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 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
176 typedef typename base_class::rcu_lock rcu_lock; ///< RCU scoped lock
177 typedef typename base_class::exempt_ptr exempt_ptr; ///< pointer to extracted node
178 /// Group of \p extract_xxx functions require external locking if underlying ordered list requires that
179 static CDS_CONSTEXPR const bool c_bExtractLockExternal = base_class::c_bExtractLockExternal;
183 typedef typename base_class::maker::traits::key_accessor key_accessor;
188 typedef typename base_class::iterator iterator;
190 /// Const forward iterator
191 typedef typename base_class::const_iterator const_iterator;
193 /// Returns a forward iterator addressing the first element in a map
195 For empty map \code begin() == end() \endcode
199 return base_class::begin();
202 /// Returns an iterator that addresses the location succeeding the last element in a map
204 Do not use the value returned by <tt>end</tt> function to access any item.
205 The returned value can be used only to control reaching the end of the map.
206 For empty map \code begin() == end() \endcode
210 return base_class::end();
213 /// Returns a forward const iterator addressing the first element in a map
215 const_iterator begin() const
217 return base_class::begin();
219 const_iterator cbegin()
221 return base_class::cbegin();
225 /// Returns an const iterator that addresses the location succeeding the last element in a map
227 const_iterator end() const
229 return base_class::end();
231 const_iterator cend()
233 return base_class::cend();
238 /// Initializes split-ordered map of default capacity
240 The default capacity is defined in bucket table constructor.
241 See \p intrusive::split_list::expandable_bucket_table, \p intrusive::split_list::static_bucket_table
242 which selects by \p split_list::dynamic_bucket_table option.
248 /// Initializes split-ordered map
250 size_t nItemCount ///< estimated average item count
251 , size_t nLoadFactor = 1 ///< load factor - average item count per bucket. Small integer up to 10, default is 1.
253 : base_class( nItemCount, nLoadFactor )
257 /// Inserts new node with key and default value
259 The function creates a node with \p key and the default value, and then inserts the node created into the map.
262 - The \p key_type should be constructible from value of type \p K.
263 - The \p mapped_type should be default-constructible.
265 The function applies RCU lock internally.
267 Returns \p true if inserting successful, \p false otherwise.
269 template <typename K>
270 bool insert( K const& key )
272 //TODO: pass arguments by reference (make_pair makes copy)
273 return base_class::insert( std::make_pair( key, mapped_type() ) );
278 The function creates a node with copy of \p val value
279 and then inserts the node into the map.
282 - The \p key_type should be constructible from \p key of type \p K.
283 - The \p mapped_type should be constructible from \p val of type \p V.
285 The function applies RCU lock internally.
287 Returns \p true if \p val is inserted into the map, \p false otherwise.
289 template <typename K, typename V>
290 bool insert( K const& key, V const& val )
292 //TODO: pass arguments by reference (make_pair makes copy)
293 return base_class::insert( std::make_pair(key, val) );
296 /// Inserts new node and initialize it by a functor
298 This function inserts new node with key \p key and if inserting is successful then it calls
299 \p func functor with signature
302 void operator()( value_type& item );
306 The argument \p item of user-defined functor \p func is the reference
307 to the map's item inserted:
308 - <tt>item.first</tt> is a const reference to item's key that cannot be changed.
309 - <tt>item.second</tt> is a reference to item's value that may be changed.
311 It should be keep in mind that concurrent modifications of \p <tt>item.second</tt> in \p func body
312 should be careful. You shouldf guarantee that during changing item's value in \p func no any other changes
313 could be made on this \p item by concurrent threads.
315 \p func is called only if inserting is successful.
317 The function allows to split creating of new item into two part:
318 - create item from \p key;
319 - insert new item into the map;
320 - if inserting is successful, initialize the value of item by calling \p func functor
322 This can be useful if complete initialization of object of \p mapped_type is heavyweight and
323 it is preferable that the initialization should be completed only if inserting is successful.
325 The function applies RCU lock internally.
327 template <typename K, typename Func>
328 bool insert_key( K const& key, Func func )
330 //TODO: pass arguments by reference (make_pair makes copy)
331 return base_class::insert( std::make_pair( key, mapped_type() ), func );
334 /// For key \p key inserts data of type \p mapped_type created in-place from \p args
336 \p key_type should be constructible from type \p K
338 The function applies RCU lock internally.
340 Returns \p true if inserting successful, \p false otherwise.
342 template <typename K, typename... Args>
343 bool emplace( K&& key, Args&&... args )
345 return base_class::emplace( std::forward<K>(key), std::move(mapped_type(std::forward<Args>(args)...)));
348 /// Ensures that the \p key exists in the map
350 The operation performs inserting or changing data with lock-free manner.
352 If the \p key not found in the map, then the new item created from \p key
353 is inserted into the map; in this case the \p key_type should be
354 constructible from type \p K.
355 Otherwise, the functor \p func is called with item found.
356 The functor \p Func signature is:
359 void operator()( bool bNew, value_type& item );
363 - \p bNew - \p true if the item has been inserted, \p false otherwise
364 - \p item - item of the list
366 The functor may change any fields of the \p item.second that is \p mapped_type;
367 however, \p func must guarantee that during changing no any other modifications
368 could be made on this item by concurrent threads.
370 The function applies RCU lock internally.
372 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
373 \p second is true if new item has been added or \p false if the item with \p key
374 already is in the list.
376 @warning For \ref cds_intrusive_MichaelKVList_hp "MichaelKVList" as the ordered list see \ref cds_intrusive_item_creating "insert item troubleshooting".
377 \ref cds_intrusive_LazyKVList_hp "LazyKVList" provides exclusive access to inserted item and does not require any node-level
380 template <typename K, typename Func>
381 std::pair<bool, bool> ensure( K const& key, Func func )
383 //TODO: pass arguments by reference (make_pair makes copy)
384 return base_class::ensure( std::make_pair( key, mapped_type() ),
385 [&func](bool bNew, value_type& item, value_type const& /*val*/) {
390 /// Deletes \p key from the map
391 /** \anchor cds_nonintrusive_SplitListMap_rcu_erase_val
393 RCU \p synchronize method can be called. RCU should not be locked.
395 Return \p true if \p key is found and deleted, \p false otherwise
397 template <typename K>
398 bool erase( K const& key )
400 return base_class::erase( key );
403 /// Deletes the item from the map using \p pred predicate for searching
405 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_erase_val "erase(K const&)"
406 but \p pred is used for key comparing.
407 \p Less functor has the interface like \p std::less.
408 \p Less must imply the same element order as the comparator used for building the map.
410 template <typename K, typename Less>
411 bool erase_with( K const& key, Less pred )
413 return base_class::erase_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>() );
416 /// Deletes \p key from the map
417 /** \anchor cds_nonintrusive_SplitListMap_rcu_erase_func
419 The function searches an item with key \p key, calls \p f functor
420 and deletes the item. If \p key is not found, the functor is not called.
422 The functor \p Func interface is:
425 void operator()(value_type& item) { ... }
428 The functor may be passed by reference using <tt>boost:ref</tt>
430 RCU \p synchronize method can be called. RCU should not be locked.
432 Return \p true if key is found and deleted, \p false otherwise
434 template <typename K, typename Func>
435 bool erase( K const& key, Func f )
437 return base_class::erase( key, f );
440 /// Deletes the item from the map using \p pred predicate for searching
442 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_erase_func "erase(K const&, Func)"
443 but \p pred is used for key comparing.
444 \p Less functor has the interface like \p std::less.
445 \p Less must imply the same element order as the comparator used for building the map.
447 template <typename K, typename Less, typename Func>
448 bool erase_with( K const& key, Less pred, Func f )
450 return base_class::erase_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>(), f );
453 /// Extracts an item from the map
454 /** \anchor cds_nonintrusive_SplitListMap_rcu_extract
455 The function searches an item with key equal to \p key in the map,
456 unlinks it from the map, places item pointer into \p dest argument, and returns \p true.
457 If the item with the key equal to \p key is not found the function return \p false.
459 @note The function does NOT call RCU read-side lock or synchronization,
460 and does NOT dispose the item found. It just excludes the item from the map
461 and returns a pointer to item found.
462 You should lock RCU before calling of the function, and you should synchronize RCU
463 outside the RCU lock to free extracted item
466 typedef cds::urcu::gc< general_buffered<> > rcu;
467 typedef cds::container::SplitListMap< rcu, int, Foo > splitlist_map;
469 splitlist_map theMap;
472 typename splitlist_map::exempt_ptr p;
474 // first, we should lock RCU
475 typename splitlist_map::rcu_lock lock;
477 // Now, you can apply extract function
478 // Note that you must not delete the item found inside the RCU lock
479 if ( theMap.extract( p, 10 )) {
480 // do something with p
485 // We may safely release p here
486 // release() passes the pointer to RCU reclamation cycle
490 template <typename K>
491 bool extract( exempt_ptr& dest, K const& key )
493 return base_class::extract( dest, key );
496 /// Extracts an item from the map using \p pred predicate for searching
498 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_extract "extract(exempt_ptr&, K const&)"
499 but \p pred is used for key comparing.
500 \p Less functor has the interface like \p std::less.
501 \p pred must imply the same element order as the comparator used for building the map.
503 template <typename K, typename Less>
504 bool extract_with( exempt_ptr& dest, K const& key, Less pred )
506 return base_class::extract_with( dest, key, cds::details::predicate_wrapper<value_type, Less, key_accessor>());
509 /// Finds the key \p key
510 /** \anchor cds_nonintrusive_SplitListMap_rcu_find_cfunc
512 The function searches the item with key equal to \p key and calls the functor \p f for item found.
513 The interface of \p Func functor is:
516 void operator()( value_type& item );
519 where \p item is the item found.
521 You may pass \p f argument by reference using \p std::ref.
523 The functor may change \p item.second. Note that the functor is only guarantee
524 that \p item cannot be disposed during functor is executing.
525 The functor does not serialize simultaneous access to the map's \p item. If such access is
526 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
528 The function applies RCU lock internally.
530 The function returns \p true if \p key is found, \p false otherwise.
532 template <typename K, typename Func>
533 bool find( K const& key, Func f )
535 return base_class::find( key, [&f](value_type& pair, K const&){ f( pair ); } );
538 /// Finds the key \p key using \p pred predicate for searching
540 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_find_cfunc "find(K const&, Func)"
541 but \p pred is used for key comparing.
542 \p Less functor has the interface like \p std::less.
543 \p Less must imply the same element order as the comparator used for building the map.
545 template <typename K, typename Less, typename Func>
546 bool find_with( K const& key, Less pred, Func f )
548 return base_class::find_with( key,
549 cds::details::predicate_wrapper<value_type, Less, key_accessor>(),
550 [&f](value_type& pair, K const&){ f( pair ); } );
553 /// Finds the key \p key
554 /** \anchor cds_nonintrusive_SplitListMap_rcu_find_val
556 The function searches the item with key equal to \p key
557 and returns \p true if it is found, and \p false otherwise.
559 The function applies RCU lock internally.
561 template <typename K>
562 bool find( K const& key )
564 return base_class::find( key );
567 /// Finds the key \p key using \p pred predicate for searching
569 The function is an analog of \ref cds_nonintrusive_SplitListMap_rcu_find_val "find(K const&)"
570 but \p pred is used for key comparing.
571 \p Less functor has the interface like \p std::less.
572 \p Less must imply the same element order as the comparator used for building the map.
574 template <typename K, typename Less>
575 bool find_with( K const& key, Less pred )
577 return base_class::find_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>() );
580 /// Finds \p key and return the item found
581 /** \anchor cds_intrusive_SplitListMap_rcu_get
582 The function searches the item with key equal to \p key and returns the pointer to item found.
583 If \p key is not found it returns \p nullptr.
585 Note the compare functor should accept a parameter of type \p K that can be not the same as \p value_type.
587 RCU should be locked before call of this function.
588 Returned item is valid only while RCU is locked:
590 typedef cds::urcu::gc< general_buffered<> > rcu;
591 typedef cds::container::SplitListMap< rcu, int, Foo > splitlist_map;
592 splitlist_map theMap;
596 typename splitlist_map::rcu_lock lock;
598 typename splitlist_map::value_type * pVal = theMap.get( 5 );
603 // Unlock RCU by rcu_lock destructor
604 // pVal can be retired by disposer at any time after RCU has been unlocked
608 template <typename K>
609 value_type * get( K const& key )
611 return base_class::get( key );
614 /// Finds \p key with predicate specified and return the item found
616 The function is an analog of \ref cds_intrusive_SplitListMap_rcu_get "get(K const&)"
617 but \p pred is used for comparing the keys.
619 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p K
621 \p pred must imply the same element order as the comparator used for building the map.
623 template <typename K, typename Less>
624 value_type * get_with( K const& key, Less pred )
626 return base_class::get_with( key, cds::details::predicate_wrapper<value_type, Less, key_accessor>());
629 /// Clears the map (not atomic)
635 /// Checks if the map is empty
637 Emptiness is checked by item counting: if item count is zero then the map is empty.
638 Thus, the correct item counting is an important part of the map implementation.
642 return base_class::empty();
645 /// Returns item count in the map
648 return base_class::size();
652 }} // namespace cds::container
654 #endif // #ifndef __CDS_CONTAINER_SPLIT_LIST_MAP_RCU_H