3 #ifndef __CDS_CONTAINER_SKIP_LIST_SET_RCU_H
4 #define __CDS_CONTAINER_SKIP_LIST_SET_RCU_H
6 #include <cds/intrusive/skip_list_rcu.h>
7 #include <cds/container/details/make_skip_list_set.h>
9 namespace cds { namespace container {
11 /// Lock-free skip-list set (template specialization for \ref cds_urcu_desc "RCU")
12 /** @ingroup cds_nonintrusive_set
13 \anchor cds_nonintrusive_SkipListSet_rcu
15 The implementation of well-known probabilistic data structure called skip-list
16 invented by W.Pugh in his papers:
17 - [1989] W.Pugh Skip Lists: A Probabilistic Alternative to Balanced Trees
18 - [1990] W.Pugh A Skip List Cookbook
20 A skip-list is a probabilistic data structure that provides expected logarithmic
21 time search without the need of rebalance. The skip-list is a collection of sorted
22 linked list. Nodes are ordered by key. Each node is linked into a subset of the lists.
23 Each list has a level, ranging from 0 to 32. The bottom-level list contains
24 all the nodes, and each higher-level list is a sublist of the lower-level lists.
25 Each node is created with a random top level (with a random height), and belongs
26 to all lists up to that level. The probability that a node has the height 1 is 1/2.
27 The probability that a node has the height N is 1/2 ** N (more precisely,
28 the distribution depends on an random generator provided, but our generators
31 The lock-free variant of skip-list is implemented according to book
32 - [2008] M.Herlihy, N.Shavit "The Art of Multiprocessor Programming",
33 chapter 14.4 "A Lock-Free Concurrent Skiplist"
36 - \p RCU - one of \ref cds_urcu_gc "RCU type".
37 - \p T - type to be stored in the list.
38 - \p Traits - set traits, default is skip_list::traits for explanation.
40 It is possible to declare option-based list with cds::container::skip_list::make_traits metafunction istead of \p Traits template
42 Template argument list \p Options of cds::container::skip_list::make_traits metafunction are:
43 - opt::compare - key comparison functor. No default functor is provided.
44 If the option is not specified, the opt::less is used.
45 - opt::less - specifies binary predicate used for key comparison. Default is \p std::less<T>.
46 - opt::item_counter - the type of item counting feature. Default is \ref atomicity::empty_item_counter that is no item counting.
47 - opt::memory_model - C++ memory ordering model. Can be opt::v::relaxed_ordering (relaxed memory model, the default)
48 or opt::v::sequential_consistent (sequentially consisnent memory model).
49 - skip_list::random_level_generator - random level generator. Can be skip_list::xorshift, skip_list::turbo_pascal or
50 user-provided one. See skip_list::random_level_generator option description for explanation.
51 Default is \p %skip_list::turbo_pascal.
52 - opt::allocator - allocator for skip-list node. Default is \ref CDS_DEFAULT_ALLOCATOR.
53 - opt::back_off - back-off strategy used. If the option is not specified, the cds::backoff::Default is used.
54 - opt::stat - internal statistics. Available types: skip_list::stat, skip_list::empty_stat (the default)
55 - opt::rcu_check_deadlock - a deadlock checking policy. Default is opt::v::rcu_throw_deadlock
57 @note Before including <tt><cds/container/skip_list_set_rcu.h></tt> you should include appropriate RCU header file,
58 see \ref cds_urcu_gc "RCU type" for list of existing RCU class and corresponding header files.
62 The class supports a forward iterator (\ref iterator and \ref const_iterator).
63 The iteration is ordered.
65 You may iterate over skip-list set items only under RCU lock.
66 Only in this case the iterator is thread-safe since
67 while RCU is locked any set's item cannot be reclaimed.
69 The requirement of RCU lock during iterating means that deletion of the elements (i.e. \ref erase)
72 @warning The iterator object cannot be passed between threads
74 Example how to use skip-list set iterators:
76 // First, you should include the header for RCU type you have chosen
77 #include <cds/urcu/general_buffered.h>
78 #include <cds/container/skip_list_set_rcu.h>
80 typedef cds::urcu::gc< cds::urcu::general_buffered<> > rcu_type;
86 // Traits for your skip-list.
87 // At least, you should define cds::opt::less or cds::opt::compare for Foo struct
88 struct my_traits: public cds::continer::skip_list::traits
92 typedef cds::container::SkipListSet< rcu_type, Foo, my_traits > my_skiplist_set;
94 my_skiplist_set theSet;
100 // Apply RCU locking manually
101 typename rcu_type::scoped_lock sl;
103 for ( auto it = theList.begin(); it != theList.end(); ++it ) {
107 // rcu_type::scoped_lock destructor releases RCU lock implicitly
111 \warning Due to concurrent nature of skip-list set it is not guarantee that you can iterate
112 all elements in the set: any concurrent deletion can exclude the element
113 pointed by the iterator from the set, and your iteration can be terminated
114 before end of the set. Therefore, such iteration is more suitable for debugging purposes
116 The iterator class supports the following minimalistic interface:
123 iterator( iterator const& s);
125 value_type * operator ->() const;
126 value_type& operator *() const;
129 iterator& operator ++();
132 iterator& operator = (const iterator& src);
134 bool operator ==(iterator const& i ) const;
135 bool operator !=(iterator const& i ) const;
138 Note, the iterator object returned by \ref end, \p cend member functions points to \p nullptr and should not be dereferenced.
143 #ifdef CDS_DOXYGEN_INVOKED
144 typename Traits = skip_list::traits
149 class SkipListSet< cds::urcu::gc< RCU >, T, Traits >:
150 #ifdef CDS_DOXYGEN_INVOKED
151 protected intrusive::SkipListSet< cds::urcu::gc< RCU >, T, Traits >
153 protected details::make_skip_list_set< cds::urcu::gc< RCU >, T, Traits >::type
157 typedef details::make_skip_list_set< cds::urcu::gc< RCU >, T, Traits > maker;
158 typedef typename maker::type base_class;
161 typedef typename base_class::gc gc ; ///< Garbage collector used
162 typedef T value_type ; ///< Value type stored in the set
163 typedef Traits traits ; ///< Options specified
165 typedef typename base_class::back_off back_off ; ///< Back-off strategy used
166 typedef typename traits::allocator allocator_type ; ///< Allocator type used for allocate/deallocate the skip-list nodes
167 typedef typename base_class::item_counter item_counter ; ///< Item counting policy used
168 typedef typename maker::key_comparator key_comparator ; ///< key compare functor
169 typedef typename base_class::memory_model memory_model ; ///< Memory ordering. See cds::opt::memory_model option
170 typedef typename traits::random_level_generator random_level_generator ; ///< random level generator
171 typedef typename traits::stat stat ; ///< internal statistics type
172 typedef typename traits::rcu_check_deadlock rcu_check_deadlock ; ///< Deadlock checking policy
176 typedef typename maker::node_type node_type;
177 typedef typename maker::node_allocator node_allocator;
179 typedef std::unique_ptr< node_type, typename maker::node_deallocator > scoped_node_ptr;
183 typedef typename base_class::rcu_lock rcu_lock; ///< RCU scoped lock
184 /// Group of \p extract_xxx functions do not require external locking
185 static CDS_CONSTEXPR const bool c_bExtractLockExternal = base_class::c_bExtractLockExternal;
187 /// pointer to extracted node
188 using exempt_ptr = cds::urcu::exempt_ptr< gc, node_type, value_type, typename maker::intrusive_traits::disposer >;
192 unsigned int random_level()
194 return base_class::random_level();
197 value_type * to_value_ptr( node_type * pNode ) const CDS_NOEXCEPT
199 return pNode ? &pNode->m_Value : nullptr;
209 /// Destructor destroys the set object
215 typedef skip_list::details::iterator< typename base_class::iterator > iterator;
217 /// Const iterator type
218 typedef skip_list::details::iterator< typename base_class::const_iterator > const_iterator;
220 /// Returns a forward iterator addressing the first element in a set
223 return iterator( base_class::begin() );
226 /// Returns a forward const iterator addressing the first element in a set
228 const_iterator begin() const
230 return const_iterator( base_class::begin() );
232 const_iterator cbegin() const
234 return const_iterator( base_class::cbegin() );
238 /// Returns a forward iterator that addresses the location succeeding the last element in a set.
241 return iterator( base_class::end() );
244 /// Returns a forward const iterator that addresses the location succeeding the last element in a set.
246 const_iterator end() const
248 return const_iterator( base_class::end() );
250 const_iterator cend() const
252 return const_iterator( base_class::cend() );
259 The function creates a node with copy of \p val value
260 and then inserts the node created into the set.
262 The type \p Q should contain as minimum the complete key for the node.
263 The object of \ref value_type should be constructible from a value of type \p Q.
264 In trivial case, \p Q is equal to \ref value_type.
266 RCU \p synchronize method can be called. RCU should not be locked.
268 Returns \p true if \p val is inserted into the set, \p false otherwise.
270 template <typename Q>
271 bool insert( Q const& val )
273 scoped_node_ptr sp( node_allocator().New( random_level(), val ));
274 if ( base_class::insert( *sp.get() )) {
283 The function allows to split creating of new item into two part:
284 - create item with key only
285 - insert new item into the set
286 - if inserting is success, calls \p f functor to initialize value-fields of \p val.
288 The functor signature is:
290 void func( value_type& val );
292 where \p val is the item inserted. User-defined functor \p f should guarantee that during changing
293 \p val no any other changes could be made on this set's item by concurrent threads.
294 The user-defined functor is called only if the inserting is success.
296 RCU \p synchronize method can be called. RCU should not be locked.
298 template <typename Q, typename Func>
299 bool insert( Q const& val, Func f )
301 scoped_node_ptr sp( node_allocator().New( random_level(), val ));
302 if ( base_class::insert( *sp.get(), [&f]( node_type& val ) { f( val.m_Value ); } )) {
309 /// Ensures that the item exists in the set
311 The operation performs inserting or changing data with lock-free manner.
313 If the \p val key not found in the set, then the new item created from \p val
314 is inserted into the set. Otherwise, the functor \p func is called with the item found.
315 The functor \p Func should be a function with signature:
317 void func( bool bNew, value_type& item, const Q& val );
322 void operator()( bool bNew, value_type& item, const Q& val );
327 - \p bNew - \p true if the item has been inserted, \p false otherwise
328 - \p item - item of the set
329 - \p val - argument \p key passed into the \p ensure function
331 The functor may change non-key fields of the \p item; however, \p func must guarantee
332 that during changing no any other modifications could be made on this item by concurrent threads.
334 RCU \p synchronize method can be called. RCU should not be locked.
336 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
337 \p second is true if new item has been added or \p false if the item with \p key
338 already is in the set.
340 template <typename Q, typename Func>
341 std::pair<bool, bool> ensure( const Q& val, Func func )
343 scoped_node_ptr sp( node_allocator().New( random_level(), val ));
344 std::pair<bool, bool> bRes = base_class::ensure( *sp,
345 [&func, &val](bool bNew, node_type& node, node_type&){ func( bNew, node.m_Value, val ); });
346 if ( bRes.first && bRes.second )
351 /// Inserts data of type \ref value_type constructed with <tt>std::forward<Args>(args)...</tt>
353 Returns \p true if inserting successful, \p false otherwise.
355 RCU \p synchronize method can be called. RCU should not be locked.
357 template <typename... Args>
358 bool emplace( Args&&... args )
360 scoped_node_ptr sp( node_allocator().New( random_level(), std::forward<Args>(args)... ));
361 if ( base_class::insert( *sp.get() )) {
368 /// Delete \p key from the set
369 /** \anchor cds_nonintrusive_SkipListSet_rcu_erase_val
371 The item comparator should be able to compare the type \p value_type
374 RCU \p synchronize method can be called. RCU should not be locked.
376 Return \p true if key is found and deleted, \p false otherwise
378 template <typename Q>
379 bool erase( Q const& key )
381 return base_class::erase( key );
384 /// Deletes the item from the set using \p pred predicate for searching
386 The function is an analog of \ref cds_nonintrusive_SkipListSet_rcu_erase_val "erase(Q const&)"
387 but \p pred is used for key comparing.
388 \p Less functor has the interface like \p std::less.
389 \p Less must imply the same element order as the comparator used for building the set.
391 template <typename Q, typename Less>
392 bool erase_with( Q const& key, Less pred )
395 return base_class::erase_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::value_accessor >());
398 /// Delete \p key from the set
399 /** \anchor cds_nonintrusive_SkipListSet_rcu_erase_func
401 The function searches an item with key \p key, calls \p f functor
402 and deletes the item. If \p key is not found, the functor is not called.
404 The functor \p Func interface:
407 void operator()(value_type const& val);
411 Since the key of MichaelHashSet's \p value_type is not explicitly specified,
412 template parameter \p Q defines the key type searching in the list.
413 The list item comparator should be able to compare the type \p T of list item
416 RCU \p synchronize method can be called. RCU should not be locked.
418 Return \p true if key is found and deleted, \p false otherwise
422 template <typename Q, typename Func>
423 bool erase( Q const& key, Func f )
425 return base_class::erase( key, [&f]( node_type const& node) { f( node.m_Value ); } );
428 /// Deletes the item from the set using \p pred predicate for searching
430 The function is an analog of \ref cds_nonintrusive_SkipListSet_rcu_erase_func "erase(Q const&, Func)"
431 but \p pred is used for key comparing.
432 \p Less functor has the interface like \p std::less.
433 \p Less must imply the same element order as the comparator used for building the set.
435 template <typename Q, typename Less, typename Func>
436 bool erase_with( Q const& key, Less pred, Func f )
439 return base_class::erase_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::value_accessor >(),
440 [&f]( node_type const& node) { f( node.m_Value ); } );
443 /// Extracts the item from the set with specified \p key
444 /** \anchor cds_nonintrusive_SkipListSet_rcu_extract
445 The function searches an item with key equal to \p key in the set,
446 unlinks it from the set, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item found.
447 If the item is not found the function returns an empty \p exempt_ptr
449 Note the compare functor from \p Traits class' template argument
450 should accept a parameter of type \p Q that can be not the same as \p value_type.
452 RCU \p synchronize method can be called. RCU should NOT be locked.
454 The function does not free the item found.
455 The item will be implicitly freed when the returned object is destroyed or when
456 its \p release() member function is called.
458 template <typename Q>
459 exempt_ptr extract( Q const& key )
461 return exempt_ptr( base_class::do_extract( key ));
464 /// Extracts the item from the set with comparing functor \p pred
466 The function is an analog of \ref cds_nonintrusive_SkipListSet_rcu_extract "extract(exempt_ptr&, Q const&)"
467 but \p pred predicate is used for key comparing.
468 \p Less has the semantics like \p std::less.
469 \p pred must imply the same element order as the comparator used for building the set.
471 template <typename Q, typename Less>
472 exempt_ptr extract_with( Q const& key, Less pred )
475 return exempt_ptr( base_class::do_extract_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::value_accessor >()));
478 /// Extracts an item with minimal key from the set
480 The function searches an item with minimal key, unlinks it,
481 and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item.
482 If the skip-list is empty the function returns an empty \p exempt_ptr.
484 RCU \p synchronize method can be called. RCU should NOT be locked.
486 The function does not free the item found.
487 The item will be implicitly freed when the returned object is destroyed or when
488 its \p release() member function is called.
490 exempt_ptr extract_min()
492 return exempt_ptr( base_class::do_extract_min());
495 /// Extracts an item with maximal key from the set
497 The function searches an item with maximal key, unlinks it from the set,
498 and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item.
499 If the skip-list is empty the function returns an empty \p exempt_ptr.
501 RCU \p synchronize method can be called. RCU should NOT be locked.
503 The function does not free the item found.
504 The item will be implicitly freed when the returned object is destroyed or when
505 its \p release() member function is called.
507 exempt_ptr extract_max()
509 return exempt_ptr( base_class::do_extract_max());
512 /// Find the key \p val
514 @anchor cds_nonintrusive_SkipListSet_rcu_find_func
516 The function searches the item with key equal to \p val and calls the functor \p f for item found.
517 The interface of \p Func functor is:
520 void operator()( value_type& item, Q& val );
523 where \p item is the item found, \p val is the <tt>find</tt> function argument.
525 The functor may change non-key fields of \p item. Note that the functor is only guarantee
526 that \p item cannot be disposed during functor is executing.
527 The functor does not serialize simultaneous access to the set's \p item. If such access is
528 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
530 The \p val argument is non-const since it can be used as \p f functor destination i.e., the functor
531 can modify both arguments.
533 Note the hash functor specified for class \p Traits template parameter
534 should accept a parameter of type \p Q that may be not the same as \p value_type.
536 The function applies RCU lock internally.
538 The function returns \p true if \p val is found, \p false otherwise.
540 template <typename Q, typename Func>
541 bool find( Q& val, Func f )
543 return base_class::find( val, [&f]( node_type& node, Q& v ) { f( node.m_Value, v ); });
546 template <typename Q, typename Func>
547 bool find( Q const& val, Func f )
549 return base_class::find( val, [&f]( node_type& node, Q& v ) { f( node.m_Value, v ); } );
553 /// Finds the key \p val using \p pred predicate for searching
555 The function is an analog of \ref cds_nonintrusive_SkipListSet_rcu_find_func "find(Q&, Func)"
556 but \p pred is used for key comparing.
557 \p Less functor has the interface like \p std::less.
558 \p Less must imply the same element order as the comparator used for building the set.
560 template <typename Q, typename Less, typename Func>
561 bool find_with( Q& val, Less pred, Func f )
564 return base_class::find_with( val, cds::details::predicate_wrapper< node_type, Less, typename maker::value_accessor >(),
565 [&f]( node_type& node, Q& v ) { f( node.m_Value, v ); } );
568 template <typename Q, typename Less, typename Func>
569 bool find_with( Q const& val, Less pred, Func f )
572 return base_class::find_with( val, cds::details::predicate_wrapper< node_type, Less, typename maker::value_accessor >(),
573 [&f]( node_type& node, Q& v ) { f( node.m_Value, v ); } );
577 /// Find the key \p val
578 /** @anchor cds_nonintrusive_SkipListSet_rcu_find_val
580 The function searches the item with key equal to \p val
581 and returns \p true if it is found, and \p false otherwise.
583 Note the hash functor specified for class \p Traits template parameter
584 should accept a parameter of type \p Q that may be not the same as \ref value_type.
586 The function applies RCU lock internally.
588 template <typename Q>
589 bool find( Q const & val )
591 return base_class::find( val );
594 /// Finds the key \p val using \p pred predicate for searching
596 The function is an analog of \ref cds_nonintrusive_SkipListSet_rcu_find_val "find(Q const&)"
597 but \p pred is used for key comparing.
598 \p Less functor has the interface like \p std::less.
599 \p Less must imply the same element order as the comparator used for building the set.
601 template <typename Q, typename Less>
602 bool find_with( Q const& val, Less pred )
605 return base_class::find_with( val, cds::details::predicate_wrapper< node_type, Less, typename maker::value_accessor >());
608 /// Finds \p key and return the item found
609 /** \anchor cds_nonintrusive_SkipListSet_rcu_get
610 The function searches the item with key equal to \p key and returns the pointer to item found.
611 If \p key is not found it returns \p nullptr.
613 Note the compare functor in \p Traits class' template argument
614 should accept a parameter of type \p Q that can be not the same as \p value_type.
616 RCU should be locked before call of this function.
617 Returned item is valid only while RCU is locked:
619 typedef cds::container::SkipListSet< cds::urcu::gc< cds::urcu::general_buffered<> >, foo, my_traits > skip_list;
624 skip_list::rcu_lock lock;
626 foo * pVal = theList.get( 5 );
630 // Unlock RCU by rcu_lock destructor
631 // pVal can be freed at any time after RCU unlocking
635 After RCU unlocking the \p %force_dispose member function can be called manually,
636 see \ref force_dispose for explanation.
638 template <typename Q>
639 value_type * get( Q const& key )
641 return to_value_ptr( base_class::get( key ));
644 /// Finds the key \p val and return the item found
646 The function is an analog of \ref cds_nonintrusive_SkipListSet_rcu_get "get(Q const&)"
647 but \p pred is used for comparing the keys.
649 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
651 \p pred must imply the same element order as the comparator used for building the set.
653 template <typename Q, typename Less>
654 value_type * get_with( Q const& val, Less pred )
657 return to_value_ptr( base_class::get_with( val, cds::details::predicate_wrapper< node_type, Less, typename maker::value_accessor >() ));
660 /// Clears the set (non-atomic).
662 The function deletes all items from the set.
663 The function is not atomic, thus, in multi-threaded environment with parallel insertions
667 assert( set.empty() );
669 the assertion could be raised.
671 For each item the \ref disposer provided by \p Traits template parameter will be called.
678 /// Checks if the set is empty
681 return base_class::empty();
684 /// Returns item count in the set
686 The value returned depends on item counter type provided by \p Traits template parameter.
687 If it is atomicity::empty_item_counter this function always returns 0.
688 Therefore, the function is not suitable for checking the set emptiness, use \ref empty
689 member function for this purpose.
693 return base_class::size();
696 /// Returns const reference to internal statistics
697 stat const& statistics() const
699 return base_class::statistics();
702 /// Clears internal list of ready-to-delete items passing them to RCU reclamation cycle
704 See \ref cds_intrusive_SkipListSet_rcu_force_dispose "intrusive SkipListSet" for explanation
708 return base_class::force_dispose();
712 }} // namespace cds::container
714 #endif // #ifndef __CDS_CONTAINER_SKIP_LIST_SET_RCU_H