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>
36 #include <cds/details/allocator.h>
38 namespace cds { namespace intrusive {
40 /// Michael's hash set (template specialization for gc::nogc)
41 /** @ingroup cds_intrusive_map
42 \anchor cds_intrusive_MichaelHashSet_nogc
44 This specialization is so-called append-only when no item
45 reclamation may be performed. The set does not support deleting of list item.
47 See \ref cds_intrusive_MichaelHashSet_hp "MichaelHashSet" for description of template parameters.
48 The template parameter \p OrderedList should be any \p cds::gc::nogc -derived ordered list, for example,
49 \ref cds_intrusive_MichaelList_nogc "append-only MichaelList".
53 #ifdef CDS_DOXYGEN_INVOKED
54 class Traits = michael_set::traits
59 class MichaelHashSet< cds::gc::nogc, OrderedList, Traits >
62 typedef cds::gc::nogc gc; ///< Garbage collector
63 typedef OrderedList bucket_type; ///< Type of ordered list to be used as buckets
64 typedef Traits traits; ///< Set traits
66 typedef typename bucket_type::value_type value_type; ///< type of value to be stored in the set
67 typedef typename bucket_type::key_comparator key_comparator; ///< key comparing functor
68 typedef typename bucket_type::disposer disposer; ///< Node disposer functor
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
74 /// Bucket table allocator
75 typedef cds::details::Allocator< bucket_type, typename traits::allocator > bucket_table_allocator;
78 item_counter m_ItemCounter; ///< Item counter
79 hash m_HashFunctor; ///< Hash functor
80 bucket_type * m_Buckets; ///< bucket table
84 const size_t m_nHashBitmask;
89 /// Calculates hash value of \p key
91 size_t hash_value( Q const & key ) const
93 return m_HashFunctor( key ) & m_nHashBitmask;
96 /// Returns the bucket (ordered list) for \p key
98 bucket_type& bucket( Q const & key )
100 return m_Buckets[ hash_value( key ) ];
105 ///@name Forward iterators
109 The forward iterator for Michael's set is based on \p OrderedList forward iterator and has some features:
110 - it has no post-increment operator
111 - it iterates items in unordered fashion
113 typedef michael_set::details::iterator< bucket_type, false > iterator;
115 /// Const forward iterator
117 For iterator's features and requirements see \ref iterator
119 typedef michael_set::details::iterator< bucket_type, true > const_iterator;
121 /// Returns a forward iterator addressing the first element in a set
123 For empty set \code begin() == end() \endcode
127 return iterator( m_Buckets[0].begin(), m_Buckets, m_Buckets + bucket_count() );
130 /// Returns an iterator that addresses the location succeeding the last element in a set
132 Do not use the value returned by <tt>end</tt> function to access any item.
133 The returned value can be used only to control reaching the end of the set.
134 For empty set \code begin() == end() \endcode
138 return iterator( m_Buckets[bucket_count() - 1].end(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
141 /// Returns a forward const iterator addressing the first element in a set
142 const_iterator begin() const
146 /// Returns a forward const iterator addressing the first element in a set
147 const_iterator cbegin() const
149 return const_iterator( m_Buckets[0].cbegin(), m_Buckets, m_Buckets + bucket_count() );
152 /// Returns an const iterator that addresses the location succeeding the last element in a set
153 const_iterator end() const
157 /// Returns an const iterator that addresses the location succeeding the last element in a set
158 const_iterator cend() const
160 return const_iterator( m_Buckets[bucket_count() - 1].cend(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
165 /// Initializes hash set
167 The Michael's hash set is an unbounded container, but its hash table is non-expandable.
168 At construction time you should pass estimated maximum item count and a load factor.
169 The load factor is average size of one bucket - a small number between 1 and 10.
170 The bucket is an ordered single-linked list, searching in the bucket has linear complexity <tt>O(nLoadFactor)</tt>.
171 The constructor defines hash table size as rounding <tt>nMaxItemCount / nLoadFactor</tt> up to nearest power of two.
174 size_t nMaxItemCount, ///< estimation of max item count in the hash set
175 size_t nLoadFactor ///< load factor: estimation of max number of items in the bucket
176 ) : m_nHashBitmask( michael_set::details::init_hash_bitmask( nMaxItemCount, nLoadFactor ))
178 // GC and OrderedList::gc must be the same
179 static_assert( std::is_same<gc, typename bucket_type::gc>::value, "GC and OrderedList::gc must be the same");
181 // atomicity::empty_item_counter is not allowed as a item counter
182 static_assert( !std::is_same<item_counter, atomicity::empty_item_counter>::value,
183 "atomicity::empty_item_counter is not allowed as a item counter");
185 m_Buckets = bucket_table_allocator().NewArray( bucket_count() );
188 /// Clears hash set object and destroys it
192 bucket_table_allocator().Delete( m_Buckets, bucket_count() );
197 The function inserts \p val in the set if it does not contain
198 an item with key equal to \p val.
200 Returns \p true if \p val is placed into the set, \p false otherwise.
202 bool insert( value_type& val )
204 bool bRet = bucket( val ).insert( val );
210 /// Updates the element
212 The operation performs inserting or changing data with lock-free manner.
214 If the item \p val not found in the set, then \p val is inserted iff \p bAllowInsert is \p true.
215 Otherwise, the functor \p func is called with item found.
216 The functor signature is:
219 void operator()( bool bNew, value_type& item, value_type& val );
223 - \p bNew - \p true if the item has been inserted, \p false otherwise
224 - \p item - item of the set
225 - \p val - argument \p val passed into the \p %update() function
226 If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
227 refers to the same thing.
229 The functor may change non-key fields of the \p item.
231 Returns <tt> std::pair<bool, bool> </tt> where \p first is \p true if operation is successfull,
232 \p second is \p true if new item has been added or \p false if the item with \p key
233 already is in the set.
235 @warning For \ref cds_intrusive_MichaelList_hp "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
236 \ref cds_intrusive_LazyList_hp "LazyList" provides exclusive access to inserted item and does not require any node-level
239 template <typename Func>
240 std::pair<bool, bool> update( value_type& val, Func func, bool bAllowInsert = true )
242 std::pair<bool, bool> bRet = bucket( val ).update( val, func, bAllowInsert );
248 template <typename Func>
249 CDS_DEPRECATED("ensure() is deprecated, use update()")
250 std::pair<bool, bool> ensure( value_type& val, Func func )
252 return update( val, func, true );
256 /// Checks whether the set contains \p key
259 The function searches the item with key equal to \p key
260 and returns the pointer to an element found or \p nullptr.
262 Note the hash functor specified for class \p Traits template parameter
263 should accept a parameter of type \p Q that can be not the same as \p value_type.
265 template <typename Q>
266 value_type * contains( Q const& key )
268 return bucket( key ).contains( key );
271 template <typename Q>
272 CDS_DEPRECATED("use contains()")
273 value_type * find( Q const& key )
275 return contains( key );
279 /// Checks whether the set contains \p key using \p pred predicate for searching
281 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
282 \p Less functor has the interface like \p std::less.
283 \p Less must imply the same element order as the comparator used for building the set.
285 template <typename Q, typename Less>
286 value_type * contains( Q const& key, Less pred )
288 return bucket( key ).contains( key, pred );
291 template <typename Q, typename Less>
292 CDS_DEPRECATED("use contains()")
293 value_type * find_with( Q const& key, Less pred )
295 return contains( key, pred );
299 /// Finds the key \p key
300 /** \anchor cds_intrusive_MichaelHashSet_nogc_find_func
301 The function searches the item with key equal to \p key and calls the functor \p f for item found.
302 The interface of \p Func functor is:
305 void operator()( value_type& item, Q& key );
308 where \p item is the item found, \p key is the <tt>find</tt> function argument.
310 The functor can change non-key fields of \p item.
311 The functor does not serialize simultaneous access to the set \p item. If such access is
312 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
314 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
315 can modify both arguments.
317 Note the hash functor specified for class \p Traits template parameter
318 should accept a parameter of type \p Q that can be not the same as \p value_type.
320 The function returns \p true if \p key is found, \p false otherwise.
322 template <typename Q, typename Func>
323 bool find( Q& key, Func f )
325 return bucket( key ).find( key, f );
328 template <typename Q, typename Func>
329 bool find( Q const& key, Func f )
331 return bucket( key ).find( key, f );
335 /// Finds the key \p key using \p pred predicate for searching
337 The function is an analog of \ref cds_intrusive_MichaelHashSet_nogc_find_func "find(Q&, Func)"
338 but \p pred is used for key comparing.
339 \p Less functor has the interface like \p std::less.
340 \p pred must imply the same element order as the comparator used for building the set.
342 template <typename Q, typename Less, typename Func>
343 bool find_with( Q& key, Less pred, Func f )
345 return bucket( key ).find_with( key, pred, f );
348 template <typename Q, typename Less, typename Func>
349 bool find_with( Q const& key, Less pred, Func f )
351 return bucket( key ).find_with( key, pred, f );
355 /// Clears the set (non-atomic)
357 The function unlink all items from the set.
358 The function is not atomic. It cleans up each bucket and then resets the item counter to zero.
359 If there are a thread that performs insertion while \p clear is working the result is undefined in general case:
360 <tt> empty() </tt> may return \p true but the set may contain item(s).
361 Therefore, \p clear may be used only for debugging purposes.
363 For each item the \p disposer is called after unlinking.
367 for ( size_t i = 0; i < bucket_count(); ++i )
368 m_Buckets[i].clear();
369 m_ItemCounter.reset();
373 /// Checks if the set is empty
375 Emptiness is checked by item counting: if item count is zero then the set is empty.
376 Thus, the correct item counting feature is an important part of Michael's set implementation.
383 /// Returns item count in the set
386 return m_ItemCounter;
389 /// Returns the size of hash table
391 Since \p %MichaelHashSet cannot dynamically extend the hash table size,
392 the value returned is an constant depending on object initialization parameters;
393 see MichaelHashSet::MichaelHashSet for explanation.
395 size_t bucket_count() const
397 return m_nHashBitmask + 1;
402 }} // namespace cds::intrusive
404 #endif // #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_NOGC_H