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
149 typedef typename base_class::value_type node_type;
150 typedef typename maker::cxx_allocator cxx_allocator;
151 typedef typename maker::node_deallocator node_deallocator;
152 typedef typename maker::intrusive_traits::compare intrusive_key_comparator;
154 typedef typename base_class::node_type head_type;
159 typedef typename gc::template guarded_ptr< node_type, value_type, details::guarded_ptr_cast_set<node_type, value_type> > guarded_ptr;
163 static value_type& node_to_value( node_type& n )
168 static value_type const& node_to_value( node_type const& n )
173 template <typename Q>
174 static node_type * alloc_node( Q const& v )
176 return cxx_allocator().New( v );
179 template <typename... Args>
180 static node_type * alloc_node( Args&&... args )
182 return cxx_allocator().MoveNew( std::forward<Args>(args)... );
185 static void free_node( node_type * pNode )
187 cxx_allocator().Delete( pNode );
190 struct node_disposer {
191 void operator()( node_type * pNode )
196 typedef std::unique_ptr< node_type, node_disposer > scoped_node_ptr;
200 return base_class::m_Head;
203 head_type const& head() const
205 return base_class::m_Head;
210 return base_class::m_Tail;
213 head_type const& tail() const
215 return base_class::m_Tail;
221 template <bool IsConst>
222 class iterator_type: protected base_class::template iterator_type<IsConst>
224 typedef typename base_class::template iterator_type<IsConst> iterator_base;
226 iterator_type( head_type const& pNode )
227 : iterator_base( const_cast<head_type *>( &pNode ))
230 iterator_type( head_type const * pNode )
231 : iterator_base( const_cast<head_type *>( pNode ))
234 friend class LazyList;
237 typedef typename cds::details::make_const_type<value_type, IsConst>::pointer value_ptr;
238 typedef typename cds::details::make_const_type<value_type, IsConst>::reference value_ref;
243 iterator_type( const iterator_type& src )
244 : iterator_base( src )
247 value_ptr operator ->() const
249 typename iterator_base::value_ptr p = iterator_base::operator ->();
250 return p ? &(p->m_Value) : nullptr;
253 value_ref operator *() const
255 return (iterator_base::operator *()).m_Value;
259 iterator_type& operator ++()
261 iterator_base::operator ++();
266 bool operator ==(iterator_type<C> const& i ) const
268 return iterator_base::operator ==(i);
271 bool operator !=(iterator_type<C> const& i ) const
273 return iterator_base::operator !=(i);
279 ///@name Forward iterators (only for debugging purpose)
283 The forward iterator for lazy list has some features:
284 - it has no post-increment operator
285 - to protect the value, the iterator contains a GC-specific guard + another guard is required locally for increment operator.
286 For some GC (\p gc::HP), a guard is limited resource per thread, so an exception (or assertion) "no free guard"
287 may be thrown if a limit of guard count per thread is exceeded.
288 - The iterator cannot be moved across thread boundary since it contains GC's guard that is thread-private GC data.
289 - Iterator ensures thread-safety even if you delete the item that iterator points to. However, in case of concurrent
290 deleting operations it is no guarantee that you iterate all item in the list.
291 Moreover, a crash is possible when you try to iterate the next element that has been deleted by concurrent thread.
293 @warning Use this iterator on the concurrent container for debugging purpose only.
295 typedef iterator_type<false> iterator;
297 /// Const forward iterator
299 For iterator's features and requirements see \ref iterator
301 typedef iterator_type<true> const_iterator;
303 /// Returns a forward iterator addressing the first element in a list
305 For empty list \code begin() == end() \endcode
309 iterator it( head() );
310 ++it ; // skip dummy head node
314 /// Returns an iterator that addresses the location succeeding the last element in a list
316 Do not use the value returned by <tt>end</tt> function to access any item.
318 The returned value can be used only to control reaching the end of the list.
319 For empty list \code begin() == end() \endcode
323 return iterator( tail() );
326 /// Returns a forward const iterator addressing the first element in a list
327 const_iterator begin() const
329 const_iterator it( head() );
330 ++it ; // skip dummy head node
334 /// Returns a forward const iterator addressing the first element in a list
335 const_iterator cbegin() const
337 const_iterator it( head() );
338 ++it ; // skip dummy head node
342 /// Returns an const iterator that addresses the location succeeding the last element in a list
343 const_iterator end() const
345 return const_iterator( tail() );
348 /// Returns an const iterator that addresses the location succeeding the last element in a list
349 const_iterator cend() const
351 return const_iterator( tail() );
356 /// Default constructor
361 template <typename Stat, typename = std::enable_if<std::is_same<stat, lazy_list::wrapped_stat<Stat>>::value >>
362 explicit LazyList( Stat& st )
367 /// Destructor clears the list
375 The function creates a node with copy of \p val value
376 and then inserts the node created into the list.
378 The type \p Q should contain as minimum the complete key of the node.
379 The object of \ref value_type should be constructible from \p val of type \p Q.
380 In trivial case, \p Q is equal to \ref value_type.
382 Returns \p true if inserting successful, \p false otherwise.
384 template <typename Q>
385 bool insert( Q const& val )
387 return insert_at( head(), val );
392 This function inserts new node with default-constructed value and then it calls
393 \p func functor with signature
394 \code void func( value_type& item ) ;\endcode
396 The argument \p item of user-defined functor \p func is the reference
397 to the list's item inserted.
398 When \p func is called it has exclusive access to the item.
399 The user-defined functor is called only if the inserting is success.
401 The type \p Q should contain the complete key of the node.
402 The object of \p value_type should be constructible from \p key of type \p Q.
404 The function allows to split creating of new item into two part:
405 - create item from \p key with initializing key-fields only;
406 - insert new item into the list;
407 - if inserting is successful, initialize non-key fields of item by calling \p func functor
409 This can be useful if complete initialization of object of \p value_type is heavyweight and
410 it is preferable that the initialization should be completed only if inserting is successful.
412 template <typename Q, typename Func>
413 bool insert( Q const& key, Func func )
415 return insert_at( head(), key, func );
418 /// Inserts data of type \p value_type constructed from \p args
420 Returns \p true if inserting successful, \p false otherwise.
422 template <typename... Args>
423 bool emplace( Args&&... args )
425 return emplace_at( head(), std::forward<Args>(args)... );
428 /// Updates data by \p key
430 The operation performs inserting or replacing the element with lock-free manner.
432 If the \p key not found in the list, then the new item created from \p key
433 will be inserted iff \p bAllowInsert is \p true.
434 Otherwise, if \p key is found, the functor \p func is called with item found.
436 The functor \p Func signature is:
439 void operator()( bool bNew, value_type& item, Q const& val );
444 - \p bNew - \p true if the item has been inserted, \p false otherwise
445 - \p item - item of the list
446 - \p val - argument \p key passed into the \p %update() function
448 The functor may change non-key fields of the \p item;
449 during \p func call \p item is locked so it is safe to modify the item in
450 multi-threaded environment.
452 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successful,
453 \p second is true if new item has been added or \p false if the item with \p key
456 template <typename Q, typename Func>
457 std::pair<bool, bool> update( Q const& key, Func func, bool bAllowInsert = true )
459 return update_at( head(), key, func, bAllowInsert );
462 template <typename Q, typename Func>
463 CDS_DEPRECATED("ensure() is deprecated, use update()")
464 std::pair<bool, bool> ensure( Q const& key, Func f )
466 return update( key, f, true );
470 /// Deletes \p key from the list
471 /** \anchor cds_nonintrusive_LazyList_hp_erase_val
472 Since the key of LazyList's item type \p T is not explicitly specified,
473 template parameter \p Q defines the key type searching in the list.
474 The list item comparator should be able to compare the type \p T of list item
477 Return \p true if key is found and deleted, \p false otherwise
479 template <typename Q>
480 bool erase( Q const& key )
482 return erase_at( head(), key, intrusive_key_comparator(), [](value_type const&){} );
485 /// Deletes the item from the list using \p pred predicate for searching
487 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_val "erase(Q const&)"
488 but \p pred is used for key comparing.
489 \p Less functor has the interface like \p std::less.
490 \p pred must imply the same element order as the comparator used for building the list.
492 template <typename Q, typename Less>
493 bool erase_with( Q const& key, Less pred )
496 return erase_at( head(), key, typename maker::template less_wrapper<Less>::type(), [](value_type const&){} );
499 /// Deletes \p key from the list
500 /** \anchor cds_nonintrusive_LazyList_hp_erase_func
501 The function searches an item with key \p key, calls \p f functor with item found
502 and deletes the item. If \p key is not found, the functor is not called.
504 The functor \p Func interface:
507 void operator()(const value_type& val) { ... }
511 Since the key of LazyList's item type \p T is not explicitly specified,
512 template parameter \p Q defines the key type searching in the list.
513 The list item comparator should be able to compare the type \p T of list item
516 Return \p true if key is found and deleted, \p false otherwise
520 template <typename Q, typename Func>
521 bool erase( Q const& key, Func f )
523 return erase_at( head(), key, intrusive_key_comparator(), f );
526 /// Deletes the item from the list using \p pred predicate for searching
528 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_func "erase(Q const&, Func)"
529 but \p pred is used for key comparing.
530 \p Less functor has the interface like \p std::less.
531 \p pred must imply the same element order as the comparator used for building the list.
533 template <typename Q, typename Less, typename Func>
534 bool erase_with( Q const& key, Less pred, Func f )
537 return erase_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
540 /// Extracts the item from the list with specified \p key
541 /** \anchor cds_nonintrusive_LazyList_hp_extract
542 The function searches an item with key equal to \p key,
543 unlinks it from the list, and returns it as \p guarded_ptr.
544 If \p key is not found the function returns an empty guarded pointer.
546 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
548 @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
552 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
556 ord_list::guarded_ptr gp(theList.extract( 5 ));
561 // Destructor of gp releases internal HP guard and frees the item
565 template <typename Q>
566 guarded_ptr extract( Q const& key )
569 extract_at( head(), gp.guard(), key, intrusive_key_comparator() );
573 /// Extracts the item from the list with comparing functor \p pred
575 The function is an analog of \ref cds_nonintrusive_LazyList_hp_extract "extract(Q const&)"
576 but \p pred predicate is used for key comparing.
578 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
580 \p pred must imply the same element order as the comparator used for building the list.
582 template <typename Q, typename Less>
583 guarded_ptr extract_with( Q const& key, Less pred )
587 extract_at( head(), gp.guard(), key, typename maker::template less_wrapper<Less>::type() );
591 /// Checks whether the list contains \p key
593 The function searches the item with key equal to \p key
594 and returns \p true if it is found, and \p false otherwise.
596 template <typename Q>
597 bool contains( Q const& key )
599 return find_at( head(), key, intrusive_key_comparator() );
602 template <typename Q>
603 CDS_DEPRECATED("deprecated, use contains()")
604 bool find( Q const& key )
606 return contains( key );
610 /// Checks whether the list contains \p key using \p pred predicate for searching
612 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
613 \p Less functor has the interface like \p std::less.
614 \p pred must imply the same element order as the comparator used for building the list.
616 template <typename Q, typename Less>
617 bool contains( Q const& key, Less pred )
620 return find_at( head(), key, typename maker::template less_wrapper<Less>::type() );
623 template <typename Q, typename Less>
624 CDS_DEPRECATED("deprecated, use contains()")
625 bool find_with( Q const& key, Less pred )
627 return contains( key, pred );
630 /// Finds the key \p key and performs an action with it
631 /** \anchor cds_nonintrusive_LazyList_hp_find_func
632 The function searches an item with key equal to \p key and calls the functor \p f for the item found.
633 The interface of \p Func functor is:
636 void operator()( value_type& item, Q& key );
639 where \p item is the item found, \p key is the <tt>find</tt> function argument.
641 The functor may change non-key fields of \p item. Note that the function is only guarantee
642 that \p item cannot be deleted during functor is executing.
643 The function does not serialize simultaneous access to the list \p item. If such access is
644 possible you must provide your own synchronization schema to exclude unsafe item modifications.
646 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
647 may modify both arguments.
649 The function returns \p true if \p key is found, \p false otherwise.
651 template <typename Q, typename Func>
652 bool find( Q& key, Func f )
654 return find_at( head(), key, intrusive_key_comparator(), f );
657 template <typename Q, typename Func>
658 bool find( Q const& key, Func f )
660 return find_at( head(), key, intrusive_key_comparator(), f );
664 /// Finds the key \p key using \p pred predicate for searching
666 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_func "find(Q&, Func)"
667 but \p pred is used for key comparing.
668 \p Less functor has the interface like \p std::less.
669 \p pred must imply the same element order as the comparator used for building the list.
671 template <typename Q, typename Less, typename Func>
672 bool find_with( Q& key, Less pred, Func f )
675 return find_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
678 template <typename Q, typename Less, typename Func>
679 bool find_with( Q const& key, Less pred, Func f )
682 return find_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
686 /// Finds the key \p key and return the item found
687 /** \anchor cds_nonintrusive_LazyList_hp_get
688 The function searches the item with key equal to \p key
689 and returns the item found as \p guarded_ptr.
690 If \p key is not found the function returns an empty guarded pointer.
692 @note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
696 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
700 ord_list::guarded_ptr gp( theList.get( 5 ));
705 // Destructor of guarded_ptr releases internal HP guard and frees the item
709 Note the compare functor specified for class \p Traits template parameter
710 should accept a parameter of type \p Q that can be not the same as \p value_type.
712 template <typename Q>
713 guarded_ptr get( Q const& key )
716 get_at( head(), gp.guard(), key, intrusive_key_comparator() );
720 /// Finds the key \p key and return the item found
722 The function is an analog of \ref cds_nonintrusive_LazyList_hp_get "get( Q const&)"
723 but \p pred is used for comparing the keys.
725 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
727 \p pred must imply the same element order as the comparator used for building the list.
729 template <typename Q, typename Less>
730 guarded_ptr get_with( Q const& key, Less pred )
734 get_at( head(), gp.guard(), key, typename maker::template less_wrapper<Less>::type() );
738 /// Checks whether the list is empty
741 return base_class::empty();
744 /// Returns list's item count
746 The value returned depends on \p Traits::item_counter type. For \p atomicity::empty_item_counter,
747 this function always returns 0.
749 @note Even if you use real item counter and it returns 0, this fact is not mean that the list
750 is empty. To check list emptyness use \ref empty() method.
754 return base_class::size();
757 /// Returns const reference to internal statistics
758 stat const& statistics() const
760 return base_class::statistics();
771 bool insert_node( node_type * pNode )
773 return insert_node_at( head(), pNode );
776 bool insert_node_at( head_type& refHead, node_type * pNode )
778 assert( pNode != nullptr );
779 scoped_node_ptr p( pNode );
781 if ( base_class::insert_at( &refHead, *pNode )) {
789 template <typename Q>
790 bool insert_at( head_type& refHead, const Q& val )
792 return insert_node_at( refHead, alloc_node( val ));
795 template <typename... Args>
796 bool emplace_at( head_type& refHead, Args&&... args )
798 return insert_node_at( refHead, alloc_node( std::forward<Args>(args)... ));
801 template <typename Q, typename Func>
802 bool insert_at( head_type& refHead, const Q& key, Func f )
804 scoped_node_ptr pNode( alloc_node( key ));
806 if ( base_class::insert_at( &refHead, *pNode, [&f](node_type& node){ f( node_to_value(node) ); } )) {
813 template <typename Q, typename Compare, typename Func>
814 bool erase_at( head_type& refHead, const Q& key, Compare cmp, Func f )
816 return base_class::erase_at( &refHead, key, cmp, [&f](node_type const& node){ f( node_to_value(node) ); } );
819 template <typename Q, typename Compare>
820 bool extract_at( head_type& refHead, typename guarded_ptr::native_guard& guard, Q const& key, Compare cmp )
822 return base_class::extract_at( &refHead, guard, key, cmp );
825 template <typename Q, typename Func>
826 std::pair<bool, bool> update_at( head_type& refHead, const Q& key, Func f, bool bAllowInsert )
828 scoped_node_ptr pNode( alloc_node( key ));
830 std::pair<bool, bool> ret = base_class::update_at( &refHead, *pNode,
831 [&f, &key](bool bNew, node_type& node, node_type&){f( bNew, node_to_value(node), key );},
833 if ( ret.first && ret.second )
839 template <typename Q, typename Compare>
840 bool find_at( head_type& refHead, Q const& key, Compare cmp )
842 return base_class::find_at( &refHead, key, cmp );
845 template <typename Q, typename Compare, typename Func>
846 bool find_at( head_type& refHead, Q& val, Compare cmp, Func f )
848 return base_class::find_at( &refHead, val, cmp, [&f](node_type& node, Q& val){ f( node_to_value(node), val ); });
851 template <typename Q, typename Compare>
852 bool get_at( head_type& refHead, typename guarded_ptr::native_guard& guard, Q const& key, Compare cmp )
854 return base_class::get_at( &refHead, guard, key, cmp );
860 }} // namespace cds::container
862 #endif // #ifndef CDSLIB_CONTAINER_IMPL_LAZY_LIST_H