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4 (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2016
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31 #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_H
32 #define CDSLIB_INTRUSIVE_MICHAEL_SET_H
34 #include <cds/intrusive/details/michael_set_base.h>
35 #include <cds/intrusive/details/iterable_list_base.h>
37 namespace cds { namespace intrusive {
39 /// Michael's hash set
40 /** @ingroup cds_intrusive_map
41 \anchor cds_intrusive_MichaelHashSet_hp
44 - [2002] Maged Michael "High performance dynamic lock-free hash tables and list-based sets"
46 Michael's hash table algorithm is based on lock-free ordered list and it is very simple.
47 The main structure is an array \p T of size \p M. Each element in \p T is basically a pointer
48 to a hash bucket, implemented as a singly linked list. The array of buckets cannot be dynamically expanded.
49 However, each bucket may contain unbounded number of items.
51 Template parameters are:
52 - \p GC - Garbage collector used. Note the \p GC must be the same as the GC used for \p OrderedList
53 - \p OrderedList - ordered list implementation used as bucket for hash set, for example, \p MichaelList, \p LazyList, \p IterableList.
54 The intrusive ordered list implementation specifies the type \p T stored in the hash-set, the reclamation
55 schema \p GC used by hash-set, the comparison functor for the type \p T and other features specific for
57 - \p Traits - type traits. See \p michael_set::traits for explanation.
58 Instead of defining \p Traits struct you can use option-based syntax with \p michael_set::make_traits metafunction.
60 There are several specializations of \p %MichaelHashSet for each GC. You should include:
61 - <tt><cds/intrusive/michael_set_rcu.h></tt> for \ref cds_intrusive_MichaelHashSet_rcu "RCU type"
62 - <tt><cds/intrusive/michael_set_nogc.h></tt> for \ref cds_intrusive_MichaelHashSet_nogc for append-only set
63 - <tt><cds/intrusive/michael_set.h></tt> for \p gc::HP, \p gc::DHP
67 Some member functions of Michael's hash set accept the key parameter of type \p Q which differs from \p value_type.
68 It is expected that type \p Q contains full key of \p value_type, and for equal keys of type \p Q and \p value_type
69 the hash values of these keys must be equal.
70 The hash functor \p Traits::hash should accept parameters of both type:
74 std::string key_; // key field
80 size_t operator()( const std::string& s ) const
82 return std::hash( s );
85 size_t operator()( const Foo& f ) const
87 return (*this)( f.key_ );
94 First, you should define ordered list type to use in your hash set:
96 // For gc::HP-based MichaelList implementation
97 #include <cds/intrusive/michael_list_hp.h>
99 // cds::intrusive::MichaelHashSet declaration
100 #include <cds/intrusive/michael_set.h>
102 // Type of hash-set items
103 struct Foo: public cds::intrusive::michael_list::node< cds::gc::HP >
105 std::string key_ ; // key field
106 unsigned val_ ; // value field
107 // ... other value fields
110 // Declare comparator for the item
113 int operator()( const Foo& f1, const Foo& f2 ) const
115 return f1.key_.compare( f2.key_ );
119 // Declare bucket type for Michael's hash set
120 // The bucket type is any ordered list type like MichaelList, LazyList
121 typedef cds::intrusive::MichaelList< cds::gc::HP, Foo,
122 typename cds::intrusive::michael_list::make_traits<
124 cds::intrusive::opt::hook< cds::intrusive::michael_list::base_hook< cds::opt::gc< cds::gc::HP > > >
125 // item comparator option
126 ,cds::opt::compare< FooCmp >
131 Second, you should declare Michael's hash set container:
134 // Declare hash functor
135 // Note, the hash functor accepts parameter type Foo and std::string
137 size_t operator()( const Foo& f ) const
139 return cds::opt::v::hash<std::string>()( f.key_ );
141 size_t operator()( const std::string& f ) const
143 return cds::opt::v::hash<std::string>()( f );
147 // Michael's set typedef
148 typedef cds::intrusive::MichaelHashSet<
151 ,typename cds::intrusive::michael_set::make_traits<
152 cds::opt::hash< FooHash >
157 Now, you can use \p Foo_set in your application.
159 Like other intrusive containers, you may build several containers on single item structure:
161 #include <cds/intrusive/michael_list_hp.h>
162 #include <cds/intrusive/michael_list_dhp.h>
163 #include <cds/intrusive/michael_set.h>
169 // The first key is maintained by gc::HP, second key is maintained by gc::DHP garbage collectors
170 // (I don't know what is needed for, but it is correct)
172 : public cds::intrusive::michael_list::node< cds::gc::HP, tag_key1_idx >
173 , public cds::intrusive::michael_list::node< cds::gc::DHP, tag_key2_idx >
175 std::string key1_ ; // first key field
176 unsigned int key2_ ; // second key field
178 // ... value fields and fields for controlling item's lifetime
181 // Declare comparators for the item
184 int operator()( const Foo& f1, const Foo& f2 ) const { return f1.key1_.compare( f2.key1_ ) ; }
188 bool operator()( const Foo& f1, const Foo& f2 ) const { return f1.key2_ < f2.key1_ ; }
191 // Declare bucket type for Michael's hash set indexed by key1_ field and maintained by gc::HP
192 typedef cds::intrusive::MichaelList< cds::gc::HP, Foo,
193 typename cds::intrusive::michael_list::make_traits<
195 cds::intrusive::opt::hook< cds::intrusive::michael_list::base_hook< cds::opt::gc< cds::gc::HP >, tag_key1_idx > >
196 // item comparator option
197 ,cds::opt::compare< Key1Cmp >
201 // Declare bucket type for Michael's hash set indexed by key2_ field and maintained by gc::DHP
202 typedef cds::intrusive::MichaelList< cds::gc::DHP, Foo,
203 typename cds::intrusive::michael_list::make_traits<
205 cds::intrusive::opt::hook< cds::intrusive::michael_list::base_hook< cds::opt::gc< cds::gc::DHP >, tag_key2_idx > >
206 // item comparator option
207 ,cds::opt::less< Key2Less >
211 // Declare hash functor
213 size_t operator()( const Foo& f ) const { return cds::opt::v::hash<std::string>()( f.key1_ ) ; }
214 size_t operator()( const std::string& s ) const { return cds::opt::v::hash<std::string>()( s ) ; }
216 inline size_t Key2Hash( const Foo& f ) { return (size_t) f.key2_ ; }
218 // Michael's set indexed by key1_ field
219 typedef cds::intrusive::MichaelHashSet<
222 ,typename cds::intrusive::michael_set::make_traits<
223 cds::opt::hash< Key1Hash >
227 // Michael's set indexed by key2_ field
228 typedef cds::intrusive::MichaelHashSet<
231 ,typename cds::intrusive::michael_set::make_traits<
232 cds::opt::hash< Key2Hash >
240 #ifdef CDS_DOXYGEN_INVOKED
241 class Traits = michael_set::traits
249 typedef GC gc; ///< Garbage collector
250 typedef OrderedList ordered_list; ///< type of ordered list used as a bucket implementation
251 typedef Traits traits; ///< Set traits
253 typedef typename ordered_list::value_type value_type ; ///< type of value to be stored in the set
254 typedef typename ordered_list::key_comparator key_comparator ; ///< key comparing functor
255 typedef typename ordered_list::disposer disposer ; ///< Node disposer functor
256 typedef typename ordered_list::stat stat ; ///< Internal statistics
258 /// Hash functor for \p value_type and all its derivatives that you use
259 typedef typename cds::opt::v::hash_selector< typename traits::hash >::type hash;
260 typedef typename traits::item_counter item_counter; ///< Item counter type
261 typedef typename traits::allocator allocator; ///< Bucket table allocator
263 typedef typename ordered_list::guarded_ptr guarded_ptr; ///< Guarded pointer
265 /// Count of hazard pointer required for the algorithm
266 static CDS_CONSTEXPR const size_t c_nHazardPtrCount = ordered_list::c_nHazardPtrCount;
268 // GC and OrderedList::gc must be the same
269 static_assert(std::is_same<gc, typename ordered_list::gc>::value, "GC and OrderedList::gc must be the same");
271 // atomicity::empty_item_counter is not allowed as a item counter
272 static_assert(!std::is_same<item_counter, atomicity::empty_item_counter>::value,
273 "cds::atomicity::empty_item_counter is not allowed as a item counter");
277 typedef typename ordered_list::template select_stat_wrapper< typename ordered_list::stat > bucket_stat;
279 typedef typename ordered_list::template rebind_traits<
280 cds::opt::item_counter< cds::atomicity::empty_item_counter >
281 , cds::opt::stat< typename bucket_stat::wrapped_stat >
282 >::type internal_bucket_type;
284 typedef typename allocator::template rebind< internal_bucket_type >::other bucket_table_allocator;
286 hash m_HashFunctor; ///< Hash functor
287 size_t const m_nHashBitmask;
288 internal_bucket_type* m_Buckets; ///< bucket table
289 item_counter m_ItemCounter; ///< Item counter
290 typename bucket_stat::stat m_Stat; ///< Internal statistics
294 ///@name Forward iterators
298 The forward iterator for Michael's set is based on \p OrderedList forward iterator and has some features:
299 - it has no post-increment operator
300 - it iterates items in unordered fashion
301 - The iterator cannot be moved across thread boundary because it may contain GC's guard that is thread-private GC data.
303 Iterator thread safety depends on type of \p OrderedList:
304 - for \p MichaelList and \p LazyList: iterator guarantees safety even if you delete the item that iterator points to
305 because that item is guarded by hazard pointer.
306 However, in case of concurrent deleting operations it is no guarantee that you iterate all item in the set.
307 Moreover, a crash is possible when you try to iterate the next element that has been deleted by concurrent thread.
308 Use this iterator on the concurrent container for debugging purpose only.
309 - for \p IterableList: iterator is thread-safe. You may use it freely in concurrent environment.
312 typedef michael_set::details::iterator< internal_bucket_type, false > iterator;
314 /// Const forward iterator
316 For iterator's features and requirements see \ref iterator
318 typedef michael_set::details::iterator< internal_bucket_type, true > const_iterator;
320 /// Returns a forward iterator addressing the first element in a set
322 For empty set \code begin() == end() \endcode
326 return iterator( m_Buckets[0].begin(), bucket_begin(), bucket_end() );
329 /// Returns an iterator that addresses the location succeeding the last element in a set
331 Do not use the value returned by <tt>end</tt> function to access any item.
332 The returned value can be used only to control reaching the end of the set.
333 For empty set \code begin() == end() \endcode
337 return iterator( bucket_end()[-1].end(), bucket_end() - 1, bucket_end() );
340 /// Returns a forward const iterator addressing the first element in a set
341 const_iterator begin() const
343 return get_const_begin();
346 /// Returns a forward const iterator addressing the first element in a set
347 const_iterator cbegin() const
349 return get_const_begin();
352 /// Returns an const iterator that addresses the location succeeding the last element in a set
353 const_iterator end() const
355 return get_const_end();
358 /// Returns an const iterator that addresses the location succeeding the last element in a set
359 const_iterator cend() const
361 return get_const_end();
366 /// Initializes hash set
367 /** @anchor cds_intrusive_MichaelHashSet_hp_ctor
368 The Michael's hash set is an unbounded container, but its hash table is non-expandable.
369 At construction time you should pass estimated maximum item count and a load factor.
370 The load factor is average size of one bucket - a small number between 1 and 10.
371 The bucket is an ordered single-linked list, searching in the bucket has linear complexity <tt>O(nLoadFactor)</tt>.
372 The constructor defines hash table size as rounding <tt>nMaxItemCount / nLoadFactor</tt> up to nearest power of two.
375 size_t nMaxItemCount, ///< estimation of max item count in the hash set
376 size_t nLoadFactor ///< load factor: estimation of max number of items in the bucket. Small integer up to 10.
377 ) : m_nHashBitmask( michael_set::details::init_hash_bitmask( nMaxItemCount, nLoadFactor ))
378 , m_Buckets( bucket_table_allocator().allocate( bucket_count()))
380 for ( auto it = m_Buckets, itEnd = m_Buckets + bucket_count(); it != itEnd; ++it )
381 construct_bucket<bucket_stat>( it );
384 /// Clears hash set object and destroys it
389 for ( auto it = m_Buckets, itEnd = m_Buckets + bucket_count(); it != itEnd; ++it )
390 it->~internal_bucket_type();
391 bucket_table_allocator().deallocate( m_Buckets, bucket_count() );
396 The function inserts \p val in the set if it does not contain
397 an item with key equal to \p val.
399 Returns \p true if \p val is placed into the set, \p false otherwise.
401 bool insert( value_type& val )
403 bool bRet = bucket( val ).insert( val );
411 This function is intended for derived non-intrusive containers.
413 The function allows to split creating of new item into two part:
414 - create item with key only
415 - insert new item into the set
416 - if inserting is success, calls \p f functor to initialize value-field of \p val.
418 The functor signature is:
420 void func( value_type& val );
422 where \p val is the item inserted.
424 The user-defined functor is called only if the inserting is success.
426 @warning For \ref cds_intrusive_MichaelList_hp "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
427 \ref cds_intrusive_LazyList_hp "LazyList" provides exclusive access to inserted item and does not require any node-level
430 template <typename Func>
431 bool insert( value_type& val, Func f )
433 bool bRet = bucket( val ).insert( val, f );
439 /// Updates the element
441 The operation performs inserting or changing data with lock-free manner.
443 If the item \p val not found in the set, then \p val is inserted iff \p bAllowInsert is \p true.
444 Otherwise, the functor \p func is called with item found.
446 The functor signature depends of the type of \p OrderedList:
448 <b>for \p MichaelList, \p LazyList</b>
451 void operator()( bool bNew, value_type& item, value_type& val );
455 - \p bNew - \p true if the item has been inserted, \p false otherwise
456 - \p item - item of the set
457 - \p val - argument \p val passed into the \p %update() function
458 If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
459 refers to the same thing.
461 The functor may change non-key fields of the \p item.
462 @warning For \ref cds_intrusive_MichaelList_hp "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
463 \ref cds_intrusive_LazyList_hp "LazyList" provides exclusive access to inserted item and does not require any node-level
466 <b>for \p IterableList</b>
468 void func( value_type& val, value_type * old );
471 - \p val - argument \p val passed into the \p %update() function
472 - \p old - old value that will be retired. If new item has been inserted then \p old is \p nullptr.
474 Returns <tt> std::pair<bool, bool> </tt> where \p first is \p true if operation is successful,
475 \p second is \p true if new item has been added or \p false if the item with \p key
476 already is in the set.
478 template <typename Func>
479 std::pair<bool, bool> update( value_type& val, Func func, bool bAllowInsert = true )
481 std::pair<bool, bool> bRet = bucket( val ).update( val, func, bAllowInsert );
487 template <typename Func>
488 CDS_DEPRECATED("ensure() is deprecated, use update()")
489 std::pair<bool, bool> ensure( value_type& val, Func func )
491 return update( val, func, true );
495 /// Inserts or updates the node (only for \p IterableList)
497 The operation performs inserting or changing data with lock-free manner.
499 If the item \p val is not found in the set, then \p val is inserted iff \p bAllowInsert is \p true.
500 Otherwise, the current element is changed to \p val, the old element will be retired later
501 by call \p Traits::disposer.
503 Returns std::pair<bool, bool> where \p first is \p true if operation is successful,
504 \p second is \p true if \p val has been added or \p false if the item with that key
507 #ifdef CDS_DOXYGEN_INVOKED
508 std::pair<bool, bool> upsert( value_type& val, bool bAllowInsert = true )
510 template <typename Q>
511 typename std::enable_if<
512 std::is_same< Q, value_type>::value && is_iterable_list< ordered_list >::value,
513 std::pair<bool, bool>
515 upsert( Q& val, bool bAllowInsert = true )
518 std::pair<bool, bool> bRet = bucket( val ).upsert( val, bAllowInsert );
524 /// Unlinks the item \p val from the set
526 The function searches the item \p val in the set and unlink it
527 if it is found and is equal to \p val.
529 The function returns \p true if success and \p false otherwise.
531 bool unlink( value_type& val )
533 bool bRet = bucket( val ).unlink( val );
539 /// Deletes the item from the set
540 /** \anchor cds_intrusive_MichaelHashSet_hp_erase
541 The function searches an item with key equal to \p key in the set,
542 unlinks it, and returns \p true.
543 If the item with key equal to \p key is not found the function return \p false.
545 Note the hash functor should accept a parameter of type \p Q that can be not the same as \p value_type.
547 template <typename Q>
548 bool erase( Q const& key )
550 if ( bucket( key ).erase( key )) {
557 /// Deletes the item from the set using \p pred predicate for searching
559 The function is an analog of \ref cds_intrusive_MichaelHashSet_hp_erase "erase(Q const&)"
560 but \p pred is used for key comparing.
561 \p Less functor has the interface like \p std::less.
562 \p pred must imply the same element order as the comparator used for building the set.
564 template <typename Q, typename Less>
565 bool erase_with( Q const& key, Less pred )
567 if ( bucket( key ).erase_with( key, pred )) {
574 /// Deletes the item from the set
575 /** \anchor cds_intrusive_MichaelHashSet_hp_erase_func
576 The function searches an item with key equal to \p key in the set,
577 call \p f functor with item found, and unlinks it from the set.
578 The \ref disposer specified in \p OrderedList class template parameter is called
579 by garbage collector \p GC asynchronously.
581 The \p Func interface is
584 void operator()( value_type const& item );
588 If the item with key equal to \p key is not found the function return \p false.
590 Note the hash functor should accept a parameter of type \p Q that can be not the same as \p value_type.
592 template <typename Q, typename Func>
593 bool erase( Q const& key, Func f )
595 if ( bucket( key ).erase( key, f )) {
602 /// Deletes the item from the set using \p pred predicate for searching
604 The function is an analog of \ref cds_intrusive_MichaelHashSet_hp_erase_func "erase(Q const&, Func)"
605 but \p pred is used for key comparing.
606 \p Less functor has the interface like \p std::less.
607 \p pred must imply the same element order as the comparator used for building the set.
609 template <typename Q, typename Less, typename Func>
610 bool erase_with( Q const& key, Less pred, Func f )
612 if ( bucket( key ).erase_with( key, pred, f )) {
619 /// Extracts the item with specified \p key
620 /** \anchor cds_intrusive_MichaelHashSet_hp_extract
621 The function searches an item with key equal to \p key,
622 unlinks it from the set, and returns an guarded pointer to the item extracted.
623 If \p key is not found the function returns an empty guarded pointer.
625 Note the compare functor should accept a parameter of type \p Q that may be not the same as \p value_type.
627 The \p disposer specified in \p OrderedList class' template parameter is called automatically
628 by garbage collector \p GC when returned \ref guarded_ptr object will be destroyed or released.
629 @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
633 typedef cds::intrusive::MichaelHashSet< your_template_args > michael_set;
637 michael_set::guarded_ptr gp( theSet.extract( 5 ));
642 // Destructor of gp releases internal HP guard
646 template <typename Q>
647 guarded_ptr extract( Q const& key )
649 guarded_ptr gp = bucket( key ).extract( key );
655 /// Extracts the item using compare functor \p pred
657 The function is an analog of \ref cds_intrusive_MichaelHashSet_hp_extract "extract(Q const&)"
658 but \p pred predicate is used for key comparing.
660 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
662 \p pred must imply the same element order as the comparator used for building the list.
664 template <typename Q, typename Less>
665 guarded_ptr extract_with( Q const& key, Less pred )
667 guarded_ptr gp = bucket( key ).extract_with( key, pred );
673 /// Finds the key \p key
674 /** \anchor cds_intrusive_MichaelHashSet_hp_find_func
675 The function searches the item with key equal to \p key and calls the functor \p f for item found.
676 The interface of \p Func functor is:
679 void operator()( value_type& item, Q& key );
682 where \p item is the item found, \p key is the <tt>find</tt> function argument.
684 The functor may change non-key fields of \p item. Note that the functor is only guarantee
685 that \p item cannot be disposed during functor is executing.
686 The functor does not serialize simultaneous access to the set \p item. If such access is
687 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
689 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
690 may modify both arguments.
692 Note the hash functor specified for class \p Traits template parameter
693 should accept a parameter of type \p Q that can be not the same as \p value_type.
695 The function returns \p true if \p key is found, \p false otherwise.
697 template <typename Q, typename Func>
698 bool find( Q& key, Func f )
700 return bucket( key ).find( key, f );
703 template <typename Q, typename Func>
704 bool find( Q const& key, Func f )
706 return bucket( key ).find( key, f );
710 /// Finds \p key and returns iterator pointed to the item found (only for \p IterableList)
712 If \p key is not found the function returns \p end().
714 @note This function is supported only for the set based on \p IterableList
716 template <typename Q>
717 #ifdef CDS_DOXYGEN_INVOKED
720 typename std::enable_if< std::is_same<Q,Q>::value && is_iterable_list< ordered_list >::value, iterator >::type
724 internal_bucket_type& b = bucket( key );
725 typename internal_bucket_type::iterator it = b.find( key );
728 return iterator( it, &b, bucket_end());
731 template <typename Q>
732 typename std::enable_if< std::is_same<Q, Q>::value && is_iterable_list< ordered_list >::value, iterator >::type
735 internal_bucket_type& b = bucket( key );
736 typename internal_bucket_type::iterator it = b.find( key );
739 return iterator( it, &b, bucket_end() );
744 /// Finds the key \p key using \p pred predicate for searching
746 The function is an analog of \ref cds_intrusive_MichaelHashSet_hp_find_func "find(Q&, Func)"
747 but \p pred is used for key comparing.
748 \p Less functor has the interface like \p std::less.
749 \p pred must imply the same element order as the comparator used for building the set.
751 template <typename Q, typename Less, typename Func>
752 bool find_with( Q& key, Less pred, Func f )
754 return bucket( key ).find_with( key, pred, f );
757 template <typename Q, typename Less, typename Func>
758 bool find_with( Q const& key, Less pred, Func f )
760 return bucket( key ).find_with( key, pred, f );
764 /// Finds \p key using \p pred predicate and returns iterator pointed to the item found (only for \p IterableList)
766 The function is an analog of \p find(Q&) but \p pred is used for key comparing.
767 \p Less functor has the interface like \p std::less.
768 \p pred must imply the same element order as the comparator used for building the set.
770 If \p key is not found the function returns \p end().
772 @note This function is supported only for the set based on \p IterableList
774 template <typename Q, typename Less>
775 #ifdef CDS_DOXYGEN_INVOKED
778 typename std::enable_if< std::is_same<Q, Q>::value && is_iterable_list< ordered_list >::value, iterator >::type
780 find_with( Q& key, Less pred )
782 internal_bucket_type& b = bucket( key );
783 typename internal_bucket_type::iterator it = b.find_with( key, pred );
786 return iterator( it, &b, bucket_end() );
789 template <typename Q, typename Less>
790 typename std::enable_if< std::is_same<Q, Q>::value && is_iterable_list< ordered_list >::value, iterator >::type
791 find_with( Q const& key, Less pred )
793 internal_bucket_type& b = bucket( key );
794 typename internal_bucket_type::iterator it = b.find_with( key, pred );
797 return iterator( it, &b, bucket_end() );
801 /// Checks whether the set contains \p key
804 The function searches the item with key equal to \p key
805 and returns \p true if the key is found, and \p false otherwise.
807 Note the hash functor specified for class \p Traits template parameter
808 should accept a parameter of type \p Q that can be not the same as \p value_type.
810 template <typename Q>
811 bool contains( Q const& key )
813 return bucket( key ).contains( key );
816 /// Checks whether the set contains \p key using \p pred predicate for searching
818 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
819 \p Less functor has the interface like \p std::less.
820 \p Less must imply the same element order as the comparator used for building the set.
822 template <typename Q, typename Less>
823 bool contains( Q const& key, Less pred )
825 return bucket( key ).contains( key, pred );
828 /// Finds the key \p key and return the item found
829 /** \anchor cds_intrusive_MichaelHashSet_hp_get
830 The function searches the item with key equal to \p key
831 and returns the guarded pointer to the item found.
832 If \p key is not found the function returns an empty \p guarded_ptr.
834 @note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
838 typedef cds::intrusive::MichaelHashSet< your_template_params > michael_set;
842 michael_set::guarded_ptr gp( theSet.get( 5 ));
843 if ( theSet.get( 5 )) {
847 // Destructor of guarded_ptr releases internal HP guard
851 Note the compare functor specified for \p OrderedList template parameter
852 should accept a parameter of type \p Q that can be not the same as \p value_type.
854 template <typename Q>
855 guarded_ptr get( Q const& key )
857 return bucket( key ).get( key );
860 /// Finds the key \p key and return the item found
862 The function is an analog of \ref cds_intrusive_MichaelHashSet_hp_get "get( Q const&)"
863 but \p pred is used for comparing the keys.
865 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
867 \p pred must imply the same element order as the comparator used for building the set.
869 template <typename Q, typename Less>
870 guarded_ptr get_with( Q const& key, Less pred )
872 return bucket( key ).get_with( key, pred );
875 /// Clears the set (non-atomic)
877 The function unlink all items from the set.
878 The function is not atomic. It cleans up each bucket and then resets the item counter to zero.
879 If there are a thread that performs insertion while \p %clear() is working the result is undefined in general case:
880 \p empty() may return \p true but the set may contain item(s).
881 Therefore, \p %clear() may be used only for debugging purposes.
883 For each item the \p disposer is called after unlinking.
887 for ( size_t i = 0; i < bucket_count(); ++i )
888 m_Buckets[i].clear();
889 m_ItemCounter.reset();
892 /// Checks if the set is empty
894 Emptiness is checked by item counting: if item count is zero then the set is empty.
895 Thus, the correct item counting feature is an important part of Michael's set implementation.
902 /// Returns item count in the set
905 return m_ItemCounter;
908 /// Returns const reference to internal statistics
909 stat const& statistics() const
914 /// Returns the size of hash table
916 Since \p %MichaelHashSet cannot dynamically extend the hash table size,
917 the value returned is an constant depending on object initialization parameters,
918 see \p MichaelHashSet::MichaelHashSet.
920 size_t bucket_count() const
922 return m_nHashBitmask + 1;
927 internal_bucket_type * bucket_begin() const
932 internal_bucket_type * bucket_end() const
934 return m_Buckets + bucket_count();
937 const_iterator get_const_begin() const
939 return const_iterator( m_Buckets[0].cbegin(), bucket_begin(), bucket_end() );
941 const_iterator get_const_end() const
943 return const_iterator( bucket_end()[-1].cend(), bucket_end() - 1, bucket_end() );
946 template <typename Stat>
947 typename std::enable_if< Stat::empty >::type construct_bucket( internal_bucket_type * bucket )
949 new (bucket) internal_bucket_type;
952 template <typename Stat>
953 typename std::enable_if< !Stat::empty >::type construct_bucket( internal_bucket_type * bucket )
955 new (bucket) internal_bucket_type( m_Stat );
958 /// Calculates hash value of \p key
959 template <typename Q>
960 size_t hash_value( const Q& key ) const
962 return m_HashFunctor( key ) & m_nHashBitmask;
965 /// Returns the bucket (ordered list) for \p key
966 template <typename Q>
967 internal_bucket_type& bucket( const Q& key )
969 return m_Buckets[hash_value( key )];
974 }} // namespace cds::intrusive
976 #endif // ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_H