3 #ifndef __CDS_INTRUSIVE_MICHAEL_SET_NOGC_H
4 #define __CDS_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
115 return get_const_begin();
117 const_iterator cbegin()
119 return get_const_begin();
123 /// Returns an const iterator that addresses the location succeeding the last element in a set
125 const_iterator end() const
127 return get_const_end();
129 const_iterator cend()
131 return get_const_end();
137 const_iterator get_const_begin() const
139 return const_iterator( m_Buckets[0].begin(), m_Buckets, m_Buckets + bucket_count() );
141 const_iterator get_const_end() const
143 return const_iterator( m_Buckets[bucket_count() - 1].end(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
148 /// Initializes hash set
149 /** @copydetails cds_intrusive_MichaelHashSet_hp_ctor
152 size_t nMaxItemCount, ///< estimation of max item count in the hash set
153 size_t nLoadFactor ///< load factor: estimation of max number of items in the bucket
154 ) : m_nHashBitmask( michael_set::details::init_hash_bitmask( nMaxItemCount, nLoadFactor ))
156 // GC and OrderedList::gc must be the same
157 static_assert( std::is_same<gc, typename bucket_type::gc>::value, "GC and OrderedList::gc must be the same");
159 // atomicity::empty_item_counter is not allowed as a item counter
160 static_assert( !std::is_same<item_counter, atomicity::empty_item_counter>::value,
161 "atomicity::empty_item_counter is not allowed as a item counter");
163 m_Buckets = bucket_table_allocator().NewArray( bucket_count() );
166 /// Clears hash set object and destroys it
170 bucket_table_allocator().Delete( m_Buckets, bucket_count() );
175 The function inserts \p val in the set if it does not contain
176 an item with key equal to \p val.
178 Returns \p true if \p val is placed into the set, \p false otherwise.
180 bool insert( value_type& val )
182 bool bRet = bucket( val ).insert( val );
188 /// Ensures that the \p item exists in the set
190 The operation performs inserting or changing data with lock-free manner.
192 If the item \p val not found in the set, then \p val is inserted into the set.
193 Otherwise, the functor \p func is called with item found.
194 The functor signature is:
196 void func( bool bNew, value_type& item, value_type& val );
199 - \p bNew - \p true if the item has been inserted, \p false otherwise
200 - \p item - item of the set
201 - \p val - argument \p val passed into the \p ensure function
202 If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
203 refers to the same thing.
205 The functor can change non-key fields of the \p item.
207 Returns std::pair<bool, bool> where \p first is \p true if operation is successfull,
208 \p second is \p true if new item has been added or \p false if the item with \p key
209 already is in the set.
211 @warning For \ref cds_intrusive_MichaelList_hp "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
212 \ref cds_intrusive_LazyList_nogc "LazyList" provides exclusive access to inserted item and does not require any node-level
215 template <typename Func>
216 std::pair<bool, bool> ensure( value_type& val, Func func )
218 std::pair<bool, bool> bRet = bucket( val ).ensure( val, func );
219 if ( bRet.first && bRet.second )
224 /// Finds the key \p key
225 /** \anchor cds_intrusive_MichaelHashSet_nogc_find_val
226 The function searches the item with key equal to \p key
227 and returns pointer to item found, otherwise \p nullptr.
229 Note the hash functor specified for class \p Traits template parameter
230 should accept a parameter of type \p Q that can be not the same as \p value_type.
232 template <typename Q>
233 value_type * find( Q const& key )
235 return bucket( key ).find( key );
238 /// Finds the key \p key using \p pred predicate for searching
240 The function is an analog of \ref cds_intrusive_MichaelHashSet_nogc_find_val "find(Q const&)"
241 but \p pred is used for key comparing.
242 \p Less functor has the interface like \p std::less.
243 \p pred must imply the same element order as the comparator used for building the set.
245 template <typename Q, typename Less>
246 value_type * find_with( Q const& key, Less pred )
248 return bucket( key ).find_with( key, pred );
251 /// Finds the key \p key
252 /** \anchor cds_intrusive_MichaelHashSet_nogc_find_func
253 The function searches the item with key equal to \p key and calls the functor \p f for item found.
254 The interface of \p Func functor is:
257 void operator()( value_type& item, Q& key );
260 where \p item is the item found, \p key is the <tt>find</tt> function argument.
262 The functor can change non-key fields of \p item.
263 The functor does not serialize simultaneous access to the set \p item. If such access is
264 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
266 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
267 can modify both arguments.
269 Note the hash functor specified for class \p Traits template parameter
270 should accept a parameter of type \p Q that can be not the same as \p value_type.
272 The function returns \p true if \p key is found, \p false otherwise.
274 template <typename Q, typename Func>
275 bool find( Q& key, Func f )
277 return bucket( key ).find( key, f );
280 /// Finds the key \p key using \p pred predicate for searching
282 The function is an analog of \ref cds_intrusive_MichaelHashSet_nogc_find_func "find(Q&, Func)"
283 but \p pred is used for key comparing.
284 \p Less functor has the interface like \p std::less.
285 \p pred must imply the same element order as the comparator used for building the set.
287 template <typename Q, typename Less, typename Func>
288 bool find_with( Q& key, Less pred, Func f )
290 return bucket( key ).find_with( key, pred, f );
293 /// Clears the set (non-atomic)
295 The function unlink all items from the set.
296 The function is not atomic. It cleans up each bucket and then resets the item counter to zero.
297 If there are a thread that performs insertion while \p clear is working the result is undefined in general case:
298 <tt> empty() </tt> may return \p true but the set may contain item(s).
299 Therefore, \p clear may be used only for debugging purposes.
301 For each item the \p disposer is called after unlinking.
305 for ( size_t i = 0; i < bucket_count(); ++i )
306 m_Buckets[i].clear();
307 m_ItemCounter.reset();
311 /// Checks if the set is empty
313 Emptiness is checked by item counting: if item count is zero then the set is empty.
314 Thus, the correct item counting feature is an important part of Michael's set implementation.
321 /// Returns item count in the set
324 return m_ItemCounter;
327 /// Returns the size of hash table
329 Since \p %MichaelHashSet cannot dynamically extend the hash table size,
330 the value returned is an constant depending on object initialization parameters;
331 see MichaelHashSet::MichaelHashSet for explanation.
333 size_t bucket_count() const
335 return m_nHashBitmask + 1;
340 }} // namespace cds::intrusive
342 #endif // #ifndef __CDS_INTRUSIVE_MICHAEL_SET_NOGC_H