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 \p 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 of the value to be stored in the split-list.
24 - \p Traits - type traits, default is \p split_list::traits. Instead of declaring \p split_list::traits -based
25 struct you can apply option-based notation with \p split_list::make_traits metafunction.
29 The class supports a forward iterator (\ref iterator and \ref const_iterator).
30 The iteration is unordered.
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 @warning The iterator object cannot be passed between threads
38 \warning Due to concurrent nature of skip-list set it is not guarantee that you can iterate
39 all elements in the set: any concurrent deletion can exclude the element
40 pointed by the iterator from the set, and your iteration can be terminated
41 before end of the set. Therefore, such iteration is more suitable for debugging purposes
43 The iterator class supports the following minimalistic interface:
50 iterator( iterator const& s);
52 value_type * operator ->() const;
53 value_type& operator *() const;
56 iterator& operator ++();
59 iterator& operator = (const iterator& src);
61 bool operator ==(iterator const& i ) const;
62 bool operator !=(iterator const& i ) const;
65 Note, the iterator object returned by \p end(), \p cend() member functions points to \p nullptr and should not be dereferenced.
69 You should decide what garbage collector you want, and what ordered list you want to use. Split-ordered list
70 is an original data structure based on an ordered list. Suppose, you want construct split-list set based on \p cds::urcu::general_buffered<> GC
71 and \p LazyList as ordered list implementation. So, you beginning your program with following include:
73 #include <cds/urcu/general_buffered.h>
74 #include <cds/container/lazy_list_rcu.h>
75 #include <cds/container/split_list_set_rcu.h>
77 namespace cc = cds::container;
79 // The data belonged to split-ordered list
81 int nKey; // key field
82 std::string strValue ; // value field
85 The inclusion order is important:
86 - first, include one of \ref cds_urcu_gc "RCU implementation" (<tt>cds/urcu/general_buffered.h</tt> in our case)
87 - second, include file for ordered-list implementation (for this example, <tt>cds/container/lazy_list_rcu.h</tt>),
88 - then, the header for RCU-based split-list set <tt>cds/container/split_list_set_rcu.h</tt>.
90 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.
91 Note that we define several function in \p foo_hash and \p foo_less functors for different argument types since we want call our \p %SplitListSet
92 object by the key of type \p int and by the value of type \p foo.
94 The second attention: instead of using \p %LazyList in \p %SplitListSet traits we use \p cds::contaner::lazy_list_tag tag for the lazy list.
95 The split-list requires significant support from underlying ordered list class and it is not good idea to dive you
96 into deep implementation details of split-list and ordered list interrelations. The tag paradigm simplifies split-list interface.
101 size_t operator()( int key ) const { return std::hash( key ) ; }
102 size_t operator()( foo const& item ) const { return std::hash( item.nKey ) ; }
107 bool operator()(int i, foo const& f ) const { return i < f.nKey ; }
108 bool operator()(foo const& f, int i ) const { return f.nKey < i ; }
109 bool operator()(foo const& f1, foo const& f2) const { return f1.nKey < f2.nKey; }
112 // SplitListSet traits
113 struct foo_set_traits: public cc::split_list::traits
115 typedef cc::lazy_list_tag ordered_list ; // what type of ordered list we want to use
116 typedef foo_hash hash ; // hash functor for our data stored in split-list set
118 // Type traits for our LazyList class
119 struct ordered_list_traits: public cc::lazy_list::traits
121 typedef foo_less less ; // use our foo_less as comparator to order list nodes
126 Now you are ready to declare our set class based on \p %SplitListSet:
128 typedef cc::SplitListSet< cds::urcu::gc<cds::urcu::general_buffered<> >, foo, foo_set_traits > foo_set;
131 You may use the modern option-based declaration instead of classic type-traits-based one:
133 typedef cc:SplitListSet<
134 cds::urcu::gc<cds::urcu::general_buffered<> > // RCU type used
135 ,foo // type of data stored
136 ,cc::split_list::make_traits< // metafunction to build split-list traits
137 cc::split_list::ordered_list<cc::lazy_list_tag> // tag for underlying ordered list implementation
138 ,cc::opt::hash< foo_hash > // hash functor
139 ,cc::split_list::ordered_list_traits< // ordered list traits
140 cc::lazy_list::make_traits< // metafunction to build lazy list traits
141 cc::opt::less< foo_less > // less-based compare functor
147 In case of option-based declaration using \p split_list::make_traits metafunction
148 the struct \p foo_set_traits is not required.
150 Now, the set of type \p foo_set is ready to use in your program.
152 Note that in this example we show only mandatory \p traits parts, optional ones is the default and they are inherited
153 from \p container::split_list::traits.
154 There are many other options for deep tuning of the split-list and ordered-list containers.
159 #ifdef CDS_DOXYGEN_INVOKED
160 class Traits = split_list::traits
165 class SplitListSet< cds::urcu::gc< RCU >, T, Traits >:
166 #ifdef CDS_DOXYGEN_INVOKED
167 protected intrusive::SplitListSet< cds::urcu::gc< RCU >, typename Traits::ordered_list, Traits >
169 protected details::make_split_list_set< cds::urcu::gc< RCU >, T, typename Traits::ordered_list, split_list::details::wrap_set_traits<T, Traits> >::type
174 typedef details::make_split_list_set< cds::urcu::gc< RCU >, T, typename Traits::ordered_list, split_list::details::wrap_set_traits<T, Traits> > maker;
175 typedef typename maker::type base_class;
179 typedef cds::urcu::gc< RCU > gc; ///< RCU-based garbage collector
180 typedef T value_type; ///< Type of value to be storedin the set
181 typedef Traits traits; ///< \p Traits template argument
183 typedef typename maker::ordered_list ordered_list; ///< Underlying ordered list class
184 typedef typename base_class::key_comparator key_comparator; ///< key compare functor
186 /// Hash functor for \ref value_type and all its derivatives that you use
187 typedef typename base_class::hash hash;
188 typedef typename base_class::item_counter item_counter; ///< Item counter type
189 typedef typename base_class::stat stat; ///< Internal statistics
191 typedef typename base_class::rcu_lock rcu_lock ; ///< RCU scoped lock
192 /// Group of \p extract_xxx functions require external locking if underlying ordered list requires that
193 static CDS_CONSTEXPR const bool c_bExtractLockExternal = base_class::c_bExtractLockExternal;
197 typedef typename maker::cxx_node_allocator cxx_node_allocator;
198 typedef typename maker::node_type node_type;
202 /// pointer to extracted node
203 typedef cds::urcu::exempt_ptr< gc, node_type, value_type, typename maker::ordered_list_traits::disposer > exempt_ptr;
207 template <typename Q, typename Func>
208 bool find_( Q& val, Func f )
210 return base_class::find( val, [&f]( node_type& item, Q& val ) { f(item.m_Value, val) ; } );
213 template <typename Q, typename Less, typename Func>
214 bool find_with_( Q& val, Less pred, Func f )
216 return base_class::find_with( val, typename maker::template predicate_wrapper<Less>::type(),
217 [&f]( node_type& item, Q& val ) { f(item.m_Value, val) ; } );
220 template <typename Q>
221 static node_type * alloc_node( Q const& v )
223 return cxx_node_allocator().New( v );
226 template <typename... Args>
227 static node_type * alloc_node( Args&&... args )
229 return cxx_node_allocator().MoveNew( std::forward<Args>(args)...);
232 static void free_node( node_type * pNode )
234 cxx_node_allocator().Delete( pNode );
237 struct node_disposer {
238 void operator()( node_type * pNode )
243 typedef std::unique_ptr< node_type, node_disposer > scoped_node_ptr;
245 bool insert_node( node_type * pNode )
247 assert( pNode != nullptr );
248 scoped_node_ptr p(pNode);
250 if ( base_class::insert( *pNode ) ) {
262 \p IsConst - constness boolean flag
264 The forward iterator for a split-list has the following features:
265 - it has no post-increment operator
266 - it depends on underlying ordered list iterator
267 - it is safe to iterate only inside RCU critical section
268 - deleting an item pointed by the iterator can cause to deadlock
270 Therefore, the use of iterators in concurrent environment is not good idea.
271 Use it for debug purpose only.
273 template <bool IsConst>
274 class iterator_type: protected base_class::template iterator_type<IsConst>
277 typedef typename base_class::template iterator_type<IsConst> iterator_base_class;
278 friend class SplitListSet;
281 /// Value pointer type (const for const iterator)
282 typedef typename cds::details::make_const_type<value_type, IsConst>::pointer value_ptr;
283 /// Value reference type (const for const iterator)
284 typedef typename cds::details::make_const_type<value_type, IsConst>::reference value_ref;
292 iterator_type( iterator_type const& src )
293 : iterator_base_class( src )
298 explicit iterator_type( iterator_base_class const& src )
299 : iterator_base_class( src )
304 /// Dereference operator
305 value_ptr operator ->() const
307 return &(iterator_base_class::operator->()->m_Value);
310 /// Dereference operator
311 value_ref operator *() const
313 return iterator_base_class::operator*().m_Value;
317 iterator_type& operator ++()
319 iterator_base_class::operator++();
323 /// Assignment operator
324 iterator_type& operator = (iterator_type const& src)
326 iterator_base_class::operator=(src);
330 /// Equality operator
332 bool operator ==(iterator_type<C> const& i ) const
334 return iterator_base_class::operator==(i);
337 /// Equality operator
339 bool operator !=(iterator_type<C> const& i ) const
341 return iterator_base_class::operator!=(i);
346 /// Initializes split-ordered list of default capacity
348 The default capacity is defined in bucket table constructor.
349 See \p intrusive::split_list::expandable_bucket_table, \p intrusive::split_list::static_bucket_table
350 which selects by \p container::split_list::dynamic_bucket_table option.
356 /// Initializes split-ordered list
358 size_t nItemCount ///< estimated average of item count
359 , size_t nLoadFactor = 1 ///< load factor - average item count per bucket. Small integer up to 8, default is 1.
361 : base_class( nItemCount, nLoadFactor )
365 typedef iterator_type<false> iterator ; ///< Forward iterator
366 typedef iterator_type<true> const_iterator ; ///< Forward const iterator
368 /// Returns a forward iterator addressing the first element in a set
370 For empty set \code begin() == end() \endcode
374 return iterator( base_class::begin() );
377 /// Returns an iterator that addresses the location succeeding the last element in a set
379 Do not use the value returned by <tt>end</tt> function to access any item.
380 The returned value can be used only to control reaching the end of the set.
381 For empty set \code begin() == end() \endcode
385 return iterator( base_class::end() );
388 /// Returns a forward const iterator addressing the first element in a set
389 const_iterator begin() const
391 return const_iterator( base_class::begin() );
394 /// Returns an const iterator that addresses the location succeeding the last element in a set
395 const_iterator end() const
397 return const_iterator( base_class::end() );
403 The function creates a node with copy of \p val value
404 and then inserts the node created into the set.
406 The type \p Q should contain as minimum the complete key for the node.
407 The object of \p value_type should be constructible from a value of type \p Q.
408 In trivial case, \p Q is equal to \p value_type.
410 The function applies RCU lock internally.
412 Returns \p true if \p val is inserted into the set, \p false otherwise.
414 template <typename Q>
415 bool insert( Q const& val )
417 return insert_node( alloc_node( val ) );
422 The function allows to split creating of new item into two part:
423 - create item with key only
424 - insert new item into the set
425 - if inserting is success, calls \p f functor to initialize value-field of \p val.
427 The functor signature is:
429 void func( value_type& val );
431 where \p val is the item inserted. User-defined functor \p f should guarantee that during changing
432 \p val no any other changes could be made on this set's item by concurrent threads.
433 The user-defined functor is called only if the inserting is success.
435 The function applies RCU lock internally.
437 template <typename Q, typename Func>
438 bool insert( Q const& key, Func f )
440 scoped_node_ptr pNode( alloc_node( key ));
442 if ( base_class::insert( *pNode, [&f](node_type& node) { f( node.m_Value ) ; } )) {
449 /// Inserts data of type \p value_type created from \p args
451 Returns \p true if inserting successful, \p false otherwise.
453 The function applies RCU lock internally.
455 template <typename... Args>
456 bool emplace( Args&&... args )
458 return insert_node( alloc_node( std::forward<Args>(args)...));
461 /// Ensures that the \p val exists in the set
463 The operation performs inserting or changing data with lock-free manner.
465 If the \p val key not found in the set, then the new item created from \p val
466 is inserted into the set. Otherwise, the functor \p func is called with the item found.
467 The functor \p Func signature is:
470 void operator()( bool bNew, value_type& item, const Q& val );
475 - \p bNew - \p true if the item has been inserted, \p false otherwise
476 - \p item - item of the set
477 - \p val - argument \p val passed into the \p %ensure() function
479 The functor may change non-key fields of the \p item; however, \p func must guarantee
480 that during changing no any other modifications could be made on this item by concurrent threads.
482 The function applies RCU lock internally.
484 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
485 \p second is true if new item has been added or \p false if the item with \p key
486 already is in the set.
488 template <typename Q, typename Func>
489 std::pair<bool, bool> ensure( Q const& val, Func func )
491 scoped_node_ptr pNode( alloc_node( val ));
493 std::pair<bool, bool> bRet = base_class::ensure( *pNode,
494 [&func, &val]( bool bNew, node_type& item, node_type const& /*val*/ ) {
495 func( bNew, item.m_Value, val );
497 if ( bRet.first && bRet.second )
502 /// Deletes \p key from the set
503 /** \anchor cds_nonintrusive_SplitListSet_rcu_erase_val
505 Template parameter of type \p Q defines the key type searching in the list.
506 The set item comparator should be able to compare the values of type \p value_type
509 RCU \p synchronize method can be called. RCU should not be locked.
511 Return \p true if key is found and deleted, \p false otherwise
513 template <typename Q>
514 bool erase( Q const& key )
516 return base_class::erase( key );
519 /// Deletes the item from the set using \p pred predicate for searching
521 The function is an analog of \ref cds_nonintrusive_SplitListSet_rcu_erase_val "erase(Q const&)"
522 but \p pred is used for key comparing.
523 \p Less functor has the interface like \p std::less.
524 \p Less must imply the same element order as the comparator used for building the set.
526 template <typename Q, typename Less>
527 bool erase_with( Q const& key, Less pred )
529 return base_class::erase_with( key, typename maker::template predicate_wrapper<Less>::type() );
532 /// Deletes \p key from the set
533 /** \anchor cds_nonintrusive_SplitListSet_rcu_erase_func
535 The function searches an item with key \p key, calls \p f functor
536 and deletes the item. If \p key is not found, the functor is not called.
538 The functor \p Func interface:
541 void operator()(value_type const& val);
545 Template parameter of type \p Q defines the key type searching in the list.
546 The list item comparator should be able to compare the values of the type \p value_type
549 RCU \p synchronize method can be called. RCU should not be locked.
551 Return \p true if key is found and deleted, \p false otherwise
553 template <typename Q, typename Func>
554 bool erase( Q const& key, Func f )
556 return base_class::erase( key, [&f](node_type& node) { f( node.m_Value ); } );
559 /// Deletes the item from the set using \p pred predicate for searching
561 The function is an analog of \ref cds_nonintrusive_SplitListSet_rcu_erase_func "erase(Q const&, Func)"
562 but \p pred is used for key comparing.
563 \p Less functor has the interface like \p std::less.
564 \p Less must imply the same element order as the comparator used for building the set.
566 template <typename Q, typename Less, typename Func>
567 bool erase_with( Q const& key, Less pred, Func f )
569 return base_class::erase_with( key, typename maker::template predicate_wrapper<Less>::type(),
570 [&f](node_type& node) { f( node.m_Value ); } );
573 /// Extracts an item from the set
574 /** \anchor cds_nonintrusive_SplitListSet_rcu_extract
575 The function searches an item with key equal to \p key in the set,
576 unlinks it from the set, places item pointer into \p dest argument, and returns \p true.
577 If the item with the key equal to \p key is not found the function return \p false.
579 @note The function does NOT call RCU read-side lock or synchronization,
580 and does NOT dispose the item found. It just excludes the item from the set
581 and returns a pointer to item found.
582 You should lock RCU before calling of the function, and you should synchronize RCU
583 outside the RCU lock to free extracted item
586 typedef cds::urcu::gc< general_buffered<> > rcu;
587 typedef cds::container::SplitListSet< rcu, Foo > splitlist_set;
589 splitlist_set theSet;
592 splitlist_set::exempt_ptr p;
594 // first, we should lock RCU
595 splitlist_set::rcu_lock lock;
597 // Now, you can apply extract function
598 // Note that you must not delete the item found inside the RCU lock
599 if ( theSet.extract( p, 10 )) {
600 // do something with p
605 // We may safely release p here
606 // release() passes the pointer to RCU reclamation cycle
610 template <typename Q>
611 bool extract( exempt_ptr& dest, Q const& key )
613 node_type * pNode = base_class::extract_( key, key_comparator() );
621 /// Extracts an item from the set using \p pred predicate for searching
623 The function is an analog of \ref cds_nonintrusive_SplitListSet_rcu_extract "extract(exempt_ptr&, Q const&)"
624 but \p pred is used for key comparing.
625 \p Less functor has the interface like \p std::less.
626 \p pred must imply the same element order as the comparator used for building the set.
628 template <typename Q, typename Less>
629 bool extract_with( exempt_ptr& dest, Q const& key, Less pred )
631 node_type * pNode = base_class::extract_with_( key, typename maker::template predicate_wrapper<Less>::type());
639 /// Finds the key \p key
640 /** \anchor cds_nonintrusive_SplitListSet_rcu_find_func
642 The function searches the item with key equal to \p key and calls the functor \p f for item found.
643 The interface of \p Func functor is:
646 void operator()( value_type& item, Q& key );
649 where \p item is the item found, \p key is the <tt>find</tt> function argument.
651 The functor may change non-key fields of \p item. Note that the functor is only guarantee
652 that \p item cannot be disposed during functor is executing.
653 The functor does not serialize simultaneous access to the set's \p item. If such access is
654 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
656 Note the hash functor specified for class \p Traits template parameter
657 should accept a parameter of type \p Q that can be not the same as \p value_type.
659 The function makes RCU lock internally.
661 The function returns \p true if \p key is found, \p false otherwise.
663 template <typename Q, typename Func>
664 bool find( Q& key, Func f )
666 return find_( key, f );
669 /// Finds the key \p key using \p pred predicate for searching
671 The function is an analog of \ref cds_nonintrusive_SplitListSet_rcu_find_func "find(Q&, Func)"
672 but \p pred is used for key comparing.
673 \p Less functor has the interface like \p std::less.
674 \p Less must imply the same element order as the comparator used for building the set.
676 template <typename Q, typename Less, typename Func>
677 bool find_with( Q& key, Less pred, Func f )
679 return find_with_( key, pred, f );
682 /// Finds the key \p key
683 /** \anchor cds_nonintrusive_SplitListSet_rcu_find_val
685 The function searches the item with key equal to \p key
686 and returns \p true if it is found, and \p false otherwise.
688 Note the hash functor specified for class \p Traits template parameter
689 should accept a parameter of type \p Q that can be not the same as \p value_type.
691 The function makes RCU lock internally.
693 template <typename Q>
694 bool find( Q const& key )
696 return base_class::find( key );
699 /// Finds the key \p key using \p pred predicate for searching
701 The function is an analog of \ref cds_nonintrusive_SplitListSet_rcu_find_val "find(Q const&)"
702 but \p pred is used for key comparing.
703 \p Less functor has the interface like \p std::less.
704 \p Less must imply the same element order as the comparator used for building the set.
706 template <typename Q, typename Less>
707 bool find_with( Q const& key, Less pred )
709 return base_class::find_with( key, typename maker::template predicate_wrapper<Less>::type() );
712 /// Finds the key \p key and return the item found
713 /** \anchor cds_nonintrusive_SplitListSet_rcu_get
714 The function searches the item with key equal to \p key and returns the pointer to item found.
715 If \p key is not found it returns \p nullptr.
717 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
719 RCU should be locked before call of this function.
720 Returned item is valid only while RCU is locked:
722 typedef cds::urcu::gc< general_buffered<> > rcu;
723 typedef cds::container::SplitListSet< rcu, Foo > splitlist_set;
724 splitlist_set theSet;
728 splitlist_set::rcu_lock lock;
730 foo * pVal = theSet.get( 5 );
735 // Unlock RCU by rcu_lock destructor
736 // pVal can be retired by disposer at any time after RCU has been unlocked
740 template <typename Q>
741 value_type * get( Q const& key )
743 node_type * pNode = base_class::get( key );
744 return pNode ? &pNode->m_Value : nullptr;
747 /// Finds the key \p key and return the item found
749 The function is an analog of \ref cds_nonintrusive_SplitListSet_rcu_get "get(Q const&)"
750 but \p pred is used for comparing the keys.
752 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
754 \p pred must imply the same element order as the comparator used for building the set.
756 template <typename Q, typename Less>
757 value_type * get_with( Q const& key, Less pred )
759 node_type * pNode = base_class::get_with( key, typename maker::template predicate_wrapper<Less>::type());
760 return pNode ? &pNode->m_Value : nullptr;
763 /// Clears the set (not atomic)
769 /// Checks if the set is empty
771 Emptiness is checked by item counting: if item count is zero then assume that the set is empty.
772 Thus, the correct item counting feature is an important part of split-list set implementation.
776 return base_class::empty();
779 /// Returns item count in the set
782 return base_class::size();
785 /// Returns internal statistics
786 stat const& statistics() const
788 return base_class::statistics();
791 }} // namespace cds::container
793 #endif // #ifndef __CDS_CONTAINER_SPLIT_LIST_SET_RCU_H