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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, possible implementations:
54 \p MichaelList, \p LazyList, \p IterableList.
55 The intrusive ordered list implementation specifies the type \p T stored in the hash-set, the reclamation
56 schema \p GC used by hash-set, the comparison functor for the type \p T and other features specific for
58 - \p Traits - type traits. See \p michael_set::traits for explanation.
59 Instead of defining \p Traits struct you can use option-based syntax with \p michael_set::make_traits metafunction.
61 There are several specializations of \p %MichaelHashSet for each GC. You should include:
62 - <tt><cds/intrusive/michael_set_rcu.h></tt> for \ref cds_intrusive_MichaelHashSet_rcu "RCU type"
63 - <tt><cds/intrusive/michael_set_nogc.h></tt> for \ref cds_intrusive_MichaelHashSet_nogc for append-only set
64 - <tt><cds/intrusive/michael_set.h></tt> for \p gc::HP, \p gc::DHP
68 Some member functions of Michael's hash set accept the key parameter of type \p Q which differs from \p value_type.
69 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
70 the hash values of these keys must be equal.
71 The hash functor \p Traits::hash should accept parameters of both type:
75 std::string key_; // key field
81 size_t operator()( const std::string& s ) const
83 return std::hash( s );
86 size_t operator()( const Foo& f ) const
88 return (*this)( f.key_ );
95 First, you should define ordered list type to use in your hash set:
97 // For gc::HP-based MichaelList implementation
98 #include <cds/intrusive/michael_list_hp.h>
100 // cds::intrusive::MichaelHashSet declaration
101 #include <cds/intrusive/michael_set.h>
103 // Type of hash-set items
104 struct Foo: public cds::intrusive::michael_list::node< cds::gc::HP >
106 std::string key_ ; // key field
107 unsigned val_ ; // value field
108 // ... other value fields
111 // Declare comparator for the item
114 int operator()( const Foo& f1, const Foo& f2 ) const
116 return f1.key_.compare( f2.key_ );
120 // Declare bucket type for Michael's hash set
121 // The bucket type is any ordered list type like MichaelList, LazyList
122 typedef cds::intrusive::MichaelList< cds::gc::HP, Foo,
123 typename cds::intrusive::michael_list::make_traits<
125 cds::intrusive::opt::hook< cds::intrusive::michael_list::base_hook< cds::opt::gc< cds::gc::HP > > >
126 // item comparator option
127 ,cds::opt::compare< FooCmp >
132 Second, you should declare Michael's hash set container:
135 // Declare hash functor
136 // Note, the hash functor accepts parameter type Foo and std::string
138 size_t operator()( const Foo& f ) const
140 return cds::opt::v::hash<std::string>()( f.key_ );
142 size_t operator()( const std::string& f ) const
144 return cds::opt::v::hash<std::string>()( f );
148 // Michael's set typedef
149 typedef cds::intrusive::MichaelHashSet<
152 ,typename cds::intrusive::michael_set::make_traits<
153 cds::opt::hash< FooHash >
158 Now, you can use \p Foo_set in your application.
160 Like other intrusive containers, you may build several containers on single item structure:
162 #include <cds/intrusive/michael_list_hp.h>
163 #include <cds/intrusive/michael_list_dhp.h>
164 #include <cds/intrusive/michael_set.h>
170 // The first key is maintained by gc::HP, second key is maintained by gc::DHP garbage collectors
171 // (I don't know what is needed for, but it is correct)
173 : public cds::intrusive::michael_list::node< cds::gc::HP, tag_key1_idx >
174 , public cds::intrusive::michael_list::node< cds::gc::DHP, tag_key2_idx >
176 std::string key1_ ; // first key field
177 unsigned int key2_ ; // second key field
179 // ... value fields and fields for controlling item's lifetime
182 // Declare comparators for the item
185 int operator()( const Foo& f1, const Foo& f2 ) const { return f1.key1_.compare( f2.key1_ ) ; }
189 bool operator()( const Foo& f1, const Foo& f2 ) const { return f1.key2_ < f2.key1_ ; }
192 // Declare bucket type for Michael's hash set indexed by key1_ field and maintained by gc::HP
193 typedef cds::intrusive::MichaelList< cds::gc::HP, Foo,
194 typename cds::intrusive::michael_list::make_traits<
196 cds::intrusive::opt::hook< cds::intrusive::michael_list::base_hook< cds::opt::gc< cds::gc::HP >, tag_key1_idx > >
197 // item comparator option
198 ,cds::opt::compare< Key1Cmp >
202 // Declare bucket type for Michael's hash set indexed by key2_ field and maintained by gc::DHP
203 typedef cds::intrusive::MichaelList< cds::gc::DHP, Foo,
204 typename cds::intrusive::michael_list::make_traits<
206 cds::intrusive::opt::hook< cds::intrusive::michael_list::base_hook< cds::opt::gc< cds::gc::DHP >, tag_key2_idx > >
207 // item comparator option
208 ,cds::opt::less< Key2Less >
212 // Declare hash functor
214 size_t operator()( const Foo& f ) const { return cds::opt::v::hash<std::string>()( f.key1_ ) ; }
215 size_t operator()( const std::string& s ) const { return cds::opt::v::hash<std::string>()( s ) ; }
217 inline size_t Key2Hash( const Foo& f ) { return (size_t) f.key2_ ; }
219 // Michael's set indexed by key1_ field
220 typedef cds::intrusive::MichaelHashSet<
223 ,typename cds::intrusive::michael_set::make_traits<
224 cds::opt::hash< Key1Hash >
228 // Michael's set indexed by key2_ field
229 typedef cds::intrusive::MichaelHashSet<
232 ,typename cds::intrusive::michael_set::make_traits<
233 cds::opt::hash< Key2Hash >
241 #ifdef CDS_DOXYGEN_INVOKED
242 class Traits = michael_set::traits
250 typedef GC gc; ///< Garbage collector
251 typedef OrderedList ordered_list; ///< type of ordered list used as a bucket implementation
252 typedef Traits traits; ///< Set traits
254 typedef typename ordered_list::value_type value_type ; ///< type of value to be stored in the set
255 typedef typename ordered_list::key_comparator key_comparator ; ///< key comparing functor
256 typedef typename ordered_list::disposer disposer ; ///< Node disposer functor
257 #ifdef CDS_DOXYGEN_INVOKED
258 typedef typename ordered_list::stat stat ; ///< Internal statistics
261 /// Hash functor for \p value_type and all its derivatives that you use
262 typedef typename cds::opt::v::hash_selector< typename traits::hash >::type hash;
263 typedef typename traits::item_counter item_counter; ///< Item counter type
264 typedef typename traits::allocator allocator; ///< Bucket table allocator
266 typedef typename ordered_list::guarded_ptr guarded_ptr; ///< Guarded pointer
268 /// Count of hazard pointer required for the algorithm
269 static CDS_CONSTEXPR const size_t c_nHazardPtrCount = ordered_list::c_nHazardPtrCount;
271 // GC and OrderedList::gc must be the same
272 static_assert(std::is_same<gc, typename ordered_list::gc>::value, "GC and OrderedList::gc must be the same");
276 typedef typename ordered_list::template select_stat_wrapper< typename ordered_list::stat > bucket_stat;
278 typedef typename ordered_list::template rebind_traits<
279 cds::opt::item_counter< cds::atomicity::empty_item_counter >
280 , cds::opt::stat< typename bucket_stat::wrapped_stat >
281 >::type internal_bucket_type;
283 typedef typename allocator::template rebind< internal_bucket_type >::other bucket_table_allocator;
288 typedef typename bucket_stat::stat stat;
293 hash m_HashFunctor; ///< Hash functor
294 size_t const m_nHashBitmask;
295 internal_bucket_type* m_Buckets; ///< bucket table
296 item_counter m_ItemCounter; ///< Item counter
297 stat m_Stat; ///< Internal statistics
301 ///@name Forward iterators
305 The forward iterator for Michael's set is based on \p OrderedList forward iterator and has some features:
306 - it has no post-increment operator
307 - it iterates items in unordered fashion
308 - The iterator cannot be moved across thread boundary because it may contain GC's guard that is thread-private GC data.
310 Iterator thread safety depends on type of \p OrderedList:
311 - for \p MichaelList and \p LazyList: iterator guarantees safety even if you delete the item that iterator points to
312 because that item is guarded by hazard pointer.
313 However, in case of concurrent deleting operations it is no guarantee that you iterate all item in the set.
314 Moreover, a crash is possible when you try to iterate the next element that has been deleted by concurrent thread.
315 Use this iterator on the concurrent container for debugging purpose only.
316 - for \p IterableList: iterator is thread-safe. You may use it freely in concurrent environment.
318 typedef michael_set::details::iterator< internal_bucket_type, false > iterator;
320 /// Const forward iterator
322 For iterator's features and requirements see \ref iterator
324 typedef michael_set::details::iterator< internal_bucket_type, true > const_iterator;
326 /// Returns a forward iterator addressing the first element in a set
328 For empty set \code begin() == end() \endcode
332 return iterator( m_Buckets[0].begin(), bucket_begin(), bucket_end());
335 /// Returns an iterator that addresses the location succeeding the last element in a set
337 Do not use the value returned by <tt>end</tt> function to access any item.
338 The returned value can be used only to control reaching the end of the set.
339 For empty set \code begin() == end() \endcode
343 return iterator( bucket_end()[-1].end(), bucket_end() - 1, bucket_end());
346 /// Returns a forward const iterator addressing the first element in a set
347 const_iterator begin() const
349 return get_const_begin();
352 /// Returns a forward const iterator addressing the first element in a set
353 const_iterator cbegin() const
355 return get_const_begin();
358 /// Returns an const iterator that addresses the location succeeding the last element in a set
359 const_iterator end() const
361 return get_const_end();
364 /// Returns an const iterator that addresses the location succeeding the last element in a set
365 const_iterator cend() const
367 return get_const_end();
372 /// Initializes hash set
374 The Michael's hash set is an unbounded container, but its hash table is non-expandable.
375 At construction time you should pass estimated maximum item count and a load factor.
376 The load factor is average size of one bucket - a small number between 1 and 10.
377 The bucket is an ordered single-linked list, searching in the bucket has linear complexity <tt>O(nLoadFactor)</tt>.
378 The constructor defines hash table size as rounding <tt>nMaxItemCount / nLoadFactor</tt> up to nearest power of two.
381 size_t nMaxItemCount, ///< estimation of max item count in the hash set
382 size_t nLoadFactor ///< load factor: estimation of max number of items in the bucket. Small integer up to 10.
383 ) : m_nHashBitmask( michael_set::details::init_hash_bitmask( nMaxItemCount, nLoadFactor ))
384 , m_Buckets( bucket_table_allocator().allocate( bucket_count()))
386 for ( auto it = m_Buckets, itEnd = m_Buckets + bucket_count(); it != itEnd; ++it )
387 construct_bucket<bucket_stat>( it );
390 /// Clears hash set object and destroys it
395 for ( auto it = m_Buckets, itEnd = m_Buckets + bucket_count(); it != itEnd; ++it )
396 it->~internal_bucket_type();
397 bucket_table_allocator().deallocate( m_Buckets, bucket_count());
402 The function inserts \p val in the set if it does not contain
403 an item with key equal to \p val.
405 Returns \p true if \p val is placed into the set, \p false otherwise.
407 bool insert( value_type& val )
409 bool bRet = bucket( val ).insert( val );
417 This function is intended for derived non-intrusive containers.
419 The function allows to split creating of new item into two part:
420 - create item with key only
421 - insert new item into the set
422 - if inserting is success, calls \p f functor to initialize value-field of \p val.
424 The functor signature is:
426 void func( value_type& val );
428 where \p val is the item inserted.
430 The user-defined functor is called only if the inserting is success.
432 @warning For \ref cds_intrusive_MichaelList_hp "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
433 \ref cds_intrusive_LazyList_hp "LazyList" provides exclusive access to inserted item and does not require any node-level
436 template <typename Func>
437 bool insert( value_type& val, Func f )
439 bool bRet = bucket( val ).insert( val, f );
445 /// Updates the element
447 The operation performs inserting or changing data with lock-free manner.
449 If the item \p val not found in the set, then \p val is inserted iff \p bAllowInsert is \p true.
450 Otherwise, the functor \p func is called with item found.
452 The functor signature depends of the type of \p OrderedList:
454 <b>for \p MichaelList, \p LazyList</b>
457 void operator()( bool bNew, value_type& item, value_type& val );
461 - \p bNew - \p true if the item has been inserted, \p false otherwise
462 - \p item - item of the set
463 - \p val - argument \p val passed into the \p %update() function
464 If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
465 refers to the same thing.
467 The functor may change non-key fields of the \p item.
468 @warning For \ref cds_intrusive_MichaelList_hp "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
469 \ref cds_intrusive_LazyList_hp "LazyList" provides exclusive access to inserted item and does not require any node-level
472 <b>for \p IterableList</b>
474 void func( value_type& val, value_type * old );
477 - \p val - argument \p val passed into the \p %update() function
478 - \p old - old value that will be retired. If new item has been inserted then \p old is \p nullptr.
480 Returns <tt> std::pair<bool, bool> </tt> where \p first is \p true if operation is successful,
481 \p second is \p true if new item has been added or \p false if the item with \p key
482 already is in the set.
484 template <typename Func>
485 std::pair<bool, bool> update( value_type& val, Func func, bool bAllowInsert = true )
487 std::pair<bool, bool> bRet = bucket( val ).update( val, func, bAllowInsert );
493 template <typename Func>
494 CDS_DEPRECATED("ensure() is deprecated, use update()")
495 std::pair<bool, bool> ensure( value_type& val, Func func )
497 return update( val, func, true );
501 /// Inserts or updates the node (only for \p IterableList)
503 The operation performs inserting or changing data with lock-free manner.
505 If the item \p val is not found in the set, then \p val is inserted iff \p bAllowInsert is \p true.
506 Otherwise, the current element is changed to \p val, the old element will be retired later
507 by call \p Traits::disposer.
509 Returns std::pair<bool, bool> where \p first is \p true if operation is successful,
510 \p second is \p true if \p val has been added or \p false if the item with that key
513 #ifdef CDS_DOXYGEN_INVOKED
514 std::pair<bool, bool> upsert( value_type& val, bool bAllowInsert = true )
516 template <typename Q>
517 typename std::enable_if<
518 std::is_same< Q, value_type>::value && is_iterable_list< ordered_list >::value,
519 std::pair<bool, bool>
521 upsert( Q& val, bool bAllowInsert = true )
524 std::pair<bool, bool> bRet = bucket( val ).upsert( val, bAllowInsert );
530 /// Unlinks the item \p val from the set
532 The function searches the item \p val in the set and unlink it
533 if it is found and is equal to \p val.
535 The function returns \p true if success and \p false otherwise.
537 bool unlink( value_type& val )
539 bool bRet = bucket( val ).unlink( val );
545 /// Deletes the item from the set
546 /** \anchor cds_intrusive_MichaelHashSet_hp_erase
547 The function searches an item with key equal to \p key in the set,
548 unlinks it, and returns \p true.
549 If the item with key equal to \p key is not found the function return \p false.
551 Note the hash functor should accept a parameter of type \p Q that can be not the same as \p value_type.
553 template <typename Q>
554 bool erase( Q const& key )
556 if ( bucket( key ).erase( key )) {
563 /// Deletes the item from the set using \p pred predicate for searching
565 The function is an analog of \ref cds_intrusive_MichaelHashSet_hp_erase "erase(Q const&)"
566 but \p pred is used for key comparing.
567 \p Less functor has the interface like \p std::less.
568 \p pred must imply the same element order as the comparator used for building the set.
570 template <typename Q, typename Less>
571 bool erase_with( Q const& key, Less pred )
573 if ( bucket( key ).erase_with( key, pred )) {
580 /// Deletes the item from the set
581 /** \anchor cds_intrusive_MichaelHashSet_hp_erase_func
582 The function searches an item with key equal to \p key in the set,
583 call \p f functor with item found, and unlinks it from the set.
584 The \ref disposer specified in \p OrderedList class template parameter is called
585 by garbage collector \p GC asynchronously.
587 The \p Func interface is
590 void operator()( value_type const& item );
594 If the item with key equal to \p key is not found the function return \p false.
596 Note the hash functor should accept a parameter of type \p Q that can be not the same as \p value_type.
598 template <typename Q, typename Func>
599 bool erase( Q const& key, Func f )
601 if ( bucket( key ).erase( key, f )) {
608 /// Deletes the item from the set using \p pred predicate for searching
610 The function is an analog of \ref cds_intrusive_MichaelHashSet_hp_erase_func "erase(Q const&, Func)"
611 but \p pred is used for key comparing.
612 \p Less functor has the interface like \p std::less.
613 \p pred must imply the same element order as the comparator used for building the set.
615 template <typename Q, typename Less, typename Func>
616 bool erase_with( Q const& key, Less pred, Func f )
618 if ( bucket( key ).erase_with( key, pred, f )) {
625 /// Deletes the item pointed by iterator \p iter (only for \p IterableList based set)
627 Returns \p true if the operation is successful, \p false otherwise.
628 The function can return \p false if the node the iterator points to has already been deleted
631 The function does not invalidate the iterator, it remains valid and can be used for further traversing.
633 @note \p %erase_at() is supported only for \p %MichaelHashSet based on \p IterableList.
635 #ifdef CDS_DOXYGEN_INVOKED
636 bool erase_at( iterator const& iter )
638 template <typename Iterator>
639 typename std::enable_if< std::is_same<Iterator, iterator>::value && is_iterable_list< ordered_list >::value, bool >::type
640 erase_at( Iterator const& iter )
643 assert( iter != end());
644 assert( iter.bucket() != nullptr );
646 if ( iter.bucket()->erase_at( iter.underlying_iterator())) {
653 /// Extracts the item with specified \p key
654 /** \anchor cds_intrusive_MichaelHashSet_hp_extract
655 The function searches an item with key equal to \p key,
656 unlinks it from the set, and returns an guarded pointer to the item extracted.
657 If \p key is not found the function returns an empty guarded pointer.
659 Note the compare functor should accept a parameter of type \p Q that may be not the same as \p value_type.
661 The \p disposer specified in \p OrderedList class' template parameter is called automatically
662 by garbage collector \p GC when returned \ref guarded_ptr object will be destroyed or released.
663 @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
667 typedef cds::intrusive::MichaelHashSet< your_template_args > michael_set;
671 michael_set::guarded_ptr gp( theSet.extract( 5 ));
676 // Destructor of gp releases internal HP guard
680 template <typename Q>
681 guarded_ptr extract( Q const& key )
683 guarded_ptr gp = bucket( key ).extract( key );
689 /// Extracts the item using compare functor \p pred
691 The function is an analog of \ref cds_intrusive_MichaelHashSet_hp_extract "extract(Q const&)"
692 but \p pred predicate is used for key comparing.
694 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
696 \p pred must imply the same element order as the comparator used for building the list.
698 template <typename Q, typename Less>
699 guarded_ptr extract_with( Q const& key, Less pred )
701 guarded_ptr gp = bucket( key ).extract_with( key, pred );
707 /// Finds the key \p key
708 /** \anchor cds_intrusive_MichaelHashSet_hp_find_func
709 The function searches the item with key equal to \p key and calls the functor \p f for item found.
710 The interface of \p Func functor is:
713 void operator()( value_type& item, Q& key );
716 where \p item is the item found, \p key is the <tt>find</tt> function argument.
718 The functor may change non-key fields of \p item. Note that the functor is only guarantee
719 that \p item cannot be disposed during functor is executing.
720 The functor does not serialize simultaneous access to the set \p item. If such access is
721 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
723 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
724 may modify both arguments.
726 Note the hash functor specified for class \p Traits template parameter
727 should accept a parameter of type \p Q that can be not the same as \p value_type.
729 The function returns \p true if \p key is found, \p false otherwise.
731 template <typename Q, typename Func>
732 bool find( Q& key, Func f )
734 return bucket( key ).find( key, f );
737 template <typename Q, typename Func>
738 bool find( Q const& key, Func f )
740 return bucket( key ).find( key, f );
744 /// Finds \p key and returns iterator pointed to the item found (only for \p IterableList)
746 If \p key is not found the function returns \p end().
748 @note This function is supported only for the set based on \p IterableList
750 template <typename Q>
751 #ifdef CDS_DOXYGEN_INVOKED
754 typename std::enable_if< std::is_same<Q,Q>::value && is_iterable_list< ordered_list >::value, iterator >::type
758 internal_bucket_type& b = bucket( key );
759 typename internal_bucket_type::iterator it = b.find( key );
762 return iterator( it, &b, bucket_end());
765 template <typename Q>
766 typename std::enable_if< std::is_same<Q, Q>::value && is_iterable_list< ordered_list >::value, iterator >::type
769 internal_bucket_type& b = bucket( key );
770 typename internal_bucket_type::iterator it = b.find( key );
773 return iterator( it, &b, bucket_end());
778 /// Finds the key \p key using \p pred predicate for searching
780 The function is an analog of \ref cds_intrusive_MichaelHashSet_hp_find_func "find(Q&, Func)"
781 but \p pred is used for key comparing.
782 \p Less functor has the interface like \p std::less.
783 \p pred must imply the same element order as the comparator used for building the set.
785 template <typename Q, typename Less, typename Func>
786 bool find_with( Q& key, Less pred, Func f )
788 return bucket( key ).find_with( key, pred, f );
791 template <typename Q, typename Less, typename Func>
792 bool find_with( Q const& key, Less pred, Func f )
794 return bucket( key ).find_with( key, pred, f );
798 /// Finds \p key using \p pred predicate and returns iterator pointed to the item found (only for \p IterableList)
800 The function is an analog of \p find(Q&) but \p pred is used for key comparing.
801 \p Less functor has the interface like \p std::less.
802 \p pred must imply the same element order as the comparator used for building the set.
804 If \p key is not found the function returns \p end().
806 @note This function is supported only for the set based on \p IterableList
808 template <typename Q, typename Less>
809 #ifdef CDS_DOXYGEN_INVOKED
812 typename std::enable_if< std::is_same<Q, Q>::value && is_iterable_list< ordered_list >::value, iterator >::type
814 find_with( Q& key, Less pred )
816 internal_bucket_type& b = bucket( key );
817 typename internal_bucket_type::iterator it = b.find_with( key, pred );
820 return iterator( it, &b, bucket_end());
823 template <typename Q, typename Less>
824 typename std::enable_if< std::is_same<Q, Q>::value && is_iterable_list< ordered_list >::value, iterator >::type
825 find_with( Q const& key, Less pred )
827 internal_bucket_type& b = bucket( key );
828 typename internal_bucket_type::iterator it = b.find_with( key, pred );
831 return iterator( it, &b, bucket_end());
835 /// Checks whether the set contains \p key
838 The function searches the item with key equal to \p key
839 and returns \p true if the key is found, and \p false otherwise.
841 Note the hash functor specified for class \p Traits template parameter
842 should accept a parameter of type \p Q that can be not the same as \p value_type.
844 template <typename Q>
845 bool contains( Q const& key )
847 return bucket( key ).contains( key );
850 /// Checks whether the set contains \p key using \p pred predicate for searching
852 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
853 \p Less functor has the interface like \p std::less.
854 \p Less must imply the same element order as the comparator used for building the set.
856 template <typename Q, typename Less>
857 bool contains( Q const& key, Less pred )
859 return bucket( key ).contains( key, pred );
862 /// Finds the key \p key and return the item found
863 /** \anchor cds_intrusive_MichaelHashSet_hp_get
864 The function searches the item with key equal to \p key
865 and returns the guarded pointer to the item found.
866 If \p key is not found the function returns an empty \p guarded_ptr.
868 @note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
872 typedef cds::intrusive::MichaelHashSet< your_template_params > michael_set;
876 michael_set::guarded_ptr gp( theSet.get( 5 ));
877 if ( theSet.get( 5 )) {
881 // Destructor of guarded_ptr releases internal HP guard
885 Note the compare functor specified for \p OrderedList template parameter
886 should accept a parameter of type \p Q that can be not the same as \p value_type.
888 template <typename Q>
889 guarded_ptr get( Q const& key )
891 return bucket( key ).get( key );
894 /// Finds the key \p key and return the item found
896 The function is an analog of \ref cds_intrusive_MichaelHashSet_hp_get "get( Q const&)"
897 but \p pred is used for comparing the keys.
899 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
901 \p pred must imply the same element order as the comparator used for building the set.
903 template <typename Q, typename Less>
904 guarded_ptr get_with( Q const& key, Less pred )
906 return bucket( key ).get_with( key, pred );
909 /// Clears the set (non-atomic)
911 The function unlink all items from the set.
912 The function is not atomic. It cleans up each bucket and then resets the item counter to zero.
913 If there are a thread that performs insertion while \p %clear() is working the result is undefined in general case:
914 \p empty() may return \p true but the set may contain item(s).
915 Therefore, \p %clear() may be used only for debugging purposes.
917 For each item the \p disposer is called after unlinking.
921 for ( size_t i = 0; i < bucket_count(); ++i )
922 m_Buckets[i].clear();
923 m_ItemCounter.reset();
926 /// Checks if the set is empty
928 @warning If you use \p atomicity::empty_item_counter in \p traits::item_counter,
929 the function always returns \p true.
936 /// Returns item count in the set
938 If you use \p atomicity::empty_item_counter in \p traits::item_counter,
939 the function always returns 0.
943 return m_ItemCounter;
946 /// Returns const reference to internal statistics
947 stat const& statistics() const
952 /// Returns the size of hash table
954 Since \p %MichaelHashSet cannot dynamically extend the hash table size,
955 the value returned is an constant depending on object initialization parameters,
956 see \p MichaelHashSet::MichaelHashSet.
958 size_t bucket_count() const
960 return m_nHashBitmask + 1;
965 internal_bucket_type * bucket_begin() const
970 internal_bucket_type * bucket_end() const
972 return m_Buckets + bucket_count();
975 const_iterator get_const_begin() const
977 return const_iterator( m_Buckets[0].cbegin(), bucket_begin(), bucket_end());
979 const_iterator get_const_end() const
981 return const_iterator( bucket_end()[-1].cend(), bucket_end() - 1, bucket_end());
984 template <typename Stat>
985 typename std::enable_if< Stat::empty >::type construct_bucket( internal_bucket_type * bucket )
987 new (bucket) internal_bucket_type;
990 template <typename Stat>
991 typename std::enable_if< !Stat::empty >::type construct_bucket( internal_bucket_type * bucket )
993 new (bucket) internal_bucket_type( m_Stat );
996 /// Calculates hash value of \p key
997 template <typename Q>
998 size_t hash_value( const Q& key ) const
1000 return m_HashFunctor( key ) & m_nHashBitmask;
1003 /// Returns the bucket (ordered list) for \p key
1004 template <typename Q>
1005 internal_bucket_type& bucket( const Q& key )
1007 return m_Buckets[hash_value( key )];
1012 }} // namespace cds::intrusive
1014 #endif // ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_H