3 #ifndef CDSLIB_CONTAINER_SKIP_LIST_MAP_RCU_H
4 #define CDSLIB_CONTAINER_SKIP_LIST_MAP_RCU_H
6 #include <cds/container/details/skip_list_base.h>
7 #include <cds/intrusive/skip_list_rcu.h>
8 #include <cds/container/details/make_skip_list_map.h>
10 namespace cds { namespace container {
12 /// Lock-free skip-list map (template specialization for \ref cds_urcu_desc "RCU")
13 /** @ingroup cds_nonintrusive_map
14 \anchor cds_nonintrusive_SkipListMap_rcu
16 The implementation of well-known probabilistic data structure called skip-list
17 invented by W.Pugh in his papers:
18 - [1989] W.Pugh Skip Lists: A Probabilistic Alternative to Balanced Trees
19 - [1990] W.Pugh A Skip List Cookbook
21 A skip-list is a probabilistic data structure that provides expected logarithmic
22 time search without the need of rebalance. The skip-list is a collection of sorted
23 linked list. Nodes are ordered by key. Each node is linked into a subset of the lists.
24 Each list has a level, ranging from 0 to 32. The bottom-level list contains
25 all the nodes, and each higher-level list is a sublist of the lower-level lists.
26 Each node is created with a random top level (with a random height), and belongs
27 to all lists up to that level. The probability that a node has the height 1 is 1/2.
28 The probability that a node has the height N is 1/2 ** N (more precisely,
29 the distribution depends on an random generator provided, but our generators
32 The lock-free variant of skip-list is implemented according to book
33 - [2008] M.Herlihy, N.Shavit "The Art of Multiprocessor Programming",
34 chapter 14.4 "A Lock-Free Concurrent Skiplist"
37 - \p RCU - one of \ref cds_urcu_gc "RCU type".
38 - \p K - type of a key to be stored in the list.
39 - \p T - type of a value to be stored in the list.
40 - \p Traits - map traits, default is \p skip_list::traits.
41 It is possible to declare option-based list with \p cds::container::skip_list::make_traits metafunction
42 instead of \p Traits template argument.
44 Like STL map class, \p %SkipListMap stores its key-value pair as <tt>std:pair< K const, T></tt>.
46 @note Before including <tt><cds/container/skip_list_map_rcu.h></tt> you should include appropriate RCU header file,
47 see \ref cds_urcu_gc "RCU type" for list of existing RCU class and corresponding header files.
51 The class supports a forward iterator (\ref iterator and \ref const_iterator).
52 The iteration is ordered.
53 You may iterate over skip-list set items only under RCU lock.
54 Only in this case the iterator is thread-safe since
55 while RCU is locked any set's item cannot be reclaimed.
57 The requirement of RCU lock during iterating means that deletion of the elements (i.e. \ref erase)
60 @warning The iterator object cannot be passed between threads
62 The iterator class supports the following minimalistic interface:
69 iterator( iterator const& s);
71 value_type * operator ->() const;
72 value_type& operator *() const;
75 iterator& operator ++();
78 iterator& operator = (const iterator& src);
80 bool operator ==(iterator const& i ) const;
81 bool operator !=(iterator const& i ) const;
84 Note, the iterator object returned by \ref end, \p cend member functions points to \p nullptr and should not be dereferenced.
91 #ifdef CDS_DOXYGEN_INVOKED
92 typename Traits = skip_list::traits
97 class SkipListMap< cds::urcu::gc< RCU >, Key, T, Traits >:
98 #ifdef CDS_DOXYGEN_INVOKED
99 protected intrusive::SkipListSet< cds::urcu::gc< RCU >, std::pair<Key const, T>, Traits >
101 protected details::make_skip_list_map< cds::urcu::gc< RCU >, Key, T, Traits >::type
105 typedef details::make_skip_list_map< cds::urcu::gc< RCU >, Key, T, Traits > maker;
106 typedef typename maker::type base_class;
109 typedef cds::urcu::gc< RCU > gc; ///< Garbage collector used
110 typedef Key key_type; ///< Key type
111 typedef T mapped_type; ///< Mapped type
112 # ifdef CDS_DOXYGEN_INVOKED
113 typedef std::pair< K const, T> value_type; ///< Value type stored in the map
115 typedef typename maker::value_type value_type;
117 typedef Traits traits; ///< Map traits
119 typedef typename base_class::back_off back_off; ///< Back-off strategy used
120 typedef typename traits::allocator allocator_type; ///< Allocator type used for allocate/deallocate the skip-list nodes
121 typedef typename base_class::item_counter item_counter; ///< Item counting policy used
122 typedef typename maker::key_comparator key_comparator; ///< key comparison functor
123 typedef typename base_class::memory_model memory_model; ///< Memory ordering. See cds::opt::memory_model option
124 typedef typename traits::random_level_generator random_level_generator; ///< random level generator
125 typedef typename traits::stat stat; ///< internal statistics type
128 typedef cds::container::skip_list::implementation_tag implementation_tag;
133 typedef typename maker::node_type node_type;
134 typedef typename maker::node_allocator node_allocator;
136 typedef std::unique_ptr< node_type, typename maker::node_deallocator > scoped_node_ptr;
140 typedef typename base_class::rcu_lock rcu_lock; ///< RCU scoped lock
141 /// Group of \p extract_xxx functions do not require external locking
142 static CDS_CONSTEXPR const bool c_bExtractLockExternal = base_class::c_bExtractLockExternal;
144 /// pointer to extracted node
145 using exempt_ptr = cds::urcu::exempt_ptr< gc, node_type, value_type, typename maker::intrusive_type_traits::disposer >;
149 unsigned int random_level()
151 return base_class::random_level();
154 value_type * to_value_ptr( node_type * pNode ) const CDS_NOEXCEPT
156 return pNode ? &pNode->m_Value : nullptr;
166 /// Destructor destroys the set object
172 typedef skip_list::details::iterator< typename base_class::iterator > iterator;
174 /// Const iterator type
175 typedef skip_list::details::iterator< typename base_class::const_iterator > const_iterator;
177 /// Returns a forward iterator addressing the first element in a map
180 return iterator( base_class::begin() );
183 /// Returns a forward const iterator addressing the first element in a map
184 const_iterator begin() const
188 /// Returns a forward const iterator addressing the first element in a map
189 const_iterator cbegin() const
191 return const_iterator( base_class::cbegin() );
194 /// Returns a forward iterator that addresses the location succeeding the last element in a map.
197 return iterator( base_class::end() );
200 /// Returns a forward const iterator that addresses the location succeeding the last element in a map.
201 const_iterator end() const
205 /// Returns a forward const iterator that addresses the location succeeding the last element in a map.
206 const_iterator cend() const
208 return const_iterator( base_class::cend() );
212 /// Inserts new node with key and default value
214 The function creates a node with \p key and default value, and then inserts the node created into the map.
217 - The \p key_type should be constructible from a value of type \p K.
218 In trivial case, \p K is equal to \p key_type.
219 - The \p mapped_type should be default-constructible.
221 RCU \p synchronize method can be called. RCU should not be locked.
223 Returns \p true if inserting successful, \p false otherwise.
225 template <typename K>
226 bool insert( K const& key )
228 return insert_with( key, [](value_type&){} );
233 The function creates a node with copy of \p val value
234 and then inserts the node created into the map.
237 - The \p key_type should be constructible from \p key of type \p K.
238 - The \p value_type should be constructible from \p val of type \p V.
240 RCU \p synchronize method can be called. RCU should not be locked.
242 Returns \p true if \p val is inserted into the set, \p false otherwise.
244 template <typename K, typename V>
245 bool insert( K const& key, V const& val )
247 scoped_node_ptr pNode( node_allocator().New( random_level(), key, val ));
248 if ( base_class::insert( *pNode ))
256 /// Inserts new node and initialize it by a functor
258 This function inserts new node with key \p key and if inserting is successful then it calls
259 \p func functor with signature
262 void operator()( value_type& item );
266 The argument \p item of user-defined functor \p func is the reference
267 to the map's item inserted:
268 - <tt>item.first</tt> is a const reference to item's key that cannot be changed.
269 - <tt>item.second</tt> is a reference to item's value that may be changed.
271 The function allows to split creating of new item into three part:
272 - create item from \p key;
273 - insert new item into the map;
274 - if inserting is successful, initialize the value of item by calling \p func functor
276 This can be useful if complete initialization of object of \p value_type is heavyweight and
277 it is preferable that the initialization should be completed only if inserting is successful.
279 RCU \p synchronize method can be called. RCU should not be locked.
281 template <typename K, typename Func>
282 bool insert_with( const K& key, Func func )
284 scoped_node_ptr pNode( node_allocator().New( random_level(), key ));
285 if ( base_class::insert( *pNode, [&func]( node_type& item ) { func( item.m_Value ); } )) {
292 /// For key \p key inserts data of type \p value_type created in-place from \p args
294 Returns \p true if inserting successful, \p false otherwise.
296 RCU \p synchronize() method can be called. RCU should not be locked.
298 template <typename K, typename... Args>
299 bool emplace( K&& key, Args&&... args )
301 scoped_node_ptr pNode( node_allocator().New( random_level(), std::forward<K>(key), std::forward<Args>(args)... ));
302 if ( base_class::insert( *pNode )) {
309 /// Ensures that the \p key exists in the map
311 The operation performs inserting or changing data with lock-free manner.
313 If the \p key not found in the map, then the new item created from \p key
314 is inserted into the map (note that in this case the \ref key_type should be
315 constructible from type \p K).
316 Otherwise, the functor \p func is called with item found.
317 The functor \p Func interface is:
320 void operator()( bool bNew, value_type& item );
324 - \p bNew - \p true if the item has been inserted, \p false otherwise
325 - \p item - item of the list
327 The functor may change any fields of \p item.second.
329 RCU \p synchronize() method can be called. RCU should not be locked.
331 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
332 \p second is true if new item has been added or \p false if the item with \p key
333 already is in the list.
335 @warning See \ref cds_intrusive_item_creating "insert item troubleshooting"
337 template <typename K, typename Func>
338 std::pair<bool, bool> ensure( K const& key, Func func )
340 scoped_node_ptr pNode( node_allocator().New( random_level(), key ));
341 std::pair<bool, bool> res = base_class::ensure( *pNode,
342 [&func](bool bNew, node_type& item, node_type const& ){ func( bNew, item.m_Value ); }
344 if ( res.first && res.second )
349 /// Delete \p key from the map
350 /**\anchor cds_nonintrusive_SkipListMap_rcu_erase_val
352 RCU \p synchronize method can be called. RCU should not be locked.
354 Return \p true if \p key is found and deleted, \p false otherwise
356 template <typename K>
357 bool erase( K const& key )
359 return base_class::erase(key);
362 /// Deletes the item from the map using \p pred predicate for searching
364 The function is an analog of \ref cds_nonintrusive_SkipListMap_rcu_erase_val "erase(K const&)"
365 but \p pred is used for key comparing.
366 \p Less functor has the interface like \p std::less.
367 \p Less must imply the same element order as the comparator used for building the map.
369 template <typename K, typename Less>
370 bool erase_with( K const& key, Less pred )
373 return base_class::erase_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >());
376 /// Delete \p key from the map
377 /** \anchor cds_nonintrusive_SkipListMap_rcu_erase_func
379 The function searches an item with key \p key, calls \p f functor
380 and deletes the item. If \p key is not found, the functor is not called.
382 The functor \p Func interface:
385 void operator()(value_type& item) { ... }
389 RCU \p synchronize method can be called. RCU should not be locked.
391 Return \p true if key is found and deleted, \p false otherwise
393 template <typename K, typename Func>
394 bool erase( K const& key, Func f )
396 return base_class::erase( key, [&f]( node_type& node) { f( node.m_Value ); } );
399 /// Deletes the item from the map using \p pred predicate for searching
401 The function is an analog of \ref cds_nonintrusive_SkipListMap_rcu_erase_func "erase(K const&, Func)"
402 but \p pred is used for key comparing.
403 \p Less functor has the interface like \p std::less.
404 \p Less must imply the same element order as the comparator used for building the map.
406 template <typename K, typename Less, typename Func>
407 bool erase_with( K const& key, Less pred, Func f )
410 return base_class::erase_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >(),
411 [&f]( node_type& node) { f( node.m_Value ); } );
414 /// Extracts the item from the map with specified \p key
415 /** \anchor cds_nonintrusive_SkipListMap_rcu_extract
416 The function searches an item with key equal to \p key in the map,
417 unlinks it from the set, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item found.
418 If the item is not found the function returns an empty \p exempt_ptr
420 Note the compare functor from \p Traits class' template argument
421 should accept a parameter of type \p K that can be not the same as \p key_type.
423 RCU \p synchronize() method can be called. RCU should NOT be locked.
425 The function does not free the item found.
426 The item will be implicitly freed when the returned object is destroyed or when
427 its \p release() member function is called.
429 template <typename K>
430 exempt_ptr extract( K const& key )
432 return exempt_ptr( base_class::do_extract( key ));
435 /// Extracts the item from the map with comparing functor \p pred
437 The function is an analog of \p extract(K const&) but \p pred predicate is used for key comparing.
438 \p Less has the semantics like \p std::less.
439 \p pred must imply the same element order as the comparator used for building the map.
441 template <typename K, typename Less>
442 exempt_ptr extract_with( K const& key, Less pred )
445 return exempt_ptr( base_class::do_extract_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >()));
448 /// Extracts an item with minimal key from the map
450 The function searches an item with minimal key, unlinks it,
451 and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item.
452 If the skip-list is empty the function returns an empty \p exempt_ptr.
454 RCU \p synchronize method can be called. RCU should NOT be locked.
456 The function does not free the item found.
457 The item will be implicitly freed when the returned object is destroyed or when
458 its \p release() member function is called.
460 exempt_ptr extract_min()
462 return exempt_ptr( base_class::do_extract_min());
465 /// Extracts an item with maximal key from the map
467 The function searches an item with maximal key, unlinks it from the set,
468 and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item.
469 If the skip-list is empty the function returns an empty \p exempt_ptr.
471 RCU \p synchronize method can be called. RCU should NOT be locked.
473 The function does not free the item found.
474 The item will be implicitly freed when the returned object is destroyed or when
475 its \p release() member function is called.
477 exempt_ptr extract_max()
479 return exempt_ptr( base_class::do_extract_max());
482 /// Find the key \p key
483 /** \anchor cds_nonintrusive_SkipListMap_rcu_find_cfunc
485 The function searches the item with key equal to \p key and calls the functor \p f for item found.
486 The interface of \p Func functor is:
489 void operator()( value_type& item );
492 where \p item is the item found.
494 The functor may change \p item.second.
496 The function applies RCU lock internally.
498 The function returns \p true if \p key is found, \p false otherwise.
500 template <typename K, typename Func>
501 bool find( K const& key, Func f )
503 return base_class::find( key, [&f](node_type& item, K const& ) { f( item.m_Value );});
506 /// Finds the key \p val using \p pred predicate for searching
508 The function is an analog of \ref cds_nonintrusive_SkipListMap_rcu_find_cfunc "find(K const&, Func)"
509 but \p pred is used for key comparing.
510 \p Less functor has the interface like \p std::less.
511 \p Less must imply the same element order as the comparator used for building the map.
513 template <typename K, typename Less, typename Func>
514 bool find_with( K const& key, Less pred, Func f )
517 return base_class::find_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >(),
518 [&f](node_type& item, K const& ) { f( item.m_Value );});
521 /// Find the key \p key
522 /** \anchor cds_nonintrusive_SkipListMap_rcu_find_val
524 The function searches the item with key equal to \p key
525 and returns \p true if it is found, and \p false otherwise.
527 The function applies RCU lock internally.
529 template <typename K>
530 bool find( K const& key )
532 return base_class::find( key );
535 /// Finds the key \p val using \p pred predicate for searching
537 The function is an analog of \ref cds_nonintrusive_SkipListMap_rcu_find_val "find(K const&)"
538 but \p pred is used for key comparing.
539 \p Less functor has the interface like \p std::less.
540 \p Less must imply the same element order as the comparator used for building the map.
542 template <typename K, typename Less>
543 bool find_with( K const& key, Less pred )
546 return base_class::find_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >() );
549 /// Finds the key \p key and return the item found
550 /** \anchor cds_nonintrusive_SkipListMap_rcu_get
551 The function searches the item with key equal to \p key and returns the pointer to item found.
552 If \p key is not found it returns \p nullptr.
554 Note the compare functor in \p Traits class' template argument
555 should accept a parameter of type \p K that can be not the same as \p key_type.
557 RCU should be locked before call of this function.
558 Returned item is valid only while RCU is locked:
560 typedef cds::container::SkipListMap< cds::urcu::gc< cds::urcu::general_buffered<> >, int, foo, my_traits > skip_list;
565 skip_list::rcu_lock lock;
567 skip_list::value_type * pVal = theList.get( 5 );
571 // Unlock RCU by rcu_lock destructor
572 // pVal can be freed at any time after RCU unlocking
576 After RCU unlocking the \p %force_dispose member function can be called manually,
577 see \ref force_dispose for explanation.
579 template <typename K>
580 value_type * get( K const& key )
582 return to_value_ptr( base_class::get( key ));
585 /// Finds the key \p key and return the item found
587 The function is an analog of \ref cds_nonintrusive_SkipListMap_rcu_get "get(K const&)"
588 but \p pred is used for comparing the keys.
590 \p Less functor has the semantics like \p std::less but should take arguments of type \ref key_type and \p K
592 \p pred must imply the same element order as the comparator used for building the map.
594 template <typename K, typename Less>
595 value_type * get_with( K const& key, Less pred )
598 return to_value_ptr( base_class::get_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >() ));
601 /// Clears the map (not atomic)
607 /// Checks if the map is empty
609 Emptiness is checked by item counting: if item count is zero then the map is empty.
613 return base_class::empty();
616 /// Returns item count in the map
619 return base_class::size();
622 /// Returns const reference to internal statistics
623 stat const& statistics() const
625 return base_class::statistics();
628 /// Clears internal list of ready-to-delete items passing them to RCU reclamation cycle
629 /** @copydetails cds_intrusive_SkipListSet_rcu_force_dispose
633 return base_class::force_dispose();
636 }} // namespace cds::container
638 #endif // #ifndef CDSLIB_CONTAINER_SKIP_LIST_MAP_RCU_H