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;
183 typedef cds::container::split_list::implementation_tag implementation_tag;
188 typedef typename base_class::maker::traits::key_accessor key_accessor;
193 typedef typename base_class::iterator iterator;
195 /// Const forward iterator
196 typedef typename base_class::const_iterator const_iterator;
198 /// Returns a forward iterator addressing the first element in a map
200 For empty map \code begin() == end() \endcode
204 return base_class::begin();
207 /// Returns an iterator that addresses the location succeeding the last element in a map
209 Do not use the value returned by <tt>end</tt> function to access any item.
210 The returned value can be used only to control reaching the end of the map.
211 For empty map \code begin() == end() \endcode
215 return base_class::end();
218 /// Returns a forward const iterator addressing the first element in a map
220 const_iterator begin() const
222 return base_class::begin();
224 const_iterator cbegin() const
226 return base_class::cbegin();
230 /// Returns an const iterator that addresses the location succeeding the last element in a map
232 const_iterator end() const
234 return base_class::end();
236 const_iterator cend() const
238 return base_class::cend();
243 /// Initializes split-ordered map of default capacity
245 The default capacity is defined in bucket table constructor.
246 See \p intrusive::split_list::expandable_bucket_table, \p intrusive::split_list::static_bucket_table
247 which selects by \p split_list::dynamic_bucket_table option.
253 /// Initializes split-ordered map
255 size_t nItemCount ///< estimated average item count
256 , size_t nLoadFactor = 1 ///< load factor - average item count per bucket. Small integer up to 10, default is 1.
258 : base_class( nItemCount, nLoadFactor )
262 /// Inserts new node with key and default value
264 The function creates a node with \p key and the default value, and then inserts the node created into the map.
267 - The \p key_type should be constructible from value of type \p K.
268 - The \p mapped_type should be default-constructible.
270 The function applies RCU lock internally.
272 Returns \p true if inserting successful, \p false otherwise.
274 template <typename K>
275 bool insert( K const& key )
277 //TODO: pass arguments by reference (make_pair makes copy)
278 return base_class::insert( std::make_pair( key, mapped_type() ) );
283 The function creates a node with copy of \p val value
284 and then inserts the node into the map.
287 - The \p key_type should be constructible from \p key of type \p K.
288 - The \p mapped_type should be constructible from \p val of type \p V.
290 The function applies RCU lock internally.
292 Returns \p true if \p val is inserted into the map, \p false otherwise.
294 template <typename K, typename V>
295 bool insert( K const& key, V const& val )
297 //TODO: pass arguments by reference (make_pair makes copy)
298 return base_class::insert( std::make_pair(key, val) );
301 /// Inserts new node and initialize it by a functor
303 This function inserts new node with key \p key and if inserting is successful then it calls
304 \p func functor with signature
307 void operator()( value_type& item );
311 The argument \p item of user-defined functor \p func is the reference
312 to the map's item inserted:
313 - <tt>item.first</tt> is a const reference to item's key that cannot be changed.
314 - <tt>item.second</tt> is a reference to item's value that may be changed.
316 It should be keep in mind that concurrent modifications of \p <tt>item.second</tt> in \p func body
317 should be careful. You shouldf guarantee that during changing item's value in \p func no any other changes
318 could be made on this \p item by concurrent threads.
320 \p func is called only if inserting is successful.
322 The function allows to split creating of new item into two part:
323 - create item from \p key;
324 - insert new item into the map;
325 - if inserting is successful, initialize the value of item by calling \p func functor
327 This can be useful if complete initialization of object of \p mapped_type is heavyweight and
328 it is preferable that the initialization should be completed only if inserting is successful.
330 The function applies RCU lock internally.
332 template <typename K, typename Func>
333 bool insert_with( K const& key, Func func )
335 //TODO: pass arguments by reference (make_pair makes copy)
336 return base_class::insert( std::make_pair( key, mapped_type() ), func );
339 /// For key \p key inserts data of type \p mapped_type created in-place from \p args
341 \p key_type should be constructible from type \p K
343 The function applies RCU lock internally.
345 Returns \p true if inserting successful, \p false otherwise.
347 template <typename K, typename... Args>
348 bool emplace( K&& key, Args&&... args )
350 return base_class::emplace( std::forward<K>(key), std::move(mapped_type(std::forward<Args>(args)...)));
353 /// Ensures that the \p key exists in the map
355 The operation performs inserting or changing data with lock-free manner.
357 If the \p key not found in the map, then the new item created from \p key
358 is inserted into the map; in this case the \p key_type should be
359 constructible from type \p K.
360 Otherwise, the functor \p func is called with item found.
361 The functor \p Func signature is:
364 void operator()( bool bNew, value_type& item );
368 - \p bNew - \p true if the item has been inserted, \p false otherwise
369 - \p item - item of the list
371 The functor may change any fields of the \p item.second that is \p mapped_type;
372 however, \p func must guarantee that during changing no any other modifications
373 could be made on this item by concurrent threads.
375 The function applies RCU lock internally.
377 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
378 \p second is true if new item has been added or \p false if the item with \p key
379 already is in the list.
381 @warning For \ref cds_nonintrusive_MichaelKVList_gc "MichaelKVList" as the ordered list see \ref cds_intrusive_item_creating "insert item troubleshooting".
382 \ref cds_nonintrusive_LazyKVList_gc "LazyKVList" provides exclusive access to inserted item and does not require any node-level
385 template <typename K, typename Func>
386 std::pair<bool, bool> ensure( K const& key, Func func )
388 //TODO: pass arguments by reference (make_pair makes copy)
389 return base_class::ensure( std::make_pair( key, mapped_type() ),
390 [&func](bool bNew, value_type& item, value_type const& /*val*/) {
395 /// Deletes \p key from the map
396 /** \anchor cds_nonintrusive_SplitListMap_rcu_erase_val
398 RCU \p synchronize method can be called. RCU should not be locked.
400 Return \p true if \p key is found and deleted, \p false otherwise
402 template <typename K>
403 bool erase( K const& key )
405 return base_class::erase( key );
408 /// Deletes the item from the map using \p pred predicate for searching
410 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_erase_val "erase(K const&)"
411 but \p pred is used for key comparing.
412 \p Less functor has the interface like \p std::less.
413 \p Less must imply the same element order as the comparator used for building the map.
415 template <typename K, typename Less>
416 bool erase_with( K const& key, Less pred )
419 return base_class::erase_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>() );
422 /// Deletes \p key from the map
423 /** \anchor cds_nonintrusive_SplitListMap_rcu_erase_func
425 The function searches an item with key \p key, calls \p f functor
426 and deletes the item. If \p key is not found, the functor is not called.
428 The functor \p Func interface is:
431 void operator()(value_type& item) { ... }
435 RCU \p synchronize method can be called. RCU should not be locked.
437 Return \p true if key is found and deleted, \p false otherwise
439 template <typename K, typename Func>
440 bool erase( K const& key, Func f )
442 return base_class::erase( key, f );
445 /// Deletes the item from the map using \p pred predicate for searching
447 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_erase_func "erase(K const&, Func)"
448 but \p pred is used for key comparing.
449 \p Less functor has the interface like \p std::less.
450 \p Less must imply the same element order as the comparator used for building the map.
452 template <typename K, typename Less, typename Func>
453 bool erase_with( K const& key, Less pred, Func f )
456 return base_class::erase_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>(), f );
459 /// Extracts an item from the map
460 /** \anchor cds_nonintrusive_SplitListMap_rcu_extract
461 The function searches an item with key equal to \p key in the map,
462 unlinks it from the map, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item found.
463 If the item with the key equal to \p key is not found the function returns an empty \p exempt_ptr.
465 @note The function does NOT call RCU read-side lock or synchronization,
466 and does NOT dispose the item found. It just excludes the item from the map
467 and returns a pointer to item found.
468 You should lock RCU before calling of the function, and you should synchronize RCU
469 outside the RCU lock to free extracted item
472 typedef cds::urcu::gc< general_buffered<> > rcu;
473 typedef cds::container::SplitListMap< rcu, int, Foo > splitlist_map;
475 splitlist_map theMap;
478 typename splitlist_map::exempt_ptr p;
480 // first, we should lock RCU
481 typename splitlist_map::rcu_lock lock;
483 // Now, you can apply extract function
484 // Note that you must not delete the item found inside the RCU lock
485 p = theMap.extract( 10 )
487 // do something with p
492 // We may safely release p here
493 // release() passes the pointer to RCU reclamation cycle
497 template <typename K>
498 exempt_ptr extract( K const& key )
500 return base_class::extract( key );
503 /// Extracts an item from the map using \p pred predicate for searching
505 The function is an analog of \p extract(K const&) but \p pred is used for key comparing.
506 \p Less functor has the interface like \p std::less.
507 \p pred must imply the same element order as the comparator used for building the map.
509 template <typename K, typename Less>
510 exempt_ptr extract_with( K const& key, Less pred )
513 return base_class::extract_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>());
516 /// Finds the key \p key
517 /** \anchor cds_nonintrusive_SplitListMap_rcu_find_cfunc
519 The function searches the item with key equal to \p key and calls the functor \p f for item found.
520 The interface of \p Func functor is:
523 void operator()( value_type& item );
526 where \p item is the item found.
528 The functor may change \p item.second. Note that the functor is only guarantee
529 that \p item cannot be disposed during functor is executing.
530 The functor does not serialize simultaneous access to the map's \p item. If such access is
531 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
533 The function applies RCU lock internally.
535 The function returns \p true if \p key is found, \p false otherwise.
537 template <typename K, typename Func>
538 bool find( K const& key, Func f )
540 return base_class::find( key, [&f](value_type& pair, K const&){ f( pair ); } );
543 /// Finds the key \p key using \p pred predicate for searching
545 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_find_cfunc "find(K const&, Func)"
546 but \p pred is used for key comparing.
547 \p Less functor has the interface like \p std::less.
548 \p Less must imply the same element order as the comparator used for building the map.
550 template <typename K, typename Less, typename Func>
551 bool find_with( K const& key, Less pred, Func f )
554 return base_class::find_with( key,
555 cds::details::predicate_wrapper<value_type, Less, key_accessor>(),
556 [&f](value_type& pair, K const&){ f( pair ); } );
559 /// Finds the key \p key
560 /** \anchor cds_nonintrusive_SplitListMap_rcu_find_val
562 The function searches the item with key equal to \p key
563 and returns \p true if it is found, and \p false otherwise.
565 The function applies RCU lock internally.
567 template <typename K>
568 bool find( K const& key )
570 return base_class::find( key );
573 /// Finds the key \p key using \p pred predicate for searching
575 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_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<value_type, Less, key_accessor>() );
587 /// Finds \p key and return the item found
588 /** \anchor cds_intrusive_SplitListMap_rcu_get
589 The function searches the item with key equal to \p key and returns the pointer to item found.
590 If \p key is not found it returns \p nullptr.
592 Note the compare functor should accept a parameter of type \p K that can be not the same as \p value_type.
594 RCU should be locked before call of this function.
595 Returned item is valid only while RCU is locked:
597 typedef cds::urcu::gc< general_buffered<> > rcu;
598 typedef cds::container::SplitListMap< rcu, int, Foo > splitlist_map;
599 splitlist_map theMap;
603 typename splitlist_map::rcu_lock lock;
605 typename splitlist_map::value_type * pVal = theMap.get( 5 );
610 // Unlock RCU by rcu_lock destructor
611 // pVal can be retired by disposer at any time after RCU has been unlocked
615 template <typename K>
616 value_type * get( K const& key )
618 return base_class::get( key );
621 /// Finds \p key with predicate specified and return the item found
623 The function is an analog of \ref cds_intrusive_SplitListMap_rcu_get "get(K const&)"
624 but \p pred is used for comparing the keys.
626 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p K
628 \p pred must imply the same element order as the comparator used for building the map.
630 template <typename K, typename Less>
631 value_type * get_with( K const& key, Less pred )
634 return base_class::get_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>());
637 /// Clears the map (not atomic)
643 /// Checks if the map is empty
645 Emptiness is checked by item counting: if item count is zero then the map is empty.
646 Thus, the correct item counting is an important part of the map implementation.
650 return base_class::empty();
653 /// Returns item count in the map
656 return base_class::size();
659 /// Returns internal statistics
660 stat const& statistics() const
662 return base_class::statistics();
666 }} // namespace cds::container
668 #endif // #ifndef CDSLIB_CONTAINER_SPLIT_LIST_MAP_RCU_H