3 #ifndef CDSLIB_CONTAINER_SPLIT_LIST_MAP_RCU_H
4 #define CDSLIB_CONTAINER_SPLIT_LIST_MAP_RCU_H
6 #include <cds/container/split_list_set_rcu.h>
7 #include <cds/details/binary_functor_wrapper.h>
9 namespace cds { namespace container {
11 /// Split-ordered list map (template specialization for \ref cds_urcu_desc "RCU")
12 /** @ingroup cds_nonintrusive_map
13 \anchor cds_nonintrusive_SplitListMap_rcu
15 Hash table implementation based on split-ordered list algorithm discovered by Ori Shalev and Nir Shavit, see
16 - [2003] Ori Shalev, Nir Shavit "Split-Ordered Lists - Lock-free Resizable Hash Tables"
17 - [2008] Nir Shavit "The Art of Multiprocessor Programming"
19 See intrusive::SplitListSet for a brief description of the split-list algorithm.
22 - \p RCU - one of \ref cds_urcu_gc "RCU type"
23 - \p Key - key type to be stored in the map
24 - \p Value - value type to be stored in the map
25 - \p Traits - type traits, default is \p split_list::traits. Instead of declaring \p %split_list::traits -based
26 struct you may apply option-based notation with \p split_list::make_traits metafunction.
30 The class supports a forward unordered iterator (\ref iterator and \ref const_iterator).
31 You may iterate over split-list map items only under RCU lock.
32 Only in this case the iterator is thread-safe since
33 while RCU is locked any map's item cannot be reclaimed.
34 The requirement of RCU lock during iterating means that deletion of the elements
37 @warning The iterator object cannot be passed between threads.
38 Due to concurrent nature of split-list map it is not guarantee that you can iterate
39 all elements in the map: any concurrent deletion can exclude the element
40 pointed by the iterator from the map, and your iteration can be terminated
41 before end of the map. Therefore, such iteration is more suitable for debugging purposes
43 The iterator class supports the following minimalistic interface:
50 iterator( iterator const& s);
52 value_type * operator ->() const;
53 value_type& operator *() const;
56 iterator& operator ++();
59 iterator& operator = (const iterator& src);
61 bool operator ==(iterator const& i ) const;
62 bool operator !=(iterator const& i ) const;
65 Note, the iterator object returned by \ref end, \p cend member functions points to \p nullptr and should not be dereferenced.
69 You should decide what garbage collector you want, and what ordered list you want to use. Split-ordered list
70 is original data structure based on an ordered list. Suppose, you want construct split-list map based on \p cds::urcu::general_buffered<> GC
71 and \p MichaelList as ordered list implementation. Your map should map \p int key to \p std::string value.
72 So, you beginning your program with following include:
74 #include <cds/urcu/general_buffered.h>
75 #include <cds/container/michael_list_rcu.h>
76 #include <cds/container/split_list_map_rcu.h>
78 namespace cc = cds::container;
80 The inclusion order is important:
81 - first, include one of \ref cds_urcu_gc "RCU implementation" (<tt>cds/urcu/general_buffered.h</tt> in our case)
82 - second, include the header of ordered-list implementation (for this example, <tt>cds/container/michael_list_rcu.h</tt>),
83 - then, the header for RCU-based split-list map <tt>cds/container/split_list_map_rcu.h</tt>.
85 Now, you should declare traits for split-list map. The main parts of traits are a hash functor for the map key and a comparing functor for ordered list.
86 We use \p std::hash<int> and \p std::less<int>.
88 The second attention: instead of using \p %MichaelList in \p %SplitListMap traits we use a tag \p ds::contaner::michael_list_tag
89 for the Michael's list.
90 The split-list requires significant support from underlying ordered list class and it is not good idea to dive you
91 into deep implementation details of split-list and ordered list interrelations. The tag paradigm simplifies split-list interface.
94 // SplitListMap traits
95 struct foo_set_traits: public cc::split_list::traits
97 typedef cc::michael_list_tag ordered_list ; // what type of ordered list we want to use
98 typedef std::hash<int> hash ; // hash functor for the key stored in split-list map
100 // Type traits for our MichaelList class
101 struct ordered_list_traits: public cc::michael_list::traits
103 typedef std::less<int> less ; // use our std::less predicate as comparator to order list nodes
108 Now you are ready to declare our map class based on \p %SplitListMap:
110 typedef cc::SplitListMap< cds::urcu::gc<cds::urcu::general_buffered<> >, int, std::string, foo_set_traits > int_string_map;
113 You may use the modern option-based declaration instead of classic traits-based one:
115 typedef cc:SplitListMap<
116 cds::urcu::gc<cds::urcu::general_buffered<> > // RCU type
118 ,std::string // value type
119 ,cc::split_list::make_traits< // metafunction to build split-list traits
120 cc::split_list::ordered_list<cc::michael_list_tag> // tag for underlying ordered list implementation
121 ,cc::opt::hash< std::hash<int> > // hash functor
122 ,cc::split_list::ordered_list_traits< // ordered list traits desired
123 cc::michael_list::make_traits< // metafunction to build lazy list traits
124 cc::opt::less< std::less<int> > // less-based compare functor
130 In case of option-based declaration using \p split_list::make_traits metafunction the struct \p foo_set_traits is not required.
132 Now, the map of type \p int_string_map is ready to use in your program.
134 Note that in this example we show only mandatory \p traits parts, optional ones is the default and they are inherited
135 from cds::container::split_list::traits.
136 There are many other useful options for deep tuning the split-list and ordered-list containers.
142 #ifdef CDS_DOXYGEN_INVOKED
143 class Traits = split_list::traits
148 class SplitListMap< cds::urcu::gc< RCU >, Key, Value, Traits >:
149 protected container::SplitListSet<
150 cds::urcu::gc< RCU >,
151 std::pair<Key const, Value>,
152 split_list::details::wrap_map_traits<Key, Value, Traits>
156 typedef container::SplitListSet<
157 cds::urcu::gc< RCU >,
158 std::pair<Key const, Value>,
159 split_list::details::wrap_map_traits<Key, Value, Traits>
164 typedef cds::urcu::gc< RCU > gc; ///< Garbage collector
165 typedef Key key_type; ///< key type
166 typedef Value mapped_type; ///< type of value to be stored in the map
167 typedef Traits traits; ///< Map traits
169 typedef std::pair<key_type const, mapped_type> value_type; ///< key-value pair type
170 typedef typename base_class::ordered_list ordered_list; ///< Underlying ordered list class
171 typedef typename base_class::key_comparator key_comparator; ///< key comparison functor
173 typedef typename base_class::hash hash; ///< Hash functor for \ref key_type
174 typedef typename base_class::item_counter item_counter; ///< Item counter type
175 typedef typename base_class::stat stat; ///< Internal statistics
177 typedef typename base_class::rcu_lock rcu_lock; ///< RCU scoped lock
178 typedef typename base_class::exempt_ptr exempt_ptr; ///< pointer to extracted node
179 /// Group of \p extract_xxx functions require external locking if underlying ordered list requires that
180 static CDS_CONSTEXPR const bool c_bExtractLockExternal = base_class::c_bExtractLockExternal;
184 typedef typename base_class::maker::traits::key_accessor key_accessor;
189 typedef typename base_class::iterator iterator;
191 /// Const forward iterator
192 typedef typename base_class::const_iterator const_iterator;
194 /// Returns a forward iterator addressing the first element in a map
196 For empty map \code begin() == end() \endcode
200 return base_class::begin();
203 /// Returns an iterator that addresses the location succeeding the last element in a map
205 Do not use the value returned by <tt>end</tt> function to access any item.
206 The returned value can be used only to control reaching the end of the map.
207 For empty map \code begin() == end() \endcode
211 return base_class::end();
214 /// Returns a forward const iterator addressing the first element in a map
216 const_iterator begin() const
218 return base_class::begin();
220 const_iterator cbegin() const
222 return base_class::cbegin();
226 /// Returns an const iterator that addresses the location succeeding the last element in a map
228 const_iterator end() const
230 return base_class::end();
232 const_iterator cend() const
234 return base_class::cend();
239 /// Initializes split-ordered map of default capacity
241 The default capacity is defined in bucket table constructor.
242 See \p intrusive::split_list::expandable_bucket_table, \p intrusive::split_list::static_bucket_table
243 which selects by \p split_list::dynamic_bucket_table option.
249 /// Initializes split-ordered map
251 size_t nItemCount ///< estimated average item count
252 , size_t nLoadFactor = 1 ///< load factor - average item count per bucket. Small integer up to 10, default is 1.
254 : base_class( nItemCount, nLoadFactor )
258 /// Inserts new node with key and default value
260 The function creates a node with \p key and the default value, and then inserts the node created into the map.
263 - The \p key_type should be constructible from value of type \p K.
264 - The \p mapped_type should be default-constructible.
266 The function applies RCU lock internally.
268 Returns \p true if inserting successful, \p false otherwise.
270 template <typename K>
271 bool insert( K const& key )
273 //TODO: pass arguments by reference (make_pair makes copy)
274 return base_class::insert( std::make_pair( key, mapped_type() ) );
279 The function creates a node with copy of \p val value
280 and then inserts the node into the map.
283 - The \p key_type should be constructible from \p key of type \p K.
284 - The \p mapped_type should be constructible from \p val of type \p V.
286 The function applies RCU lock internally.
288 Returns \p true if \p val is inserted into the map, \p false otherwise.
290 template <typename K, typename V>
291 bool insert( K const& key, V const& val )
293 //TODO: pass arguments by reference (make_pair makes copy)
294 return base_class::insert( std::make_pair(key, val) );
297 /// Inserts new node and initialize it by a functor
299 This function inserts new node with key \p key and if inserting is successful then it calls
300 \p func functor with signature
303 void operator()( value_type& item );
307 The argument \p item of user-defined functor \p func is the reference
308 to the map's item inserted:
309 - <tt>item.first</tt> is a const reference to item's key that cannot be changed.
310 - <tt>item.second</tt> is a reference to item's value that may be changed.
312 It should be keep in mind that concurrent modifications of \p <tt>item.second</tt> in \p func body
313 should be careful. You shouldf guarantee that during changing item's value in \p func no any other changes
314 could be made on this \p item by concurrent threads.
316 \p func is called only if inserting is successful.
318 The function allows to split creating of new item into two part:
319 - create item from \p key;
320 - insert new item into the map;
321 - if inserting is successful, initialize the value of item by calling \p func functor
323 This can be useful if complete initialization of object of \p mapped_type is heavyweight and
324 it is preferable that the initialization should be completed only if inserting is successful.
326 The function applies RCU lock internally.
328 template <typename K, typename Func>
329 bool insert_with( K const& key, Func func )
331 //TODO: pass arguments by reference (make_pair makes copy)
332 return base_class::insert( std::make_pair( key, mapped_type() ), func );
335 /// For key \p key inserts data of type \p mapped_type created in-place from \p args
337 \p key_type should be constructible from type \p K
339 The function applies RCU lock internally.
341 Returns \p true if inserting successful, \p false otherwise.
343 template <typename K, typename... Args>
344 bool emplace( K&& key, Args&&... args )
346 return base_class::emplace( std::forward<K>(key), std::move(mapped_type(std::forward<Args>(args)...)));
349 /// Ensures that the \p key exists in the map
351 The operation performs inserting or changing data with lock-free manner.
353 If the \p key not found in the map, then the new item created from \p key
354 is inserted into the map; in this case the \p key_type should be
355 constructible from type \p K.
356 Otherwise, the functor \p func is called with item found.
357 The functor \p Func signature is:
360 void operator()( bool bNew, value_type& item );
364 - \p bNew - \p true if the item has been inserted, \p false otherwise
365 - \p item - item of the list
367 The functor may change any fields of the \p item.second that is \p mapped_type;
368 however, \p func must guarantee that during changing no any other modifications
369 could be made on this item by concurrent threads.
371 The function applies RCU lock internally.
373 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
374 \p second is true if new item has been added or \p false if the item with \p key
375 already is in the list.
377 @warning For \ref cds_nonintrusive_MichaelKVList_gc "MichaelKVList" as the ordered list see \ref cds_intrusive_item_creating "insert item troubleshooting".
378 \ref cds_nonintrusive_LazyKVList_gc "LazyKVList" provides exclusive access to inserted item and does not require any node-level
381 template <typename K, typename Func>
382 std::pair<bool, bool> ensure( K const& key, Func func )
384 //TODO: pass arguments by reference (make_pair makes copy)
385 return base_class::ensure( std::make_pair( key, mapped_type() ),
386 [&func](bool bNew, value_type& item, value_type const& /*val*/) {
391 /// Deletes \p key from the map
392 /** \anchor cds_nonintrusive_SplitListMap_rcu_erase_val
394 RCU \p synchronize method can be called. RCU should not be locked.
396 Return \p true if \p key is found and deleted, \p false otherwise
398 template <typename K>
399 bool erase( K const& key )
401 return base_class::erase( key );
404 /// Deletes the item from the map using \p pred predicate for searching
406 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_erase_val "erase(K const&)"
407 but \p pred is used for key comparing.
408 \p Less functor has the interface like \p std::less.
409 \p Less must imply the same element order as the comparator used for building the map.
411 template <typename K, typename Less>
412 bool erase_with( K const& key, Less pred )
415 return base_class::erase_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>() );
418 /// Deletes \p key from the map
419 /** \anchor cds_nonintrusive_SplitListMap_rcu_erase_func
421 The function searches an item with key \p key, calls \p f functor
422 and deletes the item. If \p key is not found, the functor is not called.
424 The functor \p Func interface is:
427 void operator()(value_type& item) { ... }
431 RCU \p synchronize method can be called. RCU should not be locked.
433 Return \p true if key is found and deleted, \p false otherwise
435 template <typename K, typename Func>
436 bool erase( K const& key, Func f )
438 return base_class::erase( key, f );
441 /// Deletes the item from the map using \p pred predicate for searching
443 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_erase_func "erase(K const&, Func)"
444 but \p pred is used for key comparing.
445 \p Less functor has the interface like \p std::less.
446 \p Less must imply the same element order as the comparator used for building the map.
448 template <typename K, typename Less, typename Func>
449 bool erase_with( K const& key, Less pred, Func f )
452 return base_class::erase_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>(), f );
455 /// Extracts an item from the map
456 /** \anchor cds_nonintrusive_SplitListMap_rcu_extract
457 The function searches an item with key equal to \p key in the map,
458 unlinks it from the map, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item found.
459 If the item with the key equal to \p key is not found the function returns an empty \p exempt_ptr.
461 @note The function does NOT call RCU read-side lock or synchronization,
462 and does NOT dispose the item found. It just excludes the item from the map
463 and returns a pointer to item found.
464 You should lock RCU before calling of the function, and you should synchronize RCU
465 outside the RCU lock to free extracted item
468 typedef cds::urcu::gc< general_buffered<> > rcu;
469 typedef cds::container::SplitListMap< rcu, int, Foo > splitlist_map;
471 splitlist_map theMap;
474 typename splitlist_map::exempt_ptr p;
476 // first, we should lock RCU
477 typename splitlist_map::rcu_lock lock;
479 // Now, you can apply extract function
480 // Note that you must not delete the item found inside the RCU lock
481 p = theMap.extract( 10 )
483 // do something with p
488 // We may safely release p here
489 // release() passes the pointer to RCU reclamation cycle
493 template <typename K>
494 exempt_ptr extract( K const& key )
496 return base_class::extract( key );
499 /// Extracts an item from the map using \p pred predicate for searching
501 The function is an analog of \p extract(K const&) but \p pred is used for key comparing.
502 \p Less functor has the interface like \p std::less.
503 \p pred must imply the same element order as the comparator used for building the map.
505 template <typename K, typename Less>
506 exempt_ptr extract_with( K const& key, Less pred )
509 return base_class::extract_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>());
512 /// Finds the key \p key
513 /** \anchor cds_nonintrusive_SplitListMap_rcu_find_cfunc
515 The function searches the item with key equal to \p key and calls the functor \p f for item found.
516 The interface of \p Func functor is:
519 void operator()( value_type& item );
522 where \p item is the item found.
524 The functor may change \p item.second. Note that the functor is only guarantee
525 that \p item cannot be disposed during functor is executing.
526 The functor does not serialize simultaneous access to the map's \p item. If such access is
527 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
529 The function applies RCU lock internally.
531 The function returns \p true if \p key is found, \p false otherwise.
533 template <typename K, typename Func>
534 bool find( K const& key, Func f )
536 return base_class::find( key, [&f](value_type& pair, K const&){ f( pair ); } );
539 /// Finds the key \p key using \p pred predicate for searching
541 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_find_cfunc "find(K const&, Func)"
542 but \p pred is used for key comparing.
543 \p Less functor has the interface like \p std::less.
544 \p Less must imply the same element order as the comparator used for building the map.
546 template <typename K, typename Less, typename Func>
547 bool find_with( K const& key, Less pred, Func f )
550 return base_class::find_with( key,
551 cds::details::predicate_wrapper<value_type, Less, key_accessor>(),
552 [&f](value_type& pair, K const&){ f( pair ); } );
555 /// Finds the key \p key
556 /** \anchor cds_nonintrusive_SplitListMap_rcu_find_val
558 The function searches the item with key equal to \p key
559 and returns \p true if it is found, and \p false otherwise.
561 The function applies RCU lock internally.
563 template <typename K>
564 bool find( K const& key )
566 return base_class::find( key );
569 /// Finds the key \p key using \p pred predicate for searching
571 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_find_val "find(K const&)"
572 but \p pred is used for key comparing.
573 \p Less functor has the interface like \p std::less.
574 \p Less must imply the same element order as the comparator used for building the map.
576 template <typename K, typename Less>
577 bool find_with( K const& key, Less pred )
580 return base_class::find_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>() );
583 /// Finds \p key and return the item found
584 /** \anchor cds_intrusive_SplitListMap_rcu_get
585 The function searches the item with key equal to \p key and returns the pointer to item found.
586 If \p key is not found it returns \p nullptr.
588 Note the compare functor should accept a parameter of type \p K that can be not the same as \p value_type.
590 RCU should be locked before call of this function.
591 Returned item is valid only while RCU is locked:
593 typedef cds::urcu::gc< general_buffered<> > rcu;
594 typedef cds::container::SplitListMap< rcu, int, Foo > splitlist_map;
595 splitlist_map theMap;
599 typename splitlist_map::rcu_lock lock;
601 typename splitlist_map::value_type * pVal = theMap.get( 5 );
606 // Unlock RCU by rcu_lock destructor
607 // pVal can be retired by disposer at any time after RCU has been unlocked
611 template <typename K>
612 value_type * get( K const& key )
614 return base_class::get( key );
617 /// Finds \p key with predicate specified and return the item found
619 The function is an analog of \ref cds_intrusive_SplitListMap_rcu_get "get(K const&)"
620 but \p pred is used for comparing the keys.
622 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p K
624 \p pred must imply the same element order as the comparator used for building the map.
626 template <typename K, typename Less>
627 value_type * get_with( K const& key, Less pred )
630 return base_class::get_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>());
633 /// Clears the map (not atomic)
639 /// Checks if the map is empty
641 Emptiness is checked by item counting: if item count is zero then the map is empty.
642 Thus, the correct item counting is an important part of the map implementation.
646 return base_class::empty();
649 /// Returns item count in the map
652 return base_class::size();
655 /// Returns internal statistics
656 stat const& statistics() const
658 return base_class::statistics();
662 }} // namespace cds::container
664 #endif // #ifndef CDSLIB_CONTAINER_SPLIT_LIST_MAP_RCU_H