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

// Copyright (C) 2010 Free Software Foundation, Inc.

//

// This file is part of the GNU ISO C++ Library.  This library is free

// software; you can redistribute it and/or modify it under the

// terms of the GNU General Public License as published by the

// Free Software Foundation; either version 3, or (at your option)

// any later version.

// This library is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional

// permissions described in the GCC Runtime Library Exception, version

// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and

// a copy of the GCC Runtime Library Exception along with this program;

// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see

// <http://www.gnu.org/licenses/>.

/** @file tr1/hashtable_policy.h

 *  This is an internal header file, included by other library headers.

 *  You should not attempt to use it directly.

 */

namespace std

{

namespace tr1

{

namespace __detail

{

  // Helper function: return distance(first, last) for forward

  // iterators, or 0 for input iterators.

  template<class _Iterator>

    inline typename std::iterator_traits<_Iterator>::difference_type

    __distance_fw(_Iterator __first, _Iterator __last,

                  std::input_iterator_tag)

    { return 0; }

  template<class _Iterator>

    inline typename std::iterator_traits<_Iterator>::difference_type

    __distance_fw(_Iterator __first, _Iterator __last,

                  std::forward_iterator_tag)

    { return std::distance(__first, __last); }

  template<class _Iterator>

    inline typename std::iterator_traits<_Iterator>::difference_type

    __distance_fw(_Iterator __first, _Iterator __last)

    {

      typedef typename std::iterator_traits<_Iterator>::iterator_category _Tag;

      return __distance_fw(__first, __last, _Tag());

    }

  // Auxiliary types used for all instantiations of _Hashtable: nodes

  // and iterators.

  // Nodes, used to wrap elements stored in the hash table.  A policy

  // template parameter of class template _Hashtable controls whether

  // nodes also store a hash code. In some cases (e.g. strings) this

  // may be a performance win.

  template<typename _Value, bool __cache_hash_code>

    struct _Hash_node;

  template<typename _Value>

    struct _Hash_node<_Value, true>

    {

      _Value       _M_v;

      std::size_t  _M_hash_code;

      _Hash_node*  _M_next;

    };

  template<typename _Value>

    struct _Hash_node<_Value, false>

    {

      _Value       _M_v;

      _Hash_node*  _M_next;

    };

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

  // buckets.

  template<typename _Value, bool __cache>

    struct _Node_iterator_base

    {

      _Node_iterator_base(_Hash_node<_Value, __cache>* __p)

      : _M_cur(__p) { }

      void

      _M_incr()

      { _M_cur = _M_cur->_M_next; }

      _Hash_node<_Value, __cache>*  _M_cur;

    };

  template<typename _Value, bool __cache>

    inline bool

    operator==(const _Node_iterator_base<_Value, __cache>& __x,

               const _Node_iterator_base<_Value, __cache>& __y)

    { return __x._M_cur == __y._M_cur; }

  template<typename _Value, bool __cache>

    inline bool

    operator!=(const _Node_iterator_base<_Value, __cache>& __x,

               const _Node_iterator_base<_Value, __cache>& __y)

    { return __x._M_cur != __y._M_cur; }

  template<typename _Value, bool __constant_iterators, bool __cache>

    struct _Node_iterator

    : public _Node_iterator_base<_Value, __cache>

    {

      typedef _Value                                   value_type;

      typedef typename

      __gnu_cxx::__conditional_type<__constant_iterators,

                                    const _Value*, _Value*>::__type

                                                       pointer;

      typedef typename

      __gnu_cxx::__conditional_type<__constant_iterators,

                                    const _Value&, _Value&>::__type

                                                       reference;

      typedef std::ptrdiff_t                           difference_type;

      typedef std::forward_iterator_tag                iterator_category;

      _Node_iterator()

      : _Node_iterator_base<_Value, __cache>(0) { }

      explicit

      _Node_iterator(_Hash_node<_Value, __cache>* __p)

      : _Node_iterator_base<_Value, __cache>(__p) { }

      reference

      operator*() const

      { return this->_M_cur->_M_v; }

      pointer

      operator->() const

      { return &this->_M_cur->_M_v; }

      _Node_iterator&

      operator++()

      {

        this->_M_incr();

        return *this;

      }

      _Node_iterator

      operator++(int)

      {

        _Node_iterator __tmp(*this);

        this->_M_incr();

        return __tmp;

      }

    };

  template<typename _Value, bool __constant_iterators, bool __cache>

    struct _Node_const_iterator

    : public _Node_iterator_base<_Value, __cache>

    {

      typedef _Value                                   value_type;

      typedef const _Value*                            pointer;

      typedef const _Value&                            reference;

      typedef std::ptrdiff_t                           difference_type;

      typedef std::forward_iterator_tag                iterator_category;

      _Node_const_iterator()

      : _Node_iterator_base<_Value, __cache>(0) { }

      explicit

      _Node_const_iterator(_Hash_node<_Value, __cache>* __p)

      : _Node_iterator_base<_Value, __cache>(__p) { }

      _Node_const_iterator(const _Node_iterator<_Value, __constant_iterators,

                           __cache>& __x)

      : _Node_iterator_base<_Value, __cache>(__x._M_cur) { }

      reference

      operator*() const

      { return this->_M_cur->_M_v; }

      pointer

      operator->() const

      { return &this->_M_cur->_M_v; }

      _Node_const_iterator&

      operator++()

      {

        this->_M_incr();

        return *this;

      }

      _Node_const_iterator

      operator++(int)

      {

        _Node_const_iterator __tmp(*this);

        this->_M_incr();

        return __tmp;

      }

    };

  template<typename _Value, bool __cache>

    struct _Hashtable_iterator_base

    {

      _Hashtable_iterator_base(_Hash_node<_Value, __cache>* __node,

                               _Hash_node<_Value, __cache>** __bucket)

      : _M_cur_node(__node), _M_cur_bucket(__bucket) { }

      void

      _M_incr()

      {

        _M_cur_node = _M_cur_node->_M_next;

        if (!_M_cur_node)

          _M_incr_bucket();

      }

      void

      _M_incr_bucket();

      _Hash_node<_Value, __cache>*   _M_cur_node;

      _Hash_node<_Value, __cache>**  _M_cur_bucket;

    };

  // Global iterators, used for arbitrary iteration within a hash

  // table.  Larger and more expensive than local iterators.

  template<typename _Value, bool __cache>

    void

    _Hashtable_iterator_base<_Value, __cache>::

    _M_incr_bucket()

    {

      ++_M_cur_bucket;

      // This loop requires the bucket array to have a non-null sentinel.

      while (!*_M_cur_bucket)

        ++_M_cur_bucket;

      _M_cur_node = *_M_cur_bucket;

    }

  template<typename _Value, bool __cache>

    inline bool

    operator==(const _Hashtable_iterator_base<_Value, __cache>& __x,

               const _Hashtable_iterator_base<_Value, __cache>& __y)

    { return __x._M_cur_node == __y._M_cur_node; }

  template<typename _Value, bool __cache>

    inline bool

    operator!=(const _Hashtable_iterator_base<_Value, __cache>& __x,

               const _Hashtable_iterator_base<_Value, __cache>& __y)

    { return __x._M_cur_node != __y._M_cur_node; }

  template<typename _Value, bool __constant_iterators, bool __cache>

    struct _Hashtable_iterator

    : public _Hashtable_iterator_base<_Value, __cache>

    {

      typedef _Value                                   value_type;

      typedef typename

      __gnu_cxx::__conditional_type<__constant_iterators,

                                    const _Value*, _Value*>::__type

                                                       pointer;

      typedef typename

      __gnu_cxx::__conditional_type<__constant_iterators,

                                    const _Value&, _Value&>::__type

                                                       reference;

      typedef std::ptrdiff_t                           difference_type;

      typedef std::forward_iterator_tag                iterator_category;

      _Hashtable_iterator()

      : _Hashtable_iterator_base<_Value, __cache>(0, 0) { }

      _Hashtable_iterator(_Hash_node<_Value, __cache>* __p,

                          _Hash_node<_Value, __cache>** __b)

      : _Hashtable_iterator_base<_Value, __cache>(__p, __b) { }

      explicit

      _Hashtable_iterator(_Hash_node<_Value, __cache>** __b)

      : _Hashtable_iterator_base<_Value, __cache>(*__b, __b) { }

      reference

      operator*() const

      { return this->_M_cur_node->_M_v; }

      pointer

      operator->() const

      { return &this->_M_cur_node->_M_v; }

      _Hashtable_iterator&

      operator++()

      {

        this->_M_incr();

        return *this;

      }

      _Hashtable_iterator

      operator++(int)

      {

        _Hashtable_iterator __tmp(*this);

        this->_M_incr();

        return __tmp;

      }

    };

  template<typename _Value, bool __constant_iterators, bool __cache>

    struct _Hashtable_const_iterator

    : public _Hashtable_iterator_base<_Value, __cache>

    {

      typedef _Value                                   value_type;

      typedef const _Value*                            pointer;

      typedef const _Value&                            reference;

      typedef std::ptrdiff_t                           difference_type;

      typedef std::forward_iterator_tag                iterator_category;

      _Hashtable_const_iterator()

      : _Hashtable_iterator_base<_Value, __cache>(0, 0) { }

      _Hashtable_const_iterator(_Hash_node<_Value, __cache>* __p,

                                _Hash_node<_Value, __cache>** __b)

      : _Hashtable_iterator_base<_Value, __cache>(__p, __b) { }

      explicit

      _Hashtable_const_iterator(_Hash_node<_Value, __cache>** __b)

      : _Hashtable_iterator_base<_Value, __cache>(*__b, __b) { }

      _Hashtable_const_iterator(const _Hashtable_iterator<_Value,

                                __constant_iterators, __cache>& __x)

      : _Hashtable_iterator_base<_Value, __cache>(__x._M_cur_node,

                                                  __x._M_cur_bucket) { }

      reference

      operator*() const

      { return this->_M_cur_node->_M_v; }

      pointer

      operator->() const

      { return &this->_M_cur_node->_M_v; }

      _Hashtable_const_iterator&

      operator++()

      {

        this->_M_incr();

        return *this;

      }

      _Hashtable_const_iterator

      operator++(int)

      {

        _Hashtable_const_iterator __tmp(*this);

        this->_M_incr();

        return __tmp;

      }

    };

  // Many of class template _Hashtable's template parameters are policy

  // classes.  These are defaults for the policies.

  // Default range hashing function: use division to fold a large number

  // into the range [0, N).

  struct _Mod_range_hashing

  {

    typedef std::size_t first_argument_type;

    typedef std::size_t second_argument_type;

    typedef std::size_t result_type;

    result_type

    operator()(first_argument_type __num, second_argument_type __den) const

    { return __num % __den; }

  };

  // Default ranged hash function H.  In principle it should be a

  // function object composed from objects of type H1 and H2 such that

  // h(k, N) = h2(h1(k), N), but that would mean making extra copies of

  // h1 and h2.  So instead we'll just use a tag to tell class template

  // hashtable to do that composition.

  struct _Default_ranged_hash { };

  // Default value for rehash policy.  Bucket size is (usually) the

  // smallest prime that keeps the load factor small enough.

  struct _Prime_rehash_policy

  {

    _Prime_rehash_policy(float __z = 1.0)

    : _M_max_load_factor(__z), _M_growth_factor(2.f), _M_next_resize(0) { }

    float

    max_load_factor() const

    { return _M_max_load_factor; }

    // Return a bucket size no smaller than n.

    std::size_t

    _M_next_bkt(std::size_t __n) const;

    // Return a bucket count appropriate for n elements

    std::size_t

    _M_bkt_for_elements(std::size_t __n) const;

    // __n_bkt is current bucket count, __n_elt is current element count,

    // and __n_ins is number of elements to be inserted.  Do we need to

    // increase bucket count?  If so, return make_pair(true, n), where n

    // is the new bucket count.  If not, return make_pair(false, 0).

    std::pair<bool, std::size_t>

    _M_need_rehash(std::size_t __n_bkt, std::size_t __n_elt,

                   std::size_t __n_ins) const;

    enum { _S_n_primes = sizeof(unsigned long) != 8 ? 256 : 256 + 48 };

    float                _M_max_load_factor;

    float                _M_growth_factor;

    mutable std::size_t  _M_next_resize;

  };

  extern const unsigned long __prime_list[];

  // XXX This is a hack.  There's no good reason for any of

  // _Prime_rehash_policy's member functions to be inline.  

  // Return a prime no smaller than n.

  inline std::size_t

  _Prime_rehash_policy::

  _M_next_bkt(std::size_t __n) const

  {

    const unsigned long* __p = std::lower_bound(__prime_list, __prime_list

                                                + _S_n_primes, __n);

    _M_next_resize =

      static_cast<std::size_t>(__builtin_ceil(*__p * _M_max_load_factor));

    return *__p;

  }

  // Return the smallest prime p such that alpha p >= n, where alpha

  // is the load factor.

  inline std::size_t

  _Prime_rehash_policy::

  _M_bkt_for_elements(std::size_t __n) const

  {

    const float __min_bkts = __n / _M_max_load_factor;

    const unsigned long* __p = std::lower_bound(__prime_list, __prime_list

                                                + _S_n_primes, __min_bkts);

    _M_next_resize =

      static_cast<std::size_t>(__builtin_ceil(*__p * _M_max_load_factor));

    return *__p;

  }

  // Finds the smallest prime p such that alpha p > __n_elt + __n_ins.

  // If p > __n_bkt, return make_pair(true, p); otherwise return

  // make_pair(false, 0).  In principle this isn't very different from 

  // _M_bkt_for_elements.

  // The only tricky part is that we're caching the element count at

  // which we need to rehash, so we don't have to do a floating-point

  // multiply for every insertion.

  inline std::pair<bool, std::size_t>

  _Prime_rehash_policy::

  _M_need_rehash(std::size_t __n_bkt, std::size_t __n_elt,

                 std::size_t __n_ins) const

  {

    if (__n_elt + __n_ins > _M_next_resize)

      {

        float __min_bkts = ((float(__n_ins) + float(__n_elt))

                            / _M_max_load_factor);

        if (__min_bkts > __n_bkt)

          {

            __min_bkts = std::max(__min_bkts, _M_growth_factor * __n_bkt);

            const unsigned long* __p =

              std::lower_bound(__prime_list, __prime_list + _S_n_primes,

                               __min_bkts);

            _M_next_resize = static_cast<std::size_t>

              (__builtin_ceil(*__p * _M_max_load_factor));

            return std::make_pair(true, *__p);

          }

        else

          {

            _M_next_resize = static_cast<std::size_t>

              (__builtin_ceil(__n_bkt * _M_max_load_factor));

            return std::make_pair(false, 0);

          }

      }

    else

      return std::make_pair(false, 0);

  }

  // Base classes for std::tr1::_Hashtable.  We define these base

  // classes because in some cases we want to do different things

  // depending on the value of a policy class.  In some cases the

  // policy class affects which member functions and nested typedefs

  // are defined; we handle that by specializing base class templates.

  // Several of the base class templates need to access other members

  // of class template _Hashtable, so we use the "curiously recurring

  // template pattern" for them.

  // class template _Map_base.  If the hashtable has a value type of the

  // form pair<T1, T2> and a key extraction policy that returns the

  // first part of the pair, the hashtable gets a mapped_type typedef.

  // If it satisfies those criteria and also has unique keys, then it

  // also gets an operator[].  

  template<typename _Key, typename _Value, typename _Ex, bool __unique,

           typename _Hashtable>

    struct _Map_base { };

  template<typename _Key, typename _Pair, typename _Hashtable>

    struct _Map_base<_Key, _Pair, std::_Select1st<_Pair>, false, _Hashtable>

    {

      typedef typename _Pair::second_type mapped_type;

    };

  template<typename _Key, typename _Pair, typename _Hashtable>

    struct _Map_base<_Key, _Pair, std::_Select1st<_Pair>, true, _Hashtable>

    {

      typedef typename _Pair::second_type mapped_type;

      mapped_type&

      operator[](const _Key& __k);

    };

  template<typename _Key, typename _Pair, typename _Hashtable>

    typename _Map_base<_Key, _Pair, std::_Select1st<_Pair>,

                       true, _Hashtable>::mapped_type&

    _Map_base<_Key, _Pair, std::_Select1st<_Pair>, true, _Hashtable>::

    operator[](const _Key& __k)

    {

      _Hashtable* __h = static_cast<_Hashtable*>(this);

      typename _Hashtable::_Hash_code_type __code = __h->_M_hash_code(__k);

      std::size_t __n = __h->_M_bucket_index(__k, __code,

                                             __h->_M_bucket_count);

      typename _Hashtable::_Node* __p =

        __h->_M_find_node(__h->_M_buckets[__n], __k, __code);

      if (!__p)

        return __h->_M_insert_bucket(std::make_pair(__k, mapped_type()),

                                     __n, __code)->second;

      return (__p->_M_v).second;

    }

  // class template _Rehash_base.  Give hashtable the max_load_factor

  // functions iff the rehash policy is _Prime_rehash_policy.

  template<typename _RehashPolicy, typename _Hashtable>

    struct _Rehash_base { };

  template<typename _Hashtable>

    struct _Rehash_base<_Prime_rehash_policy, _Hashtable>

    {

      float

      max_load_factor() const

      {

        const _Hashtable* __this = static_cast<const _Hashtable*>(this);

        return __this->__rehash_policy().max_load_factor();

      }

      void

      max_load_factor(float __z)

      {

        _Hashtable* __this = static_cast<_Hashtable*>(this);

        __this->__rehash_policy(_Prime_rehash_policy(__z));

      }

    };

  // Class template _Hash_code_base.  Encapsulates two policy issues that

  // aren't quite orthogonal.

  //   (1) the difference between using a ranged hash function and using

  //       the combination of a hash function and a range-hashing function.

  //       In the former case we don't have such things as hash codes, so

  //       we have a dummy type as placeholder.

  //   (2) Whether or not we cache hash codes.  Caching hash codes is

  //       meaningless if we have a ranged hash function.

  // We also put the key extraction and equality comparison function 

  // objects here, for convenience.

  // Primary template: unused except as a hook for specializations.  

  template<typename _Key, typename _Value,

           typename _ExtractKey, typename _Equal,

           typename _H1, typename _H2, typename _Hash,

           bool __cache_hash_code>

    struct _Hash_code_base;

  // Specialization: ranged hash function, no caching hash codes.  H1

  // and H2 are provided but ignored.  We define a dummy hash code type.

  template<typename _Key, typename _Value,

           typename _ExtractKey, typename _Equal,

           typename _H1, typename _H2, typename _Hash>

    struct _Hash_code_base<_Key, _Value, _ExtractKey, _Equal, _H1, _H2,

                           _Hash, false>

    {

    protected:

      _Hash_code_base(const _ExtractKey& __ex, const _Equal& __eq,

                      const _H1&, const _H2&, const _Hash& __h)

      : _M_extract(__ex), _M_eq(__eq), _M_ranged_hash(__h) { }

      typedef void* _Hash_code_type;

      _Hash_code_type

      _M_hash_code(const _Key& __key) const

      { return 0; }

      std::size_t

      _M_bucket_index(const _Key& __k, _Hash_code_type,

                      std::size_t __n) const

      { return _M_ranged_hash(__k, __n); }

      std::size_t

      _M_bucket_index(const _Hash_node<_Value, false>* __p,

                      std::size_t __n) const

      { return _M_ranged_hash(_M_extract(__p->_M_v), __n); }

      bool

      _M_compare(const _Key& __k, _Hash_code_type,

                 _Hash_node<_Value, false>* __n) const

      { return _M_eq(__k, _M_extract(__n->_M_v)); }

      void

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

      { }

      void

      _M_copy_code(_Hash_node<_Value, false>*,

                   const _Hash_node<_Value, false>*) const

      { }

      void

      _M_swap(_Hash_code_base& __x)

      {

        std::swap(_M_extract, __x._M_extract);

        std::swap(_M_eq, __x._M_eq);

        std::swap(_M_ranged_hash, __x._M_ranged_hash);

      }

    protected:

      _ExtractKey  _M_extract;

      _Equal       _M_eq;

      _Hash        _M_ranged_hash;

    };

  // No specialization for ranged hash function while caching hash codes.

  // That combination is meaningless, and trying to do it is an error.

  // Specialization: ranged hash function, cache hash codes.  This

  // combination is meaningless, so we provide only a declaration

  // and no definition.  

  template<typename _Key, typename _Value,

           typename _ExtractKey, typename _Equal,

           typename _H1, typename _H2, typename _Hash>

    struct _Hash_code_base<_Key, _Value, _ExtractKey, _Equal, _H1, _H2,

                           _Hash, true>;

  // Specialization: hash function and range-hashing function, no

  // caching of hash codes.  H is provided but ignored.  Provides

  // typedef and accessor required by TR1.  

  template<typename _Key, typename _Value,

           typename _ExtractKey, typename _Equal,

           typename _H1, typename _H2>

    struct _Hash_code_base<_Key, _Value, _ExtractKey, _Equal, _H1, _H2,

                           _Default_ranged_hash, false>

    {

      typedef _H1 hasher;

      hasher

      hash_function() const

      { return _M_h1; }

    protected:

      _Hash_code_base(const _ExtractKey& __ex, const _Equal& __eq,

                      const _H1& __h1, const _H2& __h2,

                      const _Default_ranged_hash&)

      : _M_extract(__ex), _M_eq(__eq), _M_h1(__h1), _M_h2(__h2) { }

      typedef std::size_t _Hash_code_type;

      _Hash_code_type

      _M_hash_code(const _Key& __k) const

      { return _M_h1(__k); }

      std::size_t

      _M_bucket_index(const _Key&, _Hash_code_type __c,

                      std::size_t __n) const

      { return _M_h2(__c, __n); }

      std::size_t

      _M_bucket_index(const _Hash_node<_Value, false>* __p,

                      std::size_t __n) const

      { return _M_h2(_M_h1(_M_extract(__p->_M_v)), __n); }

      bool

      _M_compare(const _Key& __k, _Hash_code_type,

                 _Hash_node<_Value, false>* __n) const

      { return _M_eq(__k, _M_extract(__n->_M_v)); }