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/
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31 #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_NOGC_H
32 #define CDSLIB_INTRUSIVE_MICHAEL_SET_NOGC_H
34 #include <cds/intrusive/details/michael_set_base.h>
35 #include <cds/gc/nogc.h>
37 namespace cds { namespace intrusive {
39 /// Michael's hash set (template specialization for gc::nogc)
40 /** @ingroup cds_intrusive_map
41 \anchor cds_intrusive_MichaelHashSet_nogc
43 This specialization is so-called append-only when no item
44 reclamation may be performed. The set does not support deleting of list item.
46 See \ref cds_intrusive_MichaelHashSet_hp "MichaelHashSet" for description of template parameters.
47 The template parameter \p OrderedList should be any \p cds::gc::nogc -derived ordered list, for example,
48 \ref cds_intrusive_MichaelList_nogc "append-only MichaelList".
52 #ifdef CDS_DOXYGEN_INVOKED
53 class Traits = michael_set::traits
58 class MichaelHashSet< cds::gc::nogc, OrderedList, Traits >
61 typedef cds::gc::nogc gc; ///< Garbage collector
62 typedef OrderedList ordered_list; ///< type of ordered list used as a bucket implementation
63 typedef Traits traits; ///< Set traits
65 typedef typename ordered_list::value_type value_type; ///< type of value to be stored in the set
66 typedef typename ordered_list::key_comparator key_comparator; ///< key comparing functor
67 typedef typename ordered_list::disposer disposer; ///< Node disposer functor
68 typedef typename ordered_list::stat stat; ///< Internal statistics
70 /// Hash functor for \p value_type and all its derivatives that you use
71 typedef typename cds::opt::v::hash_selector< typename traits::hash >::type hash;
72 typedef typename traits::item_counter item_counter; ///< Item counter type
73 typedef typename traits::allocator allocator; ///< Bucket table allocator
75 // GC and OrderedList::gc must be the same
76 static_assert(std::is_same<gc, typename ordered_list::gc>::value, "GC and OrderedList::gc must be the same");
78 // atomicity::empty_item_counter is not allowed as a item counter
79 static_assert(!std::is_same<item_counter, atomicity::empty_item_counter>::value,
80 "atomicity::empty_item_counter is not allowed as a item counter");
84 typedef typename ordered_list::template select_stat_wrapper< typename ordered_list::stat > bucket_stat;
86 typedef typename ordered_list::template rebind_traits<
87 cds::opt::item_counter< cds::atomicity::empty_item_counter >
88 , cds::opt::stat< typename bucket_stat::wrapped_stat >
89 >::type internal_bucket_type;
91 typedef typename allocator::template rebind< internal_bucket_type >::other bucket_table_allocator;
93 hash m_HashFunctor; ///< Hash functor
94 const size_t m_nHashBitmask;
95 internal_bucket_type * m_Buckets; ///< bucket table
96 item_counter m_ItemCounter; ///< Item counter
97 typename bucket_stat::stat m_Stat; ///< Internal statistics
102 /// Calculates hash value of \p key
103 template <typename Q>
104 size_t hash_value( Q const & key ) const
106 return m_HashFunctor( key ) & m_nHashBitmask;
109 /// Returns the bucket (ordered list) for \p key
110 template <typename Q>
111 internal_bucket_type& bucket( Q const & key )
113 return m_Buckets[ hash_value( key ) ];
118 ///@name Forward iterators
122 The forward iterator for Michael's set is based on \p OrderedList forward iterator and has some features:
123 - it has no post-increment operator
124 - it iterates items in unordered fashion
126 The iterator interface:
130 // Default constructor
134 iterator( iterator const& src );
136 // Dereference operator
137 value_type * operator ->() const;
139 // Dereference operator
140 value_type& operator *() const;
142 // Preincrement operator
143 iterator& operator ++();
145 // Assignment operator
146 iterator& operator = (iterator const& src);
148 // Equality operators
149 bool operator ==(iterator const& i ) const;
150 bool operator !=(iterator const& i ) const;
154 typedef michael_set::details::iterator< internal_bucket_type, false > iterator;
156 /// Const forward iterator
158 For iterator's features and requirements see \ref iterator
160 typedef michael_set::details::iterator< internal_bucket_type, true > const_iterator;
162 /// Returns a forward iterator addressing the first element in a set
164 For empty set \code begin() == end() \endcode
168 return iterator( m_Buckets[0].begin(), m_Buckets, m_Buckets + bucket_count() );
171 /// Returns an iterator that addresses the location succeeding the last element in a set
173 Do not use the value returned by <tt>end</tt> function to access any item.
174 The returned value can be used only to control reaching the end of the set.
175 For empty set \code begin() == end() \endcode
179 return iterator( m_Buckets[bucket_count() - 1].end(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
182 /// Returns a forward const iterator addressing the first element in a set
183 const_iterator begin() const
187 /// Returns a forward const iterator addressing the first element in a set
188 const_iterator cbegin() const
190 return const_iterator( m_Buckets[0].cbegin(), m_Buckets, m_Buckets + bucket_count() );
193 /// Returns an const iterator that addresses the location succeeding the last element in a set
194 const_iterator end() const
198 /// Returns an const iterator that addresses the location succeeding the last element in a set
199 const_iterator cend() const
201 return const_iterator( m_Buckets[bucket_count() - 1].cend(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
206 /// Initializes hash set
208 The Michael's hash set is an unbounded container, but its hash table is non-expandable.
209 At construction time you should pass estimated maximum item count and a load factor.
210 The load factor is average size of one bucket - a small number between 1 and 10.
211 The bucket is an ordered single-linked list, searching in the bucket has linear complexity <tt>O(nLoadFactor)</tt>.
212 The constructor defines hash table size as rounding <tt>nMaxItemCount / nLoadFactor</tt> up to nearest power of two.
215 size_t nMaxItemCount, ///< estimation of max item count in the hash set
216 size_t nLoadFactor ///< load factor: estimation of max number of items in the bucket
217 ) : m_nHashBitmask( michael_set::details::init_hash_bitmask( nMaxItemCount, nLoadFactor ))
218 , m_Buckets( bucket_table_allocator().allocate( bucket_count() ) )
220 for ( auto it = m_Buckets, itEnd = m_Buckets + bucket_count(); it != itEnd; ++it )
221 construct_bucket<bucket_stat>( it );
224 /// Clears hash set object and destroys it
229 for ( auto it = m_Buckets, itEnd = m_Buckets + bucket_count(); it != itEnd; ++it )
230 it->~internal_bucket_type();
231 bucket_table_allocator().deallocate( m_Buckets, bucket_count() );
236 The function inserts \p val in the set if it does not contain
237 an item with key equal to \p val.
239 Returns \p true if \p val is placed into the set, \p false otherwise.
241 bool insert( value_type& val )
243 bool bRet = bucket( val ).insert( val );
249 /// Updates the element
251 The operation performs inserting or changing data with lock-free manner.
253 If the item \p val not found in the set, then \p val is inserted iff \p bAllowInsert is \p true.
254 Otherwise, the functor \p func is called with item found.
255 The functor signature is:
258 void operator()( bool bNew, value_type& item, value_type& val );
262 - \p bNew - \p true if the item has been inserted, \p false otherwise
263 - \p item - item of the set
264 - \p val - argument \p val passed into the \p %update() function
265 If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
266 refers to the same thing.
268 The functor may change non-key fields of the \p item.
270 Returns <tt> std::pair<bool, bool> </tt> where \p first is \p true if operation is successful,
271 \p second is \p true if new item has been added or \p false if the item with \p key
272 already is in the set.
274 @warning For \ref cds_intrusive_MichaelList_hp "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
275 \ref cds_intrusive_LazyList_hp "LazyList" provides exclusive access to inserted item and does not require any node-level
278 template <typename Func>
279 std::pair<bool, bool> update( value_type& val, Func func, bool bAllowInsert = true )
281 std::pair<bool, bool> bRet = bucket( val ).update( val, func, bAllowInsert );
287 template <typename Func>
288 CDS_DEPRECATED("ensure() is deprecated, use update()")
289 std::pair<bool, bool> ensure( value_type& val, Func func )
291 return update( val, func, true );
295 /// Checks whether the set contains \p key
298 The function searches the item with key equal to \p key
299 and returns the pointer to an element found or \p nullptr.
301 Note the hash functor specified for class \p Traits template parameter
302 should accept a parameter of type \p Q that can be not the same as \p value_type.
304 template <typename Q>
305 value_type * contains( Q const& key )
307 return bucket( key ).contains( key );
310 template <typename Q>
311 CDS_DEPRECATED("use contains()")
312 value_type * find( Q const& key )
314 return contains( key );
318 /// Checks whether the set contains \p key using \p pred predicate for searching
320 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
321 \p Less functor has the interface like \p std::less.
322 \p Less must imply the same element order as the comparator used for building the set.
324 template <typename Q, typename Less>
325 value_type * contains( Q const& key, Less pred )
327 return bucket( key ).contains( key, pred );
330 template <typename Q, typename Less>
331 CDS_DEPRECATED("use contains()")
332 value_type * find_with( Q const& key, Less pred )
334 return contains( key, pred );
338 /// Finds the key \p key
339 /** \anchor cds_intrusive_MichaelHashSet_nogc_find_func
340 The function searches the item with key equal to \p key and calls the functor \p f for item found.
341 The interface of \p Func functor is:
344 void operator()( value_type& item, Q& key );
347 where \p item is the item found, \p key is the <tt>find</tt> function argument.
349 The functor can change non-key fields of \p item.
350 The functor does not serialize simultaneous access to the set \p item. If such access is
351 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
353 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
354 can modify both arguments.
356 Note the hash functor specified for class \p Traits template parameter
357 should accept a parameter of type \p Q that can be not the same as \p value_type.
359 The function returns \p true if \p key is found, \p false otherwise.
361 template <typename Q, typename Func>
362 bool find( Q& key, Func f )
364 return bucket( key ).find( key, f );
367 template <typename Q, typename Func>
368 bool find( Q const& key, Func f )
370 return bucket( key ).find( key, f );
374 /// Finds the key \p key using \p pred predicate for searching
376 The function is an analog of \ref cds_intrusive_MichaelHashSet_nogc_find_func "find(Q&, Func)"
377 but \p pred is used for key comparing.
378 \p Less functor has the interface like \p std::less.
379 \p pred must imply the same element order as the comparator used for building the set.
381 template <typename Q, typename Less, typename Func>
382 bool find_with( Q& key, Less pred, Func f )
384 return bucket( key ).find_with( key, pred, f );
387 template <typename Q, typename Less, typename Func>
388 bool find_with( Q const& key, Less pred, Func f )
390 return bucket( key ).find_with( key, pred, f );
394 /// Clears the set (non-atomic)
396 The function unlink all items from the set.
397 The function is not atomic. It cleans up each bucket and then resets the item counter to zero.
398 If there are a thread that performs insertion while \p %clear() is working the result is undefined in general case:
399 <tt> empty() </tt> may return \p true but the set may contain item(s).
400 Therefore, \p %clear() may be used only for debugging purposes.
402 For each item the \p disposer is called after unlinking.
406 for ( size_t i = 0; i < bucket_count(); ++i )
407 m_Buckets[i].clear();
408 m_ItemCounter.reset();
412 /// Checks if the set is empty
414 Emptiness is checked by item counting: if item count is zero then the set is empty.
415 Thus, the correct item counting feature is an important part of Michael's set implementation.
422 /// Returns item count in the set
425 return m_ItemCounter;
428 /// Returns the size of hash table
430 Since \p %MichaelHashSet cannot dynamically extend the hash table size,
431 the value returned is an constant depending on object initialization parameters;
432 see MichaelHashSet::MichaelHashSet for explanation.
434 size_t bucket_count() const
436 return m_nHashBitmask + 1;
439 /// Returns const reference to internal statistics
440 stat const& statistics() const
447 template <typename Stat>
448 typename std::enable_if< Stat::empty >::type construct_bucket( internal_bucket_type * bucket )
450 new (bucket) internal_bucket_type;
453 template <typename Stat>
454 typename std::enable_if< !Stat::empty >::type construct_bucket( internal_bucket_type * bucket )
456 new (bucket) internal_bucket_type( m_Stat );
461 }} // namespace cds::intrusive
463 #endif // #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_NOGC_H