3 #ifndef __CDS_CONTAINER_SKIP_LIST_MAP_RCU_H
4 #define __CDS_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
129 typedef typename maker::node_type node_type;
130 typedef typename maker::node_allocator node_allocator;
132 typedef std::unique_ptr< node_type, typename maker::node_deallocator > scoped_node_ptr;
136 typedef typename base_class::rcu_lock rcu_lock; ///< RCU scoped lock
137 /// Group of \p extract_xxx functions do not require external locking
138 static CDS_CONSTEXPR const bool c_bExtractLockExternal = base_class::c_bExtractLockExternal;
140 /// pointer to extracted node
141 using exempt_ptr = cds::urcu::exempt_ptr< gc, node_type, value_type, typename maker::intrusive_type_traits::disposer >;
145 unsigned int random_level()
147 return base_class::random_level();
150 value_type * to_value_ptr( node_type * pNode ) const CDS_NOEXCEPT
152 return pNode ? &pNode->m_Value : nullptr;
162 /// Destructor destroys the set object
168 typedef skip_list::details::iterator< typename base_class::iterator > iterator;
170 /// Const iterator type
171 typedef skip_list::details::iterator< typename base_class::const_iterator > const_iterator;
173 /// Returns a forward iterator addressing the first element in a map
176 return iterator( base_class::begin() );
179 /// Returns a forward const iterator addressing the first element in a map
180 const_iterator begin() const
184 /// Returns a forward const iterator addressing the first element in a map
185 const_iterator cbegin() const
187 return const_iterator( base_class::cbegin() );
190 /// Returns a forward iterator that addresses the location succeeding the last element in a map.
193 return iterator( base_class::end() );
196 /// Returns a forward const iterator that addresses the location succeeding the last element in a map.
197 const_iterator end() const
201 /// Returns a forward const iterator that addresses the location succeeding the last element in a map.
202 const_iterator cend() const
204 return const_iterator( base_class::cend() );
208 /// Inserts new node with key and default value
210 The function creates a node with \p key and default value, and then inserts the node created into the map.
213 - The \p key_type should be constructible from a value of type \p K.
214 In trivial case, \p K is equal to \p key_type.
215 - The \p mapped_type should be default-constructible.
217 RCU \p synchronize method can be called. RCU should not be locked.
219 Returns \p true if inserting successful, \p false otherwise.
221 template <typename K>
222 bool insert( K const& key )
224 return insert_with( key, [](value_type&){} );
229 The function creates a node with copy of \p val value
230 and then inserts the node created into the map.
233 - The \p key_type should be constructible from \p key of type \p K.
234 - The \p value_type should be constructible from \p val of type \p V.
236 RCU \p synchronize method can be called. RCU should not be locked.
238 Returns \p true if \p val is inserted into the set, \p false otherwise.
240 template <typename K, typename V>
241 bool insert( K const& key, V const& val )
243 scoped_node_ptr pNode( node_allocator().New( random_level(), key, val ));
244 if ( base_class::insert( *pNode ))
252 /// Inserts new node and initialize it by a functor
254 This function inserts new node with key \p key and if inserting is successful then it calls
255 \p func functor with signature
258 void operator()( value_type& item );
262 The argument \p item of user-defined functor \p func is the reference
263 to the map's item inserted:
264 - <tt>item.first</tt> is a const reference to item's key that cannot be changed.
265 - <tt>item.second</tt> is a reference to item's value that may be changed.
267 The function allows to split creating of new item into three part:
268 - create item from \p key;
269 - insert new item into the map;
270 - if inserting is successful, initialize the value of item by calling \p func functor
272 This can be useful if complete initialization of object of \p value_type is heavyweight and
273 it is preferable that the initialization should be completed only if inserting is successful.
275 RCU \p synchronize method can be called. RCU should not be locked.
277 template <typename K, typename Func>
278 bool insert_with( const K& key, Func func )
280 scoped_node_ptr pNode( node_allocator().New( random_level(), key ));
281 if ( base_class::insert( *pNode, [&func]( node_type& item ) { func( item.m_Value ); } )) {
288 /// For key \p key inserts data of type \p value_type created in-place from \p args
290 Returns \p true if inserting successful, \p false otherwise.
292 RCU \p synchronize() method can be called. RCU should not be locked.
294 template <typename K, typename... Args>
295 bool emplace( K&& key, Args&&... args )
297 scoped_node_ptr pNode( node_allocator().New( random_level(), std::forward<K>(key), std::forward<Args>(args)... ));
298 if ( base_class::insert( *pNode )) {
305 /// Ensures that the \p key exists in the map
307 The operation performs inserting or changing data with lock-free manner.
309 If the \p key not found in the map, then the new item created from \p key
310 is inserted into the map (note that in this case the \ref key_type should be
311 constructible from type \p K).
312 Otherwise, the functor \p func is called with item found.
313 The functor \p Func interface is:
316 void operator()( bool bNew, value_type& item );
320 - \p bNew - \p true if the item has been inserted, \p false otherwise
321 - \p item - item of the list
323 The functor may change any fields of \p item.second.
325 RCU \p synchronize() method can be called. RCU should not be locked.
327 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
328 \p second is true if new item has been added or \p false if the item with \p key
329 already is in the list.
331 @warning See \ref cds_intrusive_item_creating "insert item troubleshooting"
333 template <typename K, typename Func>
334 std::pair<bool, bool> ensure( K const& key, Func func )
336 scoped_node_ptr pNode( node_allocator().New( random_level(), key ));
337 std::pair<bool, bool> res = base_class::ensure( *pNode,
338 [&func](bool bNew, node_type& item, node_type const& ){ func( bNew, item.m_Value ); }
340 if ( res.first && res.second )
345 /// Delete \p key from the map
346 /**\anchor cds_nonintrusive_SkipListMap_rcu_erase_val
348 RCU \p synchronize method can be called. RCU should not be locked.
350 Return \p true if \p key is found and deleted, \p false otherwise
352 template <typename K>
353 bool erase( K const& key )
355 return base_class::erase(key);
358 /// Deletes the item from the map using \p pred predicate for searching
360 The function is an analog of \ref cds_nonintrusive_SkipListMap_rcu_erase_val "erase(K const&)"
361 but \p pred is used for key comparing.
362 \p Less functor has the interface like \p std::less.
363 \p Less must imply the same element order as the comparator used for building the map.
365 template <typename K, typename Less>
366 bool erase_with( K const& key, Less pred )
369 return base_class::erase_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >());
372 /// Delete \p key from the map
373 /** \anchor cds_nonintrusive_SkipListMap_rcu_erase_func
375 The function searches an item with key \p key, calls \p f functor
376 and deletes the item. If \p key is not found, the functor is not called.
378 The functor \p Func interface:
381 void operator()(value_type& item) { ... }
385 RCU \p synchronize method can be called. RCU should not be locked.
387 Return \p true if key is found and deleted, \p false otherwise
389 template <typename K, typename Func>
390 bool erase( K const& key, Func f )
392 return base_class::erase( key, [&f]( node_type& node) { f( node.m_Value ); } );
395 /// Deletes the item from the map using \p pred predicate for searching
397 The function is an analog of \ref cds_nonintrusive_SkipListMap_rcu_erase_func "erase(K const&, Func)"
398 but \p pred is used for key comparing.
399 \p Less functor has the interface like \p std::less.
400 \p Less must imply the same element order as the comparator used for building the map.
402 template <typename K, typename Less, typename Func>
403 bool erase_with( K const& key, Less pred, Func f )
406 return base_class::erase_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >(),
407 [&f]( node_type& node) { f( node.m_Value ); } );
410 /// Extracts the item from the map with specified \p key
411 /** \anchor cds_nonintrusive_SkipListMap_rcu_extract
412 The function searches an item with key equal to \p key in the map,
413 unlinks it from the set, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item found.
414 If the item is not found the function returns an empty \p exempt_ptr
416 Note the compare functor from \p Traits class' template argument
417 should accept a parameter of type \p K that can be not the same as \p key_type.
419 RCU \p synchronize() method can be called. RCU should NOT be locked.
421 The function does not free the item found.
422 The item will be implicitly freed when the returned object is destroyed or when
423 its \p release() member function is called.
425 template <typename K>
426 exempt_ptr extract( K const& key )
428 return exempt_ptr( base_class::do_extract( key ));
431 /// Extracts the item from the map with comparing functor \p pred
433 The function is an analog of \ref cds_nonintrusive_SkipListMap_rcu_extract "extract(exempt_ptr&, K const&)"
434 but \p pred predicate is used for key comparing.
435 \p Less has the semantics like \p std::less.
436 \p pred must imply the same element order as the comparator used for building the map.
438 template <typename K, typename Less>
439 exempt_ptr extract_with( K const& key, Less pred )
442 return exempt_ptr( base_class::do_extract_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >()));
445 /// Extracts an item with minimal key from the map
447 The function searches an item with minimal key, unlinks it,
448 and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item.
449 If the skip-list is empty the function returns an empty \p exempt_ptr.
451 RCU \p synchronize method can be called. RCU should NOT be locked.
453 The function does not free the item found.
454 The item will be implicitly freed when the returned object is destroyed or when
455 its \p release() member function is called.
457 exempt_ptr extract_min()
459 return exempt_ptr( base_class::do_extract_min());
462 /// Extracts an item with maximal key from the map
464 The function searches an item with maximal key, unlinks it from the set,
465 and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item.
466 If the skip-list is empty the function returns an empty \p exempt_ptr.
468 RCU \p synchronize method can be called. RCU should NOT be locked.
470 The function does not free the item found.
471 The item will be implicitly freed when the returned object is destroyed or when
472 its \p release() member function is called.
474 exempt_ptr extract_max()
476 return exempt_ptr( base_class::do_extract_max());
479 /// Find the key \p key
480 /** \anchor cds_nonintrusive_SkipListMap_rcu_find_cfunc
482 The function searches the item with key equal to \p key and calls the functor \p f for item found.
483 The interface of \p Func functor is:
486 void operator()( value_type& item );
489 where \p item is the item found.
491 The functor may change \p item.second.
493 The function applies RCU lock internally.
495 The function returns \p true if \p key is found, \p false otherwise.
497 template <typename K, typename Func>
498 bool find( K const& key, Func f )
500 return base_class::find( key, [&f](node_type& item, K const& ) { f( item.m_Value );});
503 /// Finds the key \p val using \p pred predicate for searching
505 The function is an analog of \ref cds_nonintrusive_SkipListMap_rcu_find_cfunc "find(K const&, Func)"
506 but \p pred is used for key comparing.
507 \p Less functor has the interface like \p std::less.
508 \p Less must imply the same element order as the comparator used for building the map.
510 template <typename K, typename Less, typename Func>
511 bool find_with( K const& key, Less pred, Func f )
514 return base_class::find_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >(),
515 [&f](node_type& item, K const& ) { f( item.m_Value );});
518 /// Find the key \p key
519 /** \anchor cds_nonintrusive_SkipListMap_rcu_find_val
521 The function searches the item with key equal to \p key
522 and returns \p true if it is found, and \p false otherwise.
524 The function applies RCU lock internally.
526 template <typename K>
527 bool find( K const& key )
529 return base_class::find( key );
532 /// Finds the key \p val using \p pred predicate for searching
534 The function is an analog of \ref cds_nonintrusive_SkipListMap_rcu_find_val "find(K const&)"
535 but \p pred is used for key comparing.
536 \p Less functor has the interface like \p std::less.
537 \p Less must imply the same element order as the comparator used for building the map.
539 template <typename K, typename Less>
540 bool find_with( K const& key, Less pred )
543 return base_class::find_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >() );
546 /// Finds the key \p key and return the item found
547 /** \anchor cds_nonintrusive_SkipListMap_rcu_get
548 The function searches the item with key equal to \p key and returns the pointer to item found.
549 If \p key is not found it returns \p nullptr.
551 Note the compare functor in \p Traits class' template argument
552 should accept a parameter of type \p K that can be not the same as \p key_type.
554 RCU should be locked before call of this function.
555 Returned item is valid only while RCU is locked:
557 typedef cds::container::SkipListMap< cds::urcu::gc< cds::urcu::general_buffered<> >, int, foo, my_traits > skip_list;
562 skip_list::rcu_lock lock;
564 skip_list::value_type * pVal = theList.get( 5 );
568 // Unlock RCU by rcu_lock destructor
569 // pVal can be freed at any time after RCU unlocking
573 After RCU unlocking the \p %force_dispose member function can be called manually,
574 see \ref force_dispose for explanation.
576 template <typename K>
577 value_type * get( K const& key )
579 return to_value_ptr( base_class::get( key ));
582 /// Finds the key \p key and return the item found
584 The function is an analog of \ref cds_nonintrusive_SkipListMap_rcu_get "get(K const&)"
585 but \p pred is used for comparing the keys.
587 \p Less functor has the semantics like \p std::less but should take arguments of type \ref key_type and \p K
589 \p pred must imply the same element order as the comparator used for building the map.
591 template <typename K, typename Less>
592 value_type * get_with( K const& key, Less pred )
595 return to_value_ptr( base_class::get_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >() ));
598 /// Clears the map (not atomic)
604 /// Checks if the map is empty
606 Emptiness is checked by item counting: if item count is zero then the map is empty.
610 return base_class::empty();
613 /// Returns item count in the map
616 return base_class::size();
619 /// Returns const reference to internal statistics
620 stat const& statistics() const
622 return base_class::statistics();
625 /// Clears internal list of ready-to-delete items passing them to RCU reclamation cycle
626 /** @copydetails cds_intrusive_SkipListSet_rcu_force_dispose
630 return base_class::force_dispose();
633 }} // namespace cds::container
635 #endif // #ifndef __CDS_CONTAINER_SKIP_LIST_MAP_RCU_H