3 #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_NOGC_H
4 #define CDSLIB_INTRUSIVE_MICHAEL_SET_NOGC_H
6 #include <cds/intrusive/details/michael_set_base.h>
7 #include <cds/gc/nogc.h>
8 #include <cds/details/allocator.h>
10 namespace cds { namespace intrusive {
12 /// Michael's hash set (template specialization for gc::nogc)
13 /** @ingroup cds_intrusive_map
14 \anchor cds_intrusive_MichaelHashSet_nogc
16 This specialization is so-called append-only when no item
17 reclamation may be performed. The set does not support deleting of list item.
19 See \ref cds_intrusive_MichaelHashSet_hp "MichaelHashSet" for description of template parameters.
20 The template parameter \p OrderedList should be any \p cds::gc::nogc -derived ordered list, for example,
21 \ref cds_intrusive_MichaelList_nogc "append-only MichaelList".
25 #ifdef CDS_DOXYGEN_INVOKED
26 class Traits = michael_set::traits
31 class MichaelHashSet< cds::gc::nogc, OrderedList, Traits >
34 typedef cds::gc::nogc gc; ///< Garbage collector
35 typedef OrderedList bucket_type; ///< Type of ordered list to be used as buckets
36 typedef Traits traits; ///< Set traits
38 typedef typename bucket_type::value_type value_type; ///< type of value to be stored in the set
39 typedef typename bucket_type::key_comparator key_comparator; ///< key comparing functor
40 typedef typename bucket_type::disposer disposer; ///< Node disposer functor
42 /// Hash functor for \p value_type and all its derivatives that you use
43 typedef typename cds::opt::v::hash_selector< typename traits::hash >::type hash;
44 typedef typename traits::item_counter item_counter; ///< Item counter type
46 /// Bucket table allocator
47 typedef cds::details::Allocator< bucket_type, typename traits::allocator > bucket_table_allocator;
50 item_counter m_ItemCounter; ///< Item counter
51 hash m_HashFunctor; ///< Hash functor
52 bucket_type * m_Buckets; ///< bucket table
56 const size_t m_nHashBitmask;
61 /// Calculates hash value of \p key
63 size_t hash_value( Q const & key ) const
65 return m_HashFunctor( key ) & m_nHashBitmask;
68 /// Returns the bucket (ordered list) for \p key
70 bucket_type& bucket( Q const & key )
72 return m_Buckets[ hash_value( key ) ];
79 The forward iterator for Michael's set is based on \p OrderedList forward iterator and has some features:
80 - it has no post-increment operator
81 - it iterates items in unordered fashion
83 typedef michael_set::details::iterator< bucket_type, false > iterator;
85 /// Const forward iterator
87 For iterator's features and requirements see \ref iterator
89 typedef michael_set::details::iterator< bucket_type, true > const_iterator;
91 /// Returns a forward iterator addressing the first element in a set
93 For empty set \code begin() == end() \endcode
97 return iterator( m_Buckets[0].begin(), m_Buckets, m_Buckets + bucket_count() );
100 /// Returns an iterator that addresses the location succeeding the last element in a set
102 Do not use the value returned by <tt>end</tt> function to access any item.
103 The returned value can be used only to control reaching the end of the set.
104 For empty set \code begin() == end() \endcode
108 return iterator( m_Buckets[bucket_count() - 1].end(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
111 /// Returns a forward const iterator addressing the first element in a set
113 const_iterator begin() const
117 const_iterator cbegin() const
119 return const_iterator( m_Buckets[0].cbegin(), m_Buckets, m_Buckets + bucket_count() );
123 /// Returns an const iterator that addresses the location succeeding the last element in a set
125 const_iterator end() const
129 const_iterator cend() const
131 return const_iterator( m_Buckets[bucket_count() - 1].cend(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
136 /// Initializes hash set
138 The Michael's hash set is an unbounded container, but its hash table is non-expandable.
139 At construction time you should pass estimated maximum item count and a load factor.
140 The load factor is average size of one bucket - a small number between 1 and 10.
141 The bucket is an ordered single-linked list, searching in the bucket has linear complexity <tt>O(nLoadFactor)</tt>.
142 The constructor defines hash table size as rounding <tt>nMaxItemCount / nLoadFactor</tt> up to nearest power of two.
145 size_t nMaxItemCount, ///< estimation of max item count in the hash set
146 size_t nLoadFactor ///< load factor: estimation of max number of items in the bucket
147 ) : m_nHashBitmask( michael_set::details::init_hash_bitmask( nMaxItemCount, nLoadFactor ))
149 // GC and OrderedList::gc must be the same
150 static_assert( std::is_same<gc, typename bucket_type::gc>::value, "GC and OrderedList::gc must be the same");
152 // atomicity::empty_item_counter is not allowed as a item counter
153 static_assert( !std::is_same<item_counter, atomicity::empty_item_counter>::value,
154 "atomicity::empty_item_counter is not allowed as a item counter");
156 m_Buckets = bucket_table_allocator().NewArray( bucket_count() );
159 /// Clears hash set object and destroys it
163 bucket_table_allocator().Delete( m_Buckets, bucket_count() );
168 The function inserts \p val in the set if it does not contain
169 an item with key equal to \p val.
171 Returns \p true if \p val is placed into the set, \p false otherwise.
173 bool insert( value_type& val )
175 bool bRet = bucket( val ).insert( val );
181 /// Updates the element
183 The operation performs inserting or changing data with lock-free manner.
185 If the item \p val not found in the set, then \p val is inserted iff \p bAllowInsert is \p true.
186 Otherwise, the functor \p func is called with item found.
187 The functor signature is:
190 void operator()( bool bNew, value_type& item, value_type& val );
194 - \p bNew - \p true if the item has been inserted, \p false otherwise
195 - \p item - item of the set
196 - \p val - argument \p val passed into the \p %update() function
197 If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
198 refers to the same thing.
200 The functor may change non-key fields of the \p item.
202 Returns <tt> std::pair<bool, bool> </tt> where \p first is \p true if operation is successfull,
203 \p second is \p true if new item has been added or \p false if the item with \p key
204 already is in the set.
206 @warning For \ref cds_intrusive_MichaelList_hp "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
207 \ref cds_intrusive_LazyList_hp "LazyList" provides exclusive access to inserted item and does not require any node-level
210 template <typename Func>
211 std::pair<bool, bool> update( value_type& val, Func func, bool bAllowInsert = true )
213 std::pair<bool, bool> bRet = bucket( val ).update( val, func, bAllowInsert );
219 template <typename Func>
220 CDS_DEPRECATED("ensure() is deprecated, use update()")
221 std::pair<bool, bool> ensure( value_type& val, Func func )
223 return update( val, func, true );
227 /// Checks whether the set contains \p key
230 The function searches the item with key equal to \p key
231 and returns the pointer to an element found or \p nullptr.
233 Note the hash functor specified for class \p Traits template parameter
234 should accept a parameter of type \p Q that can be not the same as \p value_type.
236 template <typename Q>
237 value_type * contains( Q const& key )
239 return bucket( key ).contains( key );
242 template <typename Q>
243 CDS_DEPRECATED("use contains()")
244 value_type * find( Q const& key )
246 return contains( key );
250 /// Checks whether the set contains \p key using \p pred predicate for searching
252 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
253 \p Less functor has the interface like \p std::less.
254 \p Less must imply the same element order as the comparator used for building the set.
256 template <typename Q, typename Less>
257 value_type * contains( Q const& key, Less pred )
259 return bucket( key ).contains( key, pred );
262 template <typename Q, typename Less>
263 CDS_DEPRECATED("use contains()")
264 value_type * find_with( Q const& key, Less pred )
266 return contains( key, pred );
270 /// Finds the key \p key
271 /** \anchor cds_intrusive_MichaelHashSet_nogc_find_func
272 The function searches the item with key equal to \p key and calls the functor \p f for item found.
273 The interface of \p Func functor is:
276 void operator()( value_type& item, Q& key );
279 where \p item is the item found, \p key is the <tt>find</tt> function argument.
281 The functor can change non-key fields of \p item.
282 The functor does not serialize simultaneous access to the set \p item. If such access is
283 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
285 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
286 can modify both arguments.
288 Note the hash functor specified for class \p Traits template parameter
289 should accept a parameter of type \p Q that can be not the same as \p value_type.
291 The function returns \p true if \p key is found, \p false otherwise.
293 template <typename Q, typename Func>
294 bool find( Q& key, Func f )
296 return bucket( key ).find( key, f );
299 template <typename Q, typename Func>
300 bool find( Q const& key, Func f )
302 return bucket( key ).find( key, f );
306 /// Finds the key \p key using \p pred predicate for searching
308 The function is an analog of \ref cds_intrusive_MichaelHashSet_nogc_find_func "find(Q&, Func)"
309 but \p pred is used for key comparing.
310 \p Less functor has the interface like \p std::less.
311 \p pred must imply the same element order as the comparator used for building the set.
313 template <typename Q, typename Less, typename Func>
314 bool find_with( Q& key, Less pred, Func f )
316 return bucket( key ).find_with( key, pred, f );
319 template <typename Q, typename Less, typename Func>
320 bool find_with( Q const& key, Less pred, Func f )
322 return bucket( key ).find_with( key, pred, f );
326 /// Clears the set (non-atomic)
328 The function unlink all items from the set.
329 The function is not atomic. It cleans up each bucket and then resets the item counter to zero.
330 If there are a thread that performs insertion while \p clear is working the result is undefined in general case:
331 <tt> empty() </tt> may return \p true but the set may contain item(s).
332 Therefore, \p clear may be used only for debugging purposes.
334 For each item the \p disposer is called after unlinking.
338 for ( size_t i = 0; i < bucket_count(); ++i )
339 m_Buckets[i].clear();
340 m_ItemCounter.reset();
344 /// Checks if the set is empty
346 Emptiness is checked by item counting: if item count is zero then the set is empty.
347 Thus, the correct item counting feature is an important part of Michael's set implementation.
354 /// Returns item count in the set
357 return m_ItemCounter;
360 /// Returns the size of hash table
362 Since \p %MichaelHashSet cannot dynamically extend the hash table size,
363 the value returned is an constant depending on object initialization parameters;
364 see MichaelHashSet::MichaelHashSet for explanation.
366 size_t bucket_count() const
368 return m_nHashBitmask + 1;
373 }} // namespace cds::intrusive
375 #endif // #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_NOGC_H