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>
9 #include <cds/details/functor_wrapper.h>
11 namespace cds { namespace container {
13 /// Lock-free skip-list map (template specialization for \ref cds_urcu_desc "RCU")
14 /** @ingroup cds_nonintrusive_map
15 \anchor cds_nonintrusive_SkipListMap_rcu
17 The implementation of well-known probabilistic data structure called skip-list
18 invented by W.Pugh in his papers:
19 - [1989] W.Pugh Skip Lists: A Probabilistic Alternative to Balanced Trees
20 - [1990] W.Pugh A Skip List Cookbook
22 A skip-list is a probabilistic data structure that provides expected logarithmic
23 time search without the need of rebalance. The skip-list is a collection of sorted
24 linked list. Nodes are ordered by key. Each node is linked into a subset of the lists.
25 Each list has a level, ranging from 0 to 32. The bottom-level list contains
26 all the nodes, and each higher-level list is a sublist of the lower-level lists.
27 Each node is created with a random top level (with a random height), and belongs
28 to all lists up to that level. The probability that a node has the height 1 is 1/2.
29 The probability that a node has the height N is 1/2 ** N (more precisely,
30 the distribution depends on an random generator provided, but our generators
33 The lock-free variant of skip-list is implemented according to book
34 - [2008] M.Herlihy, N.Shavit "The Art of Multiprocessor Programming",
35 chapter 14.4 "A Lock-Free Concurrent Skiplist"
38 - \p RCU - one of \ref cds_urcu_gc "RCU type".
39 - \p K - type of a key to be stored in the list.
40 - \p T - type of a value to be stored in the list.
41 - \p Traits - type traits. See skip_list::type_traits for explanation.
43 It is possible to declare option-based list with cds::container::skip_list::make_traits metafunction istead of \p Traits template
45 Template argument list \p Options of cds::container::skip_list::make_traits metafunction are:
46 - opt::compare - key compare functor. No default functor is provided.
47 If the option is not specified, the opt::less is used.
48 - opt::less - specifies binary predicate used for key comparison. Default is \p std::less<K>.
49 - opt::item_counter - the type of item counting feature. Default is \ref atomicity::empty_item_counter that is no item counting.
50 - opt::memory_model - C++ memory ordering model. Can be opt::v::relaxed_ordering (relaxed memory model, the default)
51 or opt::v::sequential_consistent (sequentially consisnent memory model).
52 - skip_list::random_level_generator - random level generator. Can be skip_list::xorshift, skip_list::turbo_pascal or
53 user-provided one. See skip_list::random_level_generator option description for explanation.
54 Default is \p %skip_list::turbo_pascal.
55 - opt::allocator - allocator for skip-list node. Default is \ref CDS_DEFAULT_ALLOCATOR.
56 - opt::back_off - back-off strategy used. If the option is not specified, the cds::backoff::Default is used.
57 - opt::stat - internal statistics. Available types: skip_list::stat, skip_list::empty_stat (the default)
58 - opt::rcu_check_deadlock - a deadlock checking policy. Default is opt::v::rcu_throw_deadlock
60 Like STL map class, \p %SkipListMap stores its key-value pair as <tt>std:pair< K const, T></tt>.
62 @note Before including <tt><cds/container/skip_list_map_rcu.h></tt> you should include appropriate RCU header file,
63 see \ref cds_urcu_gc "RCU type" for list of existing RCU class and corresponding header files.
67 The class supports a forward iterator (\ref iterator and \ref const_iterator).
68 The iteration is ordered.
69 You may iterate over skip-list set items only under RCU lock.
70 Only in this case the iterator is thread-safe since
71 while RCU is locked any set's item cannot be reclaimed.
73 The requirement of RCU lock during iterating means that deletion of the elements (i.e. \ref erase)
76 @warning The iterator object cannot be passed between threads
78 The iterator class supports the following minimalistic interface:
85 iterator( iterator const& s);
87 value_type * operator ->() const;
88 value_type& operator *() const;
91 iterator& operator ++();
94 iterator& operator = (const iterator& src);
96 bool operator ==(iterator const& i ) const;
97 bool operator !=(iterator const& i ) const;
100 Note, the iterator object returned by \ref end, \p cend member functions points to \p nullptr and should not be dereferenced.
107 #ifdef CDS_DOXYGEN_INVOKED
108 typename Traits = skip_list::type_traits
113 class SkipListMap< cds::urcu::gc< RCU >, Key, T, Traits >:
114 #ifdef CDS_DOXYGEN_INVOKED
115 protected intrusive::SkipListSet< cds::urcu::gc< RCU >, std::pair<Key const, T>, Traits >
117 protected details::make_skip_list_map< cds::urcu::gc< RCU >, Key, T, Traits >::type
121 typedef details::make_skip_list_map< cds::urcu::gc< RCU >, Key, T, Traits > maker;
122 typedef typename maker::type base_class;
125 typedef typename base_class::gc gc ; ///< Garbage collector used
126 typedef Key key_type ; ///< Key type
127 typedef T mapped_type ; ///< Mapped type
128 # ifdef CDS_DOXYGEN_INVOKED
129 typedef std::pair< K const, T> value_type ; ///< Value type stored in the map
131 typedef typename maker::value_type value_type;
133 typedef Traits options ; ///< Options specified
135 typedef typename base_class::back_off back_off ; ///< Back-off strategy used
136 typedef typename options::allocator allocator_type ; ///< Allocator type used for allocate/deallocate the skip-list nodes
137 typedef typename base_class::item_counter item_counter ; ///< Item counting policy used
138 typedef typename maker::key_comparator key_comparator ; ///< key comparison functor
139 typedef typename base_class::memory_model memory_model ; ///< Memory ordering. See cds::opt::memory_model option
140 typedef typename options::random_level_generator random_level_generator ; ///< random level generator
141 typedef typename options::stat stat ; ///< internal statistics type
145 typedef typename maker::node_type node_type;
146 typedef typename maker::node_allocator node_allocator;
148 typedef std::unique_ptr< node_type, typename maker::node_deallocator > scoped_node_ptr;
152 typedef typename base_class::rcu_lock rcu_lock; ///< RCU scoped lock
153 /// Group of \p extract_xxx functions do not require external locking
154 static CDS_CONSTEXPR_CONST bool c_bExtractLockExternal = base_class::c_bExtractLockExternal;
156 /// pointer to extracted node
157 typedef cds::urcu::exempt_ptr< gc, node_type, value_type, typename maker::intrusive_type_traits::disposer > exempt_ptr;
161 unsigned int random_level()
163 return base_class::random_level();
166 value_type * to_value_ptr( node_type * pNode ) const CDS_NOEXCEPT
168 return pNode ? &pNode->m_Value : nullptr;
178 /// Destructor destroys the set object
184 typedef skip_list::details::iterator< typename base_class::iterator > iterator;
186 /// Const iterator type
187 typedef skip_list::details::iterator< typename base_class::const_iterator > const_iterator;
189 /// Returns a forward iterator addressing the first element in a map
192 return iterator( base_class::begin() );
195 /// Returns a forward const iterator addressing the first element in a map
197 const_iterator begin() const
201 const_iterator cbegin()
203 return const_iterator( base_class::cbegin() );
207 /// Returns a forward iterator that addresses the location succeeding the last element in a map.
210 return iterator( base_class::end() );
213 /// Returns a forward const iterator that addresses the location succeeding the last element in a map.
215 const_iterator end() const
219 const_iterator cend()
221 return const_iterator( base_class::cend() );
226 /// Inserts new node with key and default value
228 The function creates a node with \p key and default value, and then inserts the node created into the map.
231 - The \ref key_type should be constructible from a value of type \p K.
232 In trivial case, \p K is equal to \ref key_type.
233 - The \ref mapped_type should be default-constructible.
235 RCU \p synchronize method can be called. RCU should not be locked.
237 Returns \p true if inserting successful, \p false otherwise.
239 template <typename K>
240 bool insert( K const& key )
242 return insert_key( key, [](value_type&){} );
247 The function creates a node with copy of \p val value
248 and then inserts the node created into the map.
251 - The \ref key_type should be constructible from \p key of type \p K.
252 - The \ref value_type should be constructible from \p val of type \p V.
254 RCU \p synchronize method can be called. RCU should not be locked.
256 Returns \p true if \p val is inserted into the set, \p false otherwise.
258 template <typename K, typename V>
259 bool insert( K const& key, V const& val )
261 scoped_node_ptr pNode( node_allocator().New( random_level(), key, val ));
262 if ( base_class::insert( *pNode ))
270 /// Inserts new node and initialize it by a functor
272 This function inserts new node with key \p key and if inserting is successful then it calls
273 \p func functor with signature
276 void operator()( value_type& item );
280 The argument \p item of user-defined functor \p func is the reference
281 to the map's item inserted:
282 - <tt>item.first</tt> is a const reference to item's key that cannot be changed.
283 - <tt>item.second</tt> is a reference to item's value that may be changed.
285 The user-defined functor can be passed by reference using <tt>boost::ref</tt>
286 and it is called only if inserting is successful.
288 The key_type should be constructible from value of type \p K.
290 The function allows to split creating of new item into two part:
291 - create item from \p key;
292 - insert new item into the map;
293 - if inserting is successful, initialize the value of item by calling \p func functor
295 This can be useful if complete initialization of object of \p value_type is heavyweight and
296 it is preferable that the initialization should be completed only if inserting is successful.
298 RCU \p synchronize method can be called. RCU should not be locked.
300 template <typename K, typename Func>
301 bool insert_key( const K& key, Func func )
303 scoped_node_ptr pNode( node_allocator().New( random_level(), key ));
304 if ( base_class::insert( *pNode, [&func]( node_type& item ) { cds::unref(func)( item.m_Value ); } )) {
311 /// For key \p key inserts data of type \ref value_type constructed with <tt>std::forward<Args>(args)...</tt>
313 Returns \p true if inserting successful, \p false otherwise.
315 RCU \p synchronize method can be called. RCU should not be locked.
317 template <typename K, typename... Args>
318 bool emplace( K&& key, Args&&... args )
320 scoped_node_ptr pNode( node_allocator().New( random_level(), std::forward<K>(key), std::forward<Args>(args)... ));
321 if ( base_class::insert( *pNode )) {
328 /// Ensures that the \p key exists in the map
330 The operation performs inserting or changing data with lock-free manner.
332 If the \p key not found in the map, then the new item created from \p key
333 is inserted into the map (note that in this case the \ref key_type should be
334 constructible from type \p K).
335 Otherwise, the functor \p func is called with item found.
336 The functor \p Func may be a function with signature:
338 void func( bool bNew, value_type& item );
343 void operator()( bool bNew, value_type& item );
348 - \p bNew - \p true if the item has been inserted, \p false otherwise
349 - \p item - item of the list
351 The functor may change any fields of the \p item.second that is \ref value_type.
353 You may pass \p func argument by reference using <tt>boost::ref</tt>.
355 RCU \p synchronize method can be called. RCU should not be locked.
357 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
358 \p second is true if new item has been added or \p false if the item with \p key
359 already is in the list.
361 template <typename K, typename Func>
362 std::pair<bool, bool> ensure( K const& key, Func func )
364 scoped_node_ptr pNode( node_allocator().New( random_level(), key ));
365 std::pair<bool, bool> res = base_class::ensure( *pNode,
366 [&func](bool bNew, node_type& item, node_type const& ){ cds::unref(func)( bNew, item.m_Value ); }
368 if ( res.first && res.second )
373 /// Delete \p key from the map
374 /**\anchor cds_nonintrusive_SkipListMap_rcu_erase_val
376 RCU \p synchronize method can be called. RCU should not be locked.
378 Return \p true if \p key is found and deleted, \p false otherwise
380 template <typename K>
381 bool erase( K const& key )
383 return base_class::erase(key);
386 /// Deletes the item from the map using \p pred predicate for searching
388 The function is an analog of \ref cds_nonintrusive_SkipListMap_rcu_erase_val "erase(K const&)"
389 but \p pred is used for key comparing.
390 \p Less functor has the interface like \p std::less.
391 \p Less must imply the same element order as the comparator used for building the map.
393 template <typename K, typename Less>
394 bool erase_with( K const& key, Less pred )
396 return base_class::erase_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >());
399 /// Delete \p key from the map
400 /** \anchor cds_nonintrusive_SkipListMap_rcu_erase_func
402 The function searches an item with key \p key, calls \p f functor
403 and deletes the item. If \p key is not found, the functor is not called.
405 The functor \p Func interface:
408 void operator()(value_type& item) { ... }
411 The functor may be passed by reference using <tt>boost:ref</tt>
413 RCU \p synchronize method can be called. RCU should not be locked.
415 Return \p true if key is found and deleted, \p false otherwise
417 template <typename K, typename Func>
418 bool erase( K const& key, Func f )
420 return base_class::erase( key, [&f]( node_type& node) { cds::unref(f)( node.m_Value ); } );
423 /// Deletes the item from the map using \p pred predicate for searching
425 The function is an analog of \ref cds_nonintrusive_SkipListMap_rcu_erase_func "erase(K const&, Func)"
426 but \p pred is used for key comparing.
427 \p Less functor has the interface like \p std::less.
428 \p Less must imply the same element order as the comparator used for building the map.
430 template <typename K, typename Less, typename Func>
431 bool erase_with( K const& key, Less pred, Func f )
433 return base_class::erase_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >(),
434 [&f]( node_type& node) { cds::unref(f)( node.m_Value ); } );
437 /// Extracts the item from the map with specified \p key
438 /** \anchor cds_nonintrusive_SkipListMap_rcu_extract
439 The function searches an item with key equal to \p key in the map,
440 unlinks it from the set, and returns it in \p result parameter.
441 If the item with key equal to \p key is not found the function returns \p false.
443 Note the compare functor from \p Traits class' template argument
444 should accept a parameter of type \p K that can be not the same as \p key_type.
446 RCU \p synchronize method can be called. RCU should NOT be locked.
447 The function does not free the item found.
448 The item will be implicitly freed when \p result object is destroyed or when
449 <tt>result.release()</tt> is called, see cds::urcu::exempt_ptr for explanation.
450 @note Before reusing \p result object you should call its \p release() method.
452 template <typename K>
453 bool extract( exempt_ptr& result, K const& key )
455 return base_class::do_extract( result, key );
458 /// Extracts the item from the map with comparing functor \p pred
460 The function is an analog of \ref cds_nonintrusive_SkipListMap_rcu_extract "extract(exempt_ptr&, K const&)"
461 but \p pred predicate is used for key comparing.
462 \p Less has the semantics like \p std::less.
463 \p pred must imply the same element order as the comparator used for building the map.
465 template <typename K, typename Less>
466 bool extract_with( exempt_ptr& result, K const& key, Less pred )
468 return base_class::do_extract_with( result, key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >());
471 /// Extracts an item with minimal key from the map
473 The function searches an item with minimal key, unlinks it, and returns the item found in \p result parameter.
474 If the skip-list is empty the function returns \p false.
476 RCU \p synchronize method can be called. RCU should NOT be locked.
477 The function does not free the item found.
478 The item will be implicitly freed when \p result object is destroyed or when
479 <tt>result.release()</tt> is called, see cds::urcu::exempt_ptr for explanation.
480 @note Before reusing \p result object you should call its \p release() method.
482 bool extract_min( exempt_ptr& result )
484 return base_class::do_extract_min(result);
487 /// Extracts an item with maximal key from the map
489 The function searches an item with maximal key, unlinks it from the set, and returns the item found
490 in \p result parameter. If the skip-list is empty the function returns \p false.
492 RCU \p synchronize method can be called. RCU should NOT be locked.
493 The function does not free the item found.
494 The item will be implicitly freed when \p result object is destroyed or when
495 <tt>result.release()</tt> is called, see cds::urcu::exempt_ptr for explanation.
496 @note Before reusing \p result object you should call its \p release() method.
498 bool extract_max( exempt_ptr& result )
500 return base_class::do_extract_max(result);
503 /// Find the key \p key
504 /** \anchor cds_nonintrusive_SkipListMap_rcu_find_cfunc
506 The function searches the item with key equal to \p key and calls the functor \p f for item found.
507 The interface of \p Func functor is:
510 void operator()( value_type& item );
513 where \p item is the item found.
515 You can pass \p f argument by reference using <tt>boost::ref</tt> or cds::ref.
517 The functor may change \p item.second.
519 The function applies RCU lock internally.
521 The function returns \p true if \p key is found, \p false otherwise.
523 template <typename K, typename Func>
524 bool find( K const& key, Func f )
526 return base_class::find( key, [&f](node_type& item, K const& ) { cds::unref(f)( item.m_Value );});
529 /// Finds the key \p val using \p pred predicate for searching
531 The function is an analog of \ref cds_nonintrusive_SkipListMap_rcu_find_cfunc "find(K const&, Func)"
532 but \p pred is used for key comparing.
533 \p Less functor has the interface like \p std::less.
534 \p Less must imply the same element order as the comparator used for building the map.
536 template <typename K, typename Less, typename Func>
537 bool find_with( K const& key, Less pred, Func f )
539 return base_class::find_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >(),
540 [&f](node_type& item, K const& ) { cds::unref(f)( item.m_Value );});
543 /// Find the key \p key
544 /** \anchor cds_nonintrusive_SkipListMap_rcu_find_val
546 The function searches the item with key equal to \p key
547 and returns \p true if it is found, and \p false otherwise.
549 The function applies RCU lock internally.
551 template <typename K>
552 bool find( K const& key )
554 return base_class::find( key );
557 /// Finds the key \p val using \p pred predicate for searching
559 The function is an analog of \ref cds_nonintrusive_SkipListMap_rcu_find_val "find(K const&)"
560 but \p pred is used for key comparing.
561 \p Less functor has the interface like \p std::less.
562 \p Less must imply the same element order as the comparator used for building the map.
564 template <typename K, typename Less>
565 bool find_with( K const& key, Less pred )
567 return base_class::find_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >() );
570 /// Finds the key \p key and return the item found
571 /** \anchor cds_nonintrusive_SkipListMap_rcu_get
572 The function searches the item with key equal to \p key and returns the pointer to item found.
573 If \p key is not found it returns \p nullptr.
575 Note the compare functor in \p Traits class' template argument
576 should accept a parameter of type \p K that can be not the same as \p key_type.
578 RCU should be locked before call of this function.
579 Returned item is valid only while RCU is locked:
581 typedef cds::container::SkipListMap< cds::urcu::gc< cds::urcu::general_buffered<> >, int, foo, my_traits > skip_list;
586 skip_list::rcu_lock lock;
588 skip_list::value_type * pVal = theList.get( 5 );
592 // Unlock RCU by rcu_lock destructor
593 // pVal can be freed at any time after RCU unlocking
597 After RCU unlocking the \p %force_dispose member function can be called manually,
598 see \ref force_dispose for explanation.
600 template <typename K>
601 value_type * get( K const& key )
603 return to_value_ptr( base_class::get( key ));
606 /// Finds the key \p key and return the item found
608 The function is an analog of \ref cds_nonintrusive_SkipListMap_rcu_get "get(K const&)"
609 but \p pred is used for comparing the keys.
611 \p Less functor has the semantics like \p std::less but should take arguments of type \ref key_type and \p K
613 \p pred must imply the same element order as the comparator used for building the map.
615 template <typename K, typename Less>
616 value_type * get_with( K const& key, Less pred )
618 return to_value_ptr( base_class::get_with( key, cds::details::predicate_wrapper< node_type, Less, typename maker::key_accessor >() ));
627 /// Checks if the map is empty
629 Emptiness is checked by item counting: if item count is zero then the map is empty.
633 return base_class::empty();
636 /// Returns item count in the map
639 return base_class::size();
642 /// Returns const reference to internal statistics
643 stat const& statistics() const
645 return base_class::statistics();
648 /// Clears internal list of ready-to-delete items passing them to RCU reclamation cycle
650 See \ref cds_intrusive_SkipListSet_rcu_force_dispose "intrusive SkipListSet" for explanation
654 return base_class::force_dispose();
657 }} // namespace cds::container
659 #endif // #ifndef __CDS_CONTAINER_SKIP_LIST_MAP_RCU_H