3 #ifndef __CDS_CONTAINER_SPLIT_LIST_SET_RCU_H
4 #define __CDS_CONTAINER_SPLIT_LIST_SET_RCU_H
6 #include <cds/intrusive/split_list_rcu.h>
7 #include <cds/container/details/make_split_list_set.h>
9 namespace cds { namespace container {
11 /// Split-ordered list set (template specialization for \ref cds_urcu_desc "RCU")
12 /** @ingroup cds_nonintrusive_set
13 \anchor cds_nonintrusive_SplitListSet_rcu
15 Hash table implementation based on split-ordered list algorithm discovered by Ori Shalev and Nir Shavit, see
16 - [2003] Ori Shalev, Nir Shavit "Split-Ordered Lists - Lock-free Resizable Hash Tables"
17 - [2008] Nir Shavit "The Art of Multiprocessor Programming"
19 See intrusive::SplitListSet for a brief description of the split-list algorithm.
22 - \p RCU - one of \ref cds_urcu_gc "RCU type"
23 - \p T - type stored in the split-list. The type must be default- and copy-constructible.
24 - \p Traits - type traits, default is split_list::type_traits. Instead of declaring split_list::type_traits -based
25 struct you may apply option-based notation with split_list::make_traits metafunction.
29 The class supports a forward iterator (\ref iterator and \ref const_iterator).
30 The iteration is ordered.
32 You may iterate over split-list set items only under RCU lock.
33 Only in this case the iterator is thread-safe since
34 while RCU is locked any set's item cannot be reclaimed.
36 The requirement of RCU lock during iterating means that deletion of the elements (i.e. \ref erase)
39 @warning The iterator object cannot be passed between threads
41 \warning Due to concurrent nature of skip-list set it is not guarantee that you can iterate
42 all elements in the set: any concurrent deletion can exclude the element
43 pointed by the iterator from the set, and your iteration can be terminated
44 before end of the set. Therefore, such iteration is more suitable for debugging purposes
46 The iterator class supports the following minimalistic interface:
53 iterator( iterator const& s);
55 value_type * operator ->() const;
56 value_type& operator *() const;
59 iterator& operator ++();
62 iterator& operator = (const iterator& src);
64 bool operator ==(iterator const& i ) const;
65 bool operator !=(iterator const& i ) const;
68 Note, the iterator object returned by \ref end, \p cend member functions points to \p nullptr and should not be dereferenced.
72 You should decide what garbage collector you want, and what ordered list you want to use. Split-ordered list
73 is an original data structure based on an ordered list. Suppose, you want construct split-list set based on cds::urcu::general_buffered<> GC
74 and LazyList as ordered list implementation. So, you beginning your program with following include:
76 #include <cds/urcu/general_buffered.h>
77 #include <cds/container/lazy_list_rcu.h>
78 #include <cds/container/split_list_set_rcu.h>
80 namespace cc = cds::container;
82 // The data belonged to split-ordered list
84 int nKey; // key field
85 std::string strValue ; // value field
88 The inclusion order is important:
89 - first, include one of \ref cds_urcu_gc "RCU implementation" (<tt>cds/urcu/general_buffered.h</tt> in our case)
90 - second, include file for ordered-list implementation (for this example, <tt>cds/container/lazy_list_rcu.h</tt>),
91 - then, the header for RCU-based split-list set <tt>cds/container/split_list_set_rcu.h</tt>.
93 Now, you should declare traits for split-list set. The main parts of traits are a hash functor for the set and a comparing functor for ordered list.
94 Note that we define several function in <tt>foo_hash</tt> and <tt>foo_less</tt> functors for different argument types since we want call our \p %SplitListSet
95 object by the key of type <tt>int</tt> and by the value of type <tt>foo</tt>.
97 The second attention: instead of using LazyList in SplitListSet traits we use a tag <tt>cds::contaner::lazy_list_tag</tt> for the lazy list.
98 The split-list requires significant support from underlying ordered list class and it is not good idea to dive you
99 into deep implementation details of split-list and ordered list interrelations. The tag paradigm simplifies split-list interface.
104 size_t operator()( int key ) const { return std::hash( key ) ; }
105 size_t operator()( foo const& item ) const { return std::hash( item.nKey ) ; }
110 bool operator()(int i, foo const& f ) const { return i < f.nKey ; }
111 bool operator()(foo const& f, int i ) const { return f.nKey < i ; }
112 bool operator()(foo const& f1, foo const& f2) const { return f1.nKey < f2.nKey; }
115 // SplitListSet traits
116 struct foo_set_traits: public cc::split_list::type_traits
118 typedef cc::lazy_list_tag ordered_list ; // what type of ordered list we want to use
119 typedef foo_hash hash ; // hash functor for our data stored in split-list set
121 // Type traits for our LazyList class
122 struct ordered_list_traits: public cc::lazy_list::type_traits
124 typedef foo_less less ; // use our foo_less as comparator to order list nodes
129 Now you are ready to declare our set class based on \p %SplitListSet:
131 typedef cc::SplitListSet< cds::urcu::gc<cds::urcu::general_buffered<> >, foo, foo_set_traits > foo_set;
134 You may use the modern option-based declaration instead of classic type-traits-based one:
136 typedef cc:SplitListSet<
137 cds::urcu::gc<cds::urcu::general_buffered<> > // RCU type used
138 ,foo // type of data stored
139 ,cc::split_list::make_traits< // metafunction to build split-list traits
140 cc::split_list::ordered_list<cc::lazy_list_tag> // tag for underlying ordered list implementation
141 ,cc::opt::hash< foo_hash > // hash functor
142 ,cc::split_list::ordered_list_traits< // ordered list traits desired
143 cc::lazy_list::make_traits< // metafunction to build lazy list traits
144 cc::opt::less< foo_less > // less-based compare functor
150 In case of option-based declaration using split_list::make_traits metafunction
151 the struct \p foo_set_traits is not required.
153 Now, the set of type \p foo_set is ready to use in your program.
155 Note that in this example we show only mandatory type_traits parts, optional ones is the default and they are inherited
156 from cds::container::split_list::type_traits.
157 The <b>cds</b> library contains many other options for deep tuning of behavior of the split-list and
158 ordered-list containers.
163 #ifdef CDS_DOXYGEN_INVOKED
164 class Traits = split_list::type_traits
169 class SplitListSet< cds::urcu::gc< RCU >, T, Traits >:
170 #ifdef CDS_DOXYGEN_INVOKED
171 protected intrusive::SplitListSet< cds::urcu::gc< RCU >, typename Traits::ordered_list, Traits >
173 protected details::make_split_list_set< cds::urcu::gc< RCU >, T, typename Traits::ordered_list, split_list::details::wrap_set_traits<T, Traits> >::type
178 typedef details::make_split_list_set< cds::urcu::gc< RCU >, T, typename Traits::ordered_list, split_list::details::wrap_set_traits<T, Traits> > maker;
179 typedef typename maker::type base_class;
183 typedef Traits options ; ///< \p Traits template argument
184 typedef typename maker::gc gc ; ///< Garbage collector
185 typedef typename maker::value_type value_type ; ///< type of value stored in the list
186 typedef typename maker::ordered_list ordered_list ; ///< Underlying ordered list class
187 typedef typename base_class::key_comparator key_comparator; ///< key compare functor
189 /// Hash functor for \ref value_type and all its derivatives that you use
190 typedef typename base_class::hash hash;
191 typedef typename base_class::item_counter item_counter ; ///< Item counter type
193 typedef typename base_class::rcu_lock rcu_lock ; ///< RCU scoped lock
194 /// Group of \p extract_xxx functions require external locking if underlying ordered list requires that
195 static CDS_CONSTEXPR_CONST bool c_bExtractLockExternal = base_class::c_bExtractLockExternal;
199 typedef typename maker::cxx_node_allocator cxx_node_allocator;
200 typedef typename maker::node_type node_type;
204 /// pointer to extracted node
205 typedef cds::urcu::exempt_ptr< gc, node_type, value_type, typename maker::ordered_list_traits::disposer > exempt_ptr;
210 template <typename Q>
211 static node_type * alloc_node(Q const& v )
213 return cxx_node_allocator().New( v );
216 template <typename Q, typename Func>
217 bool find_( Q& val, Func f )
219 return base_class::find( val, [&f]( node_type& item, Q& val ) { f(item.m_Value, val) ; } );
222 template <typename Q, typename Less, typename Func>
223 bool find_with_( Q& val, Less pred, Func f )
225 return base_class::find_with( val, typename maker::template predicate_wrapper<Less>::type(),
226 [&f]( node_type& item, Q& val ) { f(item.m_Value, val) ; } );
230 template <typename... Args>
231 static node_type * alloc_node( Args&&... args )
233 return cxx_node_allocator().MoveNew( std::forward<Args>(args)...);
236 static void free_node( node_type * pNode )
238 cxx_node_allocator().Delete( pNode );
241 struct node_disposer {
242 void operator()( node_type * pNode )
247 typedef std::unique_ptr< node_type, node_disposer > scoped_node_ptr;
249 bool insert_node( node_type * pNode )
251 assert( pNode != nullptr );
252 scoped_node_ptr p(pNode);
254 if ( base_class::insert( *pNode ) ) {
266 \p IsConst - constness boolean flag
268 The forward iterator for a split-list has the following features:
269 - it has no post-increment operator
270 - it depends on underlying ordered list iterator
271 - it is safe to iterate only inside RCU critical section
272 - deleting an item pointed by the iterator can cause to deadlock
274 Therefore, the use of iterators in concurrent environment is not good idea.
275 Use it for debug purpose only.
277 template <bool IsConst>
278 class iterator_type: protected base_class::template iterator_type<IsConst>
281 typedef typename base_class::template iterator_type<IsConst> iterator_base_class;
282 friend class SplitListSet;
285 /// Value pointer type (const for const iterator)
286 typedef typename cds::details::make_const_type<value_type, IsConst>::pointer value_ptr;
287 /// Value reference type (const for const iterator)
288 typedef typename cds::details::make_const_type<value_type, IsConst>::reference value_ref;
296 iterator_type( iterator_type const& src )
297 : iterator_base_class( src )
302 explicit iterator_type( iterator_base_class const& src )
303 : iterator_base_class( src )
308 /// Dereference operator
309 value_ptr operator ->() const
311 return &(iterator_base_class::operator->()->m_Value);
314 /// Dereference operator
315 value_ref operator *() const
317 return iterator_base_class::operator*().m_Value;
321 iterator_type& operator ++()
323 iterator_base_class::operator++();
327 /// Assignment operator
328 iterator_type& operator = (iterator_type const& src)
330 iterator_base_class::operator=(src);
334 /// Equality operator
336 bool operator ==(iterator_type<C> const& i ) const
338 return iterator_base_class::operator==(i);
341 /// Equality operator
343 bool operator !=(iterator_type<C> const& i ) const
345 return iterator_base_class::operator!=(i);
350 /// Initializes split-ordered list of default capacity
352 The default capacity is defined in bucket table constructor.
353 See intrusive::split_list::expandable_bucket_table, intrusive::split_list::static_bucket_table
354 which selects by intrusive::split_list::dynamic_bucket_table option.
360 /// Initializes split-ordered list
362 size_t nItemCount ///< estimate average of item count
363 , size_t nLoadFactor = 1 ///< load factor - average item count per bucket. Small integer up to 8, default is 1.
365 : base_class( nItemCount, nLoadFactor )
369 typedef iterator_type<false> iterator ; ///< Forward iterator
370 typedef iterator_type<true> const_iterator ; ///< Forward const iterator
372 /// Returns a forward iterator addressing the first element in a set
374 For empty set \code begin() == end() \endcode
378 return iterator( base_class::begin() );
381 /// Returns an iterator that addresses the location succeeding the last element in a set
383 Do not use the value returned by <tt>end</tt> function to access any item.
384 The returned value can be used only to control reaching the end of the set.
385 For empty set \code begin() == end() \endcode
389 return iterator( base_class::end() );
392 /// Returns a forward const iterator addressing the first element in a set
393 const_iterator begin() const
395 return const_iterator( base_class::begin() );
398 /// Returns an const iterator that addresses the location succeeding the last element in a set
399 const_iterator end() const
401 return const_iterator( base_class::end() );
407 The function creates a node with copy of \p val value
408 and then inserts the node created into the set.
410 The type \p Q should contain as minimum the complete key for the node.
411 The object of \p value_type should be constructible from a value of type \p Q.
412 In trivial case, \p Q is equal to \p value_type.
414 The function applies RCU lock internally.
416 Returns \p true if \p val is inserted into the set, \p false otherwise.
418 template <typename Q>
419 bool insert( Q const& val )
421 return insert_node( alloc_node( val ) );
426 The function allows to split creating of new item into two part:
427 - create item with key only
428 - insert new item into the set
429 - if inserting is success, calls \p f functor to initialize value-field of \p val.
431 The functor signature is:
433 void func( value_type& val );
435 where \p val is the item inserted. User-defined functor \p f should guarantee that during changing
436 \p val no any other changes could be made on this set's item by concurrent threads.
437 The user-defined functor is called only if the inserting is success. It may be passed by reference
440 The function applies RCU lock internally.
442 template <typename Q, typename Func>
443 bool insert( Q const& val, Func f )
445 scoped_node_ptr pNode( alloc_node( val ));
447 if ( base_class::insert( *pNode, [&f](node_type& node) { f( node.m_Value ) ; } )) {
454 /// Inserts data of type \p value_type constructed with <tt>std::forward<Args>(args)...</tt>
456 Returns \p true if inserting successful, \p false otherwise.
458 The function applies RCU lock internally.
460 template <typename... Args>
461 bool emplace( Args&&... args )
463 return insert_node( alloc_node( std::forward<Args>(args)...));
466 /// Ensures that the \p item exists in the set
468 The operation performs inserting or changing data with lock-free manner.
470 If the \p val key not found in the set, then the new item created from \p val
471 is inserted into the set. Otherwise, the functor \p func is called with the item found.
472 The functor \p Func should be a function with signature:
474 void func( bool bNew, value_type& item, const Q& val );
479 void operator()( bool bNew, value_type& item, const Q& val );
484 - \p bNew - \p true if the item has been inserted, \p false otherwise
485 - \p item - item of the set
486 - \p val - argument \p val passed into the \p ensure function
488 The functor may change non-key fields of the \p item; however, \p func must guarantee
489 that during changing no any other modifications could be made on this item by concurrent threads.
491 You may pass \p func argument by reference using \p std::ref
493 The function applies RCU lock internally.
495 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
496 \p second is true if new item has been added or \p false if the item with \p key
497 already is in the set.
499 template <typename Q, typename Func>
500 std::pair<bool, bool> ensure( Q const& val, Func func )
502 scoped_node_ptr pNode( alloc_node( val ));
504 std::pair<bool, bool> bRet = base_class::ensure( *pNode,
505 [&func, &val]( bool bNew, node_type& item, node_type const& /*val*/ ) {
506 func( bNew, item.m_Value, val );
508 if ( bRet.first && bRet.second )
513 /// Deletes \p key from the set
514 /** \anchor cds_nonintrusive_SplitListSet_rcu_erase_val
516 Since the key of SplitListSet's item type \p value_type is not explicitly specified,
517 template parameter \p Q defines the key type searching in the list.
518 The set item comparator should be able to compare the values of type \p value_type
521 RCU \p synchronize method can be called. RCU should not be locked.
523 Return \p true if key is found and deleted, \p false otherwise
525 template <typename Q>
526 bool erase( Q const& key )
528 return base_class::erase( key );
531 /// Deletes the item from the set using \p pred predicate for searching
533 The function is an analog of \ref cds_nonintrusive_SplitListSet_rcu_erase_val "erase(Q const&)"
534 but \p pred is used for key comparing.
535 \p Less functor has the interface like \p std::less.
536 \p Less must imply the same element order as the comparator used for building the set.
538 template <typename Q, typename Less>
539 bool erase_with( Q const& key, Less pred )
541 return base_class::erase_with( key, typename maker::template predicate_wrapper<Less>::type() );
544 /// Deletes \p key from the set
545 /** \anchor cds_nonintrusive_SplitListSet_rcu_erase_func
547 The function searches an item with key \p key, calls \p f functor
548 and deletes the item. If \p key is not found, the functor is not called.
550 The functor \p Func interface:
553 void operator()(value_type const& val);
556 The functor may be passed by reference using <tt>boost:ref</tt>
558 Since the key of SplitListSet's \p value_type is not explicitly specified,
559 template parameter \p Q defines the key type searching in the list.
560 The list item comparator should be able to compare the values of the type \p value_type
563 RCU \p synchronize method can be called. RCU should not be locked.
565 Return \p true if key is found and deleted, \p false otherwise
567 template <typename Q, typename Func>
568 bool erase( Q const& key, Func f )
570 return base_class::erase( key, [&f](node_type& node) { f( node.m_Value ); } );
573 /// Deletes the item from the set using \p pred predicate for searching
575 The function is an analog of \ref cds_nonintrusive_SplitListSet_rcu_erase_func "erase(Q const&, Func)"
576 but \p pred is used for key comparing.
577 \p Less functor has the interface like \p std::less.
578 \p Less must imply the same element order as the comparator used for building the set.
580 template <typename Q, typename Less, typename Func>
581 bool erase_with( Q const& key, Less pred, Func f )
583 return base_class::erase_with( key, typename maker::template predicate_wrapper<Less>::type(),
584 [&f](node_type& node) { f( node.m_Value ); } );
587 /// Extracts an item from the set
588 /** \anchor cds_nonintrusive_SplitListSet_rcu_extract
589 The function searches an item with key equal to \p val in the set,
590 unlinks it from the set, places item pointer into \p dest argument, and returns \p true.
591 If the item with the key equal to \p val is not found the function return \p false.
593 @note The function does NOT call RCU read-side lock or synchronization,
594 and does NOT dispose the item found. It just excludes the item from the set
595 and returns a pointer to item found.
596 You should lock RCU before calling of the function, and you should synchronize RCU
597 outside the RCU lock to free extracted item
600 typedef cds::urcu::gc< general_buffered<> > rcu;
601 typedef cds::container::SplitListSet< rcu, Foo > splitlist_set;
603 splitlist_set theSet;
606 splitlist_set::exempt_ptr p;
608 // first, we should lock RCU
609 splitlist_set::rcu_lock lock;
611 // Now, you can apply extract function
612 // Note that you must not delete the item found inside the RCU lock
613 if ( theSet.extract( p, 10 )) {
614 // do something with p
619 // We may safely release p here
620 // release() passes the pointer to RCU reclamation cycle
624 template <typename Q>
625 bool extract( exempt_ptr& dest, Q const& val )
627 node_type * pNode = base_class::extract_( val, key_comparator() );
635 /// Extracts an item from the set using \p pred predicate for searching
637 The function is an analog of \ref cds_nonintrusive_SplitListSet_rcu_extract "extract(exempt_ptr&, Q const&)"
638 but \p pred is used for key comparing.
639 \p Less functor has the interface like \p std::less.
640 \p pred must imply the same element order as the comparator used for building the set.
642 template <typename Q, typename Less>
643 bool extract_with( exempt_ptr& dest, Q const& val, Less pred )
645 node_type * pNode = base_class::extract_with_( val, typename maker::template predicate_wrapper<Less>::type());
653 /// Finds the key \p val
654 /** \anchor cds_nonintrusive_SplitListSet_rcu_find_func
656 The function searches the item with key equal to \p val and calls the functor \p f for item found.
657 The interface of \p Func functor is:
660 void operator()( value_type& item, Q& val );
663 where \p item is the item found, \p val is the <tt>find</tt> function argument.
665 You may pass \p f argument by reference using \p std::ref.
667 The functor may change non-key fields of \p item. Note that the functor is only guarantee
668 that \p item cannot be disposed during functor is executing.
669 The functor does not serialize simultaneous access to the set's \p item. If such access is
670 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
672 The \p val argument is non-const since it can be used as \p f functor destination i.e., the functor
673 may modify both arguments.
675 Note the hash functor specified for class \p Traits template parameter
676 should accept a parameter of type \p Q that can be not the same as \p value_type.
678 The function makes RCU lock internally.
680 The function returns \p true if \p val is found, \p false otherwise.
682 template <typename Q, typename Func>
683 bool find( Q& val, Func f )
685 return find_( val, f );
688 /// Finds the key \p val using \p pred predicate for searching
690 The function is an analog of \ref cds_nonintrusive_SplitListSet_rcu_find_func "find(Q&, Func)"
691 but \p pred is used for key comparing.
692 \p Less functor has the interface like \p std::less.
693 \p Less must imply the same element order as the comparator used for building the set.
695 template <typename Q, typename Less, typename Func>
696 bool find_with( Q& val, Less pred, Func f )
698 return find_with_( val, pred, f );
701 /// Find the key \p val
702 /** \anchor cds_nonintrusive_SplitListSet_rcu_find_cfunc
704 The function searches the item with key equal to \p val and calls the functor \p f for item found.
705 The interface of \p Func functor is:
708 void operator()( value_type& item, Q const& val );
711 where \p item is the item found, \p val is the <tt>find</tt> function argument.
713 You may pass \p f argument by reference using \p std::ref.
715 The functor may change non-key fields of \p item. Note that the functor is only guarantee
716 that \p item cannot be disposed during functor is executing.
717 The functor does not serialize simultaneous access to the set's \p item. If such access is
718 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
720 Note the hash functor specified for class \p Traits template parameter
721 should accept a parameter of type \p Q that can be not the same as \p value_type.
723 The function makes RCU lock internally.
725 The function returns \p true if \p val is found, \p false otherwise.
727 template <typename Q, typename Func>
728 bool find( Q const& val, Func f )
730 return find_( val, f );
733 /// Finds the key \p val using \p pred predicate for searching
735 The function is an analog of \ref cds_nonintrusive_SplitListSet_rcu_find_cfunc "find(Q const&, Func)"
736 but \p pred is used for key comparing.
737 \p Less functor has the interface like \p std::less.
738 \p Less must imply the same element order as the comparator used for building the set.
740 template <typename Q, typename Less, typename Func>
741 bool find_with( Q const& val, Less pred, Func f )
743 return find_with_( val, pred, f );
746 /// Finds the key \p val
747 /** \anchor cds_nonintrusive_SplitListSet_rcu_find_val
749 The function searches the item with key equal to \p val
750 and returns \p true if it is found, and \p false otherwise.
752 Note the hash functor specified for class \p Traits template parameter
753 should accept a parameter of type \p Q that can be not the same as \p value_type.
755 The function makes RCU lock internally.
757 template <typename Q>
758 bool find( Q const& val )
760 return base_class::find( val );
763 /// Finds the key \p val using \p pred predicate for searching
765 The function is an analog of \ref cds_nonintrusive_SplitListSet_rcu_find_val "find(Q const&)"
766 but \p pred is used for key comparing.
767 \p Less functor has the interface like \p std::less.
768 \p Less must imply the same element order as the comparator used for building the set.
770 template <typename Q, typename Less>
771 bool find_with( Q const& val, Less pred )
773 return base_class::find_with( val, typename maker::template predicate_wrapper<Less>::type() );
776 /// Finds the key \p val and return the item found
777 /** \anchor cds_nonintrusive_SplitListSet_rcu_get
778 The function searches the item with key equal to \p val and returns the pointer to item found.
779 If \p val is not found it returns \p nullptr.
781 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
783 RCU should be locked before call of this function.
784 Returned item is valid only while RCU is locked:
786 typedef cds::urcu::gc< general_buffered<> > rcu;
787 typedef cds::container::SplitListSet< rcu, Foo > splitlist_set;
788 splitlist_set theSet;
792 splitlist_set::rcu_lock lock;
794 foo * pVal = theSet.get( 5 );
799 // Unlock RCU by rcu_lock destructor
800 // pVal can be retired by disposer at any time after RCU has been unlocked
804 template <typename Q>
805 value_type * get( Q const& val )
807 node_type * pNode = base_class::get( val );
808 return pNode ? &pNode->m_Value : nullptr;
811 /// Finds the key \p val and return the item found
813 The function is an analog of \ref cds_nonintrusive_SplitListSet_rcu_get "get(Q const&)"
814 but \p pred is used for comparing the keys.
816 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
818 \p pred must imply the same element order as the comparator used for building the set.
820 template <typename Q, typename Less>
821 value_type * get_with( Q const& val, Less pred )
823 node_type * pNode = base_class::get_with( val, typename maker::template predicate_wrapper<Less>::type());
824 return pNode ? &pNode->m_Value : nullptr;
827 /// Clears the set (non-atomic)
829 The function unlink all items from the set.
830 The function is not atomic and not lock-free and should be used for debugging only.
832 RCU \p synchronize method can be called. RCU should not be locked.
839 /// Checks if the set is empty
841 Emptiness is checked by item counting: if item count is zero then assume that the set is empty.
842 Thus, the correct item counting feature is an important part of split-list set implementation.
846 return base_class::empty();
849 /// Returns item count in the set
852 return base_class::size();
857 }} // namespace cds::container
859 #endif // #ifndef __CDS_CONTAINER_SPLIT_LIST_SET_RCU_H