3 #ifndef CDSLIB_CONTAINER_IMPL_SKIP_LIST_MAP_H
4 #define CDSLIB_CONTAINER_IMPL_SKIP_LIST_MAP_H
6 #include <cds/container/details/guarded_ptr_cast.h>
8 namespace cds { namespace container {
10 /// Lock-free skip-list map
11 /** @ingroup cds_nonintrusive_map
12 \anchor cds_nonintrusive_SkipListMap_hp
14 The implementation of well-known probabilistic data structure called skip-list
15 invented by W.Pugh in his papers:
16 - [1989] W.Pugh Skip Lists: A Probabilistic Alternative to Balanced Trees
17 - [1990] W.Pugh A Skip List Cookbook
19 A skip-list is a probabilistic data structure that provides expected logarithmic
20 time search without the need of rebalance. The skip-list is a collection of sorted
21 linked list. Nodes are ordered by key. Each node is linked into a subset of the lists.
22 Each list has a level, ranging from 0 to 32. The bottom-level list contains
23 all the nodes, and each higher-level list is a sublist of the lower-level lists.
24 Each node is created with a random top level (with a random height), and belongs
25 to all lists up to that level. The probability that a node has the height 1 is 1/2.
26 The probability that a node has the height N is 1/2 ** N (more precisely,
27 the distribution depends on an random generator provided, but our generators
30 The lock-free variant of skip-list is implemented according to book
31 - [2008] M.Herlihy, N.Shavit "The Art of Multiprocessor Programming",
32 chapter 14.4 "A Lock-Free Concurrent Skiplist"
35 - \p GC - Garbage collector used.
36 - \p K - type of a key to be stored in the list.
37 - \p T - type of a value to be stored in the list.
38 - \p Traits - map traits, default is \p skip_list::traits
39 It is possible to declare option-based list with \p cds::container::skip_list::make_traits metafunction
40 istead of \p Traits template argument.
42 Like STL map class, \p %SkipListMap stores the key-value pair as <tt>std:pair< K const, T></tt>.
44 @warning The skip-list requires up to 67 hazard pointers that may be critical for some GCs for which
45 the guard count is limited (like \p gc::HP). Those GCs should be explicitly initialized with
46 hazard pointer enough: \code cds::gc::HP myhp( 67 ) \endcode. Otherwise an run-time exception may be raised
47 when you try to create skip-list object.
49 @note There are several specializations of \p %SkipListMap for each \p GC. You should include:
50 - <tt><cds/container/skip_list_map_hp.h></tt> for \p gc::HP garbage collector
51 - <tt><cds/container/skip_list_map_dhp.h></tt> for \p gc::DHP garbage collector
52 - <tt><cds/container/skip_list_map_rcu.h></tt> for \ref cds_nonintrusive_SkipListMap_rcu "RCU type"
53 - <tt><cds/container/skip_list_map_nogc.h></tt> for \ref cds_nonintrusive_SkipListMap_nogc "non-deletable SkipListMap"
57 The class supports a forward iterator (\ref iterator and \ref const_iterator).
58 The iteration is ordered.
59 The iterator object is thread-safe: the element pointed by the iterator object is guarded,
60 so, the element cannot be reclaimed while the iterator object is alive.
61 However, passing an iterator object between threads is dangerous.
63 \warning Due to concurrent nature of skip-list map it is not guarantee that you can iterate
64 all elements in the map: any concurrent deletion can exclude the element
65 pointed by the iterator from the map, and your iteration can be terminated
66 before end of the map. Therefore, such iteration is more suitable for debugging purpose only
68 Remember, each iterator object requires 2 additional hazard pointers, that may be
69 a limited resource for \p GC like \p gc::HP (for gc::DHP the count of
72 The iterator class supports the following minimalistic interface:
79 iterator( iterator const& s);
81 value_type * operator ->() const;
82 value_type& operator *() const;
85 iterator& operator ++();
88 iterator& operator = (const iterator& src);
90 bool operator ==(iterator const& i ) const;
91 bool operator !=(iterator const& i ) const;
94 Note, the iterator object returned by \ref end, \ cend member functions points to \p nullptr and should not be dereferenced.
101 #ifdef CDS_DOXYGEN_INVOKED
102 typename Traits = skip_list::traits
108 #ifdef CDS_DOXYGEN_INVOKED
109 protected intrusive::SkipListSet< GC, std::pair<Key const, T>, Traits >
111 protected details::make_skip_list_map< GC, Key, T, Traits >::type
115 typedef details::make_skip_list_map< GC, Key, T, Traits > maker;
116 typedef typename maker::type base_class;
119 typedef GC gc; ///< Garbage collector
120 typedef Key key_type; ///< Key type
121 typedef T mapped_type; ///< Mapped type
122 typedef Traits traits; ///< Map traits
123 # ifdef CDS_DOXYGEN_INVOKED
124 typedef std::pair< K const, T> value_type; ///< Key-value pair to be stored in the map
126 typedef typename maker::value_type value_type;
129 typedef typename base_class::back_off back_off; ///< Back-off strategy
130 typedef typename traits::allocator allocator_type; ///< Allocator type used for allocate/deallocate the skip-list nodes
131 typedef typename base_class::item_counter item_counter; ///< Item counting policy used
132 typedef typename maker::key_comparator key_comparator; ///< key comparison functor
133 typedef typename base_class::memory_model memory_model; ///< Memory ordering, see \p cds::opt::memory_model
134 typedef typename traits::random_level_generator random_level_generator ; ///< random level generator
135 typedef typename traits::stat stat; ///< internal statistics type
138 typedef cds::container::skip_list::implementation_tag implementation_tag;
143 typedef typename maker::node_type node_type;
144 typedef typename maker::node_allocator node_allocator;
146 typedef std::unique_ptr< node_type, typename maker::node_deallocator > scoped_node_ptr;
151 typedef typename gc::template guarded_ptr< node_type, value_type, details::guarded_ptr_cast_set<node_type, value_type> > guarded_ptr;
155 unsigned int random_level()
157 return base_class::random_level();
167 /// Destructor destroys the set object
173 typedef skip_list::details::iterator< typename base_class::iterator > iterator;
175 /// Const iterator type
176 typedef skip_list::details::iterator< typename base_class::const_iterator > const_iterator;
178 /// Returns a forward iterator addressing the first element in a map
181 return iterator( base_class::begin() );
184 /// Returns a forward const iterator addressing the first element in a map
185 const_iterator begin() const
189 /// Returns a forward const iterator addressing the first element in a map
190 const_iterator cbegin() const
192 return const_iterator( base_class::cbegin() );
195 /// Returns a forward iterator that addresses the location succeeding the last element in a map.
198 return iterator( base_class::end() );
201 /// Returns a forward const iterator that addresses the location succeeding the last element in a map.
202 const_iterator end() const
206 /// Returns a forward const iterator that addresses the location succeeding the last element in a map.
207 const_iterator cend() const
209 return const_iterator( base_class::cend() );
213 /// Inserts new node with key and default value
215 The function creates a node with \p key and default value, and then inserts the node created into the map.
218 - The \p key_type should be constructible from a value of type \p K.
219 In trivial case, \p K is equal to \p key_type.
220 - The \p mapped_type should be default-constructible.
222 Returns \p true if inserting successful, \p false otherwise.
224 template <typename K>
225 bool insert( K const& key )
227 return insert_with( key, [](value_type&){} );
232 The function creates a node with copy of \p val value
233 and then inserts the node created into the map.
236 - The \p key_type should be constructible from \p key of type \p K.
237 - The \p value_type should be constructible from \p val of type \p V.
239 Returns \p true if \p val is inserted into the set, \p false otherwise.
241 template <typename K, typename V>
242 bool insert( K const& key, V const& val )
244 return insert_with( key, [&val](value_type& item) { item.second = val ; } );
247 /// Inserts new node and initialize it by a functor
249 This function inserts new node with key \p key and if inserting is successful then it calls
250 \p func functor with signature
253 void operator()( value_type& item );
257 The argument \p item of user-defined functor \p func is the reference
258 to the map's item inserted:
259 - <tt>item.first</tt> is a const reference to item's key that cannot be changed.
260 - <tt>item.second</tt> is a reference to item's value that may be changed.
262 \p key_type should be constructible from value of type \p K.
264 The function allows to split creating of new item into two part:
265 - create item from \p key;
266 - insert new item into the map;
267 - if inserting is successful, initialize the value of item by calling \p func functor
269 This can be useful if complete initialization of object of \p value_type is heavyweight and
270 it is preferable that the initialization should be completed only if inserting is successful.
272 template <typename K, typename Func>
273 bool insert_with( const K& key, Func func )
275 scoped_node_ptr pNode( node_allocator().New( random_level(), key ));
276 if ( base_class::insert( *pNode, [&func]( node_type& item ) { func( item.m_Value ); } )) {
283 /// For key \p key inserts data of type \p value_type created in-place from <tt>std::forward<Args>(args)...</tt>
285 Returns \p true if inserting successful, \p false otherwise.
287 template <typename K, typename... Args>
288 bool emplace( K&& key, Args&&... args )
290 scoped_node_ptr pNode( node_allocator().New( random_level(), std::forward<K>(key), std::forward<Args>(args)... ));
291 if ( base_class::insert( *pNode )) {
298 /// Updates data by \p key
300 The operation performs inserting or changing data with lock-free manner.
302 If the \p key not found in the map, then the new item created from \p key
303 will be inserted into the map iff \p bInsert is \p true
304 (note that in this case the \ref key_type should be constructible from type \p K).
305 Otherwise, if \p key is found, the functor \p func is called with item found.
306 The functor \p Func signature:
309 void operator()( bool bNew, value_type& item );
313 - \p bNew - \p true if the item has been inserted, \p false otherwise
314 - \p item - item of the map
316 The functor may change any fields of the \p item.second that is \ref value_type.
318 Returns <tt> std::pair<bool, bool> </tt> where \p first is \p true if operation is successfull,
319 \p second is \p true if new item has been added or \p false if \p key already exists.
321 @warning See \ref cds_intrusive_item_creating "insert item troubleshooting"
323 template <typename K, typename Func>
324 std::pair<bool, bool> update( K const& key, Func func, bool bInsert = true )
326 scoped_node_ptr pNode( node_allocator().New( random_level(), key ));
327 std::pair<bool, bool> res = base_class::update( *pNode,
328 [&func](bool bNew, node_type& item, node_type const& ){ func( bNew, item.m_Value );},
331 if ( res.first && res.second )
337 // Deprecated, use update()
338 template <typename K, typename Func>
339 std::pair<bool, bool> ensure( K const& key, Func func )
341 return update( key, func, true );
345 /// Delete \p key from the map
346 /** \anchor cds_nonintrusive_SkipListMap_erase_val
348 Return \p true if \p key is found and deleted, \p false otherwise
350 template <typename K>
351 bool erase( K const& key )
353 return base_class::erase(key);
356 /// Deletes the item from the map using \p pred predicate for searching
358 The function is an analog of \ref cds_nonintrusive_SkipListMap_erase_val "erase(K const&)"
359 but \p pred is used for key comparing.
360 \p Less functor has the interface like \p std::less.
361 \p Less must imply the same element order as the comparator used for building the map.
363 template <typename K, typename Less>
364 bool erase_with( K const& key, Less pred )
367 return base_class::erase_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >());
370 /// Delete \p key from the map
371 /** \anchor cds_nonintrusive_SkipListMap_erase_func
373 The function searches an item with key \p key, calls \p f functor
374 and deletes the item. If \p key is not found, the functor is not called.
376 The functor \p Func interface:
379 void operator()(value_type& item) { ... }
383 Return \p true if key is found and deleted, \p false otherwise
385 template <typename K, typename Func>
386 bool erase( K const& key, Func f )
388 return base_class::erase( key, [&f]( node_type& node) { f( node.m_Value ); } );
391 /// Deletes the item from the map using \p pred predicate for searching
393 The function is an analog of \ref cds_nonintrusive_SkipListMap_erase_func "erase(K const&, Func)"
394 but \p pred is used for key comparing.
395 \p Less functor has the interface like \p std::less.
396 \p Less must imply the same element order as the comparator used for building the map.
398 template <typename K, typename Less, typename Func>
399 bool erase_with( K const& key, Less pred, Func f )
402 return base_class::erase_with( key,
403 cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >(),
404 [&f]( node_type& node) { f( node.m_Value ); } );
407 /// Extracts the item from the map with specified \p key
408 /** \anchor cds_nonintrusive_SkipListMap_hp_extract
409 The function searches an item with key equal to \p key in the map,
410 unlinks it from the map, and returns a guarded pointer to the item found.
411 If \p key is not found the function returns an empty guarded pointer.
413 Note the compare functor should accept a parameter of type \p K that can be not the same as \p key_type.
415 The item extracted is freed automatically by garbage collector \p GC
416 when returned \p guarded_ptr object will be destroyed or released.
417 @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
421 typedef cds::container::SkipListMap< cds::gc::HP, int, foo, my_traits > skip_list;
425 skip_list::guarded_ptr gp( theList.extract( 5 ));
430 // Destructor of gp releases internal HP guard and frees the pointer
434 template <typename K>
435 guarded_ptr extract( K const& key )
438 base_class::extract_( gp.guard(), key, typename base_class::key_comparator() );
442 /// Extracts the item from the map with comparing functor \p pred
444 The function is an analog of \ref cds_nonintrusive_SkipListMap_hp_extract "extract(K const&)"
445 but \p pred predicate is used for key comparing.
447 \p Less functor has the semantics like \p std::less but should take arguments of type \ref key_type and \p K
449 \p pred must imply the same element order as the comparator used for building the map.
451 template <typename K, typename Less>
452 guarded_ptr extract_with( K const& key, Less pred )
455 typedef cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor > wrapped_less;
457 base_class::extract_( gp.guard(), key, cds::opt::details::make_comparator_from_less<wrapped_less>() );
461 /// Extracts an item with minimal key from the map
463 The function searches an item with minimal key, unlinks it, and returns an guarded pointer to the item found.
464 If the skip-list is empty the function returns an empty guarded pointer.
466 The item extracted is freed automatically by garbage collector \p GC
467 when returned \p guarded_ptr object will be destroyed or released.
468 @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
472 typedef cds::continer::SkipListMap< cds::gc::HP, int, foo, my_traits > skip_list;
476 skip_list::guarded_ptr gp( theList.extract_min());
481 // Destructor of gp releases internal HP guard and then frees the pointer
485 guarded_ptr extract_min()
488 base_class::extract_min_( gp.guard() );
492 /// Extracts an item with maximal key from the map
494 The function searches an item with maximal key, unlinks it, and returns a guarded pointer to item found.
495 If the skip-list is empty the function returns an empty \p guarded_ptr.
497 The item found is freed by garbage collector \p GC automatically
498 when returned \p guarded_ptr object will be destroyed or released.
499 @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
503 typedef cds::container::SkipListMap< cds::gc::HP, int, foo, my_traits > skip_list;
507 skip_list::guarded_ptr gp( theList.extract_max());
512 // Destructor of gp releases internal HP guard and then frees the pointer
516 guarded_ptr extract_max()
519 base_class::extract_max_( gp.guard() );
523 /// Find the key \p key
524 /** \anchor cds_nonintrusive_SkipListMap_find_cfunc
526 The function searches the item with key equal to \p key and calls the functor \p f for item found.
527 The interface of \p Func functor is:
530 void operator()( value_type& item );
533 where \p item is the item found.
535 The functor may change \p item.second.
537 The function returns \p true if \p key is found, \p false otherwise.
539 template <typename K, typename Func>
540 bool find( K const& key, Func f )
542 return base_class::find( key, [&f](node_type& item, K const& ) { f( item.m_Value );});
545 /// Finds the key \p val using \p pred predicate for searching
547 The function is an analog of \ref cds_nonintrusive_SkipListMap_find_cfunc "find(K const&, Func)"
548 but \p pred is used for key comparing.
549 \p Less functor has the interface like \p std::less.
550 \p Less must imply the same element order as the comparator used for building the map.
552 template <typename K, typename Less, typename Func>
553 bool find_with( K const& key, Less pred, Func f )
556 return base_class::find_with( key,
557 cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >(),
558 [&f](node_type& item, K const& ) { f( item.m_Value );});
561 /// Find the key \p key
562 /** \anchor cds_nonintrusive_SkipListMap_find_val
564 The function searches the item with key equal to \p key
565 and returns \p true if it is found, and \p false otherwise.
567 template <typename K>
568 bool find( K const& key )
570 return base_class::find( key );
573 /// Finds the key \p val using \p pred predicate for searching
575 The function is an analog of \ref cds_nonintrusive_SkipListMap_find_val "find(K const&)"
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 map.
580 template <typename K, typename Less>
581 bool find_with( K const& key, Less pred )
584 return base_class::find_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >() );
587 /// Finds the key \p key and return the item found
588 /** \anchor cds_nonintrusive_SkipListMap_hp_get
589 The function searches the item with key equal to \p key
590 and returns an guarded pointer to the item found.
591 If \p key is not found the function returns an empty guarded pointer.
593 It is safe when a concurrent thread erases the item returned as \p guarded_ptr.
594 In this case the item will be freed later by garbage collector \p GC automatically
595 when \p guarded_ptr object will be destroyed or released.
596 @note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
600 typedef cds::container::SkipListMap< cds::gc::HP, int, foo, my_traits > skip_list;
604 skip_list::guarded_ptr gp( theList.get( 5 ));
609 // Destructor of guarded_ptr releases internal HP guard
613 Note the compare functor specified for class \p Traits template parameter
614 should accept a parameter of type \p K that can be not the same as \p value_type.
616 template <typename K>
617 guarded_ptr get( K const& key )
620 base_class::get_with_( gp.guard(), key, typename base_class::key_comparator() );
624 /// Finds the key \p key and return the item found
626 The function is an analog of \ref cds_nonintrusive_SkipListMap_hp_get "get( K const&)"
627 but \p pred is used for comparing the keys.
629 \p Less functor has the semantics like \p std::less but should take arguments of type \ref key_type and \p K
631 \p pred must imply the same element order as the comparator used for building the map.
633 template <typename K, typename Less>
634 guarded_ptr get_with( K const& key, Less pred )
637 typedef cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor > wrapped_less;
639 base_class::get_with_( gp.guard(), key, cds::opt::details::make_comparator_from_less< wrapped_less >());
649 /// Checks if the map is empty
652 return base_class::empty();
655 /// Returns item count in the map
658 return base_class::size();
661 /// Returns const reference to internal statistics
662 stat const& statistics() const
664 return base_class::statistics();
667 }} // namespace cds::container
669 #endif // #ifndef CDSLIB_CONTAINER_IMPL_SKIP_LIST_MAP_H