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 The iterator interface:
117 // Default constructor
121 iterator( iterator const& src );
123 // Dereference operator
124 value_type * operator ->() const;
126 // Dereference operator
127 value_type& operator *() const;
129 // Preincrement operator
130 iterator& operator ++();
132 // Assignment operator
133 iterator& operator = (iterator const& src);
135 // Equality operators
136 bool operator ==(iterator const& i ) const;
137 bool operator !=(iterator const& i ) const;
141 typedef michael_set::details::iterator< bucket_type, false > iterator;
143 /// Const forward iterator
145 For iterator's features and requirements see \ref iterator
147 typedef michael_set::details::iterator< bucket_type, true > const_iterator;
149 /// Returns a forward iterator addressing the first element in a set
151 For empty set \code begin() == end() \endcode
155 return iterator( m_Buckets[0].begin(), m_Buckets, m_Buckets + bucket_count() );
158 /// Returns an iterator that addresses the location succeeding the last element in a set
160 Do not use the value returned by <tt>end</tt> function to access any item.
161 The returned value can be used only to control reaching the end of the set.
162 For empty set \code begin() == end() \endcode
166 return iterator( m_Buckets[bucket_count() - 1].end(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
169 /// Returns a forward const iterator addressing the first element in a set
170 const_iterator begin() const
174 /// Returns a forward const iterator addressing the first element in a set
175 const_iterator cbegin() const
177 return const_iterator( m_Buckets[0].cbegin(), m_Buckets, m_Buckets + bucket_count() );
180 /// Returns an const iterator that addresses the location succeeding the last element in a set
181 const_iterator end() const
185 /// Returns an const iterator that addresses the location succeeding the last element in a set
186 const_iterator cend() const
188 return const_iterator( m_Buckets[bucket_count() - 1].cend(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
193 /// Initializes hash set
195 The Michael's hash set is an unbounded container, but its hash table is non-expandable.
196 At construction time you should pass estimated maximum item count and a load factor.
197 The load factor is average size of one bucket - a small number between 1 and 10.
198 The bucket is an ordered single-linked list, searching in the bucket has linear complexity <tt>O(nLoadFactor)</tt>.
199 The constructor defines hash table size as rounding <tt>nMaxItemCount / nLoadFactor</tt> up to nearest power of two.
202 size_t nMaxItemCount, ///< estimation of max item count in the hash set
203 size_t nLoadFactor ///< load factor: estimation of max number of items in the bucket
204 ) : m_nHashBitmask( michael_set::details::init_hash_bitmask( nMaxItemCount, nLoadFactor ))
206 // GC and OrderedList::gc must be the same
207 static_assert( std::is_same<gc, typename bucket_type::gc>::value, "GC and OrderedList::gc must be the same");
209 // atomicity::empty_item_counter is not allowed as a item counter
210 static_assert( !std::is_same<item_counter, atomicity::empty_item_counter>::value,
211 "atomicity::empty_item_counter is not allowed as a item counter");
213 m_Buckets = bucket_table_allocator().NewArray( bucket_count() );
216 /// Clears hash set object and destroys it
220 bucket_table_allocator().Delete( m_Buckets, bucket_count() );
225 The function inserts \p val in the set if it does not contain
226 an item with key equal to \p val.
228 Returns \p true if \p val is placed into the set, \p false otherwise.
230 bool insert( value_type& val )
232 bool bRet = bucket( val ).insert( val );
238 /// Updates the element
240 The operation performs inserting or changing data with lock-free manner.
242 If the item \p val not found in the set, then \p val is inserted iff \p bAllowInsert is \p true.
243 Otherwise, the functor \p func is called with item found.
244 The functor signature is:
247 void operator()( bool bNew, value_type& item, value_type& val );
251 - \p bNew - \p true if the item has been inserted, \p false otherwise
252 - \p item - item of the set
253 - \p val - argument \p val passed into the \p %update() function
254 If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
255 refers to the same thing.
257 The functor may change non-key fields of the \p item.
259 Returns <tt> std::pair<bool, bool> </tt> where \p first is \p true if operation is successfull,
260 \p second is \p true if new item has been added or \p false if the item with \p key
261 already is in the set.
263 @warning For \ref cds_intrusive_MichaelList_hp "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
264 \ref cds_intrusive_LazyList_hp "LazyList" provides exclusive access to inserted item and does not require any node-level
267 template <typename Func>
268 std::pair<bool, bool> update( value_type& val, Func func, bool bAllowInsert = true )
270 std::pair<bool, bool> bRet = bucket( val ).update( val, func, bAllowInsert );
276 template <typename Func>
277 CDS_DEPRECATED("ensure() is deprecated, use update()")
278 std::pair<bool, bool> ensure( value_type& val, Func func )
280 return update( val, func, true );
284 /// Checks whether the set contains \p key
287 The function searches the item with key equal to \p key
288 and returns the pointer to an element found or \p nullptr.
290 Note the hash functor specified for class \p Traits template parameter
291 should accept a parameter of type \p Q that can be not the same as \p value_type.
293 template <typename Q>
294 value_type * contains( Q const& key )
296 return bucket( key ).contains( key );
299 template <typename Q>
300 CDS_DEPRECATED("use contains()")
301 value_type * find( Q const& key )
303 return contains( key );
307 /// Checks whether the set contains \p key using \p pred predicate for searching
309 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
310 \p Less functor has the interface like \p std::less.
311 \p Less must imply the same element order as the comparator used for building the set.
313 template <typename Q, typename Less>
314 value_type * contains( Q const& key, Less pred )
316 return bucket( key ).contains( key, pred );
319 template <typename Q, typename Less>
320 CDS_DEPRECATED("use contains()")
321 value_type * find_with( Q const& key, Less pred )
323 return contains( key, pred );
327 /// Finds the key \p key
328 /** \anchor cds_intrusive_MichaelHashSet_nogc_find_func
329 The function searches the item with key equal to \p key and calls the functor \p f for item found.
330 The interface of \p Func functor is:
333 void operator()( value_type& item, Q& key );
336 where \p item is the item found, \p key is the <tt>find</tt> function argument.
338 The functor can change non-key fields of \p item.
339 The functor does not serialize simultaneous access to the set \p item. If such access is
340 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
342 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
343 can modify both arguments.
345 Note the hash functor specified for class \p Traits template parameter
346 should accept a parameter of type \p Q that can be not the same as \p value_type.
348 The function returns \p true if \p key is found, \p false otherwise.
350 template <typename Q, typename Func>
351 bool find( Q& key, Func f )
353 return bucket( key ).find( key, f );
356 template <typename Q, typename Func>
357 bool find( Q const& key, Func f )
359 return bucket( key ).find( key, f );
363 /// Finds the key \p key using \p pred predicate for searching
365 The function is an analog of \ref cds_intrusive_MichaelHashSet_nogc_find_func "find(Q&, Func)"
366 but \p pred is used for key comparing.
367 \p Less functor has the interface like \p std::less.
368 \p pred must imply the same element order as the comparator used for building the set.
370 template <typename Q, typename Less, typename Func>
371 bool find_with( Q& key, Less pred, Func f )
373 return bucket( key ).find_with( key, pred, f );
376 template <typename Q, typename Less, typename Func>
377 bool find_with( Q const& key, Less pred, Func f )
379 return bucket( key ).find_with( key, pred, f );
383 /// Clears the set (non-atomic)
385 The function unlink all items from the set.
386 The function is not atomic. It cleans up each bucket and then resets the item counter to zero.
387 If there are a thread that performs insertion while \p %clear() is working the result is undefined in general case:
388 <tt> empty() </tt> may return \p true but the set may contain item(s).
389 Therefore, \p %clear() may be used only for debugging purposes.
391 For each item the \p disposer is called after unlinking.
395 for ( size_t i = 0; i < bucket_count(); ++i )
396 m_Buckets[i].clear();
397 m_ItemCounter.reset();
401 /// Checks if the set is empty
403 Emptiness is checked by item counting: if item count is zero then the set is empty.
404 Thus, the correct item counting feature is an important part of Michael's set implementation.
411 /// Returns item count in the set
414 return m_ItemCounter;
417 /// Returns the size of hash table
419 Since \p %MichaelHashSet cannot dynamically extend the hash table size,
420 the value returned is an constant depending on object initialization parameters;
421 see MichaelHashSet::MichaelHashSet for explanation.
423 size_t bucket_count() const
425 return m_nHashBitmask + 1;
430 }} // namespace cds::intrusive
432 #endif // #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_NOGC_H