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_CONTAINER_IMPL_LAZY_LIST_H
32 #define CDSLIB_CONTAINER_IMPL_LAZY_LIST_H
35 #include <cds/container/details/guarded_ptr_cast.h>
37 namespace cds { namespace container {
40 /** @ingroup cds_nonintrusive_list
41 @anchor cds_nonintrusive_LazyList_gc
43 Usually, ordered single-linked list is used as a building block for the hash table implementation.
44 The complexity of searching is <tt>O(N)</tt>.
47 - [2005] Steve Heller, Maurice Herlihy, Victor Luchangco, Mark Moir, William N. Scherer III, and Nir Shavit
48 "A Lazy Concurrent List-Based Set Algorithm"
50 The lazy list is based on an optimistic locking scheme for inserts and removes,
51 eliminating the need to use the equivalent of an atomically markable
52 reference. It also has a novel wait-free membership \p find() operation
53 that does not need to perform cleanup operations and is more efficient.
55 It is non-intrusive version of \p cds::intrusive::LazyList class.
58 - \p GC - garbage collector: \p gc::HP, \p gp::DHP
59 - \p T - type to be stored in the list.
60 - \p Traits - type traits, default is \p lazy_list::traits.
61 It is possible to declare option-based list with \p lazy_list::make_traits metafunction istead of \p Traits template
62 argument. For example, the following traits-based declaration of \p gc::HP lazy list
64 #include <cds/container/lazy_list_hp.h>
65 // Declare comparator for the item
67 int operator ()( int i1, int i2 )
74 struct my_traits: public cds::container::lazy_list::traits
76 typedef my_compare compare;
79 // Declare traits-based list
80 typedef cds::container::LazyList< cds::gc::HP, int, my_traits > traits_based_list;
82 is equal to the following option-based list:
84 #include <cds/container/lazy_list_hp.h>
86 // my_compare is the same
88 // Declare option-based list
89 typedef cds::container::LazyList< cds::gc::HP, int,
90 typename cds::container::lazy_list::make_traits<
91 cds::container::opt::compare< my_compare > // item comparator option
96 Unlike standard container, this implementation does not divide type \p T into key and value part and
97 may be used as main building block for hash set algorithms.
99 The key is a function (or a part) of type \p T, and the comparing function is specified by \p Traits::compare functor
100 or \p Traits::less predicate.
102 \p LazyKVList is a key-value version of lazy non-intrusive list that is closer to the C++ std library approach.
105 There are different specializations of this template for each garbage collecting schema used.
106 You should include appropriate .h-file depending on GC you are using:
107 - for gc::HP: <tt> <cds/container/lazy_list_hp.h> </tt>
108 - for gc::DHP: <tt> <cds/container/lazy_list_dhp.h> </tt>
109 - for \ref cds_urcu_desc "RCU": <tt> <cds/container/lazy_list_rcu.h> </tt>
110 - for gc::nogc: <tt> <cds/container/lazy_list_nogc.h> </tt>
115 #ifdef CDS_DOXYGEN_INVOKED
116 typename Traits = lazy_list::traits
122 #ifdef CDS_DOXYGEN_INVOKED
123 protected intrusive::LazyList< GC, T, Traits >
125 protected details::make_lazy_list< GC, T, Traits >::type
129 typedef details::make_lazy_list< GC, T, Traits > maker;
130 typedef typename maker::type base_class;
134 typedef GC gc; ///< Garbage collector used
135 typedef T value_type; ///< Type of value stored in the list
136 typedef Traits traits; ///< List traits
138 typedef typename base_class::back_off back_off; ///< Back-off strategy used
139 typedef typename maker::allocator_type allocator_type; ///< Allocator type used for allocate/deallocate the nodes
140 typedef typename base_class::item_counter item_counter; ///< Item counting policy used
141 typedef typename maker::key_comparator key_comparator; ///< key comparison functor
142 typedef typename base_class::memory_model memory_model; ///< Memory ordering. See cds::opt::memory_model option
143 typedef typename base_class::stat stat; ///< Internal statistics
145 static CDS_CONSTEXPR const size_t c_nHazardPtrCount = base_class::c_nHazardPtrCount; ///< Count of hazard pointer required for the algorithm
148 // Rebind traits (split-list support)
149 template <typename... Options>
150 struct rebind_traits {
154 , typename cds::opt::make_options< traits, Options...>::type
159 template <typename Stat>
160 using select_stat_wrapper = typename base_class::template select_stat_wrapper< Stat >;
165 typedef typename base_class::value_type node_type;
166 typedef typename maker::cxx_allocator cxx_allocator;
167 typedef typename maker::node_deallocator node_deallocator;
168 typedef typename maker::intrusive_traits::compare intrusive_key_comparator;
170 typedef typename base_class::node_type head_type;
172 struct node_disposer {
173 void operator()( node_type * pNode )
178 typedef std::unique_ptr< node_type, node_disposer > scoped_node_ptr;
184 typedef typename gc::template guarded_ptr< node_type, value_type, details::guarded_ptr_cast_set<node_type, value_type> > guarded_ptr;
188 template <bool IsConst>
189 class iterator_type: protected base_class::template iterator_type<IsConst>
191 typedef typename base_class::template iterator_type<IsConst> iterator_base;
193 iterator_type( head_type const& pNode )
194 : iterator_base( const_cast<head_type *>( &pNode ))
197 iterator_type( head_type const * pNode )
198 : iterator_base( const_cast<head_type *>( pNode ))
201 friend class LazyList;
204 typedef typename cds::details::make_const_type<value_type, IsConst>::pointer value_ptr;
205 typedef typename cds::details::make_const_type<value_type, IsConst>::reference value_ref;
210 iterator_type( iterator_type const& src )
211 : iterator_base( src )
214 value_ptr operator ->() const
216 typename iterator_base::value_ptr p = iterator_base::operator ->();
217 return p ? &(p->m_Value) : nullptr;
220 value_ref operator *() const
222 return (iterator_base::operator *()).m_Value;
226 iterator_type& operator ++()
228 iterator_base::operator ++();
233 bool operator ==(iterator_type<C> const& i ) const
235 return iterator_base::operator ==(i);
238 bool operator !=(iterator_type<C> const& i ) const
240 return iterator_base::operator !=(i);
246 ///@name Forward iterators (only for debugging purpose)
250 The forward iterator for lazy list has some features:
251 - it has no post-increment operator
252 - to protect the value, the iterator contains a GC-specific guard + another guard is required locally for increment operator.
253 For some GC (\p gc::HP), a guard is limited resource per thread, so an exception (or assertion) "no free guard"
254 may be thrown if a limit of guard count per thread is exceeded.
255 - The iterator cannot be moved across thread boundary since it contains GC's guard that is thread-private GC data.
256 - Iterator ensures thread-safety even if you delete the item that iterator points to. However, in case of concurrent
257 deleting operations it is no guarantee that you iterate all item in the list.
258 Moreover, a crash is possible when you try to iterate the next element that has been deleted by concurrent thread.
260 @warning Use this iterator on the concurrent container for debugging purpose only.
262 typedef iterator_type<false> iterator;
264 /// Const forward iterator
266 For iterator's features and requirements see \ref iterator
268 typedef iterator_type<true> const_iterator;
270 /// Returns a forward iterator addressing the first element in a list
272 For empty list \code begin() == end() \endcode
276 iterator it( head() );
277 ++it ; // skip dummy head node
281 /// Returns an iterator that addresses the location succeeding the last element in a list
283 Do not use the value returned by <tt>end</tt> function to access any item.
285 The returned value can be used only to control reaching the end of the list.
286 For empty list \code begin() == end() \endcode
290 return iterator( tail() );
293 /// Returns a forward const iterator addressing the first element in a list
294 const_iterator begin() const
296 const_iterator it( head() );
297 ++it ; // skip dummy head node
301 /// Returns a forward const iterator addressing the first element in a list
302 const_iterator cbegin() const
304 const_iterator it( head() );
305 ++it ; // skip dummy head node
309 /// Returns an const iterator that addresses the location succeeding the last element in a list
310 const_iterator end() const
312 return const_iterator( tail() );
315 /// Returns an const iterator that addresses the location succeeding the last element in a list
316 const_iterator cend() const
318 return const_iterator( tail() );
323 /// Default constructor
328 template <typename Stat, typename = std::enable_if<std::is_same<stat, lazy_list::wrapped_stat<Stat>>::value >>
329 explicit LazyList( Stat& st )
334 /// Destructor clears the list
342 The function creates a node with copy of \p val value
343 and then inserts the node created into the list.
345 The type \p Q should contain as minimum the complete key of the node.
346 The object of \ref value_type should be constructible from \p val of type \p Q.
347 In trivial case, \p Q is equal to \ref value_type.
349 Returns \p true if inserting successful, \p false otherwise.
351 template <typename Q>
352 bool insert( Q&& val )
354 return insert_at( head(), std::forward<Q>( val ));
359 This function inserts new node with default-constructed value and then it calls
360 \p func functor with signature
361 \code void func( value_type& item ) ;\endcode
363 The argument \p item of user-defined functor \p func is the reference
364 to the list's item inserted.
365 When \p func is called it has exclusive access to the item.
366 The user-defined functor is called only if the inserting is success.
368 The type \p Q should contain the complete key of the node.
369 The object of \p value_type should be constructible from \p key of type \p Q.
371 The function allows to split creating of new item into two part:
372 - create item from \p key with initializing key-fields only;
373 - insert new item into the list;
374 - if inserting is successful, initialize non-key fields of item by calling \p func functor
376 This can be useful if complete initialization of object of \p value_type is heavyweight and
377 it is preferable that the initialization should be completed only if inserting is successful.
379 template <typename Q, typename Func>
380 bool insert( Q&& key, Func func )
382 return insert_at( head(), std::forward<Q>( key ), func );
385 /// Inserts data of type \p value_type constructed from \p args
387 Returns \p true if inserting successful, \p false otherwise.
389 template <typename... Args>
390 bool emplace( Args&&... args )
392 return emplace_at( head(), std::forward<Args>(args)... );
395 /// Updates data by \p key
397 The operation performs inserting or replacing the element with lock-free manner.
399 If the \p key not found in the list, then the new item created from \p key
400 will be inserted iff \p bAllowInsert is \p true.
401 Otherwise, if \p key is found, the functor \p func is called with item found.
403 The functor \p Func signature is:
406 void operator()( bool bNew, value_type& item, Q const& key );
411 - \p bNew - \p true if the item has been inserted, \p false otherwise
412 - \p item - item of the list
413 - \p key - argument \p key passed into the \p %update() function
415 The functor may change non-key fields of the \p item;
416 during \p func call \p item is locked so it is safe to modify the item in
417 multi-threaded environment.
419 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successful,
420 \p second is true if new item has been added or \p false if the item with \p key
423 template <typename Q, typename Func>
424 std::pair<bool, bool> update( Q const& key, Func func, bool bAllowInsert = true )
426 return update_at( head(), key, func, bAllowInsert );
429 template <typename Q, typename Func>
430 CDS_DEPRECATED("ensure() is deprecated, use update()")
431 std::pair<bool, bool> ensure( Q const& key, Func f )
433 return update( key, f, true );
437 /// Deletes \p key from the list
438 /** \anchor cds_nonintrusive_LazyList_hp_erase_val
439 Since the key of LazyList's item type \p T is not explicitly specified,
440 template parameter \p Q defines the key type searching in the list.
441 The list item comparator should be able to compare the type \p T of list item
444 Return \p true if key is found and deleted, \p false otherwise
446 template <typename Q>
447 bool erase( Q const& key )
449 return erase_at( head(), key, intrusive_key_comparator(), [](value_type const&){} );
452 /// Deletes the item from the list using \p pred predicate for searching
454 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_val "erase(Q const&)"
455 but \p pred is used for key comparing.
456 \p Less functor has the interface like \p std::less.
457 \p pred must imply the same element order as the comparator used for building the list.
459 template <typename Q, typename Less>
460 bool erase_with( Q const& key, Less pred )
463 return erase_at( head(), key, typename maker::template less_wrapper<Less>::type(), [](value_type const&){} );
466 /// Deletes \p key from the list
467 /** \anchor cds_nonintrusive_LazyList_hp_erase_func
468 The function searches an item with key \p key, calls \p f functor with item found
469 and deletes the item. If \p key is not found, the functor is not called.
471 The functor \p Func interface:
474 void operator()(const value_type& val) { ... }
478 Since the key of LazyList's item type \p T is not explicitly specified,
479 template parameter \p Q defines the key type searching in the list.
480 The list item comparator should be able to compare the type \p T of list item
483 Return \p true if key is found and deleted, \p false otherwise
487 template <typename Q, typename Func>
488 bool erase( Q const& key, Func f )
490 return erase_at( head(), key, intrusive_key_comparator(), f );
493 /// Deletes the item from the list using \p pred predicate for searching
495 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_func "erase(Q const&, Func)"
496 but \p pred is used for key comparing.
497 \p Less functor has the interface like \p std::less.
498 \p pred must imply the same element order as the comparator used for building the list.
500 template <typename Q, typename Less, typename Func>
501 bool erase_with( Q const& key, Less pred, Func f )
504 return erase_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
507 /// Extracts the item from the list with specified \p key
508 /** \anchor cds_nonintrusive_LazyList_hp_extract
509 The function searches an item with key equal to \p key,
510 unlinks it from the list, and returns it as \p guarded_ptr.
511 If \p key is not found the function returns an empty guarded pointer.
513 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
515 @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
519 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
523 ord_list::guarded_ptr gp(theList.extract( 5 ));
528 // Destructor of gp releases internal HP guard and frees the item
532 template <typename Q>
533 guarded_ptr extract( Q const& key )
536 extract_at( head(), gp.guard(), key, intrusive_key_comparator() );
540 /// Extracts the item from the list with comparing functor \p pred
542 The function is an analog of \ref cds_nonintrusive_LazyList_hp_extract "extract(Q const&)"
543 but \p pred predicate is used for key comparing.
545 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
547 \p pred must imply the same element order as the comparator used for building the list.
549 template <typename Q, typename Less>
550 guarded_ptr extract_with( Q const& key, Less pred )
554 extract_at( head(), gp.guard(), key, typename maker::template less_wrapper<Less>::type() );
558 /// Checks whether the list contains \p key
560 The function searches the item with key equal to \p key
561 and returns \p true if it is found, and \p false otherwise.
563 template <typename Q>
564 bool contains( Q const& key )
566 return find_at( head(), key, intrusive_key_comparator() );
569 template <typename Q>
570 CDS_DEPRECATED("deprecated, use contains()")
571 bool find( Q const& key )
573 return contains( key );
577 /// Checks whether the list contains \p key using \p pred predicate for searching
579 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
580 \p Less functor has the interface like \p std::less.
581 \p pred must imply the same element order as the comparator used for building the list.
583 template <typename Q, typename Less>
584 bool contains( Q const& key, Less pred )
587 return find_at( head(), key, typename maker::template less_wrapper<Less>::type() );
590 template <typename Q, typename Less>
591 CDS_DEPRECATED("deprecated, use contains()")
592 bool find_with( Q const& key, Less pred )
594 return contains( key, pred );
597 /// Finds the key \p key and performs an action with it
598 /** \anchor cds_nonintrusive_LazyList_hp_find_func
599 The function searches an item with key equal to \p key and calls the functor \p f for the item found.
600 The interface of \p Func functor is:
603 void operator()( value_type& item, Q& key );
606 where \p item is the item found, \p key is the <tt>find</tt> function argument.
608 The functor may change non-key fields of \p item. Note that the function is only guarantee
609 that \p item cannot be deleted during functor is executing.
610 The function does not serialize simultaneous access to the list \p item. If such access is
611 possible you must provide your own synchronization schema to exclude unsafe item modifications.
613 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
614 may modify both arguments.
616 The function returns \p true if \p key is found, \p false otherwise.
618 template <typename Q, typename Func>
619 bool find( Q& key, Func f )
621 return find_at( head(), key, intrusive_key_comparator(), f );
624 template <typename Q, typename Func>
625 bool find( Q const& key, Func f )
627 return find_at( head(), key, intrusive_key_comparator(), f );
631 /// Finds the key \p key using \p pred predicate for searching
633 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_func "find(Q&, Func)"
634 but \p pred is used for key comparing.
635 \p Less functor has the interface like \p std::less.
636 \p pred must imply the same element order as the comparator used for building the list.
638 template <typename Q, typename Less, typename Func>
639 bool find_with( Q& key, Less pred, Func f )
642 return find_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
645 template <typename Q, typename Less, typename Func>
646 bool find_with( Q const& key, Less pred, Func f )
649 return find_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
653 /// Finds the key \p key and return the item found
654 /** \anchor cds_nonintrusive_LazyList_hp_get
655 The function searches the item with key equal to \p key
656 and returns the item found as \p guarded_ptr.
657 If \p key is not found the function returns an empty guarded pointer.
659 @note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
663 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
667 ord_list::guarded_ptr gp( theList.get( 5 ));
672 // Destructor of guarded_ptr releases internal HP guard and frees the item
676 Note the compare functor specified for class \p Traits template parameter
677 should accept a parameter of type \p Q that can be not the same as \p value_type.
679 template <typename Q>
680 guarded_ptr get( Q const& key )
683 get_at( head(), gp.guard(), key, intrusive_key_comparator() );
687 /// Finds the key \p key and return the item found
689 The function is an analog of \ref cds_nonintrusive_LazyList_hp_get "get( Q const&)"
690 but \p pred is used for comparing the keys.
692 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
694 \p pred must imply the same element order as the comparator used for building the list.
696 template <typename Q, typename Less>
697 guarded_ptr get_with( Q const& key, Less pred )
701 get_at( head(), gp.guard(), key, typename maker::template less_wrapper<Less>::type() );
705 /// Checks whether the list is empty
708 return base_class::empty();
711 /// Returns list's item count
713 The value returned depends on \p Traits::item_counter type. For \p atomicity::empty_item_counter,
714 this function always returns 0.
716 @note Even if you use real item counter and it returns 0, this fact is not mean that the list
717 is empty. To check list emptyness use \ref empty() method.
721 return base_class::size();
724 /// Returns const reference to internal statistics
725 stat const& statistics() const
727 return base_class::statistics();
738 static value_type& node_to_value( node_type& n )
743 static value_type const& node_to_value( node_type const& n )
748 template <typename Q>
749 static node_type * alloc_node( Q const& v )
751 return cxx_allocator().New( v );
754 template <typename... Args>
755 static node_type * alloc_node( Args&&... args )
757 return cxx_allocator().MoveNew( std::forward<Args>( args )... );
760 static void free_node( node_type * pNode )
762 cxx_allocator().Delete( pNode );
767 return base_class::m_Head;
770 head_type const& head() const
772 return base_class::m_Head;
777 return base_class::m_Tail;
780 head_type const& tail() const
782 return base_class::m_Tail;
785 bool insert_node( node_type * pNode )
787 return insert_node_at( head(), pNode );
790 bool insert_node_at( head_type& refHead, node_type * pNode )
792 assert( pNode != nullptr );
793 scoped_node_ptr p( pNode );
795 if ( base_class::insert_at( &refHead, *pNode )) {
803 template <typename Q>
804 bool insert_at( head_type& refHead, Q&& val )
806 return insert_node_at( refHead, alloc_node( std::forward<Q>( val )));
809 template <typename... Args>
810 bool emplace_at( head_type& refHead, Args&&... args )
812 return insert_node_at( refHead, alloc_node( std::forward<Args>(args)... ));
815 template <typename Q, typename Func>
816 bool insert_at( head_type& refHead, Q&& key, Func f )
818 scoped_node_ptr pNode( alloc_node( std::forward<Q>( key )));
820 if ( base_class::insert_at( &refHead, *pNode, [&f](node_type& node){ f( node_to_value(node) ); } )) {
827 template <typename Q, typename Compare, typename Func>
828 bool erase_at( head_type& refHead, Q const& key, Compare cmp, Func f )
830 return base_class::erase_at( &refHead, key, cmp, [&f](node_type const& node){ f( node_to_value(node) ); } );
833 template <typename Q, typename Compare>
834 bool extract_at( head_type& refHead, typename guarded_ptr::native_guard& guard, Q const& key, Compare cmp )
836 return base_class::extract_at( &refHead, guard, key, cmp );
839 template <typename Q, typename Func>
840 std::pair<bool, bool> update_at( head_type& refHead, Q const& key, Func f, bool bAllowInsert )
842 scoped_node_ptr pNode( alloc_node( key ));
844 std::pair<bool, bool> ret = base_class::update_at( &refHead, *pNode,
845 [&f, &key](bool bNew, node_type& node, node_type&) { f( bNew, node_to_value(node), key );},
847 if ( ret.first && ret.second )
853 template <typename Q, typename Compare>
854 bool find_at( head_type& refHead, Q const& key, Compare cmp )
856 return base_class::find_at( &refHead, key, cmp );
859 template <typename Q, typename Compare, typename Func>
860 bool find_at( head_type& refHead, Q& val, Compare cmp, Func f )
862 return base_class::find_at( &refHead, val, cmp, [&f](node_type& node, Q& val){ f( node_to_value(node), val ); });
865 template <typename Q, typename Compare>
866 bool get_at( head_type& refHead, typename guarded_ptr::native_guard& guard, Q const& key, Compare cmp )
868 return base_class::get_at( &refHead, guard, key, cmp );
874 }} // namespace cds::container
876 #endif // #ifndef CDSLIB_CONTAINER_IMPL_LAZY_LIST_H