2 This file is a part of libcds - Concurrent Data Structures library
4 (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2017
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31 #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_RCU_H
32 #define CDSLIB_INTRUSIVE_MICHAEL_SET_RCU_H
34 #include <cds/intrusive/details/michael_set_base.h>
36 namespace cds { namespace intrusive {
38 /// Michael's hash set, \ref cds_urcu_desc "RCU" specialization
39 /** @ingroup cds_intrusive_map
40 \anchor cds_intrusive_MichaelHashSet_rcu
43 - [2002] Maged Michael "High performance dynamic lock-free hash tables and list-based sets"
45 Michael's hash table algorithm is based on lock-free ordered list and it is very simple.
46 The main structure is an array \p T of size \p M. Each element in \p T is basically a pointer
47 to a hash bucket, implemented as a singly linked list. The array of buckets cannot be dynamically expanded.
48 However, each bucket may contain unbounded number of items.
50 Template parameters are:
51 - \p RCU - one of \ref cds_urcu_gc "RCU type"
52 - \p OrderedList - ordered list implementation used as bucket for hash set, for example, MichaelList, LazyList.
53 The intrusive ordered list implementation specifies the type \p T stored in the hash-set, the reclamation
54 schema \p GC used by hash-set, the comparison functor for the type \p T and other features specific for
56 - \p Traits - type traits, default is \p michael_set::traits.
57 Instead of defining \p Traits struct you can use option-based syntax with \p michael_set::make_traits metafunction.
60 Before including <tt><cds/intrusive/michael_set_rcu.h></tt> you should include appropriate RCU header file,
61 see \ref cds_urcu_gc "RCU type" for list of existing RCU class and corresponding header files.
62 For example, for \ref cds_urcu_general_buffered_gc "general-purpose buffered RCU" you should include:
64 #include <cds/urcu/general_buffered.h>
65 #include <cds/intrusive/michael_list_rcu.h>
66 #include <cds/intrusive/michael_set_rcu.h>
69 // Hash functor for struct Foo
71 size_t operator()( Foo const& foo ) const { return ... }
74 // Now, you can declare Michael's list for type Foo and default traits:
75 typedef cds::intrusive::MichaelList<cds::urcu::gc< general_buffered<> >, Foo > rcu_michael_list;
77 // Declare Michael's set with MichaelList as bucket type
78 typedef cds::intrusive::MichaelSet<
79 cds::urcu::gc< general_buffered<> >,
81 cds::intrusive::michael_set::make_traits<
82 cds::opt::::hash< foo_hash >
86 // Declares hash set for 1000000 items with load factor 2
87 rcu_michael_set theSet( 1000000, 2 );
89 // Now you can use theSet object in many threads without any synchronization.
95 #ifdef CDS_DOXYGEN_INVOKED
96 class Traits = michael_set::traits
101 class MichaelHashSet< cds::urcu::gc< RCU >, OrderedList, Traits >
104 typedef cds::urcu::gc< RCU > gc; ///< RCU schema
105 typedef OrderedList ordered_list; ///< type of ordered list used as a bucket implementation
106 typedef Traits traits; ///< Set traits
108 typedef typename ordered_list::value_type value_type; ///< type of value stored in the list
109 typedef typename ordered_list::key_comparator key_comparator; ///< key comparing functor
110 typedef typename ordered_list::disposer disposer; ///< Node disposer functor
111 #ifdef CDS_DOXYGEN_INVOKED
112 typedef typename ordered_list::stat stat; ///< Internal statistics
115 /// Hash functor for \ref value_type and all its derivatives that you use
116 typedef typename cds::opt::v::hash_selector< typename traits::hash >::type hash;
117 typedef typename traits::item_counter item_counter; ///< Item counter type
118 typedef typename traits::allocator allocator; ///< Bucket table allocator
120 typedef typename ordered_list::rcu_lock rcu_lock; ///< RCU scoped lock
121 /// Group of \p extract_xxx functions require external locking if underlying ordered list requires that
122 static CDS_CONSTEXPR const bool c_bExtractLockExternal = ordered_list::c_bExtractLockExternal;
124 // GC and OrderedList::gc must be the same
125 static_assert(std::is_same<gc, typename ordered_list::gc>::value, "GC and OrderedList::gc must be the same");
129 typedef typename ordered_list::template select_stat_wrapper< typename ordered_list::stat > bucket_stat;
131 typedef typename ordered_list::template rebind_traits<
132 cds::opt::item_counter< cds::atomicity::empty_item_counter >
133 , cds::opt::stat< typename bucket_stat::wrapped_stat >
134 >::type internal_bucket_type;
136 typedef typename allocator::template rebind< internal_bucket_type >::other bucket_table_allocator;
140 typedef typename internal_bucket_type::exempt_ptr exempt_ptr; ///< pointer to extracted node
141 typedef typename internal_bucket_type::raw_ptr raw_ptr; ///< Return type of \p get() member function and its derivatives
144 typedef typename bucket_stat::stat stat;
149 hash m_HashFunctor; ///< Hash functor
150 size_t const m_nHashBitmask;
151 internal_bucket_type* m_Buckets; ///< bucket table
152 item_counter m_ItemCounter; ///< Item counter
153 stat m_Stat; ///< Internal statistics
157 ///@name Forward iterators (thread-safe under RCU lock)
161 The forward iterator for Michael's set is based on \p OrderedList forward iterator and has some features:
162 - it has no post-increment operator
163 - it iterates items in unordered fashion
165 You may safely use iterators in multi-threaded environment only under RCU lock.
166 Otherwise, a crash is possible if another thread deletes the element the iterator points to.
168 The iterator interface:
172 // Default constructor
176 iterator( iterator const& src );
178 // Dereference operator
179 value_type * operator ->() const;
181 // Dereference operator
182 value_type& operator *() const;
184 // Preincrement operator
185 iterator& operator ++();
187 // Assignment operator
188 iterator& operator = (iterator const& src);
190 // Equality operators
191 bool operator ==(iterator const& i ) const;
192 bool operator !=(iterator const& i ) const;
196 typedef michael_set::details::iterator< internal_bucket_type, false > iterator;
198 /// Const forward iterator
200 For iterator's features and requirements see \ref iterator
202 typedef michael_set::details::iterator< internal_bucket_type, true > const_iterator;
204 /// Returns a forward iterator addressing the first element in a set
206 For empty set \code begin() == end() \endcode
210 return iterator( m_Buckets[0].begin(), m_Buckets, m_Buckets + bucket_count());
213 /// Returns an iterator that addresses the location succeeding the last element in a set
215 Do not use the value returned by <tt>end</tt> function to access any item.
216 The returned value can be used only to control reaching the end of the set.
217 For empty set \code begin() == end() \endcode
221 return iterator( m_Buckets[bucket_count() - 1].end(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count());
224 /// Returns a forward const iterator addressing the first element in a set
225 const_iterator begin() const
230 /// Returns a forward const iterator addressing the first element in a set
231 const_iterator cbegin() const
233 return const_iterator( m_Buckets[0].cbegin(), m_Buckets, m_Buckets + bucket_count());
236 /// Returns an const iterator that addresses the location succeeding the last element in a set
237 const_iterator end() const
242 /// Returns an const iterator that addresses the location succeeding the last element in a set
243 const_iterator cend() const
245 return const_iterator( m_Buckets[bucket_count() - 1].cend(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count());
250 /// Initialize hash set
252 The Michael's hash set is an unbounded container, but its hash table is non-expandable.
253 At construction time you should pass estimated maximum item count and a load factor.
254 The load factor is average size of one bucket - a small number between 1 and 10.
255 The bucket is an ordered single-linked list, the complexity of searching in the bucket is linear <tt>O(nLoadFactor)</tt>.
256 The constructor defines hash table size as rounding <tt>nMaxItemCount / nLoadFactor</tt> up to nearest power of two.
259 size_t nMaxItemCount, ///< estimation of max item count in the hash set
260 size_t nLoadFactor ///< load factor: average size of the bucket
261 ) : m_nHashBitmask( michael_set::details::init_hash_bitmask( nMaxItemCount, nLoadFactor ))
262 , m_Buckets( bucket_table_allocator().allocate( bucket_count()))
264 for ( auto it = m_Buckets, itEnd = m_Buckets + bucket_count(); it != itEnd; ++it )
265 construct_bucket<bucket_stat>( it );
268 /// Clear hash set and destroy it
273 for ( auto it = m_Buckets, itEnd = m_Buckets + bucket_count(); it != itEnd; ++it )
274 it->~internal_bucket_type();
275 bucket_table_allocator().deallocate( m_Buckets, bucket_count());
280 The function inserts \p val in the set if it does not contain
281 an item with key equal to \p val.
283 Returns \p true if \p val is placed into the set, \p false otherwise.
285 bool insert( value_type& val )
287 bool bRet = bucket( val ).insert( val );
295 This function is intended for derived non-intrusive containers.
297 The function allows to split creating of new item into two part:
298 - create item with key only
299 - insert new item into the set
300 - if inserting is success, calls \p f functor to initialize value-field of \p val.
302 The functor signature is:
304 void func( value_type& val );
306 where \p val is the item inserted.
307 The user-defined functor is called only if the inserting is success.
309 @warning For \ref cds_intrusive_MichaelList_rcu "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
310 \ref cds_intrusive_LazyList_rcu "LazyList" provides exclusive access to inserted item and does not require any node-level
313 template <typename Func>
314 bool insert( value_type& val, Func f )
316 bool bRet = bucket( val ).insert( val, f );
322 /// Updates the element
324 The operation performs inserting or changing data with lock-free manner.
326 If the item \p val not found in the set, then \p val is inserted iff \p bAllowInsert is \p true.
327 Otherwise, the functor \p func is called with item found.
328 The functor signature is:
331 void operator()( bool bNew, value_type& item, value_type& val );
335 - \p bNew - \p true if the item has been inserted, \p false otherwise
336 - \p item - item of the set
337 - \p val - argument \p val passed into the \p %update() function
338 If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
339 refers to the same thing.
341 The functor may change non-key fields of the \p item.
343 Returns <tt> std::pair<bool, bool> </tt> where \p first is \p true if operation is successful,
344 \p second is \p true if new item has been added or \p false if the item with \p key
345 already is in the set.
347 @warning For \ref cds_intrusive_MichaelList_hp "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
348 \ref cds_intrusive_LazyList_hp "LazyList" provides exclusive access to inserted item and does not require any node-level
351 template <typename Func>
352 std::pair<bool, bool> update( value_type& val, Func func, bool bAllowInsert = true )
354 std::pair<bool, bool> bRet = bucket( val ).update( val, func, bAllowInsert );
360 template <typename Func>
361 CDS_DEPRECATED("ensure() is deprecated, use update()")
362 std::pair<bool, bool> ensure( value_type& val, Func func )
364 return update( val, func, true );
368 /// Unlinks the item \p val from the set
370 The function searches the item \p val in the set and unlink it from the set
371 if it is found and is equal to \p val.
373 The function returns \p true if success and \p false otherwise.
375 bool unlink( value_type& val )
377 bool bRet = bucket( val ).unlink( val );
383 /// Deletes the item from the set
384 /** \anchor cds_intrusive_MichaelHashSet_rcu_erase
385 The function searches an item with key equal to \p key in the set,
386 unlinks it from the set, and returns \p true.
387 If the item with key equal to \p key is not found the function return \p false.
389 Note the hash functor should accept a parameter of type \p Q that may be not the same as \p value_type.
391 template <typename Q>
392 bool erase( Q const& key )
394 if ( bucket( key ).erase( key )) {
401 /// Deletes the item from the set using \p pred predicate for searching
403 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_erase "erase(Q const&)"
404 but \p pred is used for key comparing.
405 \p Less functor has the interface like \p std::less.
406 \p pred must imply the same element order as the comparator used for building the set.
408 template <typename Q, typename Less>
409 bool erase_with( Q const& key, Less pred )
411 if ( bucket( key ).erase_with( key, pred )) {
418 /// Deletes the item from the set
419 /** \anchor cds_intrusive_MichaelHashSet_rcu_erase_func
420 The function searches an item with key equal to \p key in the set,
421 call \p f functor with item found, and unlinks it from the set.
422 The \ref disposer specified in \p OrderedList class template parameter is called
423 by garbage collector \p GC asynchronously.
425 The \p Func interface is
428 void operator()( value_type const& item );
432 If the item with key equal to \p key is not found the function return \p false.
434 Note the hash functor should accept a parameter of type \p Q that can be not the same as \p value_type.
436 template <typename Q, typename Func>
437 bool erase( const Q& key, Func f )
439 if ( bucket( key ).erase( key, f )) {
446 /// Deletes the item from the set using \p pred predicate for searching
448 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_erase_func "erase(Q const&)"
449 but \p pred is used for key comparing.
450 \p Less functor has the interface like \p std::less.
451 \p pred must imply the same element order as the comparator used for building the set.
453 template <typename Q, typename Less, typename Func>
454 bool erase_with( const Q& key, Less pred, Func f )
456 if ( bucket( key ).erase_with( key, pred, f )) {
463 /// Extracts an item from the set
464 /** \anchor cds_intrusive_MichaelHashSet_rcu_extract
465 The function searches an item with key equal to \p key in the set,
466 unlinks it from the set, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item found.
467 If the item with the key equal to \p key is not found the function returns an empty \p exempt_ptr.
469 Depends on \p ordered_list you should or should not lock RCU before calling of this function:
470 - for the set based on \ref cds_intrusive_MichaelList_rcu "MichaelList" RCU should not be locked
471 - for the set based on \ref cds_intrusive_LazyList_rcu "LazyList" RCU should be locked
473 See ordered list implementation for details.
476 #include <cds/urcu/general_buffered.h>
477 #include <cds/intrusive/michael_list_rcu.h>
478 #include <cds/intrusive/michael_set_rcu.h>
480 typedef cds::urcu::gc< general_buffered<> > rcu;
481 typedef cds::intrusive::MichaelList< rcu, Foo > rcu_michael_list;
482 typedef cds::intrusive::MichaelHashSet< rcu, rcu_michael_list, foo_traits > rcu_michael_set;
484 rcu_michael_set theSet;
487 typename rcu_michael_set::exempt_ptr p;
489 // For MichaelList we should not lock RCU
491 // Now, you can apply extract function
492 // Note that you must not delete the item found inside the RCU lock
493 p = theSet.extract( 10 )
495 // do something with p
499 // We may safely release p here
500 // release() passes the pointer to RCU reclamation cycle:
501 // it invokes RCU retire_ptr function with the disposer you provided for rcu_michael_list.
505 template <typename Q>
506 exempt_ptr extract( Q const& key )
508 exempt_ptr p( bucket( key ).extract( key ));
514 /// Extracts an item from the set using \p pred predicate for searching
516 The function is an analog of \p extract(Q const&) but \p pred is used for key comparing.
517 \p Less functor has the interface like \p std::less.
518 \p pred must imply the same element order as the comparator used for building the set.
520 template <typename Q, typename Less>
521 exempt_ptr extract_with( Q const& key, Less pred )
523 exempt_ptr p( bucket( key ).extract_with( key, pred ));
529 /// Checks whether the set contains \p key
532 The function searches the item with key equal to \p key
533 and returns \p true if the key is found, and \p false otherwise.
535 Note the hash functor specified for class \p Traits template parameter
536 should accept a parameter of type \p Q that can be not the same as \p value_type.
538 template <typename Q>
539 bool contains( Q const& key )
541 return bucket( key ).contains( key );
544 template <typename Q>
545 CDS_DEPRECATED("use contains()")
546 bool find( Q const& key )
548 return contains( key );
552 /// Checks whether the set contains \p key using \p pred predicate for searching
554 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
555 \p Less functor has the interface like \p std::less.
556 \p Less must imply the same element order as the comparator used for building the set.
558 template <typename Q, typename Less>
559 bool contains( Q const& key, Less pred )
561 return bucket( key ).contains( key, pred );
564 template <typename Q, typename Less>
565 CDS_DEPRECATED("use contains()")
566 bool find_with( Q const& key, Less pred )
568 return contains( key, pred );
572 /// Find the key \p key
573 /** \anchor cds_intrusive_MichaelHashSet_rcu_find_func
574 The function searches the item with key equal to \p key and calls the functor \p f for item found.
575 The interface of \p Func functor is:
578 void operator()( value_type& item, Q& key );
581 where \p item is the item found, \p key is the <tt>find</tt> function argument.
583 The functor can change non-key fields of \p item.
584 The functor does not serialize simultaneous access to the set \p item. If such access is
585 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
587 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
588 can modify both arguments.
590 Note the hash functor specified for class \p Traits template parameter
591 should accept a parameter of type \p Q that can be not the same as \p value_type.
593 The function returns \p true if \p key is found, \p false otherwise.
595 template <typename Q, typename Func>
596 bool find( Q& key, Func f )
598 return bucket( key ).find( key, f );
601 template <typename Q, typename Func>
602 bool find( Q const& key, Func f )
604 return bucket( key ).find( key, f );
608 /// Finds the key \p key using \p pred predicate for searching
610 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_find_func "find(Q&, Func)"
611 but \p pred is used for key comparing.
612 \p Less functor has the interface like \p std::less.
613 \p pred must imply the same element order as the comparator used for building the set.
615 template <typename Q, typename Less, typename Func>
616 bool find_with( Q& key, Less pred, Func f )
618 return bucket( key ).find_with( key, pred, f );
621 template <typename Q, typename Less, typename Func>
622 bool find_with( Q const& key, Less pred, Func f )
624 return bucket( key ).find_with( key, pred, f );
628 /// Finds the key \p key and return the item found
629 /** \anchor cds_intrusive_MichaelHashSet_rcu_get
630 The function searches the item with key equal to \p key and returns the pointer to item found.
631 If \p key is not found it returns \p nullptr.
632 Note the type of returned value depends on underlying \p ordered_list.
633 For details, see documentation of ordered list you use.
635 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
637 RCU should be locked before call of this function.
638 Returned item is valid only while RCU is locked:
640 typedef cds::intrusive::MichaelHashSet< your_template_parameters > hash_set;
643 // Result of get() call
644 typename hash_set::raw_ptr ptr;
647 hash_set::rcu_lock lock;
649 ptr = theSet.get( 5 );
654 // Unlock RCU by rcu_lock destructor
655 // ptr can be reclaimed by disposer at any time after RCU has been unlocked
659 template <typename Q>
660 raw_ptr get( Q const& key )
662 return bucket( key ).get( key );
665 /// Finds the key \p key and return the item found
667 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_get "get(Q const&)"
668 but \p pred is used for comparing the keys.
670 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
672 \p pred must imply the same element order as the comparator used for building the set.
674 template <typename Q, typename Less>
675 raw_ptr get_with( Q const& key, Less pred )
677 return bucket( key ).get_with( key, pred );
680 /// Clears the set (non-atomic)
682 The function unlink all items from the set.
683 The function is not atomic. It cleans up each bucket and then resets the item counter to zero.
684 If there are a thread that performs insertion while \p clear is working the result is undefined in general case:
685 <tt> empty() </tt> may return \p true but the set may contain item(s).
686 Therefore, \p clear may be used only for debugging purposes.
688 For each item the \p disposer is called after unlinking.
692 for ( size_t i = 0; i < bucket_count(); ++i )
693 m_Buckets[i].clear();
694 m_ItemCounter.reset();
698 /// Checks if the set is empty
700 @warning If you use \p atomicity::empty_item_counter in \p traits::item_counter,
701 the function always returns \p true.
708 /// Returns item count in the set
710 If you use \p atomicity::empty_item_counter in \p traits::item_counter,
711 the function always returns 0.
715 return m_ItemCounter;
718 /// Returns the size of hash table
720 Since %MichaelHashSet cannot dynamically extend the hash table size,
721 the value returned is an constant depending on object initialization parameters;
722 see \ref cds_intrusive_MichaelHashSet_hp "MichaelHashSet" for explanation.
724 size_t bucket_count() const
726 return m_nHashBitmask + 1;
729 /// Returns const reference to internal statistics
730 stat const& statistics() const
737 template <typename Stat>
738 typename std::enable_if< Stat::empty >::type construct_bucket( internal_bucket_type * bkt )
740 new (bkt) internal_bucket_type;
743 template <typename Stat>
744 typename std::enable_if< !Stat::empty >::type construct_bucket( internal_bucket_type * bkt )
746 new (bkt) internal_bucket_type( m_Stat );
749 /// Calculates hash value of \p key
750 template <typename Q>
751 size_t hash_value( Q const& key ) const
753 return m_HashFunctor( key ) & m_nHashBitmask;
756 /// Returns the bucket (ordered list) for \p key
757 template <typename Q>
758 internal_bucket_type& bucket( Q const& key )
760 return m_Buckets[hash_value( key )];
762 template <typename Q>
763 internal_bucket_type const& bucket( Q const& key ) const
765 return m_Buckets[hash_value( key )];
770 }} // namespace cds::intrusive
772 #endif // #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_NOGC_H