2 This file is a part of libcds - Concurrent Data Structures library
4 (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2016
6 Source code repo: http://github.com/khizmax/libcds/
7 Download: http://sourceforge.net/projects/libcds/files/
9 Redistribution and use in source and binary forms, with or without
10 modification, are permitted provided that the following conditions are met:
12 * Redistributions of source code must retain the above copyright notice, this
13 list of conditions and the following disclaimer.
15 * Redistributions in binary form must reproduce the above copyright notice,
16 this list of conditions and the following disclaimer in the documentation
17 and/or other materials provided with the distribution.
19 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
20 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
22 DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
23 FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
25 SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
26 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
27 OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31 #ifndef CDSLIB_CONTAINER_MICHAEL_SET_RCU_H
32 #define CDSLIB_CONTAINER_MICHAEL_SET_RCU_H
34 #include <cds/container/details/michael_set_base.h>
35 #include <cds/details/allocator.h>
37 namespace cds { namespace container {
39 /// Michael's hash set (template specialization for \ref cds_urcu_desc "RCU")
40 /** @ingroup cds_nonintrusive_set
41 \anchor cds_nonintrusive_MichaelHashSet_rcu
44 - [2002] Maged Michael "High performance dynamic lock-free hash tables and list-based sets"
46 Michael's hash table algorithm is based on lock-free ordered list and it is very simple.
47 The main structure is an array \p T of size \p M. Each element in \p T is basically a pointer
48 to a hash bucket, implemented as a singly linked list. The array of buckets cannot be dynamically expanded.
49 However, each bucket may contain unbounded number of items.
51 Template parameters are:
52 - \p RCU - one of \ref cds_urcu_gc "RCU type"
53 - \p OrderedList - ordered list implementation used as the bucket for hash set, for example,
54 \ref cds_nonintrusive_MichaelList_rcu "MichaelList".
55 The ordered list implementation specifies the type \p T stored in the hash-set,
56 the comparison functor for the type \p T and other features specific for
58 - \p Traits - set traits, default is michael_set::traits.
59 Instead of defining \p Traits struct you may use option-based syntax with michael_set::make_traits metafunction.
61 About hash functor see \ref cds_nonintrusive_MichaelHashSet_hash_functor "MichaelSet hash functor".
65 Suppose, we have the following type \p Foo that we want to store in your \p %MichaelHashSet:
68 int nKey ; // key field
69 int nVal ; // value field
73 To use \p %MichaelHashSet for \p Foo values, you should first choose suitable ordered list class
74 that will be used as a bucket for the set. We will cds::urcu::general_buffered<> RCU type and
75 MichaelList as a bucket type.
76 You should include RCU-related header file (<tt>cds/urcu/general_buffered.h</tt> in this example)
77 before including <tt>cds/container/michael_set_rcu.h</tt>.
78 Also, for ordered list we should develop a comparator for our \p Foo struct.
80 #include <cds/urcu/general_buffered.h>
81 #include <cds/container/michael_list_rcu.h>
82 #include <cds/container/michael_set_rcu.h>
84 namespace cc = cds::container;
88 int operator ()(Foo const& v1, Foo const& v2 ) const
90 if ( std::less( v1.nKey, v2.nKey ))
92 return std::less(v2.nKey, v1.nKey) ? 1 : 0;
97 typedef cc::MichaelList< cds::urcu::gc< cds::urcu::general_buffered<> >, Foo,
98 typename cc::michael_list::make_traits<
99 cc::opt::compare< Foo_cmp > // item comparator option
103 // Hash functor for Foo
105 size_t operator ()( int i ) const
107 return std::hash( i );
109 size_t operator()( Foo const& i ) const
111 return std::hash( i.nKey );
116 // Note that \p RCU template parameter of ordered list must be equal \p RCU for the set.
117 typedef cc::MichaelHashSet< cds::urcu::gc< cds::urcu::general_buffered<> >, bucket_list,
118 cc::michael_set::make_traits<
119 cc::opt::hash< foo_hash >
129 #ifdef CDS_DOXYGEN_INVOKED
130 class Traits = michael_set::traits
135 class MichaelHashSet< cds::urcu::gc< RCU >, OrderedList, Traits >
138 typedef cds::urcu::gc< RCU > gc; ///< RCU used as garbage collector
139 typedef OrderedList bucket_type; ///< type of ordered list to be used as a bucket implementation
140 typedef Traits traits; ///< Set traits
142 typedef typename bucket_type::value_type value_type; ///< type of value to be stored in the list
143 typedef typename bucket_type::key_comparator key_comparator; ///< key comparing functor
145 /// Hash functor for \ref value_type and all its derivatives that you use
146 typedef typename cds::opt::v::hash_selector< typename traits::hash >::type hash;
147 typedef typename traits::item_counter item_counter; ///< Item counter type
149 /// Bucket table allocator
150 typedef cds::details::Allocator< bucket_type, typename traits::allocator > bucket_table_allocator;
152 typedef typename bucket_type::rcu_lock rcu_lock; ///< RCU scoped lock
153 typedef typename bucket_type::exempt_ptr exempt_ptr; ///< pointer to extracted node
154 typedef typename bucket_type::raw_ptr raw_ptr; ///< Return type of \p get() member function and its derivatives
155 /// Group of \p extract_xxx functions require external locking if underlying ordered list requires that
156 static CDS_CONSTEXPR const bool c_bExtractLockExternal = bucket_type::c_bExtractLockExternal;
159 item_counter m_ItemCounter; ///< Item counter
160 hash m_HashFunctor; ///< Hash functor
161 bucket_type * m_Buckets; ///< bucket table
165 const size_t m_nHashBitmask;
170 /// Calculates hash value of \p key
171 template <typename Q>
172 size_t hash_value( Q const& key ) const
174 return m_HashFunctor( key ) & m_nHashBitmask;
177 /// Returns the bucket (ordered list) for \p key
178 template <typename Q>
179 bucket_type& bucket( Q const& key )
181 return m_Buckets[ hash_value( key ) ];
183 template <typename Q>
184 bucket_type const& bucket( Q const& key ) const
186 return m_Buckets[ hash_value( key ) ];
190 ///@name Forward iterators (thread-safe under RCU lock)
194 The forward iterator for Michael's set is based on \p OrderedList forward iterator and has some features:
195 - it has no post-increment operator
196 - it iterates items in unordered fashion
198 You may safely use iterators in multi-threaded environment only under RCU lock.
199 Otherwise, a crash is possible if another thread deletes the element the iterator points to.
201 The iterator interface:
205 // Default constructor
209 iterator( iterator const& src );
211 // Dereference operator
212 value_type * operator ->() const;
214 // Dereference operator
215 value_type& operator *() const;
217 // Preincrement operator
218 iterator& operator ++();
220 // Assignment operator
221 iterator& operator = (iterator const& src);
223 // Equality operators
224 bool operator ==(iterator const& i ) const;
225 bool operator !=(iterator const& i ) const;
229 typedef michael_set::details::iterator< bucket_type, false > iterator;
231 /// Const forward iterator
232 typedef michael_set::details::iterator< bucket_type, true > const_iterator;
234 /// Returns a forward iterator addressing the first element in a set
236 For empty set \code begin() == end() \endcode
240 return iterator( m_Buckets[0].begin(), m_Buckets, m_Buckets + bucket_count() );
243 /// Returns an iterator that addresses the location succeeding the last element in a set
245 Do not use the value returned by <tt>end</tt> function to access any item.
246 The returned value can be used only to control reaching the end of the set.
247 For empty set \code begin() == end() \endcode
251 return iterator( m_Buckets[bucket_count() - 1].end(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
254 /// Returns a forward const iterator addressing the first element in a set
255 const_iterator begin() const
257 return get_const_begin();
260 /// Returns a forward const iterator addressing the first element in a set
261 const_iterator cbegin() const
263 return get_const_begin();
266 /// Returns an const iterator that addresses the location succeeding the last element in a set
267 const_iterator end() const
269 return get_const_end();
272 /// Returns an const iterator that addresses the location succeeding the last element in a set
273 const_iterator cend() const
275 return get_const_end();
281 const_iterator get_const_begin() const
283 return const_iterator( const_cast<bucket_type const&>(m_Buckets[0]).begin(), m_Buckets, m_Buckets + bucket_count() );
285 const_iterator get_const_end() const
287 return const_iterator( const_cast<bucket_type const&>(m_Buckets[bucket_count() - 1]).end(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
292 /// Initialize hash set
294 The Michael's hash set is non-expandable container. You should point the average count of items \p nMaxItemCount
295 when you create an object.
296 \p nLoadFactor parameter defines average count of items per bucket and it should be small number between 1 and 10.
297 Remember, since the bucket implementation is an ordered list, searching in the bucket is linear [<tt>O(nLoadFactor)</tt>].
299 The ctor defines hash table size as rounding <tt>nMaxItemCount / nLoadFactor</tt> up to nearest power of two.
302 size_t nMaxItemCount, ///< estimation of max item count in the hash set
303 size_t nLoadFactor ///< load factor: estimation of max number of items in the bucket
304 ) : m_nHashBitmask( michael_set::details::init_hash_bitmask( nMaxItemCount, nLoadFactor ))
306 // GC and OrderedList::gc must be the same
307 static_assert( std::is_same<gc, typename bucket_type::gc>::value, "GC and OrderedList::gc must be the same");
309 // atomicity::empty_item_counter is not allowed as a item counter
310 static_assert( !std::is_same<item_counter, atomicity::empty_item_counter>::value,
311 "atomicity::empty_item_counter is not allowed as a item counter");
313 m_Buckets = bucket_table_allocator().NewArray( bucket_count() );
316 /// Clears hash set and destroys it
320 bucket_table_allocator().Delete( m_Buckets, bucket_count() );
325 The function creates a node with copy of \p val value
326 and then inserts the node created into the set.
328 The type \p Q should contain as minimum the complete key for the node.
329 The object of \ref value_type should be constructible from a value of type \p Q.
330 In trivial case, \p Q is equal to \ref value_type.
332 The function applies RCU lock internally.
334 Returns \p true if \p val is inserted into the set, \p false otherwise.
336 template <typename Q>
337 bool insert( Q const& val )
339 const bool bRet = bucket( val ).insert( val );
347 The function allows to split creating of new item into two part:
348 - create item with key only
349 - insert new item into the set
350 - if inserting is success, calls \p f functor to initialize value-fields of \p val.
352 The functor signature is:
354 void func( value_type& val );
356 where \p val is the item inserted.
357 The user-defined functor is called only if the inserting is success.
359 The function applies RCU lock internally.
361 @warning For \ref cds_nonintrusive_MichaelList_rcu "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
362 \ref cds_nonintrusive_LazyList_rcu "LazyList" provides exclusive access to inserted item and does not require any node-level
365 template <typename Q, typename Func>
366 bool insert( Q const& val, Func f )
368 const bool bRet = bucket( val ).insert( val, f );
374 /// Ensures that the item exists in the set
376 The operation performs inserting or changing data with lock-free manner.
378 If the \p val key not found in the set, then the new item created from \p val
379 is inserted into the set. Otherwise, the functor \p func is called with the item found.
380 The functor \p Func signature is:
383 void operator()( bool bNew, value_type& item, const Q& val );
388 - \p bNew - \p true if the item has been inserted, \p false otherwise
389 - \p item - item of the set
390 - \p val - argument \p key passed into the \p ensure function
392 The functor may change non-key fields of the \p item.
394 The function applies RCU lock internally.
396 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
397 \p second is true if new item has been added or \p false if the item with \p key
398 already is in the set.
400 @warning For \ref cds_nonintrusive_MichaelList_rcu "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
401 \ref cds_nonintrusive_LazyList_rcu "LazyList" provides exclusive access to inserted item and does not require any node-level
404 /// Updates the element
406 The operation performs inserting or changing data with lock-free manner.
408 If the item \p val not found in the set, then \p val is inserted iff \p bAllowInsert is \p true.
409 Otherwise, the functor \p func is called with item found.
410 The functor signature is:
413 void operator()( bool bNew, value_type& item, Q const& val );
417 - \p bNew - \p true if the item has been inserted, \p false otherwise
418 - \p item - item of the set
419 - \p val - argument \p val passed into the \p %update() function
421 The functor may change non-key fields of the \p item.
423 The function applies RCU lock internally.
425 Returns <tt> std::pair<bool, bool> </tt> where \p first is \p true if operation is successfull,
426 \p second is \p true if new item has been added or \p false if the item with \p key
427 already is in the set.
429 @warning For \ref cds_intrusive_MichaelList_hp "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
430 \ref cds_intrusive_LazyList_hp "LazyList" provides exclusive access to inserted item and does not require any node-level
433 template <typename Q, typename Func>
434 std::pair<bool, bool> update( const Q& val, Func func, bool bAllowInsert = true )
436 std::pair<bool, bool> bRet = bucket( val ).update( val, func, bAllowInsert );
441 template <typename Q, typename Func>
442 CDS_DEPRECATED("ensure() is deprecated, use update()")
443 std::pair<bool, bool> ensure( const Q& val, Func func )
445 return update( val, func, true );
449 /// Inserts data of type \p value_type created from \p args
451 Returns \p true if inserting successful, \p false otherwise.
453 The function applies RCU lock internally.
455 template <typename... Args>
456 bool emplace( Args&&... args )
458 bool bRet = bucket( value_type(std::forward<Args>(args)...) ).emplace( std::forward<Args>(args)... );
464 /// Deletes \p key from the set
465 /** \anchor cds_nonintrusive_MichealSet_rcu_erase_val
467 Since the key of MichaelHashSet's item type \p value_type is not explicitly specified,
468 template parameter \p Q defines the key type searching in the list.
469 The set item comparator should be able to compare the type \p value_type
472 RCU \p synchronize method can be called. RCU should not be locked.
474 Return \p true if key is found and deleted, \p false otherwise
476 template <typename Q>
477 bool erase( Q const& key )
479 const bool bRet = bucket( key ).erase( key );
485 /// Deletes the item from the set using \p pred predicate for searching
487 The function is an analog of \ref cds_nonintrusive_MichealSet_rcu_erase_val "erase(Q const&)"
488 but \p pred is used for key comparing.
489 \p Less functor has the interface like \p std::less.
490 \p Less must imply the same element order as the comparator used for building the set.
492 template <typename Q, typename Less>
493 bool erase_with( Q const& key, Less pred )
495 const bool bRet = bucket( key ).erase_with( key, pred );
501 /// Deletes \p key from the set
502 /** \anchor cds_nonintrusive_MichealSet_rcu_erase_func
504 The function searches an item with key \p key, calls \p f functor
505 and deletes the item. If \p key is not found, the functor is not called.
507 The functor \p Func interface:
510 void operator()(value_type const& val);
514 Since the key of %MichaelHashSet's \p value_type is not explicitly specified,
515 template parameter \p Q defines the key type searching in the list.
516 The list item comparator should be able to compare the type \p T of list item
519 RCU \p synchronize method can be called. RCU should not be locked.
521 Return \p true if key is found and deleted, \p false otherwise
523 template <typename Q, typename Func>
524 bool erase( Q const& key, Func f )
526 const bool bRet = bucket( key ).erase( key, f );
532 /// Deletes the item from the set using \p pred predicate for searching
534 The function is an analog of \ref cds_nonintrusive_MichealSet_rcu_erase_func "erase(Q const&, Func)"
535 but \p pred is used for key comparing.
536 \p Less functor has the interface like \p std::less.
537 \p Less must imply the same element order as the comparator used for building the set.
539 template <typename Q, typename Less, typename Func>
540 bool erase_with( Q const& key, Less pred, Func f )
542 const bool bRet = bucket( key ).erase_with( key, pred, f );
548 /// Extracts an item from the set
549 /** \anchor cds_nonintrusive_MichaelHashSet_rcu_extract
550 The function searches an item with key equal to \p key in the set,
551 unlinks it from the set, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item found.
552 If the item with the key equal to \p key is not found the function return an empty \p exempt_ptr.
554 The function just excludes the item from the set and returns a pointer to item found.
555 Depends on \p bucket_type you should or should not lock RCU before calling of this function:
556 - for the set based on \ref cds_nonintrusive_MichaelList_rcu "MichaelList" RCU should not be locked
557 - for the set based on \ref cds_nonintrusive_LazyList_rcu "LazyList" RCU should be locked
558 See ordered list implementation for details.
561 #include <cds/urcu/general_buffered.h>
562 #include <cds/container/michael_list_rcu.h>
563 #include <cds/container/michael_set_rcu.h>
565 typedef cds::urcu::gc< general_buffered<> > rcu;
566 typedef cds::container::MichaelList< rcu, Foo > rcu_michael_list;
567 typedef cds::container::MichaelHashSet< rcu, rcu_michael_list, foo_traits > rcu_michael_set;
569 rcu_michael_set theSet;
572 typename rcu_michael_set::exempt_ptr p;
574 // For MichaelList we should not lock RCU
576 // Note that you must not delete the item found inside the RCU lock
577 p = theSet.extract( 10 );
579 // do something with p
583 // We may safely release p here
584 // release() passes the pointer to RCU reclamation cycle
588 template <typename Q>
589 exempt_ptr extract( Q const& key )
591 exempt_ptr p = bucket( key ).extract( key );
597 /// Extracts an item from the set using \p pred predicate for searching
599 The function is an analog of \p extract(Q const&) but \p pred is used for key comparing.
600 \p Less functor has the interface like \p std::less.
601 \p pred must imply the same element order as the comparator used for building the set.
603 template <typename Q, typename Less>
604 exempt_ptr extract_with( Q const& key, Less pred )
606 exempt_ptr p = bucket( key ).extract_with( key, pred );
612 /// Finds the key \p key
613 /** \anchor cds_nonintrusive_MichealSet_rcu_find_func
615 The function searches the item with key equal to \p key and calls the functor \p f for item found.
616 The interface of \p Func functor is:
619 void operator()( value_type& item, Q& key );
622 where \p item is the item found, \p key is the <tt>find</tt> function argument.
624 The functor may change non-key fields of \p item. Note that the functor is only guarantee
625 that \p item cannot be disposed during functor is executing.
626 The functor does not serialize simultaneous access to the set's \p item. If such access is
627 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
629 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
630 can modify both arguments.
632 Note the hash functor specified for class \p Traits template parameter
633 should accept a parameter of type \p Q that may be not the same as \p value_type.
635 The function applies RCU lock internally.
637 The function returns \p true if \p key is found, \p false otherwise.
639 template <typename Q, typename Func>
640 bool find( Q& key, Func f )
642 return bucket( key ).find( key, f );
645 template <typename Q, typename Func>
646 bool find( Q const& key, Func f )
648 return bucket( key ).find( key, f );
652 /// Finds the key \p key using \p pred predicate for searching
654 The function is an analog of \ref cds_nonintrusive_MichealSet_rcu_find_func "find(Q&, Func)"
655 but \p pred is used for key comparing.
656 \p Less functor has the interface like \p std::less.
657 \p Less must imply the same element order as the comparator used for building the set.
659 template <typename Q, typename Less, typename Func>
660 bool find_with( Q& key, Less pred, Func f )
662 return bucket( key ).find_with( key, pred, f );
665 template <typename Q, typename Less, typename Func>
666 bool find_with( Q const& key, Less pred, Func f )
668 return bucket( key ).find_with( key, pred, f );
672 /// Checks whether the set contains \p key
675 The function searches the item with key equal to \p key
676 and returns \p true if the key is found, and \p false otherwise.
678 Note the hash functor specified for class \p Traits template parameter
679 should accept a parameter of type \p Q that can be not the same as \p value_type.
681 template <typename Q>
682 bool contains( Q const& key )
684 return bucket( key ).contains( key );
687 template <typename Q>
688 CDS_DEPRECATED("use contains()")
689 bool find( Q const& key )
691 return contains( key );
695 /// Checks whether the set contains \p key using \p pred predicate for searching
697 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
698 \p Less functor has the interface like \p std::less.
699 \p Less must imply the same element order as the comparator used for building the set.
701 template <typename Q, typename Less>
702 bool contains( Q const& key, Less pred )
704 return bucket( key ).contains( key, pred );
707 template <typename Q, typename Less>
708 CDS_DEPRECATED("use contains()")
709 bool find_with( Q const& key, Less pred )
711 return contains( key, pred );
715 /// Finds the key \p key and return the item found
716 /** \anchor cds_nonintrusive_MichaelHashSet_rcu_get
717 The function searches the item with key equal to \p key and returns the pointer to item found.
718 If \p key is not found it returns \p nullptr.
719 Note the type of returned value depends on underlying \p bucket_type.
720 For details, see documentation of ordered list you use.
722 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
724 RCU should be locked before call of this function.
725 Returned item is valid only while RCU is locked:
727 typedef cds::container::MichaelHashSet< your_template_parameters > hash_set;
729 typename hash_set::raw_ptr gp;
733 hash_set::rcu_lock lock;
735 gp = theSet.get( 5 );
740 // Unlock RCU by rcu_lock destructor
741 // gp can be reclaimed at any time after RCU has been unlocked
745 template <typename Q>
746 raw_ptr get( Q const& key )
748 return bucket( key ).get( key );
751 /// Finds the key \p key and return the item found
753 The function is an analog of \ref cds_nonintrusive_MichaelHashSet_rcu_get "get(Q const&)"
754 but \p pred is used for comparing the keys.
756 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
758 \p pred must imply the same element order as the comparator used for building the set.
760 template <typename Q, typename Less>
761 raw_ptr get_with( Q const& key, Less pred )
763 return bucket( key ).get_with( key, pred );
766 /// Clears the set (not atomic)
769 for ( size_t i = 0; i < bucket_count(); ++i )
770 m_Buckets[i].clear();
771 m_ItemCounter.reset();
774 /// Checks if the set is empty
776 Emptiness is checked by item counting: if item count is zero then the set is empty.
777 Thus, the correct item counting feature is an important part of Michael's set implementation.
784 /// Returns item count in the set
787 return m_ItemCounter;
790 /// Returns the size of hash table
792 Since \p %MichaelHashSet cannot dynamically extend the hash table size,
793 the value returned is an constant depending on object initialization parameters;
794 see MichaelHashSet::MichaelHashSet for explanation.
796 size_t bucket_count() const
798 return m_nHashBitmask + 1;
802 }} // namespace cds::container
804 #endif // ifndef CDSLIB_CONTAINER_MICHAEL_SET_RCU_H