1 // Internal policy header for TR1 unordered_set and unordered_map -*- C++ -*-
3 // Copyright (C) 2010, 2011 Free Software Foundation, Inc.
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
25 /** @file tr1/hashtable_policy.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly.
28 * @headername{tr1/unordered_map, tr1/unordered_set}
31 namespace std _GLIBCXX_VISIBILITY(default)
37 _GLIBCXX_BEGIN_NAMESPACE_VERSION
39 // Helper function: return distance(first, last) for forward
40 // iterators, or 0 for input iterators.
41 template<class _Iterator>
42 inline typename std::iterator_traits<_Iterator>::difference_type
43 __distance_fw(_Iterator __first, _Iterator __last,
44 std::input_iterator_tag)
47 template<class _Iterator>
48 inline typename std::iterator_traits<_Iterator>::difference_type
49 __distance_fw(_Iterator __first, _Iterator __last,
50 std::forward_iterator_tag)
51 { return std::distance(__first, __last); }
53 template<class _Iterator>
54 inline typename std::iterator_traits<_Iterator>::difference_type
55 __distance_fw(_Iterator __first, _Iterator __last)
57 typedef typename std::iterator_traits<_Iterator>::iterator_category _Tag;
58 return __distance_fw(__first, __last, _Tag());
61 // Auxiliary types used for all instantiations of _Hashtable: nodes
64 // Nodes, used to wrap elements stored in the hash table. A policy
65 // template parameter of class template _Hashtable controls whether
66 // nodes also store a hash code. In some cases (e.g. strings) this
67 // may be a performance win.
68 template<typename _Value, bool __cache_hash_code>
71 template<typename _Value>
72 struct _Hash_node<_Value, true>
75 std::size_t _M_hash_code;
79 template<typename _Value>
80 struct _Hash_node<_Value, false>
86 // Local iterators, used to iterate within a bucket but not between
88 template<typename _Value, bool __cache>
89 struct _Node_iterator_base
91 _Node_iterator_base(_Hash_node<_Value, __cache>* __p)
96 { _M_cur = _M_cur->_M_next; }
98 _Hash_node<_Value, __cache>* _M_cur;
101 template<typename _Value, bool __cache>
103 operator==(const _Node_iterator_base<_Value, __cache>& __x,
104 const _Node_iterator_base<_Value, __cache>& __y)
105 { return __x._M_cur == __y._M_cur; }
107 template<typename _Value, bool __cache>
109 operator!=(const _Node_iterator_base<_Value, __cache>& __x,
110 const _Node_iterator_base<_Value, __cache>& __y)
111 { return __x._M_cur != __y._M_cur; }
113 template<typename _Value, bool __constant_iterators, bool __cache>
114 struct _Node_iterator
115 : public _Node_iterator_base<_Value, __cache>
117 typedef _Value value_type;
119 __gnu_cxx::__conditional_type<__constant_iterators,
120 const _Value*, _Value*>::__type
123 __gnu_cxx::__conditional_type<__constant_iterators,
124 const _Value&, _Value&>::__type
126 typedef std::ptrdiff_t difference_type;
127 typedef std::forward_iterator_tag iterator_category;
130 : _Node_iterator_base<_Value, __cache>(0) { }
133 _Node_iterator(_Hash_node<_Value, __cache>* __p)
134 : _Node_iterator_base<_Value, __cache>(__p) { }
138 { return this->_M_cur->_M_v; }
142 { return std::__addressof(this->_M_cur->_M_v); }
154 _Node_iterator __tmp(*this);
160 template<typename _Value, bool __constant_iterators, bool __cache>
161 struct _Node_const_iterator
162 : public _Node_iterator_base<_Value, __cache>
164 typedef _Value value_type;
165 typedef const _Value* pointer;
166 typedef const _Value& reference;
167 typedef std::ptrdiff_t difference_type;
168 typedef std::forward_iterator_tag iterator_category;
170 _Node_const_iterator()
171 : _Node_iterator_base<_Value, __cache>(0) { }
174 _Node_const_iterator(_Hash_node<_Value, __cache>* __p)
175 : _Node_iterator_base<_Value, __cache>(__p) { }
177 _Node_const_iterator(const _Node_iterator<_Value, __constant_iterators,
179 : _Node_iterator_base<_Value, __cache>(__x._M_cur) { }
183 { return this->_M_cur->_M_v; }
187 { return std::__addressof(this->_M_cur->_M_v); }
189 _Node_const_iterator&
199 _Node_const_iterator __tmp(*this);
205 template<typename _Value, bool __cache>
206 struct _Hashtable_iterator_base
208 _Hashtable_iterator_base(_Hash_node<_Value, __cache>* __node,
209 _Hash_node<_Value, __cache>** __bucket)
210 : _M_cur_node(__node), _M_cur_bucket(__bucket) { }
215 _M_cur_node = _M_cur_node->_M_next;
223 _Hash_node<_Value, __cache>* _M_cur_node;
224 _Hash_node<_Value, __cache>** _M_cur_bucket;
227 // Global iterators, used for arbitrary iteration within a hash
228 // table. Larger and more expensive than local iterators.
229 template<typename _Value, bool __cache>
231 _Hashtable_iterator_base<_Value, __cache>::
236 // This loop requires the bucket array to have a non-null sentinel.
237 while (!*_M_cur_bucket)
239 _M_cur_node = *_M_cur_bucket;
242 template<typename _Value, bool __cache>
244 operator==(const _Hashtable_iterator_base<_Value, __cache>& __x,
245 const _Hashtable_iterator_base<_Value, __cache>& __y)
246 { return __x._M_cur_node == __y._M_cur_node; }
248 template<typename _Value, bool __cache>
250 operator!=(const _Hashtable_iterator_base<_Value, __cache>& __x,
251 const _Hashtable_iterator_base<_Value, __cache>& __y)
252 { return __x._M_cur_node != __y._M_cur_node; }
254 template<typename _Value, bool __constant_iterators, bool __cache>
255 struct _Hashtable_iterator
256 : public _Hashtable_iterator_base<_Value, __cache>
258 typedef _Value value_type;
260 __gnu_cxx::__conditional_type<__constant_iterators,
261 const _Value*, _Value*>::__type
264 __gnu_cxx::__conditional_type<__constant_iterators,
265 const _Value&, _Value&>::__type
267 typedef std::ptrdiff_t difference_type;
268 typedef std::forward_iterator_tag iterator_category;
270 _Hashtable_iterator()
271 : _Hashtable_iterator_base<_Value, __cache>(0, 0) { }
273 _Hashtable_iterator(_Hash_node<_Value, __cache>* __p,
274 _Hash_node<_Value, __cache>** __b)
275 : _Hashtable_iterator_base<_Value, __cache>(__p, __b) { }
278 _Hashtable_iterator(_Hash_node<_Value, __cache>** __b)
279 : _Hashtable_iterator_base<_Value, __cache>(*__b, __b) { }
283 { return this->_M_cur_node->_M_v; }
287 { return std::__addressof(this->_M_cur_node->_M_v); }
299 _Hashtable_iterator __tmp(*this);
305 template<typename _Value, bool __constant_iterators, bool __cache>
306 struct _Hashtable_const_iterator
307 : public _Hashtable_iterator_base<_Value, __cache>
309 typedef _Value value_type;
310 typedef const _Value* pointer;
311 typedef const _Value& reference;
312 typedef std::ptrdiff_t difference_type;
313 typedef std::forward_iterator_tag iterator_category;
315 _Hashtable_const_iterator()
316 : _Hashtable_iterator_base<_Value, __cache>(0, 0) { }
318 _Hashtable_const_iterator(_Hash_node<_Value, __cache>* __p,
319 _Hash_node<_Value, __cache>** __b)
320 : _Hashtable_iterator_base<_Value, __cache>(__p, __b) { }
323 _Hashtable_const_iterator(_Hash_node<_Value, __cache>** __b)
324 : _Hashtable_iterator_base<_Value, __cache>(*__b, __b) { }
326 _Hashtable_const_iterator(const _Hashtable_iterator<_Value,
327 __constant_iterators, __cache>& __x)
328 : _Hashtable_iterator_base<_Value, __cache>(__x._M_cur_node,
329 __x._M_cur_bucket) { }
333 { return this->_M_cur_node->_M_v; }
337 { return std::__addressof(this->_M_cur_node->_M_v); }
339 _Hashtable_const_iterator&
346 _Hashtable_const_iterator
349 _Hashtable_const_iterator __tmp(*this);
356 // Many of class template _Hashtable's template parameters are policy
357 // classes. These are defaults for the policies.
359 // Default range hashing function: use division to fold a large number
360 // into the range [0, N).
361 struct _Mod_range_hashing
363 typedef std::size_t first_argument_type;
364 typedef std::size_t second_argument_type;
365 typedef std::size_t result_type;
368 operator()(first_argument_type __num, second_argument_type __den) const
369 { return __num % __den; }
372 // Default ranged hash function H. In principle it should be a
373 // function object composed from objects of type H1 and H2 such that
374 // h(k, N) = h2(h1(k), N), but that would mean making extra copies of
375 // h1 and h2. So instead we'll just use a tag to tell class template
376 // hashtable to do that composition.
377 struct _Default_ranged_hash { };
379 // Default value for rehash policy. Bucket size is (usually) the
380 // smallest prime that keeps the load factor small enough.
381 struct _Prime_rehash_policy
383 _Prime_rehash_policy(float __z = 1.0)
384 : _M_max_load_factor(__z), _M_growth_factor(2.f), _M_next_resize(0) { }
387 max_load_factor() const
388 { return _M_max_load_factor; }
390 // Return a bucket size no smaller than n.
392 _M_next_bkt(std::size_t __n) const;
394 // Return a bucket count appropriate for n elements
396 _M_bkt_for_elements(std::size_t __n) const;
398 // __n_bkt is current bucket count, __n_elt is current element count,
399 // and __n_ins is number of elements to be inserted. Do we need to
400 // increase bucket count? If so, return make_pair(true, n), where n
401 // is the new bucket count. If not, return make_pair(false, 0).
402 std::pair<bool, std::size_t>
403 _M_need_rehash(std::size_t __n_bkt, std::size_t __n_elt,
404 std::size_t __n_ins) const;
406 enum { _S_n_primes = sizeof(unsigned long) != 8 ? 256 : 256 + 48 };
408 float _M_max_load_factor;
409 float _M_growth_factor;
410 mutable std::size_t _M_next_resize;
413 extern const unsigned long __prime_list[];
415 // XXX This is a hack. There's no good reason for any of
416 // _Prime_rehash_policy's member functions to be inline.
418 // Return a prime no smaller than n.
420 _Prime_rehash_policy::
421 _M_next_bkt(std::size_t __n) const
423 const unsigned long* __p = std::lower_bound(__prime_list, __prime_list
426 static_cast<std::size_t>(__builtin_ceil(*__p * _M_max_load_factor));
430 // Return the smallest prime p such that alpha p >= n, where alpha
431 // is the load factor.
433 _Prime_rehash_policy::
434 _M_bkt_for_elements(std::size_t __n) const
436 const float __min_bkts = __n / _M_max_load_factor;
437 const unsigned long* __p = std::lower_bound(__prime_list, __prime_list
438 + _S_n_primes, __min_bkts);
440 static_cast<std::size_t>(__builtin_ceil(*__p * _M_max_load_factor));
444 // Finds the smallest prime p such that alpha p > __n_elt + __n_ins.
445 // If p > __n_bkt, return make_pair(true, p); otherwise return
446 // make_pair(false, 0). In principle this isn't very different from
447 // _M_bkt_for_elements.
449 // The only tricky part is that we're caching the element count at
450 // which we need to rehash, so we don't have to do a floating-point
451 // multiply for every insertion.
453 inline std::pair<bool, std::size_t>
454 _Prime_rehash_policy::
455 _M_need_rehash(std::size_t __n_bkt, std::size_t __n_elt,
456 std::size_t __n_ins) const
458 if (__n_elt + __n_ins > _M_next_resize)
460 float __min_bkts = ((float(__n_ins) + float(__n_elt))
461 / _M_max_load_factor);
462 if (__min_bkts > __n_bkt)
464 __min_bkts = std::max(__min_bkts, _M_growth_factor * __n_bkt);
465 const unsigned long* __p =
466 std::lower_bound(__prime_list, __prime_list + _S_n_primes,
468 _M_next_resize = static_cast<std::size_t>
469 (__builtin_ceil(*__p * _M_max_load_factor));
470 return std::make_pair(true, *__p);
474 _M_next_resize = static_cast<std::size_t>
475 (__builtin_ceil(__n_bkt * _M_max_load_factor));
476 return std::make_pair(false, 0);
480 return std::make_pair(false, 0);
483 // Base classes for std::tr1::_Hashtable. We define these base
484 // classes because in some cases we want to do different things
485 // depending on the value of a policy class. In some cases the
486 // policy class affects which member functions and nested typedefs
487 // are defined; we handle that by specializing base class templates.
488 // Several of the base class templates need to access other members
489 // of class template _Hashtable, so we use the "curiously recurring
490 // template pattern" for them.
492 // class template _Map_base. If the hashtable has a value type of the
493 // form pair<T1, T2> and a key extraction policy that returns the
494 // first part of the pair, the hashtable gets a mapped_type typedef.
495 // If it satisfies those criteria and also has unique keys, then it
496 // also gets an operator[].
497 template<typename _Key, typename _Value, typename _Ex, bool __unique,
499 struct _Map_base { };
501 template<typename _Key, typename _Pair, typename _Hashtable>
502 struct _Map_base<_Key, _Pair, std::_Select1st<_Pair>, false, _Hashtable>
504 typedef typename _Pair::second_type mapped_type;
507 template<typename _Key, typename _Pair, typename _Hashtable>
508 struct _Map_base<_Key, _Pair, std::_Select1st<_Pair>, true, _Hashtable>
510 typedef typename _Pair::second_type mapped_type;
513 operator[](const _Key& __k);
516 template<typename _Key, typename _Pair, typename _Hashtable>
517 typename _Map_base<_Key, _Pair, std::_Select1st<_Pair>,
518 true, _Hashtable>::mapped_type&
519 _Map_base<_Key, _Pair, std::_Select1st<_Pair>, true, _Hashtable>::
520 operator[](const _Key& __k)
522 _Hashtable* __h = static_cast<_Hashtable*>(this);
523 typename _Hashtable::_Hash_code_type __code = __h->_M_hash_code(__k);
524 std::size_t __n = __h->_M_bucket_index(__k, __code,
525 __h->_M_bucket_count);
527 typename _Hashtable::_Node* __p =
528 __h->_M_find_node(__h->_M_buckets[__n], __k, __code);
530 return __h->_M_insert_bucket(std::make_pair(__k, mapped_type()),
531 __n, __code)->second;
532 return (__p->_M_v).second;
535 // class template _Rehash_base. Give hashtable the max_load_factor
536 // functions iff the rehash policy is _Prime_rehash_policy.
537 template<typename _RehashPolicy, typename _Hashtable>
538 struct _Rehash_base { };
540 template<typename _Hashtable>
541 struct _Rehash_base<_Prime_rehash_policy, _Hashtable>
544 max_load_factor() const
546 const _Hashtable* __this = static_cast<const _Hashtable*>(this);
547 return __this->__rehash_policy().max_load_factor();
551 max_load_factor(float __z)
553 _Hashtable* __this = static_cast<_Hashtable*>(this);
554 __this->__rehash_policy(_Prime_rehash_policy(__z));
558 // Class template _Hash_code_base. Encapsulates two policy issues that
559 // aren't quite orthogonal.
560 // (1) the difference between using a ranged hash function and using
561 // the combination of a hash function and a range-hashing function.
562 // In the former case we don't have such things as hash codes, so
563 // we have a dummy type as placeholder.
564 // (2) Whether or not we cache hash codes. Caching hash codes is
565 // meaningless if we have a ranged hash function.
566 // We also put the key extraction and equality comparison function
567 // objects here, for convenience.
569 // Primary template: unused except as a hook for specializations.
570 template<typename _Key, typename _Value,
571 typename _ExtractKey, typename _Equal,
572 typename _H1, typename _H2, typename _Hash,
573 bool __cache_hash_code>
574 struct _Hash_code_base;
576 // Specialization: ranged hash function, no caching hash codes. H1
577 // and H2 are provided but ignored. We define a dummy hash code type.
578 template<typename _Key, typename _Value,
579 typename _ExtractKey, typename _Equal,
580 typename _H1, typename _H2, typename _Hash>
581 struct _Hash_code_base<_Key, _Value, _ExtractKey, _Equal, _H1, _H2,
585 _Hash_code_base(const _ExtractKey& __ex, const _Equal& __eq,
586 const _H1&, const _H2&, const _Hash& __h)
587 : _M_extract(__ex), _M_eq(__eq), _M_ranged_hash(__h) { }
589 typedef void* _Hash_code_type;
592 _M_hash_code(const _Key& __key) const
596 _M_bucket_index(const _Key& __k, _Hash_code_type,
597 std::size_t __n) const
598 { return _M_ranged_hash(__k, __n); }
601 _M_bucket_index(const _Hash_node<_Value, false>* __p,
602 std::size_t __n) const
603 { return _M_ranged_hash(_M_extract(__p->_M_v), __n); }
606 _M_compare(const _Key& __k, _Hash_code_type,
607 _Hash_node<_Value, false>* __n) const
608 { return _M_eq(__k, _M_extract(__n->_M_v)); }
611 _M_store_code(_Hash_node<_Value, false>*, _Hash_code_type) const
615 _M_copy_code(_Hash_node<_Value, false>*,
616 const _Hash_node<_Value, false>*) const
620 _M_swap(_Hash_code_base& __x)
622 std::swap(_M_extract, __x._M_extract);
623 std::swap(_M_eq, __x._M_eq);
624 std::swap(_M_ranged_hash, __x._M_ranged_hash);
628 _ExtractKey _M_extract;
630 _Hash _M_ranged_hash;
634 // No specialization for ranged hash function while caching hash codes.
635 // That combination is meaningless, and trying to do it is an error.
638 // Specialization: ranged hash function, cache hash codes. This
639 // combination is meaningless, so we provide only a declaration
640 // and no definition.
641 template<typename _Key, typename _Value,
642 typename _ExtractKey, typename _Equal,
643 typename _H1, typename _H2, typename _Hash>
644 struct _Hash_code_base<_Key, _Value, _ExtractKey, _Equal, _H1, _H2,
647 // Specialization: hash function and range-hashing function, no
648 // caching of hash codes. H is provided but ignored. Provides
649 // typedef and accessor required by TR1.
650 template<typename _Key, typename _Value,
651 typename _ExtractKey, typename _Equal,
652 typename _H1, typename _H2>
653 struct _Hash_code_base<_Key, _Value, _ExtractKey, _Equal, _H1, _H2,
654 _Default_ranged_hash, false>
659 hash_function() const
663 _Hash_code_base(const _ExtractKey& __ex, const _Equal& __eq,
664 const _H1& __h1, const _H2& __h2,
665 const _Default_ranged_hash&)
666 : _M_extract(__ex), _M_eq(__eq), _M_h1(__h1), _M_h2(__h2) { }
668 typedef std::size_t _Hash_code_type;
671 _M_hash_code(const _Key& __k) const
672 { return _M_h1(__k); }
675 _M_bucket_index(const _Key&, _Hash_code_type __c,
676 std::size_t __n) const
677 { return _M_h2(__c, __n); }
680 _M_bucket_index(const _Hash_node<_Value, false>* __p,
681 std::size_t __n) const
682 { return _M_h2(_M_h1(_M_extract(__p->_M_v)), __n); }
685 _M_compare(const _Key& __k, _Hash_code_type,
686 _Hash_node<_Value, false>* __n) const
687 { return _M_eq(__k, _M_extract(__n->_M_v)); }
690 _M_store_code(_Hash_node<_Value, false>*, _Hash_code_type) const
694 _M_copy_code(_Hash_node<_Value, false>*,
695 const _Hash_node<_Value, false>*) const
699 _M_swap(_Hash_code_base& __x)
701 std::swap(_M_extract, __x._M_extract);
702 std::swap(_M_eq, __x._M_eq);
703 std::swap(_M_h1, __x._M_h1);
704 std::swap(_M_h2, __x._M_h2);
708 _ExtractKey _M_extract;
714 // Specialization: hash function and range-hashing function,
715 // caching hash codes. H is provided but ignored. Provides
716 // typedef and accessor required by TR1.
717 template<typename _Key, typename _Value,
718 typename _ExtractKey, typename _Equal,
719 typename _H1, typename _H2>
720 struct _Hash_code_base<_Key, _Value, _ExtractKey, _Equal, _H1, _H2,
721 _Default_ranged_hash, true>
726 hash_function() const
730 _Hash_code_base(const _ExtractKey& __ex, const _Equal& __eq,
731 const _H1& __h1, const _H2& __h2,
732 const _Default_ranged_hash&)
733 : _M_extract(__ex), _M_eq(__eq), _M_h1(__h1), _M_h2(__h2) { }
735 typedef std::size_t _Hash_code_type;
738 _M_hash_code(const _Key& __k) const
739 { return _M_h1(__k); }
742 _M_bucket_index(const _Key&, _Hash_code_type __c,
743 std::size_t __n) const
744 { return _M_h2(__c, __n); }
747 _M_bucket_index(const _Hash_node<_Value, true>* __p,
748 std::size_t __n) const
749 { return _M_h2(__p->_M_hash_code, __n); }
752 _M_compare(const _Key& __k, _Hash_code_type __c,
753 _Hash_node<_Value, true>* __n) const
754 { return __c == __n->_M_hash_code && _M_eq(__k, _M_extract(__n->_M_v)); }
757 _M_store_code(_Hash_node<_Value, true>* __n, _Hash_code_type __c) const
758 { __n->_M_hash_code = __c; }
761 _M_copy_code(_Hash_node<_Value, true>* __to,
762 const _Hash_node<_Value, true>* __from) const
763 { __to->_M_hash_code = __from->_M_hash_code; }
766 _M_swap(_Hash_code_base& __x)
768 std::swap(_M_extract, __x._M_extract);
769 std::swap(_M_eq, __x._M_eq);
770 std::swap(_M_h1, __x._M_h1);
771 std::swap(_M_h2, __x._M_h2);
775 _ExtractKey _M_extract;
780 _GLIBCXX_END_NAMESPACE_VERSION
781 } // namespace __detail