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 typedef cds::intrusive::michael_set::implementation_tag implementation_tag;
54 item_counter m_ItemCounter; ///< Item counter
55 hash m_HashFunctor; ///< Hash functor
56 bucket_type * m_Buckets; ///< bucket table
60 const size_t m_nHashBitmask;
65 /// Calculates hash value of \p key
67 size_t hash_value( Q const & key ) const
69 return m_HashFunctor( key ) & m_nHashBitmask;
72 /// Returns the bucket (ordered list) for \p key
74 bucket_type& bucket( Q const & key )
76 return m_Buckets[ hash_value( key ) ];
83 The forward iterator for Michael's set is based on \p OrderedList forward iterator and has some features:
84 - it has no post-increment operator
85 - it iterates items in unordered fashion
87 typedef michael_set::details::iterator< bucket_type, false > iterator;
89 /// Const forward iterator
91 For iterator's features and requirements see \ref iterator
93 typedef michael_set::details::iterator< bucket_type, true > const_iterator;
95 /// Returns a forward iterator addressing the first element in a set
97 For empty set \code begin() == end() \endcode
101 return iterator( m_Buckets[0].begin(), m_Buckets, m_Buckets + bucket_count() );
104 /// Returns an iterator that addresses the location succeeding the last element in a set
106 Do not use the value returned by <tt>end</tt> function to access any item.
107 The returned value can be used only to control reaching the end of the set.
108 For empty set \code begin() == end() \endcode
112 return iterator( m_Buckets[bucket_count() - 1].end(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
115 /// Returns a forward const iterator addressing the first element in a set
117 const_iterator begin() const
121 const_iterator cbegin() const
123 return const_iterator( m_Buckets[0].cbegin(), m_Buckets, m_Buckets + bucket_count() );
127 /// Returns an const iterator that addresses the location succeeding the last element in a set
129 const_iterator end() const
133 const_iterator cend() const
135 return const_iterator( m_Buckets[bucket_count() - 1].cend(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
140 /// Initializes hash set
141 /** @copydetails cds_intrusive_MichaelHashSet_hp_ctor
144 size_t nMaxItemCount, ///< estimation of max item count in the hash set
145 size_t nLoadFactor ///< load factor: estimation of max number of items in the bucket
146 ) : m_nHashBitmask( michael_set::details::init_hash_bitmask( nMaxItemCount, nLoadFactor ))
148 // GC and OrderedList::gc must be the same
149 static_assert( std::is_same<gc, typename bucket_type::gc>::value, "GC and OrderedList::gc must be the same");
151 // atomicity::empty_item_counter is not allowed as a item counter
152 static_assert( !std::is_same<item_counter, atomicity::empty_item_counter>::value,
153 "atomicity::empty_item_counter is not allowed as a item counter");
155 m_Buckets = bucket_table_allocator().NewArray( bucket_count() );
158 /// Clears hash set object and destroys it
162 bucket_table_allocator().Delete( m_Buckets, bucket_count() );
167 The function inserts \p val in the set if it does not contain
168 an item with key equal to \p val.
170 Returns \p true if \p val is placed into the set, \p false otherwise.
172 bool insert( value_type& val )
174 bool bRet = bucket( val ).insert( val );
180 /// Ensures that the \p item exists in the set
182 The operation performs inserting or changing data with lock-free manner.
184 If the item \p val not found in the set, then \p val is inserted into the set.
185 Otherwise, the functor \p func is called with item found.
186 The functor signature is:
188 void func( bool bNew, value_type& item, value_type& val );
191 - \p bNew - \p true if the item has been inserted, \p false otherwise
192 - \p item - item of the set
193 - \p val - argument \p val passed into the \p ensure function
194 If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
195 refers to the same thing.
197 The functor can change non-key fields of the \p item.
199 Returns std::pair<bool, bool> where \p first is \p true if operation is successfull,
200 \p second is \p true if new item has been added or \p false if the item with \p key
201 already is in the set.
203 @warning For \ref cds_intrusive_MichaelList_hp "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
204 \ref cds_intrusive_LazyList_nogc "LazyList" provides exclusive access to inserted item and does not require any node-level
207 template <typename Func>
208 std::pair<bool, bool> ensure( value_type& val, Func func )
210 std::pair<bool, bool> bRet = bucket( val ).ensure( val, func );
211 if ( bRet.first && bRet.second )
216 /// Finds the key \p key
217 /** \anchor cds_intrusive_MichaelHashSet_nogc_find_val
218 The function searches the item with key equal to \p key
219 and returns pointer to item found, otherwise \p nullptr.
221 Note the hash functor specified for class \p Traits template parameter
222 should accept a parameter of type \p Q that can be not the same as \p value_type.
224 template <typename Q>
225 value_type * find( Q const& key )
227 return bucket( key ).find( key );
230 /// Finds the key \p key using \p pred predicate for searching
232 The function is an analog of \ref cds_intrusive_MichaelHashSet_nogc_find_val "find(Q const&)"
233 but \p pred is used for key comparing.
234 \p Less functor has the interface like \p std::less.
235 \p pred must imply the same element order as the comparator used for building the set.
237 template <typename Q, typename Less>
238 value_type * find_with( Q const& key, Less pred )
240 return bucket( key ).find_with( key, pred );
243 /// Finds the key \p key
244 /** \anchor cds_intrusive_MichaelHashSet_nogc_find_func
245 The function searches the item with key equal to \p key and calls the functor \p f for item found.
246 The interface of \p Func functor is:
249 void operator()( value_type& item, Q& key );
252 where \p item is the item found, \p key is the <tt>find</tt> function argument.
254 The functor can change non-key fields of \p item.
255 The functor does not serialize simultaneous access to the set \p item. If such access is
256 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
258 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
259 can modify both arguments.
261 Note the hash functor specified for class \p Traits template parameter
262 should accept a parameter of type \p Q that can be not the same as \p value_type.
264 The function returns \p true if \p key is found, \p false otherwise.
266 template <typename Q, typename Func>
267 bool find( Q& key, Func f )
269 return bucket( key ).find( key, f );
272 template <typename Q, typename Func>
273 bool find( Q const& key, Func f )
275 return bucket( key ).find( key, f );
279 /// Finds the key \p key using \p pred predicate for searching
281 The function is an analog of \ref cds_intrusive_MichaelHashSet_nogc_find_func "find(Q&, Func)"
282 but \p pred is used for key comparing.
283 \p Less functor has the interface like \p std::less.
284 \p pred must imply the same element order as the comparator used for building the set.
286 template <typename Q, typename Less, typename Func>
287 bool find_with( Q& key, Less pred, Func f )
289 return bucket( key ).find_with( key, pred, f );
292 template <typename Q, typename Less, typename Func>
293 bool find_with( Q const& key, Less pred, Func f )
295 return bucket( key ).find_with( key, pred, f );
299 /// Clears the set (non-atomic)
301 The function unlink all items from the set.
302 The function is not atomic. It cleans up each bucket and then resets the item counter to zero.
303 If there are a thread that performs insertion while \p clear is working the result is undefined in general case:
304 <tt> empty() </tt> may return \p true but the set may contain item(s).
305 Therefore, \p clear may be used only for debugging purposes.
307 For each item the \p disposer is called after unlinking.
311 for ( size_t i = 0; i < bucket_count(); ++i )
312 m_Buckets[i].clear();
313 m_ItemCounter.reset();
317 /// Checks if the set is empty
319 Emptiness is checked by item counting: if item count is zero then the set is empty.
320 Thus, the correct item counting feature is an important part of Michael's set implementation.
327 /// Returns item count in the set
330 return m_ItemCounter;
333 /// Returns the size of hash table
335 Since \p %MichaelHashSet cannot dynamically extend the hash table size,
336 the value returned is an constant depending on object initialization parameters;
337 see MichaelHashSet::MichaelHashSet for explanation.
339 size_t bucket_count() const
341 return m_nHashBitmask + 1;
346 }} // namespace cds::intrusive
348 #endif // #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_NOGC_H