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 ) ];
107 The forward iterator for Michael's set is based on \p OrderedList forward iterator and has some features:
108 - it has no post-increment operator
109 - it iterates items in unordered fashion
111 typedef michael_set::details::iterator< bucket_type, false > iterator;
113 /// Const forward iterator
115 For iterator's features and requirements see \ref iterator
117 typedef michael_set::details::iterator< bucket_type, true > const_iterator;
119 /// Returns a forward iterator addressing the first element in a set
121 For empty set \code begin() == end() \endcode
125 return iterator( m_Buckets[0].begin(), m_Buckets, m_Buckets + bucket_count() );
128 /// Returns an iterator that addresses the location succeeding the last element in a set
130 Do not use the value returned by <tt>end</tt> function to access any item.
131 The returned value can be used only to control reaching the end of the set.
132 For empty set \code begin() == end() \endcode
136 return iterator( m_Buckets[bucket_count() - 1].end(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
139 /// Returns a forward const iterator addressing the first element in a set
141 const_iterator begin() const
145 const_iterator cbegin() const
147 return const_iterator( m_Buckets[0].cbegin(), m_Buckets, m_Buckets + bucket_count() );
151 /// Returns an const iterator that addresses the location succeeding the last element in a set
153 const_iterator end() const
157 const_iterator cend() const
159 return const_iterator( m_Buckets[bucket_count() - 1].cend(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
164 /// Initializes hash set
166 The Michael's hash set is an unbounded container, but its hash table is non-expandable.
167 At construction time you should pass estimated maximum item count and a load factor.
168 The load factor is average size of one bucket - a small number between 1 and 10.
169 The bucket is an ordered single-linked list, searching in the bucket has linear complexity <tt>O(nLoadFactor)</tt>.
170 The constructor defines hash table size as rounding <tt>nMaxItemCount / nLoadFactor</tt> up to nearest power of two.
173 size_t nMaxItemCount, ///< estimation of max item count in the hash set
174 size_t nLoadFactor ///< load factor: estimation of max number of items in the bucket
175 ) : m_nHashBitmask( michael_set::details::init_hash_bitmask( nMaxItemCount, nLoadFactor ))
177 // GC and OrderedList::gc must be the same
178 static_assert( std::is_same<gc, typename bucket_type::gc>::value, "GC and OrderedList::gc must be the same");
180 // atomicity::empty_item_counter is not allowed as a item counter
181 static_assert( !std::is_same<item_counter, atomicity::empty_item_counter>::value,
182 "atomicity::empty_item_counter is not allowed as a item counter");
184 m_Buckets = bucket_table_allocator().NewArray( bucket_count() );
187 /// Clears hash set object and destroys it
191 bucket_table_allocator().Delete( m_Buckets, bucket_count() );
196 The function inserts \p val in the set if it does not contain
197 an item with key equal to \p val.
199 Returns \p true if \p val is placed into the set, \p false otherwise.
201 bool insert( value_type& val )
203 bool bRet = bucket( val ).insert( val );
209 /// Updates the element
211 The operation performs inserting or changing data with lock-free manner.
213 If the item \p val not found in the set, then \p val is inserted iff \p bAllowInsert is \p true.
214 Otherwise, the functor \p func is called with item found.
215 The functor signature is:
218 void operator()( bool bNew, value_type& item, value_type& val );
222 - \p bNew - \p true if the item has been inserted, \p false otherwise
223 - \p item - item of the set
224 - \p val - argument \p val passed into the \p %update() function
225 If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
226 refers to the same thing.
228 The functor may change non-key fields of the \p item.
230 Returns <tt> std::pair<bool, bool> </tt> where \p first is \p true if operation is successfull,
231 \p second is \p true if new item has been added or \p false if the item with \p key
232 already is in the set.
234 @warning For \ref cds_intrusive_MichaelList_hp "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
235 \ref cds_intrusive_LazyList_hp "LazyList" provides exclusive access to inserted item and does not require any node-level
238 template <typename Func>
239 std::pair<bool, bool> update( value_type& val, Func func, bool bAllowInsert = true )
241 std::pair<bool, bool> bRet = bucket( val ).update( val, func, bAllowInsert );
247 template <typename Func>
248 CDS_DEPRECATED("ensure() is deprecated, use update()")
249 std::pair<bool, bool> ensure( value_type& val, Func func )
251 return update( val, func, true );
255 /// Checks whether the set contains \p key
258 The function searches the item with key equal to \p key
259 and returns the pointer to an element found or \p nullptr.
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 template <typename Q>
265 value_type * contains( Q const& key )
267 return bucket( key ).contains( key );
270 template <typename Q>
271 CDS_DEPRECATED("use contains()")
272 value_type * find( Q const& key )
274 return contains( key );
278 /// Checks whether the set contains \p key using \p pred predicate for searching
280 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
281 \p Less functor has the interface like \p std::less.
282 \p Less must imply the same element order as the comparator used for building the set.
284 template <typename Q, typename Less>
285 value_type * contains( Q const& key, Less pred )
287 return bucket( key ).contains( key, pred );
290 template <typename Q, typename Less>
291 CDS_DEPRECATED("use contains()")
292 value_type * find_with( Q const& key, Less pred )
294 return contains( key, pred );
298 /// Finds the key \p key
299 /** \anchor cds_intrusive_MichaelHashSet_nogc_find_func
300 The function searches the item with key equal to \p key and calls the functor \p f for item found.
301 The interface of \p Func functor is:
304 void operator()( value_type& item, Q& key );
307 where \p item is the item found, \p key is the <tt>find</tt> function argument.
309 The functor can change non-key fields of \p item.
310 The functor does not serialize simultaneous access to the set \p item. If such access is
311 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
313 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
314 can modify both arguments.
316 Note the hash functor specified for class \p Traits template parameter
317 should accept a parameter of type \p Q that can be not the same as \p value_type.
319 The function returns \p true if \p key is found, \p false otherwise.
321 template <typename Q, typename Func>
322 bool find( Q& key, Func f )
324 return bucket( key ).find( key, f );
327 template <typename Q, typename Func>
328 bool find( Q const& key, Func f )
330 return bucket( key ).find( key, f );
334 /// Finds the key \p key using \p pred predicate for searching
336 The function is an analog of \ref cds_intrusive_MichaelHashSet_nogc_find_func "find(Q&, Func)"
337 but \p pred is used for key comparing.
338 \p Less functor has the interface like \p std::less.
339 \p pred must imply the same element order as the comparator used for building the set.
341 template <typename Q, typename Less, typename Func>
342 bool find_with( Q& key, Less pred, Func f )
344 return bucket( key ).find_with( key, pred, f );
347 template <typename Q, typename Less, typename Func>
348 bool find_with( Q const& key, Less pred, Func f )
350 return bucket( key ).find_with( key, pred, f );
354 /// Clears the set (non-atomic)
356 The function unlink all items from the set.
357 The function is not atomic. It cleans up each bucket and then resets the item counter to zero.
358 If there are a thread that performs insertion while \p clear is working the result is undefined in general case:
359 <tt> empty() </tt> may return \p true but the set may contain item(s).
360 Therefore, \p clear may be used only for debugging purposes.
362 For each item the \p disposer is called after unlinking.
366 for ( size_t i = 0; i < bucket_count(); ++i )
367 m_Buckets[i].clear();
368 m_ItemCounter.reset();
372 /// Checks if the set is empty
374 Emptiness is checked by item counting: if item count is zero then the set is empty.
375 Thus, the correct item counting feature is an important part of Michael's set implementation.
382 /// Returns item count in the set
385 return m_ItemCounter;
388 /// Returns the size of hash table
390 Since \p %MichaelHashSet cannot dynamically extend the hash table size,
391 the value returned is an constant depending on object initialization parameters;
392 see MichaelHashSet::MichaelHashSet for explanation.
394 size_t bucket_count() const
396 return m_nHashBitmask + 1;
401 }} // namespace cds::intrusive
403 #endif // #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_NOGC_H