3 #ifndef CDSLIB_CONTAINER_IMPL_LAZY_LIST_H
4 #define CDSLIB_CONTAINER_IMPL_LAZY_LIST_H
7 #include <cds/container/details/guarded_ptr_cast.h>
9 namespace cds { namespace container {
12 /** @ingroup cds_nonintrusive_list
13 @anchor cds_nonintrusive_LazyList_gc
15 Usually, ordered single-linked list is used as a building block for the hash table implementation.
16 The complexity of searching is <tt>O(N)</tt>.
19 - [2005] Steve Heller, Maurice Herlihy, Victor Luchangco, Mark Moir, William N. Scherer III, and Nir Shavit
20 "A Lazy Concurrent List-Based Set Algorithm"
22 The lazy list is based on an optimistic locking scheme for inserts and removes,
23 eliminating the need to use the equivalent of an atomically markable
24 reference. It also has a novel wait-free membership \p find() operation
25 that does not need to perform cleanup operations and is more efficient.
27 It is non-intrusive version of \p cds::intrusive::LazyList class.
30 - \p GC - garbage collector: \p gc::HP, \p gp::DHP
31 - \p T - type to be stored in the list.
32 - \p Traits - type traits, default is \p lazy_list::traits.
33 It is possible to declare option-based list with \p lazy_list::make_traits metafunction istead of \p Traits template
34 argument. For example, the following traits-based declaration of \p gc::HP lazy list
36 #include <cds/container/lazy_list_hp.h>
37 // Declare comparator for the item
39 int operator ()( int i1, int i2 )
46 struct my_traits: public cds::container::lazy_list::traits
48 typedef my_compare compare;
51 // Declare traits-based list
52 typedef cds::container::LazyList< cds::gc::HP, int, my_traits > traits_based_list;
54 is equal to the following option-based list:
56 #include <cds/container/lazy_list_hp.h>
58 // my_compare is the same
60 // Declare option-based list
61 typedef cds::container::LazyList< cds::gc::HP, int,
62 typename cds::container::lazy_list::make_traits<
63 cds::container::opt::compare< my_compare > // item comparator option
68 Unlike standard container, this implementation does not divide type \p T into key and value part and
69 may be used as main building block for hash set algorithms.
71 The key is a function (or a part) of type \p T, and the comparing function is specified by \p Traits::compare functor
72 or \p Traits::less predicate.
74 \p LazyKVList is a key-value version of lazy non-intrusive list that is closer to the C++ std library approach.
77 There are different specializations of this template for each garbage collecting schema used.
78 You should include appropriate .h-file depending on GC you are using:
79 - for gc::HP: <tt> <cds/container/lazy_list_hp.h> </tt>
80 - for gc::DHP: <tt> <cds/container/lazy_list_dhp.h> </tt>
81 - for \ref cds_urcu_desc "RCU": <tt> <cds/container/lazy_list_rcu.h> </tt>
82 - for gc::nogc: <tt> <cds/container/lazy_list_nogc.h> </tt>
87 #ifdef CDS_DOXYGEN_INVOKED
88 typename Traits = lazy_list::traits
94 #ifdef CDS_DOXYGEN_INVOKED
95 protected intrusive::LazyList< GC, T, Traits >
97 protected details::make_lazy_list< GC, T, Traits >::type
101 typedef details::make_lazy_list< GC, T, Traits > maker;
102 typedef typename maker::type base_class;
106 typedef GC gc; ///< Garbage collector used
107 typedef T value_type; ///< Type of value stored in the list
108 typedef Traits traits; ///< List traits
110 typedef typename base_class::back_off back_off; ///< Back-off strategy used
111 typedef typename maker::allocator_type allocator_type; ///< Allocator type used for allocate/deallocate the nodes
112 typedef typename base_class::item_counter item_counter; ///< Item counting policy used
113 typedef typename maker::key_comparator key_comparator; ///< key comparison functor
114 typedef typename base_class::memory_model memory_model; ///< Memory ordering. See cds::opt::memory_model option
118 typedef typename base_class::value_type node_type;
119 typedef typename maker::cxx_allocator cxx_allocator;
120 typedef typename maker::node_deallocator node_deallocator;
121 typedef typename maker::intrusive_traits::compare intrusive_key_comparator;
123 typedef typename base_class::node_type head_type;
128 typedef typename gc::template guarded_ptr< node_type, value_type, details::guarded_ptr_cast_set<node_type, value_type> > guarded_ptr;
132 static value_type& node_to_value( node_type& n )
136 static value_type const& node_to_value( node_type const& n )
144 template <typename Q>
145 static node_type * alloc_node( Q const& v )
147 return cxx_allocator().New( v );
150 template <typename... Args>
151 static node_type * alloc_node( Args&&... args )
153 return cxx_allocator().MoveNew( std::forward<Args>(args)... );
156 static void free_node( node_type * pNode )
158 cxx_allocator().Delete( pNode );
161 struct node_disposer {
162 void operator()( node_type * pNode )
167 typedef std::unique_ptr< node_type, node_disposer > scoped_node_ptr;
171 return base_class::m_Head;
174 head_type const& head() const
176 return base_class::m_Head;
181 return base_class::m_Tail;
184 head_type const& tail() const
186 return base_class::m_Tail;
192 template <bool IsConst>
193 class iterator_type: protected base_class::template iterator_type<IsConst>
195 typedef typename base_class::template iterator_type<IsConst> iterator_base;
197 iterator_type( head_type const& pNode )
198 : iterator_base( const_cast<head_type *>( &pNode ))
201 iterator_type( head_type const * pNode )
202 : iterator_base( const_cast<head_type *>( pNode ))
205 friend class LazyList;
208 typedef typename cds::details::make_const_type<value_type, IsConst>::pointer value_ptr;
209 typedef typename cds::details::make_const_type<value_type, IsConst>::reference value_ref;
214 iterator_type( const iterator_type& src )
215 : iterator_base( src )
218 value_ptr operator ->() const
220 typename iterator_base::value_ptr p = iterator_base::operator ->();
221 return p ? &(p->m_Value) : nullptr;
224 value_ref operator *() const
226 return (iterator_base::operator *()).m_Value;
230 iterator_type& operator ++()
232 iterator_base::operator ++();
237 bool operator ==(iterator_type<C> const& i ) const
239 return iterator_base::operator ==(i);
242 bool operator !=(iterator_type<C> const& i ) const
244 return iterator_base::operator !=(i);
252 The forward iterator for lazy list has some features:
253 - it has no post-increment operator
254 - to protect the value, the iterator contains a GC-specific guard + another guard is required locally for increment operator.
255 For some GC (\p gc::HP), a guard is limited resource per thread, so an exception (or assertion) "no free guard"
256 may be thrown if a limit of guard count per thread is exceeded.
257 - The iterator cannot be moved across thread boundary since it contains GC's guard that is thread-private GC data.
258 - Iterator ensures thread-safety even if you delete the item that iterator points to. However, in case of concurrent
259 deleting operations it is no guarantee that you iterate all item in the list.
261 Therefore, the use of iterators in concurrent environment is not good idea. Use the iterator on the concurrent container
262 for debug purpose only.
264 typedef iterator_type<false> iterator;
266 /// Const forward iterator
268 For iterator's features and requirements see \ref iterator
270 typedef iterator_type<true> const_iterator;
272 /// Returns a forward iterator addressing the first element in a list
274 For empty list \code begin() == end() \endcode
278 iterator it( head() );
279 ++it ; // skip dummy head node
283 /// Returns an iterator that addresses the location succeeding the last element in a list
285 Do not use the value returned by <tt>end</tt> function to access any item.
287 The returned value can be used only to control reaching the end of the list.
288 For empty list \code begin() == end() \endcode
292 return iterator( tail() );
295 /// Returns a forward const iterator addressing the first element in a list
297 const_iterator begin() const
299 const_iterator it( head() );
300 ++it ; // skip dummy head node
303 const_iterator cbegin() const
305 const_iterator it( head() );
306 ++it ; // skip dummy head node
311 /// Returns an const iterator that addresses the location succeeding the last element in a list
313 const_iterator end() const
315 return const_iterator( tail() );
317 const_iterator cend() const
319 return const_iterator( tail() );
324 /// Default constructor
328 /// Destructor clears the list
336 The function creates a node with copy of \p val value
337 and then inserts the node created into the list.
339 The type \p Q should contain as minimum the complete key of the node.
340 The object of \ref value_type should be constructible from \p val of type \p Q.
341 In trivial case, \p Q is equal to \ref value_type.
343 Returns \p true if inserting successful, \p false otherwise.
345 template <typename Q>
346 bool insert( Q const& val )
348 return insert_at( head(), val );
353 This function inserts new node with default-constructed value and then it calls
354 \p func functor with signature
355 \code void func( value_type& item ) ;\endcode
357 The argument \p item of user-defined functor \p func is the reference
358 to the list's item inserted.
359 When \p func is called it has exclusive access to the item.
360 The user-defined functor is called only if the inserting is success.
362 The type \p Q should contain the complete key of the node.
363 The object of \p value_type should be constructible from \p key of type \p Q.
365 The function allows to split creating of new item into two part:
366 - create item from \p key with initializing key-fields only;
367 - insert new item into the list;
368 - if inserting is successful, initialize non-key fields of item by calling \p func functor
370 This can be useful if complete initialization of object of \p value_type is heavyweight and
371 it is preferable that the initialization should be completed only if inserting is successful.
373 template <typename Q, typename Func>
374 bool insert( Q const& key, Func func )
376 return insert_at( head(), key, func );
379 /// Inserts data of type \p value_type constructed from \p args
381 Returns \p true if inserting successful, \p false otherwise.
383 template <typename... Args>
384 bool emplace( Args&&... args )
386 return emplace_at( head(), std::forward<Args>(args)... );
389 /// Updates data by \p key
391 The operation performs inserting or replacing the element with lock-free manner.
393 If the \p key not found in the list, then the new item created from \p key
394 will be inserted iff \p bAllowInsert is \p true.
395 Otherwise, if \p key is found, the functor \p func is called with item found.
397 The functor \p Func signature is:
400 void operator()( bool bNew, value_type& item, Q const& val );
405 - \p bNew - \p true if the item has been inserted, \p false otherwise
406 - \p item - item of the list
407 - \p val - argument \p key passed into the \p %update() function
409 The functor may change non-key fields of the \p item;
410 during \p func call \p item is locked so it is safe to modify the item in
411 multi-threaded environment.
413 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
414 \p second is true if new item has been added or \p false if the item with \p key
417 template <typename Q, typename Func>
418 std::pair<bool, bool> update( Q const& key, Func func, bool bAllowInsert = true )
420 return update_at( head(), key, func, bAllowInsert );
423 template <typename Q, typename Func>
424 CDS_DEPRECATED("ensure() is deprecated, use update()")
425 std::pair<bool, bool> ensure( Q const& key, Func f )
427 return update( key, f, true );
431 /// Deletes \p key from the list
432 /** \anchor cds_nonintrusive_LazyList_hp_erase_val
433 Since the key of LazyList's item type \p T is not explicitly specified,
434 template parameter \p Q defines the key type searching in the list.
435 The list item comparator should be able to compare the type \p T of list item
438 Return \p true if key is found and deleted, \p false otherwise
440 template <typename Q>
441 bool erase( Q const& key )
443 return erase_at( head(), key, intrusive_key_comparator(), [](value_type const&){} );
446 /// Deletes the item from the list using \p pred predicate for searching
448 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_val "erase(Q const&)"
449 but \p pred is used for key comparing.
450 \p Less functor has the interface like \p std::less.
451 \p pred must imply the same element order as the comparator used for building the list.
453 template <typename Q, typename Less>
454 bool erase_with( Q const& key, Less pred )
457 return erase_at( head(), key, typename maker::template less_wrapper<Less>::type(), [](value_type const&){} );
460 /// Deletes \p key from the list
461 /** \anchor cds_nonintrusive_LazyList_hp_erase_func
462 The function searches an item with key \p key, calls \p f functor with item found
463 and deletes the item. If \p key is not found, the functor is not called.
465 The functor \p Func interface:
468 void operator()(const value_type& 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
481 template <typename Q, typename Func>
482 bool erase( Q const& key, Func f )
484 return erase_at( head(), key, intrusive_key_comparator(), f );
487 /// Deletes the item from the list using \p pred predicate for searching
489 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_func "erase(Q const&, Func)"
490 but \p pred is used for key comparing.
491 \p Less functor has the interface like \p std::less.
492 \p pred must imply the same element order as the comparator used for building the list.
494 template <typename Q, typename Less, typename Func>
495 bool erase_with( Q const& key, Less pred, Func f )
498 return erase_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
501 /// Extracts the item from the list with specified \p key
502 /** \anchor cds_nonintrusive_LazyList_hp_extract
503 The function searches an item with key equal to \p key,
504 unlinks it from the list, and returns it as \p guarded_ptr.
505 If \p key is not found the function returns an empty guarded pointer.
507 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
509 @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
513 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
517 ord_list::guarded_ptr gp(theList.extract( 5 ));
522 // Destructor of gp releases internal HP guard and frees the item
526 template <typename Q>
527 guarded_ptr extract( Q const& key )
530 extract_at( head(), gp.guard(), key, intrusive_key_comparator() );
534 /// Extracts the item from the list with comparing functor \p pred
536 The function is an analog of \ref cds_nonintrusive_LazyList_hp_extract "extract(Q const&)"
537 but \p pred predicate is used for key comparing.
539 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
541 \p pred must imply the same element order as the comparator used for building the list.
543 template <typename Q, typename Less>
544 guarded_ptr extract_with( Q const& key, Less pred )
548 extract_at( head(), gp.guard(), key, typename maker::template less_wrapper<Less>::type() );
552 /// Checks whether the list contains \p key
554 The function searches the item with key equal to \p key
555 and returns \p true if it is found, and \p false otherwise.
557 template <typename Q>
558 bool contains( Q const& key )
560 return find_at( head(), key, intrusive_key_comparator() );
563 template <typename Q>
564 CDS_DEPRECATED("deprecated, use contains()")
565 bool find( Q const& key )
567 return contains( key );
571 /// Checks whether the list contains \p key using \p pred predicate for searching
573 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
574 \p Less functor has the interface like \p std::less.
575 \p pred must imply the same element order as the comparator used for building the list.
577 template <typename Q, typename Less>
578 bool contains( Q const& key, Less pred )
581 return find_at( head(), key, typename maker::template less_wrapper<Less>::type() );
584 template <typename Q, typename Less>
585 CDS_DEPRECATED("deprecated, use contains()")
586 bool find_with( Q const& key, Less pred )
588 return contains( key, pred );
591 /// Finds the key \p key and performs an action with it
592 /** \anchor cds_nonintrusive_LazyList_hp_find_func
593 The function searches an item with key equal to \p key and calls the functor \p f for the item found.
594 The interface of \p Func functor is:
597 void operator()( value_type& item, Q& key );
600 where \p item is the item found, \p key is the <tt>find</tt> function argument.
602 The functor may change non-key fields of \p item. Note that the function is only guarantee
603 that \p item cannot be deleted during functor is executing.
604 The function does not serialize simultaneous access to the list \p item. If such access is
605 possible you must provide your own synchronization schema to exclude unsafe item modifications.
607 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
608 may modify both arguments.
610 The function returns \p true if \p key is found, \p false otherwise.
612 template <typename Q, typename Func>
613 bool find( Q& key, Func f )
615 return find_at( head(), key, intrusive_key_comparator(), f );
618 template <typename Q, typename Func>
619 bool find( Q const& key, Func f )
621 return find_at( head(), key, intrusive_key_comparator(), f );
625 /// Finds the key \p key using \p pred predicate for searching
627 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_func "find(Q&, Func)"
628 but \p pred is used for key comparing.
629 \p Less functor has the interface like \p std::less.
630 \p pred must imply the same element order as the comparator used for building the list.
632 template <typename Q, typename Less, typename Func>
633 bool find_with( Q& key, Less pred, Func f )
636 return find_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
639 template <typename Q, typename Less, typename Func>
640 bool find_with( Q const& key, Less pred, Func f )
643 return find_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
647 /// Finds the key \p key and return the item found
648 /** \anchor cds_nonintrusive_LazyList_hp_get
649 The function searches the item with key equal to \p key
650 and returns the item found as \p guarded_ptr.
651 If \p key is not found the function returns an empty guarded pointer.
653 @note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
657 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
661 ord_list::guarded_ptr gp( theList.get( 5 ));
666 // Destructor of guarded_ptr releases internal HP guard and frees the item
670 Note the compare functor specified for class \p Traits template parameter
671 should accept a parameter of type \p Q that can be not the same as \p value_type.
673 template <typename Q>
674 guarded_ptr get( Q const& key )
677 get_at( head(), gp.guard(), key, intrusive_key_comparator() );
681 /// Finds the key \p key and return the item found
683 The function is an analog of \ref cds_nonintrusive_LazyList_hp_get "get( Q const&)"
684 but \p pred is used for comparing the keys.
686 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
688 \p pred must imply the same element order as the comparator used for building the list.
690 template <typename Q, typename Less>
691 guarded_ptr get_with( Q const& key, Less pred )
695 get_at( head(), gp.guard(), key, typename maker::template less_wrapper<Less>::type() );
699 /// Checks whether the list is empty
702 return base_class::empty();
705 /// Returns list's item count
707 The value returned depends on \p Traits::item_counter type. For \p atomicity::empty_item_counter,
708 this function always returns 0.
710 @note Even if you use real item counter and it returns 0, this fact is not mean that the list
711 is empty. To check list emptyness use \ref empty() method.
715 return base_class::size();
726 bool insert_node_at( head_type& refHead, node_type * pNode )
728 assert( pNode != nullptr );
729 scoped_node_ptr p( pNode );
731 if ( base_class::insert_at( &refHead, *pNode )) {
739 template <typename Q>
740 bool insert_at( head_type& refHead, const Q& val )
742 return insert_node_at( refHead, alloc_node( val ));
745 template <typename... Args>
746 bool emplace_at( head_type& refHead, Args&&... args )
748 return insert_node_at( refHead, alloc_node( std::forward<Args>(args)... ));
751 template <typename Q, typename Func>
752 bool insert_at( head_type& refHead, const Q& key, Func f )
754 scoped_node_ptr pNode( alloc_node( key ));
756 if ( base_class::insert_at( &refHead, *pNode, [&f](node_type& node){ f( node_to_value(node) ); } )) {
763 template <typename Q, typename Compare, typename Func>
764 bool erase_at( head_type& refHead, const Q& key, Compare cmp, Func f )
766 return base_class::erase_at( &refHead, key, cmp, [&f](node_type const& node){ f( node_to_value(node) ); } );
769 template <typename Q, typename Compare>
770 bool extract_at( head_type& refHead, typename guarded_ptr::native_guard& guard, Q const& key, Compare cmp )
772 return base_class::extract_at( &refHead, guard, key, cmp );
775 template <typename Q, typename Func>
776 std::pair<bool, bool> update_at( head_type& refHead, const Q& key, Func f, bool bAllowInsert )
778 scoped_node_ptr pNode( alloc_node( key ));
780 std::pair<bool, bool> ret = base_class::update_at( &refHead, *pNode,
781 [&f, &key](bool bNew, node_type& node, node_type&){f( bNew, node_to_value(node), key );},
783 if ( ret.first && ret.second )
789 template <typename Q, typename Compare>
790 bool find_at( head_type& refHead, Q const& key, Compare cmp )
792 return base_class::find_at( &refHead, key, cmp );
795 template <typename Q, typename Compare, typename Func>
796 bool find_at( head_type& refHead, Q& val, Compare cmp, Func f )
798 return base_class::find_at( &refHead, val, cmp, [&f](node_type& node, Q& val){ f( node_to_value(node), val ); });
801 template <typename Q, typename Compare>
802 bool get_at( head_type& refHead, typename guarded_ptr::native_guard& guard, Q const& key, Compare cmp )
804 return base_class::get_at( &refHead, guard, key, cmp );
810 }} // namespace cds::container
812 #endif // #ifndef CDSLIB_CONTAINER_IMPL_LAZY_LIST_H