->priv_find(key, hash_func, equal_func, bucket_n, hash_value, prev);
      return const_iterator(sit, this);
   }

   //! <b>Effects</b>: Returns a range containing all elements with values equivalent
   //!   to value. Returns std::make_pair(this->end(), this->end()) if no such 
   //!   elements exist.
   //! 
   //! <b>Complexity</b>: Average case O(this->count(value)). Worst case O(this->size()).
   //! 
   //! <b>Throws</b>: If the internal hasher or the equality functor throws.
   std::pair<iterator,iterator> equal_range(const_reference value)
   {  return this->equal_range(value, this->priv_hasher(), this->priv_equal());  }

   //! <b>Requires</b>: "hash_func" must be a hash function that induces 
   //!   the same hash values as the stored hasher. The difference is that
   //!   "hash_func" hashes the given key instead of the value_type.
   //!
   //!   "equal_func" must be a equality function that induces 
   //!   the same equality as key_equal. The difference is that
   //!   "equal_func" compares an arbitrary key with the contained values.
   //!
   //! <b>Effects</b>: Returns a range containing all elements with equivalent
   //!   keys. Returns std::make_pair(this->end(), this->end()) if no such 
   //!   elements exist.
   //! 
   //! <b>Complexity</b>: Average case O(this->count(key, hash_func, equal_func)).
   //!   Worst case O(this->size()).
   //! 
   //! <b>Throws</b>: If hash_func or the equal_func throw.
   //!
   //! <b>Note</b>: This function is used when constructing a value_type
   //!   is expensive and the value_type can be compared with a cheaper
   //!   key type. Usually this key is part of the value_type.
   template<class KeyType, class KeyHasher, class KeyValueEqual>
   std::pair<iterator,iterator> equal_range
      (const KeyType &key, KeyHasher hash_func, KeyValueEqual equal_func)
   {
      size_type bucket_n1, bucket_n2, count;
      std::pair<siterator, siterator> ret = this->priv_equal_range
         (key, hash_func, equal_func, bucket_n1, bucket_n2, count);
      return std::pair<iterator, iterator>
         (iterator(ret.first, this), iterator(ret.second, this));
   }

   //! <b>Effects</b>: Returns a range containing all elements with values equivalent
   //!   to value. Returns std::make_pair(this->end(), this->end()) if no such 
   //!   elements exist.
   //! 
   //! <b>Complexity</b>: Average case O(this->count(value)). Worst case O(this->size()).
   //! 
   //! <b>Throws</b>: If the internal hasher or the equality functor throws.
   std::pair<const_iterator, const_iterator>
      equal_range(const_reference value) const
   {  return this->equal_range(value, this->priv_hasher(), this->priv_equal());  }

   //! <b>Requires</b>: "hash_func" must be a hash function that induces 
   //!   the same hash values as the stored hasher. The difference is that
   //!   "hash_func" hashes the given key instead of the value_type.
   //!
   //!   "equal_func" must be a equality function that induces 
   //!   the same equality as key_equal. The difference is that
   //!   "equal_func" compares an arbitrary key with the contained values.
   //!
   //! <b>Effects</b>: Returns a range containing all elements with equivalent
   //!   keys. Returns std::make_pair(this->end(), this->end()) if no such 
   //!   elements exist.
   //! 
   //! <b>Complexity</b>: Average case O(this->count(key, hash_func, equal_func)).
   //!   Worst case O(this->size()).
   //! 
   //! <b>Throws</b>: If the hasher or equal_func throw.
   //!
   //! <b>Note</b>: This function is used when constructing a value_type
   //!   is expensive and the value_type can be compared with a cheaper
   //!   key type. Usually this key is part of the value_type.
   template<class KeyType, class KeyHasher, class KeyValueEqual>
   std::pair<const_iterator,const_iterator> equal_range
      (const KeyType &key, KeyHasher hash_func, KeyValueEqual equal_func) const
   {
      size_type bucket_n1, bucket_n2, count;
      std::pair<siterator, siterator> ret =
         this->priv_equal_range(key, hash_func, equal_func, bucket_n1, bucket_n2, count);
      return std::pair<const_iterator, const_iterator>
         (const_iterator(ret.first, this), const_iterator(ret.second, this));
   }

   //! <b>Requires</b>: value must be an lvalue and shall be in a unordered_set of
   //!   appropriate type. Otherwise the behavior is undefined.
   //! 
   //! <b>Effects</b>: Returns: a valid iterator belonging to the unordered_set
   //!   that points to the value
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: If the internal hash function throws.
   iterator iterator_to(reference value)
   {
      return iterator(bucket_type::s_iterator_to(priv_value_to_node(value)), this);
   }

   //! <b>Requires</b>: value must be an lvalue and shall be in a unordered_set of
   //!   appropriate type. Otherwise the behavior is undefined.
   //! 
   //! <b>Effects</b>: Returns: a valid const_iterator belonging to the
   //!   unordered_set that points to the value
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: If the internal hash function throws.
   const_iterator iterator_to(const_reference value) const
   {
      return const_iterator(bucket_type::s_iterator_to(priv_value_to_node(const_cast<reference>(value))), this);
   }

   //! <b>Requires</b>: value must be an lvalue and shall be in a unordered_set of
   //!   appropriate type. Otherwise the behavior is undefined.
   //! 
   //! <b>Effects</b>: Returns: a valid local_iterator belonging to the unordered_set
   //!   that points to the value
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: Nothing.
   //! 
   //! <b>Note</b>: This static function is available only if the <i>value traits</i>
   //!   is stateless.
   static local_iterator s_local_iterator_to(reference value)
   {
      BOOST_STATIC_ASSERT((!stateful_value_traits));
      siterator sit = bucket_type::s_iterator_to(((hashtable_impl*)0)->priv_value_to_node(value));
      return local_iterator(sit, (hashtable_impl*)0);  
   }

   //! <b>Requires</b>: value must be an lvalue and shall be in a unordered_set of
   //!   appropriate type. Otherwise the behavior is undefined.
   //! 
   //! <b>Effects</b>: Returns: a valid const_local_iterator belonging to
   //!   the unordered_set that points to the value
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: Nothing.
   //! 
   //! <b>Note</b>: This static function is available only if the <i>value traits</i>
   //!   is stateless.
   static const_local_iterator s_local_iterator_to(const_reference value)
   {
      BOOST_STATIC_ASSERT((!stateful_value_traits));
      siterator sit = bucket_type::s_iterator_to(((hashtable_impl*)0)->priv_value_to_node(const_cast<value_type&>(value)));
      return const_local_iterator(sit, (hashtable_impl*)0);  
   }

   //! <b>Requires</b>: value must be an lvalue and shall be in a unordered_set of
   //!   appropriate type. Otherwise the behavior is undefined.
   //! 
   //! <b>Effects</b>: Returns: a valid local_iterator belonging to the unordered_set
   //!   that points to the value
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: Nothing.
   local_iterator local_iterator_to(reference value)
   {
      siterator sit = bucket_type::s_iterator_to(this->priv_value_to_node(value));
      return local_iterator(sit, this);  
   }

   //! <b>Requires</b>: value must be an lvalue and shall be in a unordered_set of
   //!   appropriate type. Otherwise the behavior is undefined.
   //! 
   //! <b>Effects</b>: Returns: a valid const_local_iterator belonging to
   //!   the unordered_set that points to the value
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: Nothing.
   const_local_iterator local_iterator_to(const_reference value) const
   {
      siterator sit = bucket_type::s_iterator_to
         (const_cast<node &>(this->priv_value_to_node(value)));
      return const_local_iterator(sit, this);  
   }

   //! <b>Effects</b>: Returns the number of buckets passed in the constructor
   //!   or the last rehash function.
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: Nothing.
   size_type bucket_count() const
   {  return this->priv_buckets_len();   }

   //! <b>Requires</b>: n is in the range [0, this->bucket_count()).
   //!
   //! <b>Effects</b>: Returns the number of elements in the nth bucket.
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: Nothing.
   size_type bucket_size(size_type n) const
   {  return this->priv_buckets()[n].size();   }

   //! <b>Effects</b>: Returns the index of the bucket in which elements
   //!   with keys equivalent to k would be found, if any such element existed.
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: If the hash functor throws.
   //!
   //! <b>Note</b>: the return value is in the range [0, this->bucket_count()).
   size_type bucket(const key_type& k)  const
   {  return this->bucket(k, this->priv_hasher());   }

   //! <b>Requires</b>: "hash_func" must be a hash function that induces 
   //!   the same hash values as the stored hasher. The difference is that
   //!   "hash_func" hashes the given key instead of the value_type.
   //!
   //! <b>Effects</b>: Returns the index of the bucket in which elements
   //!   with keys equivalent to k would be found, if any such element existed.
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: If hash_func throws.
   //!
   //! <b>Note</b>: the return value is in the range [0, this->bucket_count()).
   template<class KeyType, class KeyHasher>
   size_type bucket(const KeyType& k, const KeyHasher &hash_func)  const
   {  return priv_hash_to_bucket(hash_func(k));   }

   //! <b>Effects</b>: Returns the bucket array pointer passed in the constructor
   //!   or the last rehash function.
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: Nothing.
   bucket_ptr bucket_pointer() const
   {  return this->priv_buckets();   }

   //! <b>Requires</b>: n is in the range [0, this->bucket_count()).
   //!
   //! <b>Effects</b>: Returns a local_iterator pointing to the beginning
   //!   of the sequence stored in the bucket n.
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: Nothing.
   //! 
   //! <b>Note</b>:  [this->begin(n), this->end(n)) is a valid range
   //!   containing all of the elements in the nth bucket. 
   local_iterator begin(size_type n)
   {  return local_iterator(this->priv_buckets()[n].begin(), this);  }

   //! <b>Requires</b>: n is in the range [0, this->bucket_count()).
   //!
   //! <b>Effects</b>: Returns a const_local_iterator pointing to the beginning
   //!   of the sequence stored in the bucket n.
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: Nothing.
   //! 
   //! <b>Note</b>:  [this->begin(n), this->end(n)) is a valid range
   //!   containing all of the elements in the nth bucket. 
   const_local_iterator begin(size_type n) const
   {  return this->cbegin(n);  }

   //! <b>Requires</b>: n is in the range [0, this->bucket_count()).
   //!
   //! <b>Effects</b>: Returns a const_local_iterator pointing to the beginning
   //!   of the sequence stored in the bucket n.
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: Nothing.
   //! 
   //! <b>Note</b>:  [this->begin(n), this->end(n)) is a valid range
   //!   containing all of the elements in the nth bucket. 
   const_local_iterator cbegin(size_type n) const
   {
      siterator sit = const_cast<bucket_type&>(this->priv_buckets()[n]).begin();
      return const_local_iterator(sit, this);
   }

   //! <b>Requires</b>: n is in the range [0, this->bucket_count()).
   //!
   //! <b>Effects</b>: Returns a local_iterator pointing to the end
   //!   of the sequence stored in the bucket n.
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: Nothing.
   //! 
   //! <b>Note</b>:  [this->begin(n), this->end(n)) is a valid range
   //!   containing all of the elements in the nth bucket. 
   local_iterator end(size_type n)
   {  return local_iterator(this->priv_buckets()[n].end(), this);  }

   //! <b>Requires</b>: n is in the range [0, this->bucket_count()).
   //!
   //! <b>Effects</b>: Returns a const_local_iterator pointing to the end
   //!   of the sequence stored in the bucket n.
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: Nothing.
   //! 
   //! <b>Note</b>:  [this->begin(n), this->end(n)) is a valid range
   //!   containing all of the elements in the nth bucket.
   const_local_iterator end(size_type n) const
   {  return this->cend(n);  }

   //! <b>Requires</b>: n is in the range [0, this->bucket_count()).
   //!
   //! <b>Effects</b>: Returns a const_local_iterator pointing to the end
   //!   of the sequence stored in the bucket n.
   //! 
   //! <b>Complexity</b>: Constant.
   //! 
   //! <b>Throws</b>: Nothing.
   //! 
   //! <b>Note</b>:  [this->begin(n), this->end(n)) is a valid range
   //!   containing all of the elements in the nth bucket. 
   const_local_iterator cend(size_type n) const
   {  return const_local_iterator(const_cast<bucket_type&>(this->priv_buckets()[n]).end(), this);  }

   //! <b>Requires</b>: new_buckets must be a pointer to a new bucket array
   //!   or the same as the old bucket array. new_size is the length of the
   //!   the array pointed by new_buckets. If new_buckets == this->bucket_pointer()
   //!   n can be bigger or smaller than this->bucket_count().
   //!   'new_bucket_traits' copy constructor should not throw.
   //!
   //! <b>Effects</b>: Updates the internal reference with the new bucket erases
   //!   the values from the old bucket and inserts then in the new one.
   //!   Bucket traits hold by *this is assigned from new_bucket_traits.
   //!   If the container is configured as incremental<>, the split bucket is set
   //!   to the new bucket_len(). 
   //!
   //!   If store_hash option is true, this method does not use the hash function.
   //! 
   //! <b>Complexity</b>: Average case linear in this->size(), worst case quadratic.
   //! 
   //! <b>Throws</b>: If the hasher functor throws. Basic guarantee.
   void rehash(const bucket_traits &new_bucket_traits)
   {
      bucket_ptr new_buckets     = new_bucket_traits.bucket_begin();
      size_type  new_buckets_len = new_bucket_traits.bucket_count();
      bucket_ptr old_buckets     = this->priv_buckets();
      size_type  old_buckets_len = this->priv_buckets_len();

      //Check power of two bucket array if the option is activated      
      BOOST_INTRUSIVE_INVARIANT_ASSERT
      (!power_2_buckets || (0 == (new_buckets_len & (new_buckets_len-1u))));

      size_type n = priv_get_cache_bucket_num();
      const bool same_buffer = old_buckets == new_buckets;
      //If the new bucket length is a common factor
      //of the old one we can avoid hash calculations.
      const bool fast_shrink = (!incremental) && (old_buckets_len > new_buckets_len) && 
         (power_2_buckets ||(old_buckets_len % new_buckets_len) == 0);
      //If we are shrinking the same bucket array and it's
      //is a fast shrink, just rehash the last nodes
      size_type new_first_bucket_num = new_buckets_len;
      if(same_buffer && fast_shrink && (n < new_buckets_len)){
         n = new_buckets_len;
         new_first_bucket_num = priv_get_cache_bucket_num();
      }

      //Anti-exception stuff: they destroy the elements if something goes wrong.
      //If the source and destination buckets are the same, the second rollback function
      //is harmless, because all elements have been already unlinked and destroyed
      typedef detail::init_disposer<node_algorithms> NodeDisposer;
      NodeDisposer node_disp;
      detail::exception_array_disposer<bucket_type, NodeDisposer>
         rollback1(new_buckets[0], node_disp, new_buckets_len);
      detail::exception_array_disposer<bucket_type, NodeDisposer>
         rollback2(old_buckets[0], node_disp, old_buckets_len);

      //Put size in a safe value for rollback exception
      size_type size_backup = this->priv_size_traits().get_size();
      this->priv_size_traits().set_size(0);
      //Put cache to safe position
      priv_initialize_cache();
      priv_insertion_update_cache(size_type(0u));

      //Iterate through nodes
      for(; n < old_buckets_len; ++n){
         bucket_type &old_bucket = old_buckets[n];

         if(!fast_shrink){
            siterator before_i(old_bucket.before_begin());
            siterator end(old_bucket.end());
            siterator i(old_bucket.begin());
            for(;i != end; ++i){
               const value_type &v = priv_value_from_slist_node(i.pointed_node());
               const std::size_t hash_value = this->priv_stored_or_compute_hash(v, store_hash_t());
               const size_type new_n = priv_hash_to_bucket(hash_value, new_buckets_len, new_buckets_len);
               if(cache_begin && new_n < new_first_bucket_num)
                  new_first_bucket_num = new_n;
               siterator last = bucket_type::s_iterator_to
                  (*group_functions_t::priv_get_last_in_group
                     (dcast_bucket_ptr(i.pointed_node()), optimize_multikey_t()));
               if(same_buffer && new_n == n){
                  before_i = last;
               }
               else{
                  bucket_type &new_b = new_buckets[new_n];
                  new_b.splice_after(new_b.before_begin(), old_bucket, before_i, last);
               }
               i = before_i;
            }
         }
         else{
            const size_type new_n = priv_hash_to_bucket(n, new_buckets_len, new_buckets_len);
            if(cache_begin && new_n < new_first_bucket_num)
               new_first_bucket_num = new_n;
            bucket_type &new_b = new_buckets[new_n];
            if(!old_bucket.empty()){
               new_b.splice_after( new_b.before_begin()
                                 , old_bucket
                                 , old_bucket.before_begin()
                                 , priv_get_last(old_bucket));
            }
         }
      }

      this->priv_size_traits().set_size(size_backup);
      this->priv_split_traits().set_size(new_buckets_len);
      this->priv_real_bucket_traits() = new_bucket_traits;
      priv_initialize_cache();
      priv_insertion_update_cache(new_first_bucket_num);
      rollback1.release();
      rollback2.release();
   }

   //! <b>Requires</b>:
   //!
   //! <b>Effects</b>: 
   //! 
   //! <b>Complexity</b>: 
   //! 
   //! <b>Throws</b>: 
   //!
   //! <b>Note</b>: this method is only available if incremental<true> option is activated.
   bool incremental_rehash(bool grow = true)
   {
      //This function is only available for containers with incremental hashing
      BOOST_STATIC_ASSERT(( incremental && power_2_buckets ));
      size_type split_idx = priv_split_traits().get_size();
      size_type bucket_len = priv_buckets_len();

      if(grow){
         //Test if the split variable can be changed
         if(split_idx >= bucket_len)
            return false;

         size_type bucket_len = priv_buckets_len();
         size_type bucket_to_rehash = split_idx - bucket_len/2;
         bucket_type &old_bucket = this->priv_buckets()[bucket_to_rehash];
         siterator before_i(old_bucket.before_begin());
         siterator end(old_bucket.end());
         siterator i(old_bucket.begin());
         priv_split_traits().increment();

         //Anti-exception stuff: if an exception is thrown while
         //moving elements from old_bucket to the target bucket, all moved
         //elements are moved back to the original one.
         detail::incremental_rehash_rollback<bucket_type, split_traits> rollback
            ( this->priv_buckets()[split_idx], old_bucket, priv_split_traits());
         for(;i != end; ++i){
            const value_type &v = priv_value_from_slist_node(i.pointed_node());
            const std::size_t hash_value = this->priv_stored_or_compute_hash(v, store_hash_t());
            const size_type new_n = priv_hash_to_bucket(hash_value);
            siterator last = bucket_type::s_iterator_to
               (*group_functions_t::priv_get_last_in_group
                  (dcast_bucket_ptr(i.pointed_node()), optimize_multikey_t()));
            if(new_n == bucket_to_rehash){
               before_i = last;
            }
            else{
               bucket_type &new_b = this->priv_buckets()[new_n];
               new_b.splice_after(new_b.before_begin(), old_bucket, before_i, last);
            }
            i = before_i;
         }
         rollback.release();
         priv_erasure_update_cache();
         return true;
      }
      else{
         //Test if the split variable can be changed
         if(split_idx <= bucket_len/2)
            return false;
         const size_type target_bucket_num = split_idx - 1 - bucket_len/2;
         bucket_type &target_bucket = this->priv_buckets()[target_bucket_num];
         bucket_type &source_bucket = this->priv_buckets()[split_idx-1];
         target_bucket.splice_after(target_bucket.cbefore_begin(), source_bucket);
         priv_split_traits().decrement();
         priv_insertion_update_cache(target_bucket_num);
         return true;
      }
   }

   //! <b>Effects</b>: If new_bucket_traits.bucket_count() is not
   //!   this->bucket_count()/2 or this->bucket_count()*2, or 
   //!   this->split_bucket() != new_bucket_traits.bucket_count() returns false
   //!   and does nothing.
   //!
   //!   Otherwise, copy assigns new_bucket_traits to the internal bucket_traits
   //!   and transfers all the objects from old buckets to the new ones.
   //!   
   //! <b>Complexity</b>: Linear to size().
   //! 
   //! <b>Throws</b>: Nothing
   //!
   //! <b>Note</b>: this method is only available if incremental<true> option is activated.
   bool incremental_rehash(const bucket_traits &new_bucket_traits)
   {
      //This function is only available for containers with incremental hashing
      BOOST_STATIC_ASSERT(( incremental && power_2_buckets ));
      size_type new_bucket_traits_size = new_bucket_traits.bucket_count();
      size_type cur_bucket_traits      = this->priv_buckets_len();
      if(new_bucket_traits_size/2 != cur_bucket_traits && new_bucket_traits_size != cur_bucket_traits/2){
         return false;
      }

      const size_type split_idx = this->split_count();

      if(new_bucket_traits_size/2 == cur_bucket_traits){
         //Test if the split variable can be changed
         if(!(split_idx >= cur_bucket_traits))
            return false;
      }
      else{
         //Test if the split variable can be changed
         if(!(split_idx <= cur_bucket_traits/2))
            return false;
      }

      const size_type ini_n = priv_get_cache_bucket_num();
      const bucket_ptr old_buckets = this->priv_buckets();
      this->priv_real_bucket_traits() = new_bucket_traits;
      if(new_bucket_traits.bucket_begin() != old_buckets){
         for(size_type n = ini_n; n < split_idx; ++n){
            bucket_type &new_bucket = new_bucket_traits.bucket_begin()[n];
            bucket_type &old_bucket = old_buckets[n];
            new_bucket.splice_after(new_bucket.cbefore_begin(), old_bucket);
         }
         //Put cache to safe position
         priv_initialize_cache();
         priv_insertion_update_cache(ini_n);
      }
      return true;
   }

   //! <b>Requires</b>:
   //!
   //! <b>Effects</b>: 
   //! 
   //! <b>Complexity</b>: 
   //! 
   //! <b>Throws</b>: 
   size_type split_count() const
   {
      //This function is only available if incremental hashing is activated
      BOOST_STATIC_ASSERT(( incremental && power_2_buckets ));
      return this->priv_split_traits().get_size();
   }

   //! <b>Effects</b>: Returns the nearest new bucket count optimized for
   //!   the container that is bigger than n. This suggestion can be used
   //!   to create bucket arrays with a size that will usually improve
   //!   container's performance. If such value does not exist, the 
   //!   higher possible value is returned.
   //! 
   //! <b>Complexity</b>: Amortized constant time.
   //! 
   //! <b>Throws</b>: Nothing.
   static size_type suggested_upper_bucket_count(size_type n)
   {
      const std::size_t *primes     = &detail::prime_list_holder<0>::prime_list[0];
      const std::size_t *primes_end = primes + detail::prime_list_holder<0>::prime_list_size;
      size_type const* bound = std::lower_bound(primes, primes_end, n);
      if(bound == primes_end)
            bound--;
      return size_type(*bound);
   }

   //! <b>Effects</b>: Returns the nearest new bucket count optimized for
   //!   the container that is smaller than n. This suggestion can be used
   //!   to create bucket arrays with a size that will usually improve
   //!   container's performance. If such value does not exist, the 
   //!   lower possible value is returned.
   //! 
   //! <b>Complexity</b>: Amortized constant time.
   //! 
   //! <b>Throws</b>: Nothing.
   static size_type suggested_lower_bucket_count(size_type n)
   {
      const std::size_t *primes     = &detail::prime_list_holder<0>::prime_list[0];
      const std::size_t *primes_end = primes + detail::prime_list_holder<0>::prime_list_size;
      size_type const* bound = std::upper_bound(primes, primes_end, n);
      if(bound != primes_end)
            bound--;
      return size_type(*bound);
   }

   /// @cond
   private:

   std::size_t priv_hash_to_bucket(std::size_t hash_value) const
   {  return priv_hash_to_bucket(hash_value, this->priv_real_bucket_traits().bucket_count(), priv_split_traits().get_size()); }

   std::size_t priv_hash_to_bucket(std::size_t hash_value, std::size_t bucket_len, std::size_t split) const
   {
      std::size_t bucket_number = priv_hash_to_bucket_impl(hash_value, bucket_len, power_2_buckets_t());
      if(incremental)
         if(bucket_number >= split)
            bucket_number -= bucket_len/2;
      return bucket_number;
   }

   std::size_t priv_hash_to_bucket_impl(std::size_t hash_value, std::size_t bucket_len, detail::bool_<false>) const
   {  return hash_value % bucket_len;  }

   std::size_t priv_hash_to_bucket_impl(std::size_t hash_value, std::size_t bucket_len, detail::bool_<true>) const
   {  return hash_value & (bucket_len - 1);   }

   const key_equal &priv_equal() const
   {  return static_cast<const key_equal&>(this->data_.internal_.bucket_hash_equal_.get());  }

   key_equal &priv_equal()
   {  return static_cast<key_equal&>(this->data_.internal_.bucket_hash_equal_.get());  }

   value_type &priv_value_from_slist_node(slist_node_ptr n)
   {  return *this->get_real_value_traits().to_value_ptr(dcast_bucket_ptr(n)); }

   const value_type &priv_value_from_slist_node(slist_node_ptr n) const
   {  return *this->get_real_value_traits().to_value_ptr(dcast_bucket_ptr(n)); }

   const real_bucket_traits &priv_real_bucket_traits(detail::bool_<false>) const
   {  return this->data_.internal_.bucket_hash_equal_.bucket_hash.bucket_plus_size_.bucket_traits_;  }

   const real_bucket_traits &priv_real_bucket_traits(detail::bool_<true>) const
   {  return this->data_.internal_.bucket_hash_equal_.bucket_hash.bucket_plus_size_.bucket_traits_.get_bucket_traits(*this);  }

   real_bucket_traits &priv_real_bucket_traits(detail::bool_<false>)
   {  return this->data_.internal_.bucket_hash_equal_.bucket_hash.bucket_plus_size_.bucket_traits_;  }

   real_bucket_traits &priv_real_bucket_traits(detail::bool_<true>)
   {  return this->data_.internal_.bucket_hash_equal_.bucket_hash.bucket_plus_size_.bucket_traits_.get_bucket_traits(*this);  }

   const real_bucket_traits &priv_real_bucket_traits() const
   {  return this->priv_real_bucket_traits(detail::bool_<external_bucket_traits>());  }

   real_bucket_traits &priv_real_bucket_traits()
   {  return this->priv_real_bucket_traits(detail::bool_<external_bucket_traits>());  }

   const hasher &priv_hasher() const
   {  return static_cast<const hasher&>(this->data_.internal_.bucket_hash_equal_.bucket_hash.get());  }

   hasher &priv_hasher()
   {  return static_cast<hasher&>(this->data_.internal_.bucket_hash_equal_.bucket_hash.get());  }

   bucket_ptr priv_buckets() const
   {  return this->priv_real_bucket_traits().bucket_begin();  }

   size_type priv_buckets_len() const
   {  return this->priv_real_bucket_traits().bucket_count();  }

   static node_ptr uncast(const_node_ptr ptr)
   {  return node_ptr(const_cast<node*>(detail::get_pointer(ptr)));  }

   node &priv_value_to_node(value_type &v)
   {  return *this->get_real_value_traits().to_node_ptr(v);  }

   const node &priv_value_to_node(const value_type &v) const
   {  return *this->get_real_value_traits().to_node_ptr(v);  }

   size_traits &priv_size_traits()
   {  return this->data_.internal_.bucket_hash_equal_.bucket_hash.bucket_plus_size_;  }

   const size_traits &priv_size_traits() const
   {  return this->data_.internal_.bucket_hash_equal_.bucket_hash.bucket_plus_size_;  }

   split_traits &priv_split_traits()
   {  return this->data_.internal_;  }

   const split_traits &priv_split_traits() const
   {  return this->data_.internal_;  }

   template<class Disposer>
   void priv_erase_range_impl
      (size_type bucket_num, siterator before_first_it, siterator end, Disposer disposer, size_type &num_erased)
   {
      const bucket_ptr buckets = priv_buckets();
      bucket_type &b = buckets[bucket_num];

      if(before_first_it == b.before_begin() && end == b.end()){
         priv_erase_range_impl(bucket_num, 1, disposer, num_erased);
      }
      else{
         num_erased = 0;
         siterator to_erase(before_first_it);
         ++to_erase;
         slist_node_ptr end_ptr = end.pointed_node();
         while(to_erase != end){
            group_functions_t::priv_erase_from_group(end_ptr, dcast_bucket_ptr(to_erase.pointed_node()), optimize_multikey_t());
            to_erase = b.erase_after_and_dispose(before_first_it, make_node_disposer(disposer));
            ++num_erased;
         }
         this->priv_size_traits().set_size(this->priv_size_traits().get_size()-num_erased);
      }
   }

   template<class Disposer>
   void priv_erase_range_impl
      (size_type first_bucket_num, size_type num_buckets, Disposer disposer, size_type &num_erased)
   {
      //Now fully clear the intermediate buckets
      const bucket_ptr buckets = priv_buckets();
      num_erased = 0;
      for(size_type i = first_bucket_num; i < (num_buckets + first_bucket_num); ++i){
         bucket_type &b = buckets[i];
         siterator b_begin(b.before_begin());
         siterator nxt(b_begin);
         ++nxt;
         siterator end(b.end());
         while(nxt != end){
            priv_init_group(nxt.pointed_node(), optimize_multikey_t());
            nxt = b.erase_after_and_dispose
               (b_begin, make_node_disposer(disposer));
            this->priv_size_traits().decrement();
            ++num_erased;
         }
      }
   }

   template<class Disposer>
   void priv_erase_range( siterator before_first_it,  size_type first_bucket
                        , siterator last_it,          size_type last_bucket
                        , Disposer disposer)
   {
      size_type num_erased;
      if (first_bucket == last_bucket){
         priv_erase_range_impl(first_bucket, before_first_it, last_it, disposer, num_erased);
      }
      else {
         bucket_type *b = (&this->priv_buckets()[0]);
         priv_erase_range_impl(first_bucket, before_first_it, b[first_bucket].end(), disposer, num_erased);
         if(size_type n = (last_bucket - first_bucket - 1))
            priv_erase_range_impl(first_bucket + 1, n, disposer, num_erased);
         priv_erase_range_impl(last_bucket, b[last_bucket].before_begin(), last_it, disposer, num_erased);
      }
   }

   static node_ptr dcast_bucket_ptr(typename slist_impl::node_ptr p)
   {  return node_ptr(&static_cast<node&>(*p));   }

   std::size_t priv_stored_or_compute_hash(const value_type &v, detail::true_) const
   {  return node_traits::get_hash(this->get_real_value_traits().to_node_ptr(v));  }

   std::size_t priv_stored_or_compute_hash(const value_type &v, detail::false_) const
   {  return priv_hasher()(v);   }

   std::size_t priv_stored_hash(slist_node_ptr n, detail::true_) const
   {  return node_traits::get_hash(dcast_bucket_ptr(n));  }

   std::size_t priv_stored_hash(slist_node_ptr, detail::false_) const
   {
      //This code should never be reached!
      BOOST_INTRUSIVE_INVARIANT_ASSERT(0);
      return 0;
   }

   static void priv_store_hash(node_ptr p, std::size_t h, detail::true_)
   {  return node_traits::set_hash(p, h); }

   static void priv_store_hash(node_ptr, std::size_t, detail::false_)
   {}

   static void priv_clear_group_nodes(bucket_type &b, detail::true_)
   {
      siterator it(b.begin()), itend(b.end());
      while(it != itend){
         node_ptr to_erase(dcast_bucket_ptr(it.pointed_node()));
         ++it;
         group_algorithms::init(to_erase);
      }
   }

   static void priv_clear_group_nodes(bucket_type &, detail::false_)
   {}

   std::size_t priv_get_bucket_num(siterator it)
   {  return priv_get_bucket_num_hash_dispatch(it, store_hash_t());  }

   std::size_t priv_get_bucket_num_hash_dispatch(siterator it, detail::true_)
   {
      return this->priv_hash_to_bucket
         (this->priv_stored_hash(it.pointed_node(), store_hash_t()));
   }

   std::size_t priv_get_bucket_num_hash_dispatch(siterator it, detail::false_)
   {  return priv_get_bucket_num_no_hash_store(it, optimize_multikey_t());  }

   std::size_t priv_get_bucket_num_no_hash_store(siterator it, detail::true_)
   {
      bucket_ptr f(priv_buckets()), l(f + priv_buckets_len() - 1);
      slist_node_ptr bb = group_functions_t::priv_get_bucket_before_begin
         ( f->end().pointed_node()
         , l->end().pointed_node()
         , dcast_bucket_ptr(it.pointed_node()));
      //Now get the bucket_impl from the iterator
      const bucket_type &b = static_cast<const bucket_type&>
         (bucket_type::slist_type::container_from_end_iterator(bucket_type::s_iterator_to(*bb)));
      //Now just calculate the index b has in the bucket array
      return static_cast<size_type>(&b - &*f);
   }

   std::size_t priv_get_bucket_num_no_hash_store(siterator it, detail::false_)
   {
      bucket_ptr f(priv_buckets()), l(f + priv_buckets_len() - 1);
      slist_node_ptr first_ptr(f->cend().pointed_node())
                   , last_ptr(l->cend().pointed_node());

      //The end node is embedded in the singly linked list:
      //iterate until we reach it.
      while(!(first_ptr <= it.pointed_node() && it.pointed_node() <= last_ptr)){
         ++it;
      }
      //Now get the bucket_impl from the iterator
      const bucket_type &b = static_cast<const bucket_type&>
         (bucket_type::container_from_end_iterator(it));

      //Now just calculate the index b has in the bucket array
      return static_cast<std::size_t>(&b - &*f);
   }

   void priv_init_group(slist_node_ptr n, detail::true_)
   {  group_algorithms::init(dcast_bucket_ptr(n)); }

   void priv_init_group(slist_node_ptr, detail::false_)
   {}

   void priv_insert_in_group(node_ptr first_in_group, node_ptr n, detail::true_)
   {
      if(first_in_group){
         if(group_algorithms::unique(first_in_group))
            group_algorithms::link_after(first_in_group, n);
         else{
            group_algorithms::link_after(node_traits::get_next(first_in_group), n);
         }
      }
      else{
         group_algorithms::init_header(n);
      }
   }

   void priv_insert_in_group(node_ptr, node_ptr, detail::false_)
   {}

   siterator priv_get_previous
      (bucket_type &b, siterator i)
   {  return priv_get_previous(b, i, optimize_multikey_t());   }

   siterator priv_get_previous
      (bucket_type &b, siterator i, detail::true_)
   {
      node_ptr elem(dcast_bucket_ptr(i.pointed_node()));
      node_ptr prev_in_group(group_traits::get_next(elem));
      bool first_in_group = node_traits::get_next(prev_in_group) != elem;
      typename bucket_type::node &n = first_in_group
         ? *group_functions_t::priv_get_prev_to_first_in_group(b.end().pointed_node(), elem)
         : *group_traits::get_next(elem)
         ;
      return bucket_type::s_iterator_to(n);
   }

   siterator priv_get_previous
      (bucket_type &b, siterator i, detail::false_)
   {  return b.previous(i);   }

   static siterator priv_get_last(bucket_type &b)
   {  return priv_get_last(b, optimize_multikey_t());  }

   static siterator priv_get_last(bucket_type &b, detail::true_)
   {
      //First find the last node of p's group.
      //This requires checking the first node of the next group or
      //the bucket node.
      slist_node_ptr end_ptr(b.end().pointed_node());
      node_ptr possible_end(node_traits::get_next( dcast_bucket_ptr(end_ptr)));
      node_ptr last_node_group(possible_end);

      while(end_ptr != possible_end){
         last_node_group   = group_traits::get_next(dcast_bucket_ptr(possible_end));
         possible_end      = node_traits::get_next(last_node_group);
      }
      return bucket_type::s_iterator_to(*last_node_group);
   }

   static siterator priv_get_last(bucket_type &b, detail::false_)
   {  return b.previous(b.end());   }

   siterator priv_get_previous_and_next_in_group
      (siterator i, node_ptr &nxt_in_group)
   {
      siterator prev;
      node_ptr elem(dcast_bucket_ptr(i.pointed_node()));
      bucket_ptr f(priv_buckets()), l(f + priv_buckets_len() - 1);

      slist_node_ptr first_end_ptr(f->cend().pointed_node());
      slist_node_ptr last_end_ptr (l->cend().pointed_node());

      node_ptr nxt(node_traits::get_next(elem));
      node_ptr prev_in_group(group_traits::get_next(elem));
      bool last_in_group = (first_end_ptr <= nxt && nxt <= last_end_ptr) ||
                            (group_traits::get_next(nxt) != elem);
      bool first_in_group = node_traits::get_next(prev_in_group) != elem;
      
      if(first_in_group){
         node_ptr start_pos;
         if(last_in_group){
            start_pos = elem;
            nxt_in_group = 0;
         }
         else{
            start_pos = prev_in_group;
            nxt_in_group = node_traits::get_next(elem);
         }
         slist_node_ptr bucket_node;
         if(store_hash){
            bucket_node = this->priv_buckets()
               [this->priv_hash_to_bucket
                  (this->priv_stored_hash(elem, store_hash_t()))
               ].before_begin().pointed_node();
         }
         else{
            bucket_node = group_functions_t::priv_get_bucket_before_begin
                  (first_end_ptr, last_end_ptr, start_pos);
         }
         prev = bucket_type::s_iterator_to
            (*group_functions_t::priv_get_prev_to_first_in_group(bucket_node, elem));
      }
      else{
         if(last_in_group){
            nxt_in_group = group_functions_t::priv_get_first_in_group_of_last_in_group(elem);
         }
         else{
            nxt_in_group = node_traits::get_next(elem);
         }
         prev = bucket_type::s_iterator_to(*group_traits::get_next(elem));
      }
      return prev;
   }

   template<class Disposer>
   void priv_erase(const_iterator i, Disposer disposer, detail::true_)
   {
      siterator elem(i.slist_it());
      node_ptr nxt_in_group;
      siterator prev = priv_get_previous_and_next_in_group(elem, nxt_in_group);
      bucket_type::s_erase_after_and_dispose(prev, make_node_disposer(disposer));
      if(nxt_in_group)
         group_algorithms::unlink_after(nxt_in_group);
      if(safemode_or_autounlink)
         group_algorithms::init(dcast_bucket_ptr(elem.pointed_node()));
   }

   template <class Disposer>
   void priv_erase(const_iterator i, Disposer disposer, detail::false_)
   {
      siterator to_erase(i.slist_it());
      bucket_type &b = this->priv_buckets()[this->priv_get_bucket_num(to_erase)];
      siterator prev(priv_get_previous(b, to_erase));
      b.erase_after_and_dispose(prev, make_node_disposer(disposer));
   }

   bucket_ptr priv_invalid_bucket() const
   {
      const real_bucket_traits &rbt = this->priv_real_bucket_traits();
      return rbt.bucket_begin() + rbt.bucket_count();
   }
   
   siterator priv_invalid_local_it() const
   {  return priv_invalid_bucket()->end();  }

   siterator priv_begin() const
   {  return priv_begin(cache_begin_t()); }

   siterator priv_begin(detail::bool_<false>) const
   {
      size_type n = 0;
      size_type buckets_len = this->priv_buckets_len();
      for (n = 0; n < buckets_len; ++n){
         bucket_type &b = this->priv_buckets()[n];
         if(!b.empty()){
            return b.begin();
         }
      }
      return priv_invalid_local_it();
   }

   siterator priv_begin(detail::bool_<true>) const
   {
      if(this->data_.internal_.bucket_hash_equal_.cached_begin_ == priv_invalid_bucket()){
         return priv_invalid_local_it();
      }
      else{
         return this->data_.internal_.bucket_hash_equal_.cached_begin_->begin();
      }
   }

   void priv_initialize_cache()
   {  priv_initialize_cache(cache_begin_t());   }

   void priv_initialize_cache(detail::bool_<true>)
   {  this->data_.internal_.bucket_hash_equal_.cached_begin_ = priv_invalid_bucket();  }

   void priv_initialize_cache(detail::bool_<false>)
   {}

   void priv_insertion_update_cache(size_type insertion_bucket)
   {  priv_insertion_update_cache(insertion_bucket, cache_begin_t()); }

   void priv_insertion_update_cache(size_type insertion_bucket, detail::bool_<true>)
   {
      bucket_ptr p = priv_buckets() + insertion_bucket;
      if(p < this->data_.internal_.bucket_hash_equal_.cached_begin_){
         this->data_.internal_.bucket_hash_equal_.cached_begin_ = p;
      }
   }

   void priv_insertion_update_cache(size_type, detail::bool_<false>)
   {}

   void priv_erasure_update_cache(size_type first_bucket, size_type last_bucket)
   {  priv_erasure_update_cache(first_bucket, last_bucket, cache_begin_t()); }

   void priv_erasure_update_cache(size_type first_bucket_num, size_type last_bucket_num, detail::bool_<true>)
   {
      //If the last bucket is the end, the cache must be updated
      //to the last position if all
      if(priv_get_cache_bucket_num() == first_bucket_num   &&
         priv_buckets()[first_bucket_num].empty()          ){
         priv_set_cache(priv_buckets() + last_bucket_num);
         priv_erasure_update_cache();
      }
   }

   void priv_erasure_update_cache(size_type, size_type, detail::bool_<false>)
   {}

   void priv_erasure_update_cache()
   {  priv_erasure_update_cache(cache_begin_t()); }

   void priv_erasure_update_cache(detail::bool_<true>)
   {
      if(constant_time_size && !size()){
         priv_initialize_cache();
      }
      else{
         size_type current_n = this->data_.internal_.bucket_hash_equal_.cached_begin_ - priv_buckets();
         for( const size_type num_buckets = this->priv_buckets_len()
            ; current_n < num_buckets
            ; ++current_n, ++this->data_.internal_.bucket_hash_equal_.cached_begin_){
            if(!this->data_.internal_.bucket_hash_equal_.cached_begin_->empty()){
               return;
            }
         }
         priv_initialize_cache();
      }
   }

   void priv_erasure_update_cache(detail::bool_<false>)
   {}

   void priv_swap_cache(detail::bool_<true>, hashtable_impl &other)
   {
      std::swap( this->data_.internal_.bucket_hash_equal_.cached_begin_
               , other.data_.internal_.bucket_hash_equal_.cached_begin_);
   }

   void priv_swap_cache(detail::bool_<false>, hashtable_impl &)
   {}

   bucket_ptr priv_get_cache()
   {  return priv_get_cache(cache_begin_t());   }

   bucket_ptr priv_get_cache(detail::bool_<true>)
   {  return this->data_.internal_.bucket_hash_equal_.cached_begin_;  }

   bucket_ptr priv_get_cache(detail::bool_<false>)
   {  return this->priv_buckets();  }

   void priv_set_cache(bucket_ptr p)
   {  priv_set_cache(p, cache_begin_t());   }

   void priv_set_cache(bucket_ptr p, detail::bool_<true>)
   {  this->data_.internal_.bucket_hash_equal_.cached_begin_ = p;  }

   void priv_set_cache(bucket_ptr, detail::bool_<false>)
   {}

   size_type priv_get_cache_bucket_num()
   {  return priv_get_cache_bucket_num(cache_begin_t());   }

   size_type priv_get_cache_bucket_num(detail::bool_<true>)
   {  return this->data_.internal_.bucket_hash_equal_.cached_begin_ - this->priv_buckets();  }

   size_type priv_get_cache_bucket_num(detail::bool_<false>)
   {  return 0u;  }

   void priv_clear_buckets()
   {
      this->priv_clear_buckets
         ( priv_get_cache()
         , this->priv_buckets_len() - (priv_get_cache() - priv_buckets()));
   }

   void priv_initialize_buckets()
   {  this->priv_clear_buckets(priv_buckets(), this->priv_buckets_len());  }

   void priv_clear_buckets(bucket_ptr buckets_ptr, size_type buckets_len)
   {
      for(; buckets_len--; ++buckets_ptr){
         if(safemode_or_autounlink){
            priv_clear_group_nodes(*buckets_ptr, optimize_multikey_t());
            buckets_ptr->clear_and_dispose(detail::init_disposer<node_algorithms>());
         }
         else{
            buckets_ptr->clear();
         }
      }
      priv_initialize_cache();
   }

   template<class KeyType, class KeyHasher, class KeyValueEqual>
   siterator priv_find
      ( const KeyType &key,  KeyHasher hash_func
      , KeyValueEqual equal_func, size_type &bucket_number, std::size_t &h, siterator &previt) const
   {
      h = hash_func(key);
      return priv_find_with_hash(key, equal_func, bucket_number, h, previt);
   }

   template<class KeyType, class KeyValueEqual>
   siterator priv_find_with_hash
      ( const KeyType &key, KeyValueEqual equal_func, size_type &bucket_number, const std::size_t h, siterator &previt) const
   {
      bucket_number = priv_hash_to_bucket(h);
      bucket_type &b = this->priv_buckets()[bucket_number];
      previt = b.before_begin();
      if(constant_time_size && this->empty()){
         return priv_invalid_local_it();
      }
      
      siterator it = previt;
      ++it;

      while(it != b.end()){
         const value_type &v = priv_value_from_slist_node(it.pointed_node());
         if(compare_hash){
            std::size_t vh = this->priv_stored_or_compute_hash(v, store_hash_t());
            if(h == vh && equal_func(key, v)){
               return it;
            }
         }
         else if(equal_func(key, v)){
            return it;
         }
         if(optimize_multikey){
            previt = bucket_type::s_iterator_to
               (*group_functions_t::priv_get_last_in_group
                  (dcast_bucket_ptr(it.pointed_node()), optimize_multikey_t()));
            it = previt;
         }
         else{
            previt = it;
         }
         ++it;
      }
      previt = b.before_begin();
      return priv_invalid_local_it();
   }

   iterator priv_insert_equal_with_hash(reference value, std::size_t hash_value)
   {
      size_type bucket_num;
      siterator prev;
      siterator it = this->priv_find_with_hash
         (value, this->priv_equal(), bucket_num, hash_value, prev);
      return priv_insert_equal_find(value, bucket_num, hash_value, it);
   }

   iterator priv_insert_equal_find(reference value, size_type bucket_num, std::size_t hash_value, siterator it)
   {
      bucket_type &b = this->priv_buckets()[bucket_num];
      bool found_equal = it != priv_invalid_local_it();
      if(!found_equal){
         it = b.before_begin();
      }
      //Now store hash if needed
      node_ptr n = node_ptr(&priv_value_to_node(value));
      this->priv_store_hash(n, hash_value, store_hash_t());
      //Checks for some modes
      if(safemode_or_autounlink)
         BOOST_INTRUSIVE_SAFE_HOOK_DEFAULT_ASSERT(node_algorithms::unique(n));
      //Shorcut for optimize_multikey cases
      if(optimize_multikey){
         node_ptr first_in_group = found_equal ?
            dcast_bucket_ptr(it.pointed_node()) : node_ptr(0);
         this->priv_insert_in_group(first_in_group, n, optimize_multikey_t());
      }
      //Update cache and increment size if needed
      priv_insertion_update_cache(bucket_num);
      this->priv_size_traits().increment();
      //Insert the element in the bucket after it
      return iterator(b.insert_after(it, *n), this);
   }

   template<class KeyType, class KeyHasher, class KeyValueEqual>
   std::pair<siterator, siterator> priv_equal_range
      ( const KeyType &key
      , KeyHasher hash_func
      , KeyValueEqual equal_func
      , size_type &bucket_number_first
      , size_type &bucket_number_second
      , size_type &count) const
   {
      std::size_t h;
      count = 0;
      siterator prev;
      //Let's see if the element is present
      std::pair<siterator, siterator> to_return
         ( priv_find(key, hash_func, equal_func, bucket_number_first, h, prev)
         , priv_invalid_local_it());
      if(to_return.first == to_return.second){
         bucket_number_second = bucket_number_first;
         return to_return;
      }
      //If it's present, find the first that it's not equal in
      //the same bucket
      bucket_type &b = this->priv_buckets()[bucket_number_first];
      siterator it = to_return.first;
      if(optimize_multikey){
         to_return.second = bucket_type::s_iterator_to
            (*node_traits::get_next(group_functions_t::priv_get_last_in_group
               (dcast_bucket_ptr(it.pointed_node()), optimize_multikey_t())));
         count = std::distance(it, to_return.second);
         if(to_return.second !=  b.end()){
            bucket_number_second = bucket_number_first;
            return to_return;
         }
      }
      else{
         ++count;
         ++it;
         while(it != b.end()){
            const value_type &v = priv_value_from_slist_node(it.pointed_node());
            if(compare_hash){
               std::size_t hv = this->priv_stored_or_compute_hash(v, store_hash_t());
               if(hv != h || !equal_func(key, v)){
                  to_return.second = it;
                  bucket_number_second = bucket_number_first;
                  return to_return;
               }
            }
            else if(!equal_func(key, v)){
               to_return.second = it;
               bucket_number_second = bucket_number_first;
               return to_return;
            }
            ++it;
            ++count;
         }
      }
   
      //If we reached the end, find the first, non-empty bucket
      for(bucket_number_second = bucket_number_first+1
         ; bucket_number_second != this->priv_buckets_len()
         ; ++bucket_number_second){
         bucket_type &b = this->priv_buckets()[bucket_number_second];
         if(!b.empty()){
            to_return.second = b.begin();
            return to_return;
         }
      }

      //Otherwise, return the end node
      to_return.second = priv_invalid_local_it();
      return to_return;
   }
   /// @endcond
};

/// @cond
#if !defined(BOOST_INTRUSIVE_VARIADIC_TEMPLATES)
template < class T
         , bool UniqueKeys
         , class O1 = none, class O2 = none
         , class O3 = none, class O4 = none
         , class O5 = none, class O6 = none
         , class O7 = none, class O8 = none
         , class O9 = none, class O10= none
         >
#else
template <class T, bool UniqueKeys, class ...Options>
#endif
struct make_hashtable_opt
{
   typedef typename pack_options
      < uset_defaults<T>, 
         #if !defined(BOOST_INTRUSIVE_VARIADIC_TEMPLATES)
         O1, O2, O3, O4, O5, O6, O7, O8, O9, O10
         #else
         Options...
         #endif
      >::type packed_options;

   //Real value traits must be calculated from options
   typedef typename detail::get_value_traits
      <T, typename packed_options::value_traits>::type   value_traits;
   /// @cond
   static const bool external_value_traits =
      detail::external_value_traits_is_true<value_traits>::value;
   typedef typename detail::eval_if_c
      < external_value_traits
      , detail::eval_value_traits<value_traits>
      , detail::identity<value_traits>
      >::type                                            real_value_traits;
   typedef typename packed_options::bucket_traits        specified_bucket_traits;   
   /// @endcond

   //Real bucket traits must be calculated from options and calculated value_traits
   typedef typename detail::get_slist_impl
      <typename detail::reduced_slist_node_traits
         <typename real_value_traits::node_traits>::type
      >::type                                            slist_impl;

   typedef typename
      detail::if_c< detail::is_same
                     < specified_bucket_traits
                     , default_bucket_traits
                     >::value
                  , detail::bucket_traits_impl<slist_impl>
                  , specified_bucket_traits
                  >::type                                real_bucket_traits;

   typedef detail::usetopt
      < value_traits
      , typename packed_options::hash
      , typename packed_options::equal
      , typename packed_options::size_type
      , real_bucket_traits
      ,  (std::size_t(UniqueKeys)*detail::hash_bool_flags::unique_keys_pos)
      |  (std::size_t(packed_options::constant_time_size)*detail::hash_bool_flags::constant_time_size_pos)
      |  (std::size_t(packed_options::power_2_buckets)*detail::hash_bool_flags::power_2_buckets_pos)
      |  (std::size_t(packed_options::cache_begin)*detail::hash_bool_flags::cache_begin_pos)
      |  (std::size_t(packed_options::compare_hash)*detail::hash_bool_flags::compare_hash_pos)
      |  (std::size_t(packed_options::incremental)*detail::hash_bool_flags::incremental_pos)
      > type;
};
/// @endcond

//! Helper metafunction to define a \c hashtable that yields to the same type when the
//! same options (either explicitly or implicitly) are used.
#if defined(BOOST_INTRUSIVE_DOXYGEN_INVOKED) || defined(BOOST_INTRUSIVE_VARIADIC_TEMPLATES)
template<class T, class ...Options>
#else
template<class T, class O1 = none, class O2 = none
                , class O3 = none, class O4 = none
                , class O5 = none, class O6 = none
                , class O7 = none, class O8 = none
                , class O9 = none, class O10= none
                >
#endif
struct make_hashtable
{
   /// @cond
   typedef hashtable_impl
      <  typename make_hashtable_opt
            <T, false, 
            #if !defined(BOOST_INTRUSIVE_VARIADIC_TEMPLATES)
            O1, O2, O3, O4, O5, O6, O7, O8, O9, O10
            #else
            Options...
            #endif
         >::type
      > implementation_defined;

   /// @endcond
   typedef implementation_defined type;
};

#if !defined(BOOST_INTRUSIVE_DOXYGEN_INVOKED)

#if defined(BOOST_INTRUSIVE_VARIADIC_TEMPLATES)
template<class T, class ...Options>
#else
template<class T, class O1, class O2, class O3, class O4, class O5, class O6, class O7, class O8, class O9, class O10>
#endif
class hashtable
   :  public make_hashtable<T, 
         #if !defined(BOOST_INTRUSIVE_VARIADIC_TEMPLATES)
         O1, O2, O3, O4, O5, O6, O7, O8, O9, O10
         #else
         Options...
         #endif
         >::type
{
   typedef typename make_hashtable<T, 
      #if !defined(BOOST_INTRUSIVE_VARIADIC_TEMPLATES)
      O1, O2, O3, O4, O5, O6, O7, O8, O9, O10
      #else
      Options...
      #endif
      >::type   Base;

   public:
   typedef typename Base::value_traits       value_traits;
   typedef typename Base::real_value_traits  real_value_traits;
   typedef typename Base::iterator           iterator;
   typedef typename Base::const_iterator     const_iterator;
   typedef typename Base::bucket_ptr         bucket_ptr;
   typedef typename Base::size_type          size_type;
   typedef typename Base::hasher             hasher;
   typedef typename Base::bucket_traits      bucket_traits;
   typedef typename Base::key_equal          key_equal;

   //Assert if passed value traits are compatible with the type
   BOOST_STATIC_ASSERT((detail::is_same<typename real_value_traits::value_type, T>::value));

   hashtable ( const bucket_traits &b_traits
             , const hasher & hash_func = hasher()
             , const key_equal &equal_func = key_equal()
             , const value_traits &v_traits = value_traits())
      :  Base(b_traits, hash_func, equal_func, v_traits)
   {}
};

#endif

} //namespace intrusive 
} //namespace boost 

#include <boost/intrusive/detail/config_end.hpp>

#endif //BOOST_INTRUSIVE_HASHTABLE_HPP