3 #ifndef CDSLIB_CONTAINER_SKIP_LIST_SET_RCU_H
4 #define CDSLIB_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
175 typedef cds::container::skip_list::implementation_tag implementation_tag;
180 typedef typename maker::node_type node_type;
181 typedef typename maker::node_allocator node_allocator;
183 typedef std::unique_ptr< node_type, typename maker::node_deallocator > scoped_node_ptr;
187 typedef typename base_class::rcu_lock rcu_lock; ///< RCU scoped lock
188 /// Group of \p extract_xxx functions do not require external locking
189 static CDS_CONSTEXPR const bool c_bExtractLockExternal = base_class::c_bExtractLockExternal;
191 /// pointer to extracted node
192 using exempt_ptr = cds::urcu::exempt_ptr< gc, node_type, value_type, typename maker::intrusive_traits::disposer >;
196 struct raw_ptr_converter
198 value_type * operator()( node_type * p ) const
200 return p ? &p->m_Value : nullptr;
203 value_type& operator()( node_type& n ) const
208 value_type const& operator()( node_type const& n ) const
216 /// Result of \p get(), \p get_with() functions - pointer to the node found
217 typedef cds::urcu::raw_ptr_adaptor< value_type, typename base_class::raw_ptr, raw_ptr_converter > raw_ptr;
221 unsigned int random_level()
223 return base_class::random_level();
233 /// Destructor destroys the set object
239 typedef skip_list::details::iterator< typename base_class::iterator > iterator;
241 /// Const iterator type
242 typedef skip_list::details::iterator< typename base_class::const_iterator > const_iterator;
244 /// Returns a forward iterator addressing the first element in a set
247 return iterator( base_class::begin() );
250 /// Returns a forward const iterator addressing the first element in a set
252 const_iterator begin() const
254 return const_iterator( base_class::begin() );
256 const_iterator cbegin() const
258 return const_iterator( base_class::cbegin() );
262 /// Returns a forward iterator that addresses the location succeeding the last element in a set.
265 return iterator( base_class::end() );
268 /// Returns a forward const iterator that addresses the location succeeding the last element in a set.
270 const_iterator end() const
272 return const_iterator( base_class::end() );
274 const_iterator cend() const
276 return const_iterator( base_class::cend() );
283 The function creates a node with copy of \p val value
284 and then inserts the node created into the set.
286 The type \p Q should contain as minimum the complete key for the node.
287 The object of \ref value_type should be constructible from a value of type \p Q.
288 In trivial case, \p Q is equal to \ref value_type.
290 RCU \p synchronize method can be called. RCU should not be locked.
292 Returns \p true if \p val is inserted into the set, \p false otherwise.
294 template <typename Q>
295 bool insert( Q const& val )
297 scoped_node_ptr sp( node_allocator().New( random_level(), val ));
298 if ( base_class::insert( *sp.get() )) {
307 The function allows to split creating of new item into two part:
308 - create item with key only
309 - insert new item into the set
310 - if inserting is success, calls \p f functor to initialize value-fields of \p val.
312 The functor signature is:
314 void func( value_type& val );
316 where \p val is the item inserted. User-defined functor \p f should guarantee that during changing
317 \p val no any other changes could be made on this set's item by concurrent threads.
318 The user-defined functor is called only if the inserting is success.
320 RCU \p synchronize method can be called. RCU should not be locked.
322 template <typename Q, typename Func>
323 bool insert( Q const& val, Func f )
325 scoped_node_ptr sp( node_allocator().New( random_level(), val ));
326 if ( base_class::insert( *sp.get(), [&f]( node_type& val ) { f( val.m_Value ); } )) {
333 /// Ensures that the item exists in the set
335 The operation performs inserting or changing data with lock-free manner.
337 If the \p val key not found in the set, then the new item created from \p val
338 is inserted into the set. Otherwise, the functor \p func is called with the item found.
339 The functor \p Func should be a function with signature:
341 void func( bool bNew, value_type& item, const Q& val );
346 void operator()( bool bNew, value_type& item, const Q& val );
351 - \p bNew - \p true if the item has been inserted, \p false otherwise
352 - \p item - item of the set
353 - \p val - argument \p key passed into the \p ensure function
355 The functor may change non-key fields of the \p item; however, \p func must guarantee
356 that during changing no any other modifications could be made on this item by concurrent threads.
358 RCU \p synchronize method can be called. RCU should not be locked.
360 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
361 \p second is true if new item has been added or \p false if the item with \p key
362 already is in the set.
364 template <typename Q, typename Func>
365 std::pair<bool, bool> ensure( const Q& val, Func func )
367 scoped_node_ptr sp( node_allocator().New( random_level(), val ));
368 std::pair<bool, bool> bRes = base_class::ensure( *sp,
369 [&func, &val](bool bNew, node_type& node, node_type&){ func( bNew, node.m_Value, val ); });
370 if ( bRes.first && bRes.second )
375 /// Inserts data of type \ref value_type constructed with <tt>std::forward<Args>(args)...</tt>
377 Returns \p true if inserting successful, \p false otherwise.
379 RCU \p synchronize method can be called. RCU should not be locked.
381 template <typename... Args>
382 bool emplace( Args&&... args )
384 scoped_node_ptr sp( node_allocator().New( random_level(), std::forward<Args>(args)... ));
385 if ( base_class::insert( *sp.get() )) {
392 /// Delete \p key from the set
393 /** \anchor cds_nonintrusive_SkipListSet_rcu_erase_val
395 The item comparator should be able to compare the type \p value_type
398 RCU \p synchronize method can be called. RCU should not be locked.
400 Return \p true if key is found and deleted, \p false otherwise
402 template <typename Q>
403 bool erase( Q const& key )
405 return base_class::erase( key );
408 /// Deletes the item from the set using \p pred predicate for searching
410 The function is an analog of \ref cds_nonintrusive_SkipListSet_rcu_erase_val "erase(Q const&)"
411 but \p pred is used for key comparing.
412 \p Less functor has the interface like \p std::less.
413 \p Less must imply the same element order as the comparator used for building the set.
415 template <typename Q, typename Less>
416 bool erase_with( Q const& key, Less pred )
419 return base_class::erase_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::value_accessor >());
422 /// Delete \p key from the set
423 /** \anchor cds_nonintrusive_SkipListSet_rcu_erase_func
425 The function searches an item with key \p key, calls \p f functor
426 and deletes the item. If \p key is not found, the functor is not called.
428 The functor \p Func interface:
431 void operator()(value_type const& val);
435 Since the key of MichaelHashSet's \p value_type is not explicitly specified,
436 template parameter \p Q defines the key type searching in the list.
437 The list item comparator should be able to compare the type \p T of list item
440 RCU \p synchronize method can be called. RCU should not be locked.
442 Return \p true if key is found and deleted, \p false otherwise
446 template <typename Q, typename Func>
447 bool erase( Q const& key, Func f )
449 return base_class::erase( key, [&f]( node_type const& node) { f( node.m_Value ); } );
452 /// Deletes the item from the set using \p pred predicate for searching
454 The function is an analog of \ref cds_nonintrusive_SkipListSet_rcu_erase_func "erase(Q const&, Func)"
455 but \p pred is used for key comparing.
456 \p Less functor has the interface like \p std::less.
457 \p Less must imply the same element order as the comparator used for building the set.
459 template <typename Q, typename Less, typename Func>
460 bool erase_with( Q const& key, Less pred, Func f )
463 return base_class::erase_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::value_accessor >(),
464 [&f]( node_type const& node) { f( node.m_Value ); } );
467 /// Extracts the item from the set with specified \p key
468 /** \anchor cds_nonintrusive_SkipListSet_rcu_extract
469 The function searches an item with key equal to \p key in the set,
470 unlinks it from the set, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item found.
471 If the item is not found the function returns an empty \p exempt_ptr
473 Note the compare functor from \p Traits class' template argument
474 should accept a parameter of type \p Q that can be not the same as \p value_type.
476 RCU \p synchronize method can be called. RCU should NOT be locked.
478 The function does not free the item found.
479 The item will be implicitly freed when the returned object is destroyed or when
480 its \p release() member function is called.
482 template <typename Q>
483 exempt_ptr extract( Q const& key )
485 return exempt_ptr( base_class::do_extract( key ));
488 /// Extracts the item from the set with comparing functor \p pred
490 The function is an analog of \p extract(Q const&) but \p pred predicate is used for key comparing.
491 \p Less has the semantics like \p std::less.
492 \p pred must imply the same element order as the comparator used for building the set.
494 template <typename Q, typename Less>
495 exempt_ptr extract_with( Q const& key, Less pred )
498 return exempt_ptr( base_class::do_extract_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::value_accessor >()));
501 /// Extracts an item with minimal key from the set
503 The function searches an item with minimal key, unlinks it,
504 and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item.
505 If the skip-list is empty the function returns an empty \p exempt_ptr.
507 RCU \p synchronize method can be called. RCU should NOT be locked.
509 The function does not free the item found.
510 The item will be implicitly freed when the returned object is destroyed or when
511 its \p release() member function is called.
513 exempt_ptr extract_min()
515 return exempt_ptr( base_class::do_extract_min());
518 /// Extracts an item with maximal key from the set
520 The function searches an item with maximal key, unlinks it from the set,
521 and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item.
522 If the skip-list is empty the function returns an empty \p exempt_ptr.
524 RCU \p synchronize method can be called. RCU should NOT be locked.
526 The function does not free the item found.
527 The item will be implicitly freed when the returned object is destroyed or when
528 its \p release() member function is called.
530 exempt_ptr extract_max()
532 return exempt_ptr( base_class::do_extract_max());
535 /// Find the key \p val
537 @anchor cds_nonintrusive_SkipListSet_rcu_find_func
539 The function searches the item with key equal to \p val and calls the functor \p f for item found.
540 The interface of \p Func functor is:
543 void operator()( value_type& item, Q& val );
546 where \p item is the item found, \p val is the <tt>find</tt> function argument.
548 The functor may change non-key fields of \p item. Note that the functor is only guarantee
549 that \p item cannot be disposed during functor is executing.
550 The functor does not serialize simultaneous access to the set's \p item. If such access is
551 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
553 The \p val argument is non-const since it can be used as \p f functor destination i.e., the functor
554 can modify both arguments.
556 Note the hash functor specified for class \p Traits template parameter
557 should accept a parameter of type \p Q that may be not the same as \p value_type.
559 The function applies RCU lock internally.
561 The function returns \p true if \p val is found, \p false otherwise.
563 template <typename Q, typename Func>
564 bool find( Q& val, Func f )
566 return base_class::find( val, [&f]( node_type& node, Q& v ) { f( node.m_Value, v ); });
569 template <typename Q, typename Func>
570 bool find( Q const& val, Func f )
572 return base_class::find( val, [&f]( node_type& node, Q& v ) { f( node.m_Value, v ); } );
576 /// Finds the key \p val using \p pred predicate for searching
578 The function is an analog of \ref cds_nonintrusive_SkipListSet_rcu_find_func "find(Q&, Func)"
579 but \p pred is used for key comparing.
580 \p Less functor has the interface like \p std::less.
581 \p Less must imply the same element order as the comparator used for building the set.
583 template <typename Q, typename Less, typename Func>
584 bool find_with( Q& val, Less pred, Func f )
587 return base_class::find_with( val, cds::details::predicate_wrapper< node_type, Less, typename maker::value_accessor >(),
588 [&f]( node_type& node, Q& v ) { f( node.m_Value, v ); } );
591 template <typename Q, typename Less, typename Func>
592 bool find_with( Q const& val, Less pred, Func f )
595 return base_class::find_with( val, cds::details::predicate_wrapper< node_type, Less, typename maker::value_accessor >(),
596 [&f]( node_type& node, Q& v ) { f( node.m_Value, v ); } );
600 /// Find the key \p val
601 /** @anchor cds_nonintrusive_SkipListSet_rcu_find_val
603 The function searches the item with key equal to \p val
604 and returns \p true if it is found, and \p false otherwise.
606 Note the hash functor specified for class \p Traits template parameter
607 should accept a parameter of type \p Q that may be not the same as \ref value_type.
609 The function applies RCU lock internally.
611 template <typename Q>
612 bool find( Q const & val )
614 return base_class::find( val );
617 /// Finds the key \p val using \p pred predicate for searching
619 The function is an analog of \ref cds_nonintrusive_SkipListSet_rcu_find_val "find(Q const&)"
620 but \p pred is used for key comparing.
621 \p Less functor has the interface like \p std::less.
622 \p Less must imply the same element order as the comparator used for building the set.
624 template <typename Q, typename Less>
625 bool find_with( Q const& val, Less pred )
628 return base_class::find_with( val, cds::details::predicate_wrapper< node_type, Less, typename maker::value_accessor >());
631 /// Finds \p key and return the item found
632 /** \anchor cds_nonintrusive_SkipListSet_rcu_get
633 The function searches the item with key equal to \p key and returns a \p raw_ptr object pointed to item found.
634 If \p key is not found it returns empty \p raw_ptr.
636 Note the compare functor in \p Traits class' template argument
637 should accept a parameter of type \p Q that can be not the same as \p value_type.
639 RCU should be locked before call of this function.
640 Returned item is valid only while RCU is locked:
642 typedef cds::container::SkipListSet< cds::urcu::gc< cds::urcu::general_buffered<> >, foo, my_traits > skip_list;
645 typename skip_list::raw_ptr pVal;
648 skip_list::rcu_lock lock;
650 pVal = theList.get( 5 );
656 // You can manually release pVal after RCU-locked section
660 template <typename Q>
661 raw_ptr get( Q const& key )
663 return raw_ptr( base_class::get( key ));
666 /// Finds the key \p val and return the item found
668 The function is an analog of \ref cds_nonintrusive_SkipListSet_rcu_get "get(Q const&)"
669 but \p pred is used for comparing the keys.
671 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
673 \p pred must imply the same element order as the comparator used for building the set.
675 template <typename Q, typename Less>
676 raw_ptr get_with( Q const& val, Less pred )
679 return raw_ptr( base_class::get_with( val, cds::details::predicate_wrapper< node_type, Less, typename maker::value_accessor >() ));
682 /// Clears the set (non-atomic).
684 The function deletes all items from the set.
685 The function is not atomic, thus, in multi-threaded environment with parallel insertions
689 assert( set.empty() );
691 the assertion could be raised.
693 For each item the \ref disposer provided by \p Traits template parameter will be called.
700 /// Checks if the set is empty
703 return base_class::empty();
706 /// Returns item count in the set
708 The value returned depends on item counter type provided by \p Traits template parameter.
709 If it is atomicity::empty_item_counter this function always returns 0.
710 Therefore, the function is not suitable for checking the set emptiness, use \ref empty
711 member function for this purpose.
715 return base_class::size();
718 /// Returns const reference to internal statistics
719 stat const& statistics() const
721 return base_class::statistics();
725 }} // namespace cds::container
727 #endif // #ifndef CDSLIB_CONTAINER_SKIP_LIST_SET_RCU_H