Preview: hashtable_policy.h
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/opt/rh/gcc-toolset-14/root/usr/include/c++/14/tr1/hashtable_policy.h
// Internal policy header for TR1 unordered_set and unordered_map -*- C++ -*-
// Copyright (C) 2010-2024 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.
* Do not attempt to use it directly.
* @headername{tr1/unordered_map, tr1/unordered_set}
*/
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
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 std::__addressof(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 std::__addressof(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 std::__addressof(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 std::__addressof(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
{
// Don't include the last prime in the search, so that anything
// higher than the second-to-last prime returns a past-the-end
// iterator that can be dereferenced to get the last prime.
const unsigned long* __p
= std::lower_bound(__prime_list, __prime_list + _S_n_primes - 1, __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;
return _M_next_bkt(__builtin_ceil(__min_bkts));
}
// 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);
return std::make_pair(true,
_M_next_bkt(__builtin_ceil(__min_bkts)));
}
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)); }
void
_M_store_code(_Hash_node<_Value, false>*, _Hash_code_type) const
{ }
void
_M_copy_code(_Hash_node<_Value, false>*,
const _Hash_node<_Value, false>*) const
{ }
void
_M_swap(_Hash_code_base& __x)
{
std::swap(_M_extract, __x._M_extract);
std::swap(_M_eq, __x._M_eq);
std::swap(_M_h1, __x._M_h1);
std::swap(_M_h2, __x._M_h2);
}
protected:
_ExtractKey _M_extract;
_Equal _M_eq;
_H1 _M_h1;
_H2 _M_h2;
};
// Specialization: hash function and range-hashing function,
// caching hash codes. H is provided but ignored. Provides
// typedef and accessor required by TR1.
template<typename _Key, typename _Value,
typename _ExtractKey, typename _Equal,
typename _H1, typename _H2>
struct _Hash_code_base<_Key, _Value, _ExtractKey, _Equal, _H1, _H2,
_Default_ranged_hash, true>
{
typedef _H1 hasher;
hasher
hash_function() const
{ return _M_h1; }
protected:
_Hash_code_base(const _ExtractKey& __ex, const _Equal& __eq,
const _H1& __h1, const _H2& __h2,
const _Default_ranged_hash&)
: _M_extract(__ex), _M_eq(__eq), _M_h1(__h1), _M_h2(__h2) { }
typedef std::size_t _Hash_code_type;
_Hash_code_type
_M_hash_code(const _Key& __k) const
{ return _M_h1(__k); }
std::size_t
_M_bucket_index(const _Key&, _Hash_code_type __c,
std::size_t __n) const
{ return _M_h2(__c, __n); }
std::size_t
_M_bucket_index(const _Hash_node<_Value, true>* __p,
std::size_t __n) const
{ return _M_h2(__p->_M_hash_code, __n); }
bool
_M_compare(const _Key& __k, _Hash_code_type __c,
_Hash_node<_Value, true>* __n) const
{ return __c == __n->_M_hash_code && _M_eq(__k, _M_extract(__n->_M_v)); }
void
_M_store_code(_Hash_node<_Value, true>* __n, _Hash_code_type __c) const
{ __n->_M_hash_code = __c; }
void
_M_copy_code(_Hash_node<_Value, true>* __to,
const _Hash_node<_Value, true>* __from) const
{ __to->_M_hash_code = __from->_M_hash_code; }
void
_M_swap(_Hash_code_base& __x)
{
std::swap(_M_extract, __x._M_extract);
std::swap(_M_eq, __x._M_eq);
std::swap(_M_h1, __x._M_h1);
std::swap(_M_h2, __x._M_h2);
}
protected:
_ExtractKey _M_extract;
_Equal _M_eq;
_H1 _M_h1;
_H2 _M_h2;
};
} // namespace __detail
}
_GLIBCXX_END_NAMESPACE_VERSION
}
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