3 #ifndef __CDS_CONTAINER_SPLIT_LIST_MAP_RCU_H
4 #define __CDS_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 of an item stored in the map. It should be copy-constructible
24 - \p Value - value type stored in the map
25 - \p Traits - type traits, default is split_list::type_traits. Instead of declaring split_list::type_traits -based
26 struct you may apply option-based notation with split_list::make_traits metafunction.
30 The class supports a forward iterator (\ref iterator and \ref const_iterator).
31 The iteration is unordered.
33 You may iterate over split-list map items only under RCU lock.
34 Only in this case the iterator is thread-safe since
35 while RCU is locked any map's item cannot be reclaimed.
37 The requirement of RCU lock during iterating means that deletion of the elements (i.e. \ref erase)
40 @warning The iterator object cannot be passed between threads
42 \warning Due to concurrent nature of split-list map it is not guarantee that you can iterate
43 all elements in the map: any concurrent deletion can exclude the element
44 pointed by the iterator from the map, and your iteration can be terminated
45 before end of the map. Therefore, such iteration is more suitable for debugging purposes
47 The iterator class supports the following minimalistic interface:
54 iterator( iterator const& s);
56 value_type * operator ->() const;
57 value_type& operator *() const;
60 iterator& operator ++();
63 iterator& operator = (const iterator& src);
65 bool operator ==(iterator const& i ) const;
66 bool operator !=(iterator const& i ) const;
69 Note, the iterator object returned by \ref end, \p cend member functions points to \p nullptr and should not be dereferenced.
73 You should decide what garbage collector you want, and what ordered list you want to use. Split-ordered list
74 is original data structure based on an ordered list. Suppose, you want construct split-list map based on cds::urcu::general_buffered<> GC
75 and MichaelList as ordered list implementation. Your map should map \p int key to <tt>std::string</tt> value.
76 So, you beginning your program with following include:
78 #include <cds/urcu/general_buffered.h>
79 #include <cds/container/michael_list_rcu.h>
80 #include <cds/container/split_list_map_rcu.h>
82 namespace cc = cds::container;
84 The inclusion order is important:
85 - first, include one of \ref cds_urcu_gc "RCU implementation" (<tt>cds/urcu/general_buffered.h</tt> in our case)
86 - second, include file for ordered-list implementation (for this example, <tt>cds/container/michael_list_rcu.h</tt>),
87 - then, the header for RCU-based split-list map <tt>cds/container/split_list_map_rcu.h</tt>.
89 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.
90 We use <tt>std::hash<int></tt> as hash functor and <tt>std::less<int></tt> predicate as comparing functor.
92 The second attention: instead of using %MichaelList in %SplitListMap traits we use a tag <tt>cds::contaner::michael_list_tag</tt>
93 for the Michael's list.
94 The split-list requires significant support from underlying ordered list class and it is not good idea to dive you
95 into deep implementation details of split-list and ordered list interrelations. The tag paradigm simplifies split-list interface.
98 // SplitListMap traits
99 struct foo_set_traits: public cc::split_list::type_traits
101 typedef cc::michael_list_tag ordered_list ; // what type of ordered list we want to use
102 typedef std::hash<int> hash ; // hash functor for the key stored in split-list map
104 // Type traits for our MichaelList class
105 struct ordered_list_traits: public cc::michael_list::type_traits
107 typedef std::less<int> less ; // use our std::less predicate as comparator to order list nodes
112 Now you are ready to declare our map class based on \p %SplitListMap:
114 typedef cc::SplitListMap< cds::urcu::gc<cds::urcu::general_buffered<> >, int, std::string, foo_set_traits > int_string_map;
117 You may use the modern option-based declaration instead of classic type-traits-based one:
119 typedef cc:SplitListMap<
120 cds::urcu::gc<cds::urcu::general_buffered<> > // RCU type
122 ,std::string // value type
123 ,cc::split_list::make_traits< // metafunction to build split-list traits
124 cc::split_list::ordered_list<cc::michael_list_tag> // tag for underlying ordered list implementation
125 ,cc::opt::hash< std::hash<int> > // hash functor
126 ,cc::split_list::ordered_list_traits< // ordered list traits desired
127 cc::michael_list::make_traits< // metafunction to build lazy list traits
128 cc::opt::less< std::less<int> > // less-based compare functor
134 In case of option-based declaration using split_list::make_traits metafunction the struct \p foo_set_traits is not required.
136 Now, the map of type \p int_string_map is ready to use in your program.
138 Note that in this example we show only mandatory type_traits parts, optional ones is the default and they are inherited
139 from cds::container::split_list::type_traits.
140 The <b>cds</b> library contains many other options for deep tuning of behavior of the split-list and
141 ordered-list containers.
147 #ifdef CDS_DOXYGEN_INVOKED
148 class Traits = split_list::type_traits
153 class SplitListMap< cds::urcu::gc< RCU >, Key, Value, Traits >:
154 protected container::SplitListSet<
155 cds::urcu::gc< RCU >,
156 std::pair<Key const, Value>,
157 split_list::details::wrap_map_traits<Key, Value, Traits>
161 typedef container::SplitListSet<
162 cds::urcu::gc< RCU >,
163 std::pair<Key const, Value>,
164 split_list::details::wrap_map_traits<Key, Value, Traits>
169 typedef typename base_class::gc gc ; ///< Garbage collector
170 typedef Traits options ; ///< ]p Traits template argument
171 typedef Key key_type ; ///< key type
172 typedef Value mapped_type ; ///< type of value stored in the map
174 typedef std::pair<key_type const, mapped_type> value_type ; ///< key-value pair type
175 typedef typename base_class::ordered_list ordered_list; ///< Underlying ordered list class
176 typedef typename base_class::key_comparator key_comparator ; ///< key comparison functor
178 typedef typename base_class::hash hash ; ///< Hash functor for \ref key_type
179 typedef typename base_class::item_counter item_counter ; ///< Item counter type
181 typedef typename base_class::rcu_lock rcu_lock ; ///< RCU scoped lock
182 typedef typename base_class::exempt_ptr exempt_ptr ; ///< pointer to extracted node
183 /// Group of \p extract_xxx functions require external locking if underlying ordered list requires that
184 static CDS_CONSTEXPR_CONST bool c_bExtractLockExternal = base_class::c_bExtractLockExternal;
188 typedef typename base_class::maker::type_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()
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()
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 intrusive::split_list::expandable_bucket_table, intrusive::split_list::static_bucket_table
247 which selects by intrusive::split_list::dynamic_bucket_table option.
253 /// Initializes split-ordered map
255 size_t nItemCount ///< estimate 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 default value, and then inserts the node created into the map.
267 - The \ref key_type should be constructible from value of type \p K.
268 In trivial case, \p K is equal to \ref key_type.
269 - The \ref mapped_type should be default-constructible.
271 The function applies RCU lock internally.
273 Returns \p true if inserting successful, \p false otherwise.
275 template <typename K>
276 bool insert( K const& key )
278 //TODO: pass arguments by reference (make_pair makes copy)
279 return base_class::insert( std::make_pair( key, mapped_type() ) );
284 The function creates a node with copy of \p val value
285 and then inserts the node created into the map.
288 - The \ref key_type should be constructible from \p key of type \p K.
289 - The \ref mapped_type should be constructible from \p val of type \p V.
291 The function applies RCU lock internally.
293 Returns \p true if \p val is inserted into the map, \p false otherwise.
295 template <typename K, typename V>
296 bool insert( K const& key, V const& val )
298 //TODO: pass arguments by reference (make_pair makes copy)
299 return base_class::insert( std::make_pair(key, val) );
302 /// Inserts new node and initialize it by a functor
304 This function inserts new node with key \p key and if inserting is successful then it calls
305 \p func functor with signature
308 void operator()( value_type& item );
312 The argument \p item of user-defined functor \p func is the reference
313 to the map's item inserted:
314 - <tt>item.first</tt> is a const reference to item's key that cannot be changed.
315 - <tt>item.second</tt> is a reference to item's value that may be changed.
317 It should be keep in mind that concurrent modifications of \p <tt>item.second</tt> may be possible.
318 User-defined functor \p func should guarantee that during changing item's value no any other changes
319 could be made on this \p item by concurrent threads.
321 The user-defined functor can be passed by reference using <tt>boost::ref</tt>
322 and it is called only if inserting is successful.
324 The key_type should be constructible from value of type \p K.
326 The function allows to split creating of new item into two part:
327 - create item from \p key;
328 - insert new item into the map;
329 - if inserting is successful, initialize the value of item by calling \p func functor
331 This can be useful if complete initialization of object of \p mapped_type is heavyweight and
332 it is preferable that the initialization should be completed only if inserting is successful.
334 The function applies RCU lock internally.
336 template <typename K, typename Func>
337 bool insert_key( K const& key, Func func )
339 //TODO: pass arguments by reference (make_pair makes copy)
340 return base_class::insert( std::make_pair( key, mapped_type() ), func );
343 /// For key \p key inserts data of type \ref mapped_type constructed with <tt>std::forward<Args>(args)...</tt>
345 \p key_type should be constructible from type \p K
347 The function applies RCU lock internally.
349 Returns \p true if inserting successful, \p false otherwise.
351 template <typename K, typename... Args>
352 bool emplace( K&& key, Args&&... args )
354 return base_class::emplace( std::forward<K>(key), std::move(mapped_type(std::forward<Args>(args)...)));
357 /// Ensures that the \p key exists in the map
359 The operation performs inserting or changing data with lock-free manner.
361 If the \p key not found in the map, then the new item created from \p key
362 is inserted into the map (note that in this case the \ref key_type should be
363 constructible from type \p K).
364 Otherwise, the functor \p func is called with item found.
365 The functor \p Func may be a function with signature:
367 void func( bool bNew, value_type& item );
372 void operator()( bool bNew, value_type& item );
377 - \p bNew - \p true if the item has been inserted, \p false otherwise
378 - \p item - item of the list
380 The functor may change any fields of the \p item.second that is \ref mapped_type;
381 however, \p func must guarantee that during changing no any other modifications
382 could be made on this item by concurrent threads.
384 You may pass \p func argument by reference using <tt>boost::ref</tt>.
386 The function applies RCU lock internally.
388 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
389 \p second is true if new item has been added or \p false if the item with \p key
390 already is in the list.
392 template <typename K, typename Func>
393 std::pair<bool, bool> ensure( K const& key, Func func )
395 //TODO: pass arguments by reference (make_pair makes copy)
396 return base_class::ensure( std::make_pair( key, mapped_type() ),
397 [&func](bool bNew, value_type& item, value_type const& /*val*/) {
398 cds::unref(func)( bNew, item );
402 /// Deletes \p key from the map
403 /** \anchor cds_nonintrusive_SplitListMap_rcu_erase_val
405 RCU \p synchronize method can be called. RCU should not be locked.
407 Return \p true if \p key is found and deleted, \p false otherwise
409 template <typename K>
410 bool erase( K const& key )
412 return base_class::erase( key );
415 /// Deletes the item from the map using \p pred predicate for searching
417 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_erase_val "erase(K const&)"
418 but \p pred is used for key comparing.
419 \p Less functor has the interface like \p std::less.
420 \p Less must imply the same element order as the comparator used for building the map.
422 template <typename K, typename Less>
423 bool erase_with( K const& key, Less pred )
425 return base_class::erase_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>() );
428 /// Deletes \p key from the map
429 /** \anchor cds_nonintrusive_SplitListMap_rcu_erase_func
431 The function searches an item with key \p key, calls \p f functor
432 and deletes the item. If \p key is not found, the functor is not called.
434 The functor \p Func interface is:
437 void operator()(value_type& item) { ... }
440 The functor may be passed by reference using <tt>boost:ref</tt>
442 RCU \p synchronize method can be called. RCU should not be locked.
444 Return \p true if key is found and deleted, \p false otherwise
446 template <typename K, typename Func>
447 bool erase( K const& key, Func f )
449 return base_class::erase( key, f );
452 /// Deletes the item from the map using \p pred predicate for searching
454 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_erase_func "erase(K const&, Func)"
455 but \p pred is used for key comparing.
456 \p Less functor has the interface like \p std::less.
457 \p Less must imply the same element order as the comparator used for building the map.
459 template <typename K, typename Less, typename Func>
460 bool erase_with( K const& key, Less pred, Func f )
462 return base_class::erase_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>(), f );
465 /// Extracts an item from the map
466 /** \anchor cds_nonintrusive_SplitListMap_rcu_extract
467 The function searches an item with key equal to \p key in the map,
468 unlinks it from the map, places item pointer into \p dest argument, and returns \p true.
469 If the item with the key equal to \p key is not found the function return \p false.
471 @note The function does NOT call RCU read-side lock or synchronization,
472 and does NOT dispose the item found. It just excludes the item from the map
473 and returns a pointer to item found.
474 You should lock RCU before calling of the function, and you should synchronize RCU
475 outside the RCU lock to free extracted item
478 typedef cds::urcu::gc< general_buffered<> > rcu;
479 typedef cds::container::SplitListMap< rcu, int, Foo > splitlist_map;
481 splitlist_map theMap;
484 typename splitlist_map::exempt_ptr p;
486 // first, we should lock RCU
487 typename splitlist_map::rcu_lock lock;
489 // Now, you can apply extract function
490 // Note that you must not delete the item found inside the RCU lock
491 if ( theMap.extract( p, 10 )) {
492 // do something with p
497 // We may safely release p here
498 // release() passes the pointer to RCU reclamation cycle
502 template <typename K>
503 bool extract( exempt_ptr& dest, K const& key )
505 return base_class::extract( dest, key );
508 /// Extracts an item from the map using \p pred predicate for searching
510 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_extract "extract(exempt_ptr&, K const&)"
511 but \p pred is used for key comparing.
512 \p Less functor has the interface like \p std::less.
513 \p pred must imply the same element order as the comparator used for building the map.
515 template <typename K, typename Less>
516 bool extract_with( exempt_ptr& dest, K const& key, Less pred )
518 return base_class::extract_with( dest, key, cds::details::predicate_wrapper<value_type, Less, key_accessor>());
521 /// Finds the key \p key
522 /** \anchor cds_nonintrusive_SplitListMap_rcu_find_cfunc
524 The function searches the item with key equal to \p key and calls the functor \p f for item found.
525 The interface of \p Func functor is:
528 void operator()( value_type& item );
531 where \p item is the item found.
533 You may pass \p f argument by reference using <tt>boost::ref</tt> or cds::ref.
535 The functor may change \p item.second. Note that the functor is only guarantee
536 that \p item cannot be disposed during functor is executing.
537 The functor does not serialize simultaneous access to the map's \p item. If such access is
538 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
540 The function applies RCU lock internally.
542 The function returns \p true if \p key is found, \p false otherwise.
544 template <typename K, typename Func>
545 bool find( K const& key, Func f )
547 return base_class::find( key, [&f](value_type& pair, K const&){ cds::unref(f)( pair ); } );
550 /// Finds the key \p key using \p pred predicate for searching
552 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_find_cfunc "find(K const&, Func)"
553 but \p pred is used for key comparing.
554 \p Less functor has the interface like \p std::less.
555 \p Less must imply the same element order as the comparator used for building the map.
557 template <typename K, typename Less, typename Func>
558 bool find_with( K const& key, Less pred, Func f )
560 return base_class::find_with( key,
561 cds::details::predicate_wrapper<value_type, Less, key_accessor>(),
562 [&f](value_type& pair, K const&){ cds::unref(f)( pair ); } );
565 /// Finds the key \p key
566 /** \anchor cds_nonintrusive_SplitListMap_rcu_find_val
568 The function searches the item with key equal to \p key
569 and returns \p true if it is found, and \p false otherwise.
571 The function applies RCU lock internally.
573 template <typename K>
574 bool find( K const& key )
576 return base_class::find( key );
579 /// Finds the key \p key using \p pred predicate for searching
581 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_find_val "find(K const&)"
582 but \p pred is used for key comparing.
583 \p Less functor has the interface like \p std::less.
584 \p Less must imply the same element order as the comparator used for building the map.
586 template <typename K, typename Less>
587 bool find_with( K const& key, Less pred )
589 return base_class::find_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>() );
592 /// Finds \p key and return the item found
593 /** \anchor cds_intrusive_SplitListMap_rcu_get
594 The function searches the item with key equal to \p key and returns the pointer to item found.
595 If \p key is not found it returns \p nullptr.
597 Note the compare functor should accept a parameter of type \p K that can be not the same as \p value_type.
599 RCU should be locked before call of this function.
600 Returned item is valid only while RCU is locked:
602 typedef cds::urcu::gc< general_buffered<> > rcu;
603 typedef cds::container::SplitListMap< rcu, int, Foo > splitlist_map;
604 splitlist_map theMap;
608 typename splitlist_map::rcu_lock lock;
610 typename splitlist_map::value_type * pVal = theMap.get( 5 );
615 // Unlock RCU by rcu_lock destructor
616 // pVal can be retired by disposer at any time after RCU has been unlocked
620 template <typename K>
621 value_type * get( K const& key )
623 return base_class::get( key );
626 /// Finds \p key with predicate specified and return the item found
628 The function is an analog of \ref cds_intrusive_SplitListMap_rcu_get "get(K const&)"
629 but \p pred is used for comparing the keys.
631 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p K
633 \p pred must imply the same element order as the comparator used for building the map.
635 template <typename K, typename Less>
636 value_type * get_with( K const& key, Less pred )
638 return base_class::get_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>());
641 /// Clears the map (non-atomic)
643 The function unlink all items from the map.
644 The function is not atomic and not lock-free and should be used for debugging only.
646 RCU \p synchronize method can be called. RCU should not be locked.
653 /// Checks if the map is empty
655 Emptiness is checked by item counting: if item count is zero then the map is empty.
656 Thus, the correct item counting is an important part of the map implementation.
660 return base_class::empty();
663 /// Returns item count in the map
666 return base_class::size();
671 }} // namespace cds::container
673 #endif // #ifndef __CDS_CONTAINER_SPLIT_LIST_MAP_RCU_H