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;
181 typedef typename base_class::raw_ptr raw_ptr; ///< type of \p get() return value
185 typedef typename base_class::maker::traits::key_accessor key_accessor;
190 typedef typename base_class::iterator iterator;
192 /// Const forward iterator
193 typedef typename base_class::const_iterator const_iterator;
195 /// Returns a forward iterator addressing the first element in a map
197 For empty map \code begin() == end() \endcode
201 return base_class::begin();
204 /// Returns an iterator that addresses the location succeeding the last element in a map
206 Do not use the value returned by <tt>end</tt> function to access any item.
207 The returned value can be used only to control reaching the end of the map.
208 For empty map \code begin() == end() \endcode
212 return base_class::end();
215 /// Returns a forward const iterator addressing the first element in a map
217 const_iterator begin() const
219 return base_class::begin();
221 const_iterator cbegin() const
223 return base_class::cbegin();
227 /// Returns an const iterator that addresses the location succeeding the last element in a map
229 const_iterator end() const
231 return base_class::end();
233 const_iterator cend() const
235 return base_class::cend();
240 /// Initializes split-ordered map of default capacity
242 The default capacity is defined in bucket table constructor.
243 See \p intrusive::split_list::expandable_bucket_table, \p intrusive::split_list::static_bucket_table
244 which selects by \p split_list::dynamic_bucket_table option.
250 /// Initializes split-ordered map
252 size_t nItemCount ///< estimated average item count
253 , size_t nLoadFactor = 1 ///< load factor - average item count per bucket. Small integer up to 10, default is 1.
255 : base_class( nItemCount, nLoadFactor )
259 /// Inserts new node with key and default value
261 The function creates a node with \p key and the default value, and then inserts the node created into the map.
264 - The \p key_type should be constructible from value of type \p K.
265 - The \p mapped_type should be default-constructible.
267 The function applies RCU lock internally.
269 Returns \p true if inserting successful, \p false otherwise.
271 template <typename K>
272 bool insert( K const& key )
274 //TODO: pass arguments by reference (make_pair makes copy)
275 return base_class::insert( std::make_pair( key, mapped_type() ) );
280 The function creates a node with copy of \p val value
281 and then inserts the node into the map.
284 - The \p key_type should be constructible from \p key of type \p K.
285 - The \p mapped_type should be constructible from \p val of type \p V.
287 The function applies RCU lock internally.
289 Returns \p true if \p val is inserted into the map, \p false otherwise.
291 template <typename K, typename V>
292 bool insert( K const& key, V const& val )
294 //TODO: pass arguments by reference (make_pair makes copy)
295 return base_class::insert( std::make_pair(key, val) );
298 /// Inserts new node and initialize it by a functor
300 This function inserts new node with key \p key and if inserting is successful then it calls
301 \p func functor with signature
304 void operator()( value_type& item );
308 The argument \p item of user-defined functor \p func is the reference
309 to the map's item inserted:
310 - <tt>item.first</tt> is a const reference to item's key that cannot be changed.
311 - <tt>item.second</tt> is a reference to item's value that may be changed.
313 It should be keep in mind that concurrent modifications of \p <tt>item.second</tt> in \p func body
314 should be careful. You shouldf guarantee that during changing item's value in \p func no any other changes
315 could be made on this \p item by concurrent threads.
317 \p func is called only if inserting is successful.
319 The function allows to split creating of new item into two part:
320 - create item from \p key;
321 - insert new item into the map;
322 - if inserting is successful, initialize the value of item by calling \p func functor
324 This can be useful if complete initialization of object of \p mapped_type is heavyweight and
325 it is preferable that the initialization should be completed only if inserting is successful.
327 The function applies RCU lock internally.
329 template <typename K, typename Func>
330 bool insert_with( K const& key, Func func )
332 //TODO: pass arguments by reference (make_pair makes copy)
333 return base_class::insert( std::make_pair( key, mapped_type() ), func );
336 /// For key \p key inserts data of type \p mapped_type created in-place from \p args
338 \p key_type should be constructible from type \p K
340 The function applies RCU lock internally.
342 Returns \p true if inserting successful, \p false otherwise.
344 template <typename K, typename... Args>
345 bool emplace( K&& key, Args&&... args )
347 return base_class::emplace( std::forward<K>(key), std::move(mapped_type(std::forward<Args>(args)...)));
350 /// Updates data by \p key
352 The operation performs inserting or replacing the element with lock-free manner.
354 If the \p key not found in the map, then the new item created from \p key
355 will be inserted into the map iff \p bAllowInsert is \p true.
356 (note that in this case the \ref key_type should be constructible from type \p K).
357 Otherwise, if \p key is found, the functor \p func is called with item found.
359 The functor \p Func signature is:
362 void operator()( bool bNew, value_type& item );
366 - \p bNew - \p true if the item has been inserted, \p false otherwise
367 - \p item - the item found or inserted
369 The functor may change any fields of the \p item.second that is \p mapped_type.
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
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> update( K const& key, Func func, bool bAllowInsert = true )
384 //TODO: pass arguments by reference (make_pair makes copy)
385 return base_class::update( std::make_pair( key, mapped_type() ),
386 [&func](bool bNew, value_type& item, value_type const& /*val*/) {
392 // Deprecated, use update()
393 template <typename K, typename Func>
394 std::pair<bool, bool> ensure( K const& key, Func func )
396 return update( key, func, true );
400 /// Deletes \p key from the map
401 /** \anchor cds_nonintrusive_SplitListMap_rcu_erase_val
403 RCU \p synchronize method can be called. RCU should not be locked.
405 Return \p true if \p key is found and deleted, \p false otherwise
407 template <typename K>
408 bool erase( K const& key )
410 return base_class::erase( key );
413 /// Deletes the item from the map using \p pred predicate for searching
415 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_erase_val "erase(K const&)"
416 but \p pred is used for key comparing.
417 \p Less functor has the interface like \p std::less.
418 \p Less must imply the same element order as the comparator used for building the map.
420 template <typename K, typename Less>
421 bool erase_with( K const& key, Less pred )
424 return base_class::erase_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>() );
427 /// Deletes \p key from the map
428 /** \anchor cds_nonintrusive_SplitListMap_rcu_erase_func
430 The function searches an item with key \p key, calls \p f functor
431 and deletes the item. If \p key is not found, the functor is not called.
433 The functor \p Func interface is:
436 void operator()(value_type& item) { ... }
440 RCU \p synchronize method can be called. RCU should not be locked.
442 Return \p true if key is found and deleted, \p false otherwise
444 template <typename K, typename Func>
445 bool erase( K const& key, Func f )
447 return base_class::erase( key, f );
450 /// Deletes the item from the map using \p pred predicate for searching
452 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_erase_func "erase(K const&, Func)"
453 but \p pred is used for key comparing.
454 \p Less functor has the interface like \p std::less.
455 \p Less must imply the same element order as the comparator used for building the map.
457 template <typename K, typename Less, typename Func>
458 bool erase_with( K const& key, Less pred, Func f )
461 return base_class::erase_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>(), f );
464 /// Extracts an item from the map
465 /** \anchor cds_nonintrusive_SplitListMap_rcu_extract
466 The function searches an item with key equal to \p key in the map,
467 unlinks it from the map, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item found.
468 If the item with the key equal to \p key is not found the function returns an empty \p exempt_ptr.
470 Depends on ordered list you should or should not lock RCU before calling of this function:
471 - for the set based on \ref cds_intrusive_MichaelList_rcu "MichaelList" RCU should not be locked
472 - for the set based on \ref cds_intrusive_LazyList_rcu "LazyList" RCU should be locked
473 See ordered list implementation for details.
476 typedef cds::urcu::gc< general_buffered<> > rcu;
478 // Split-list set based on MichaelList by default
479 typedef cds::container::SplitListMap< rcu, int, Foo > splitlist_map;
481 splitlist_map theMap;
484 typename splitlist_map::exempt_ptr p;
486 // For MichaelList we should not lock RCU
488 // Now, you can apply extract function
489 p = theMap.extract( 10 )
491 // do something with p
495 // We may safely release p here
496 // release() passes the pointer to RCU reclamation cycle
500 template <typename K>
501 exempt_ptr extract( K const& key )
503 return base_class::extract( key );
506 /// Extracts an item from the map using \p pred predicate for searching
508 The function is an analog of \p extract(K const&) but \p pred is used for key comparing.
509 \p Less functor has the interface like \p std::less.
510 \p pred must imply the same element order as the comparator used for building the map.
512 template <typename K, typename Less>
513 exempt_ptr extract_with( K const& key, Less pred )
516 return base_class::extract_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>());
519 /// Finds the key \p key
520 /** \anchor cds_nonintrusive_SplitListMap_rcu_find_cfunc
522 The function searches the item with key equal to \p key and calls the functor \p f for item found.
523 The interface of \p Func functor is:
526 void operator()( value_type& item );
529 where \p item is the item found.
531 The functor may change \p item.second. Note that the functor is only guarantee
532 that \p item cannot be disposed during functor is executing.
533 The functor does not serialize simultaneous access to the map's \p item. If such access is
534 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
536 The function applies RCU lock internally.
538 The function returns \p true if \p key is found, \p false otherwise.
540 template <typename K, typename Func>
541 bool find( K const& key, Func f )
543 return base_class::find( key, [&f](value_type& pair, K const&){ f( pair ); } );
546 /// Finds the key \p key using \p pred predicate for searching
548 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_find_cfunc "find(K const&, Func)"
549 but \p pred is used for key comparing.
550 \p Less functor has the interface like \p std::less.
551 \p Less must imply the same element order as the comparator used for building the map.
553 template <typename K, typename Less, typename Func>
554 bool find_with( K const& key, Less pred, Func f )
557 return base_class::find_with( key,
558 cds::details::predicate_wrapper<value_type, Less, key_accessor>(),
559 [&f](value_type& pair, K const&){ f( pair ); } );
562 /// Checks whether the map contains \p key
564 The function searches the item with key equal to \p key
565 and returns \p true if it is found, and \p false otherwise.
567 The function applies RCU lock internally.
569 template <typename K>
570 bool contains( K const& key )
572 return base_class::contains( key );
575 // Deprecated, use contains()
576 template <typename K>
577 bool find( K const& key )
579 return base_class::find( key );
583 /// Checks whether the map contains \p key using \p pred predicate for searching
585 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
586 \p Less functor has the interface like \p std::less.
587 \p Less must imply the same element order as the comparator used for building the map.
589 template <typename K, typename Less>
590 bool contains( K const& key, Less pred )
593 return base_class::contains( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>() );
596 // Deprecated, use contains()
597 template <typename K, typename Less>
598 bool find_with( K const& key, Less pred )
600 return contains( key, pred );
604 /// Finds \p key and return the item found
605 /** \anchor cds_intrusive_SplitListMap_rcu_get
606 The function searches the item with key equal to \p key and returns the pointer to item found.
607 If \p key is not found it returns empty \p raw_ptr.
609 Note the compare functor should accept a parameter of type \p K that can be not the same as \p value_type.
611 RCU should be locked before call of this function.
612 Returned item is valid only while RCU is locked:
614 typedef cds::urcu::gc< general_buffered<> > rcu;
615 typedef cds::container::SplitListMap< rcu, int, Foo > splitlist_map;
616 splitlist_map theMap;
620 typename splitlist_map::rcu_lock lock;
622 typename splitlist_map::raw_ptr pVal = theMap.get( 5 );
627 // Unlock RCU by rcu_lock destructor
628 // pVal can be retired by disposer at any time after RCU has been unlocked
632 template <typename K>
633 raw_ptr get( K const& key )
635 return base_class::get( key );
638 /// Finds \p key with predicate specified and return the item found
640 The function is an analog of \ref cds_intrusive_SplitListMap_rcu_get "get(K const&)"
641 but \p pred is used for comparing the keys.
643 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p K
645 \p pred must imply the same element order as the comparator used for building the map.
647 template <typename K, typename Less>
648 raw_ptr get_with( K const& key, Less pred )
651 return base_class::get_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>());
654 /// Clears the map (not atomic)
660 /// Checks if the map is empty
662 Emptiness is checked by item counting: if item count is zero then the map is empty.
663 Thus, the correct item counting is an important part of the map implementation.
667 return base_class::empty();
670 /// Returns item count in the map
673 return base_class::size();
676 /// Returns internal statistics
677 stat const& statistics() const
679 return base_class::statistics();
683 }} // namespace cds::container
685 #endif // #ifndef CDSLIB_CONTAINER_SPLIT_LIST_MAP_RCU_H