3 #ifndef __CDS_CONTAINER_IMPL_LAZY_LIST_H
4 #define __CDS_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 cds::intrusive::LazyList class.
30 - \p GC - garbage collector used
31 - \p T - type stored in the list. The type must be default- and copy-constructible.
32 - \p Traits - type traits, default is lazy_list::type_traits
34 Unlike standard container, this implementation does not divide type \p T into key and value part and
35 may be used as main building block for hash set algorithms.
37 The key is a function (or a part) of type \p T, and this function is specified by <tt> Traits::compare </tt> functor
38 or <tt> Traits::less </tt> predicate.
40 LazyKVList is a key-value version of lazy non-intrusive list that is closer to the C++ std library approach.
42 It is possible to declare option-based list with cds::container::lazy_list::make_traits metafunction istead of \p Traits template
43 argument. For example, the following traits-based declaration of gc::HP lazy list
45 #include <cds/container/lazy_list_hp.h>
46 // Declare comparator for the item
48 int operator ()( int i1, int i2 )
54 // Declare type_traits
55 struct my_traits: public cds::container::lazy_list::type_traits
57 typedef my_compare compare;
60 // Declare traits-based list
61 typedef cds::container::LazyList< cds::gc::HP, int, my_traits > traits_based_list;
64 is equivalent for the following option-based list
66 #include <cds/container/lazy_list_hp.h>
68 // my_compare is the same
70 // Declare option-based list
71 typedef cds::container::LazyList< cds::gc::HP, int,
72 typename cds::container::lazy_list::make_traits<
73 cds::container::opt::compare< my_compare > // item comparator option
78 Template argument list \p Options of cds::container::lazy_list::make_traits metafunction are:
79 - opt::lock_type - lock type for per-node locking. Default is cds::lock::Spin. Note that <b>each</b> node
80 of the list has member of type \p lock_type, therefore, heavy-weighted locking primitive is not
81 acceptable as candidate for \p lock_type.
82 - opt::compare - key compare functor. No default functor is provided.
83 If the option is not specified, the opt::less is used.
84 - opt::less - specifies binary predicate used for key compare. Default is \p std::less<T>.
85 - opt::back_off - back-off strategy used. If the option is not specified, the cds::backoff::empty is used.
86 - opt::item_counter - the type of item counting feature. Default is \ref atomicity::empty_item_counter that is no item counting.
87 - opt::allocator - the allocator used for creating and freeing list's item. Default is \ref CDS_DEFAULT_ALLOCATOR macro.
88 - opt::memory_model - C++ memory ordering model. Can be opt::v::relaxed_ordering (relaxed memory model, the default)
89 or opt::v::sequential_consistent (sequentially consisnent memory model).
92 There are different specializations of this template for each garbage collecting schema used.
93 You should include appropriate .h-file depending on GC you are using:
94 - for gc::HP: \code #include <cds/container/lazy_list_hp.h> \endcode
95 - for gc::DHP: \code #include <cds/container/lazy_list_dhp.h> \endcode
96 - for \ref cds_urcu_desc "RCU": \code #include <cds/container/lazy_list_rcu.h> \endcode
97 - for gc::nogc: \code #include <cds/container/lazy_list_nogc.h> \endcode
102 #ifdef CDS_DOXYGEN_INVOKED
103 typename Traits = lazy_list::type_traits
109 #ifdef CDS_DOXYGEN_INVOKED
110 protected intrusive::LazyList< GC, T, Traits >
112 protected details::make_lazy_list< GC, T, Traits >::type
116 typedef details::make_lazy_list< GC, T, Traits > options;
117 typedef typename options::type base_class;
121 typedef T value_type ; ///< Type of value stored in the list
122 typedef typename base_class::gc gc ; ///< Garbage collector used
123 typedef typename base_class::back_off back_off ; ///< Back-off strategy used
124 typedef typename options::allocator_type allocator_type ; ///< Allocator type used for allocate/deallocate the nodes
125 typedef typename base_class::item_counter item_counter ; ///< Item counting policy used
126 typedef typename options::key_comparator key_comparator ; ///< key comparison functor
127 typedef typename base_class::memory_model memory_model ; ///< Memory ordering. See cds::opt::memory_model option
131 typedef typename base_class::value_type node_type;
132 typedef typename options::cxx_allocator cxx_allocator;
133 typedef typename options::node_deallocator node_deallocator;
134 typedef typename options::type_traits::compare intrusive_key_comparator;
136 typedef typename base_class::node_type head_type;
141 typedef cds::gc::guarded_ptr< gc, node_type, value_type, details::guarded_ptr_cast_set<node_type, value_type> > guarded_ptr;
145 static value_type& node_to_value( node_type& n )
149 static value_type const& node_to_value( node_type const& n )
157 template <typename Q>
158 static node_type * alloc_node( Q const& v )
160 return cxx_allocator().New( v );
163 template <typename... Args>
164 static node_type * alloc_node( Args&&... args )
166 return cxx_allocator().MoveNew( std::forward<Args>(args)... );
169 static void free_node( node_type * pNode )
171 cxx_allocator().Delete( pNode );
174 struct node_disposer {
175 void operator()( node_type * pNode )
180 typedef std::unique_ptr< node_type, node_disposer > scoped_node_ptr;
184 return *base_class::head();
187 head_type const& head() const
189 return *base_class::head();
194 return *base_class::tail();
197 head_type const& tail() const
199 return *base_class::tail();
205 template <bool IsConst>
206 class iterator_type: protected base_class::template iterator_type<IsConst>
208 typedef typename base_class::template iterator_type<IsConst> iterator_base;
210 iterator_type( head_type const& pNode )
211 : iterator_base( const_cast<head_type *>( &pNode ))
214 iterator_type( head_type const * pNode )
215 : iterator_base( const_cast<head_type *>( pNode ))
218 friend class LazyList;
221 typedef typename cds::details::make_const_type<value_type, IsConst>::pointer value_ptr;
222 typedef typename cds::details::make_const_type<value_type, IsConst>::reference value_ref;
227 iterator_type( const iterator_type& src )
228 : iterator_base( src )
231 value_ptr operator ->() const
233 typename iterator_base::value_ptr p = iterator_base::operator ->();
234 return p ? &(p->m_Value) : nullptr;
237 value_ref operator *() const
239 return (iterator_base::operator *()).m_Value;
243 iterator_type& operator ++()
245 iterator_base::operator ++();
250 bool operator ==(iterator_type<C> const& i ) const
252 return iterator_base::operator ==(i);
255 bool operator !=(iterator_type<C> const& i ) const
257 return iterator_base::operator !=(i);
265 The forward iterator for lazy list has some features:
266 - it has no post-increment operator
267 - to protect the value, the iterator contains a GC-specific guard + another guard is required locally for increment operator.
268 For some GC (\p gc::HP), a guard is limited resource per thread, so an exception (or assertion) "no free guard"
269 may be thrown if a limit of guard count per thread is exceeded.
270 - The iterator cannot be moved across thread boundary since it contains GC's guard that is thread-private GC data.
271 - Iterator ensures thread-safety even if you delete the item that iterator points to. However, in case of concurrent
272 deleting operations it is no guarantee that you iterate all item in the list.
274 Therefore, the use of iterators in concurrent environment is not good idea. Use the iterator on the concurrent container
275 for debug purpose only.
277 typedef iterator_type<false> iterator;
279 /// Const forward iterator
281 For iterator's features and requirements see \ref iterator
283 typedef iterator_type<true> const_iterator;
285 /// Returns a forward iterator addressing the first element in a list
287 For empty list \code begin() == end() \endcode
291 iterator it( head() );
292 ++it ; // skip dummy head node
296 /// Returns an iterator that addresses the location succeeding the last element in a list
298 Do not use the value returned by <tt>end</tt> function to access any item.
300 The returned value can be used only to control reaching the end of the list.
301 For empty list \code begin() == end() \endcode
305 return iterator( tail() );
308 /// Returns a forward const iterator addressing the first element in a list
310 const_iterator begin() const
312 const_iterator it( head() );
313 ++it ; // skip dummy head node
316 const_iterator cbegin()
318 const_iterator it( head() );
319 ++it ; // skip dummy head node
324 /// Returns an const iterator that addresses the location succeeding the last element in a list
326 const_iterator end() const
328 return const_iterator( tail() );
330 const_iterator cend()
332 return const_iterator( tail() );
337 /// Default constructor
339 Initializes empty list
355 The function creates a node with copy of \p val value
356 and then inserts the node created into the list.
358 The type \p Q should contain as minimum the complete key of the node.
359 The object of \ref value_type should be constructible from \p val of type \p Q.
360 In trivial case, \p Q is equal to \ref value_type.
362 Returns \p true if inserting successful, \p false otherwise.
364 template <typename Q>
365 bool insert( Q const& val )
367 return insert_at( head(), val );
372 This function inserts new node with default-constructed value and then it calls
373 \p func functor with signature
374 \code void func( value_type& itemValue ) ;\endcode
376 The argument \p itemValue of user-defined functor \p func is the reference
377 to the list's item inserted. User-defined functor \p func should guarantee that during changing
378 item's value no any other changes could be made on this list's item by concurrent threads.
379 The user-defined functor can be passed by reference using \p std::ref
380 and it is called only if the inserting is success.
382 The type \p Q should contain the complete key of the node.
383 The object of \ref value_type should be constructible from \p key of type \p Q.
385 The function allows to split creating of new item into two part:
386 - create item from \p key with initializing key-fields only;
387 - insert new item into the list;
388 - if inserting is successful, initialize non-key fields of item by calling \p f functor
390 This can be useful if complete initialization of object of \p value_type is heavyweight and
391 it is preferable that the initialization should be completed only if inserting is successful.
393 @warning See \ref cds_intrusive_item_creating "insert item troubleshooting"
395 template <typename Q, typename Func>
396 bool insert( Q const& key, Func func )
398 return insert_at( head(), key, func );
401 /// Inserts data of type \ref value_type constructed with <tt>std::forward<Args>(args)...</tt>
403 Returns \p true if inserting successful, \p false otherwise.
405 template <typename... Args>
406 bool emplace( Args&&... args )
408 return emplace_at( head(), std::forward<Args>(args)... );
411 /// Ensures that the \p key exists in the list
413 The operation performs inserting or changing data with lock-free manner.
415 If the \p key not found in the list, then the new item created from \p key
416 is inserted into the list. Otherwise, the functor \p func is called with the item found.
417 The functor \p Func should be a function with signature:
419 void func( bool bNew, value_type& item, const Q& val );
424 void operator()( bool bNew, value_type& item, const Q& val );
429 - \p bNew - \p true if the item has been inserted, \p false otherwise
430 - \p item - item of the list
431 - \p val - argument \p key passed into the \p ensure function
433 The functor may change non-key fields of the \p item; however, \p func must guarantee
434 that during changing no any other modifications could be made on this item by concurrent threads.
436 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
437 \p second is true if new item has been added or \p false if the item with \p key
438 already is in the list.
440 @warning See \ref cds_intrusive_item_creating "insert item troubleshooting"
442 template <typename Q, typename Func>
443 std::pair<bool, bool> ensure( Q const& key, Func f )
445 return ensure_at( head(), key, f );
448 /// Deletes \p key from the list
449 /** \anchor cds_nonintrusive_LazyList_hp_erase_val
450 Since the key of LazyList's item type \p T is not explicitly specified,
451 template parameter \p Q defines the key type searching in the list.
452 The list item comparator should be able to compare the type \p T of list item
455 Return \p true if key is found and deleted, \p false otherwise
457 template <typename Q>
458 bool erase( Q const& key )
460 return erase_at( head(), key, intrusive_key_comparator(), [](value_type const&){} );
463 /// Deletes the item from the list using \p pred predicate for searching
465 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_val "erase(Q const&)"
466 but \p pred is used for key comparing.
467 \p Less functor has the interface like \p std::less.
468 \p pred must imply the same element order as the comparator used for building the list.
470 template <typename Q, typename Less>
471 bool erase_with( Q const& key, Less pred )
473 return erase_at( head(), key, typename options::template less_wrapper<Less>::type(), [](value_type const&){} );
476 /// Deletes \p key from the list
477 /** \anchor cds_nonintrusive_LazyList_hp_erase_func
478 The function searches an item with key \p key, calls \p f functor with item found
479 and deletes the item. If \p key is not found, the functor is not called.
481 The functor \p Func interface:
484 void operator()(const value_type& val) { ... }
487 The functor may be passed by reference with <tt>boost:ref</tt>
489 Since the key of LazyList's item type \p T is not explicitly specified,
490 template parameter \p Q defines the key type searching in the list.
491 The list item comparator should be able to compare the type \p T of list item
494 Return \p true if key is found and deleted, \p false otherwise
498 template <typename Q, typename Func>
499 bool erase( Q const& key, Func f )
501 return erase_at( head(), key, intrusive_key_comparator(), f );
504 /// Deletes the item from the list using \p pred predicate for searching
506 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_func "erase(Q const&, Func)"
507 but \p pred is used for key comparing.
508 \p Less functor has the interface like \p std::less.
509 \p pred must imply the same element order as the comparator used for building the list.
511 template <typename Q, typename Less, typename Func>
512 bool erase_with( Q const& key, Less pred, Func f )
514 return erase_at( head(), key, typename options::template less_wrapper<Less>::type(), f );
517 /// Extracts the item from the list with specified \p key
518 /** \anchor cds_nonintrusive_LazyList_hp_extract
519 The function searches an item with key equal to \p key,
520 unlinks it from the list, and returns it in \p dest parameter.
521 If the item with key equal to \p key is not found the function returns \p false.
523 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
525 @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
529 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
533 ord_list::guarded_ptr gp;
534 theList.extract( gp, 5 );
538 // Destructor of gp releases internal HP guard and frees the item
542 template <typename Q>
543 bool extract( guarded_ptr& dest, Q const& key )
545 return extract_at( head(), dest.guard(), key, intrusive_key_comparator() );
548 /// Extracts the item from the list with comparing functor \p pred
550 The function is an analog of \ref cds_nonintrusive_LazyList_hp_extract "extract(guarded_ptr&, Q const&)"
551 but \p pred predicate is used for key comparing.
553 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
555 \p pred must imply the same element order as the comparator used for building the list.
557 template <typename Q, typename Less>
558 bool extract_with( guarded_ptr& dest, Q const& key, Less pred )
560 return extract_at( head(), dest.guard(), key, typename options::template less_wrapper<Less>::type() );
563 /// Finds the key \p key
564 /** \anchor cds_nonintrusive_LazyList_hp_find_val
565 The function searches the item with key equal to \p key
566 and returns \p true if it is found, and \p false otherwise
568 template <typename Q>
569 bool find( Q const& key )
571 return find_at( head(), key, intrusive_key_comparator() );
574 /// Finds the key \p val using \p pred predicate for searching
576 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_val "find(Q const&)"
577 but \p pred is used for key comparing.
578 \p Less functor has the interface like \p std::less.
579 \p pred must imply the same element order as the comparator used for building the list.
581 template <typename Q, typename Less>
582 bool find_with( Q const& key, Less pred )
584 return find_at( head(), key, typename options::template less_wrapper<Less>::type() );
587 /// Finds the key \p val and performs an action with it
588 /** \anchor cds_nonintrusive_LazyList_hp_find_func
589 The function searches an item with key equal to \p val and calls the functor \p f for the item found.
590 The interface of \p Func functor is:
593 void operator()( value_type& item, Q& val );
596 where \p item is the item found, \p val is the <tt>find</tt> function argument.
598 You may pass \p f argument by reference using \p std::ref.
600 The functor may change non-key fields of \p item. Note that the function is only guarantee
601 that \p item cannot be deleted during functor is executing.
602 The function does not serialize simultaneous access to the list \p item. If such access is
603 possible you must provide your own synchronization schema to exclude unsafe item modifications.
605 The \p val argument is non-const since it can be used as \p f functor destination i.e., the functor
606 may modify both arguments.
608 The function returns \p true if \p val is found, \p false otherwise.
610 template <typename Q, typename Func>
611 bool find( Q& val, Func f )
613 return find_at( head(), val, intrusive_key_comparator(), f );
616 /// Finds the key \p val using \p pred predicate for searching
618 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_func "find(Q&, Func)"
619 but \p pred is used for key comparing.
620 \p Less functor has the interface like \p std::less.
621 \p pred must imply the same element order as the comparator used for building the list.
623 template <typename Q, typename Less, typename Func>
624 bool find_with( Q& val, Less pred, Func f )
626 return find_at( head(), val, typename options::template less_wrapper<Less>::type(), f );
629 /// Finds the key \p val and performs an action with it
630 /** \anchor cds_nonintrusive_LazyList_hp_find_cfunc
631 The function searches an item with key equal to \p val and calls the functor \p f for the item found.
632 The interface of \p Func functor is:
635 void operator()( value_type& item, Q const& val );
638 where \p item is the item found, \p val is the <tt>find</tt> function argument.
640 You may pass \p f argument by reference using \p std::ref.
642 The function does not serialize simultaneous access to the list \p item. If such access is
643 possible you must provide your own synchronization schema to exclude unsafe item modifications.
645 The function returns \p true if \p val is found, \p false otherwise.
647 template <typename Q, typename Func>
648 bool find( Q const& val, Func f )
650 return find_at( head(), val, intrusive_key_comparator(), f );
653 /// Finds the key \p val using \p pred predicate for searching
655 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_cfunc "find(Q&, Func)"
656 but \p pred is used for key comparing.
657 \p Less functor has the interface like \p std::less.
658 \p pred must imply the same element order as the comparator used for building the list.
660 template <typename Q, typename Less, typename Func>
661 bool find_with( Q const& val, Less pred, Func f )
663 return find_at( head(), val, typename options::template less_wrapper<Less>::type(), f );
666 /// Finds the key \p val and return the item found
667 /** \anchor cds_nonintrusive_LazyList_hp_get
668 The function searches the item with key equal to \p val
669 and assigns the item found to guarded pointer \p ptr.
670 The function returns \p true if \p val is found, and \p false otherwise.
671 If \p val is not found the \p ptr parameter is not changed.
673 @note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
677 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
681 ord_list::guarded_ptr gp;
682 if ( theList.get( gp, 5 )) {
686 // Destructor of guarded_ptr releases internal HP guard and frees the item
690 Note the compare functor specified for class \p Traits template parameter
691 should accept a parameter of type \p Q that can be not the same as \p value_type.
693 template <typename Q>
694 bool get( guarded_ptr& ptr, Q const& val )
696 return get_at( head(), ptr.guard(), val, intrusive_key_comparator() );
699 /// Finds the key \p val and return the item found
701 The function is an analog of \ref cds_nonintrusive_LazyList_hp_get "get( guarded_ptr& ptr, Q const&)"
702 but \p pred is used for comparing the keys.
704 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
706 \p pred must imply the same element order as the comparator used for building the list.
708 template <typename Q, typename Less>
709 bool get_with( guarded_ptr& ptr, Q const& val, Less pred )
711 return get_at( head(), ptr.guard(), val, typename options::template less_wrapper<Less>::type() );
714 /// Checks if the list is empty
717 return base_class::empty();
720 /// Returns list's item count
722 The value returned depends on opt::item_counter option. For atomicity::empty_item_counter,
723 this function always returns 0.
725 <b>Warning</b>: even if you use real item counter and it returns 0, this fact is not mean that the list
726 is empty. To check list emptyness use \ref empty() method.
730 return base_class::size();
735 Post-condition: the list is empty
744 bool insert_node_at( head_type& refHead, node_type * pNode )
746 assert( pNode != nullptr );
747 scoped_node_ptr p( pNode );
749 if ( base_class::insert_at( &refHead, *pNode )) {
757 template <typename Q>
758 bool insert_at( head_type& refHead, const Q& val )
760 return insert_node_at( refHead, alloc_node( val ));
763 template <typename... Args>
764 bool emplace_at( head_type& refHead, Args&&... args )
766 return insert_node_at( refHead, alloc_node( std::forward<Args>(args)... ));
769 template <typename Q, typename Func>
770 bool insert_at( head_type& refHead, const Q& key, Func f )
772 scoped_node_ptr pNode( alloc_node( key ));
774 if ( base_class::insert_at( &refHead, *pNode, [&f](node_type& node){ f( node_to_value(node) ); } )) {
781 template <typename Q, typename Compare, typename Func>
782 bool erase_at( head_type& refHead, const Q& key, Compare cmp, Func f )
784 return base_class::erase_at( &refHead, key, cmp, [&f](node_type const& node){ f( node_to_value(node) ); } );
787 template <typename Q, typename Compare>
788 bool extract_at( head_type& refHead, typename gc::Guard& dest, Q const& key, Compare cmp )
790 return base_class::extract_at( &refHead, dest, key, cmp );
793 template <typename Q, typename Func>
794 std::pair<bool, bool> ensure_at( head_type& refHead, const Q& key, Func f )
796 scoped_node_ptr pNode( alloc_node( key ));
798 std::pair<bool, bool> ret = base_class::ensure_at( &refHead, *pNode,
799 [&f, &key](bool bNew, node_type& node, node_type&){f( bNew, node_to_value(node), key ); });
800 if ( ret.first && ret.second )
806 template <typename Q, typename Compare>
807 bool find_at( head_type& refHead, Q const& key, Compare cmp )
809 return base_class::find_at( &refHead, key, cmp );
812 template <typename Q, typename Compare, typename Func>
813 bool find_at( head_type& refHead, Q& val, Compare cmp, Func f )
815 return base_class::find_at( &refHead, val, cmp, [&f](node_type& node, Q& val){ f( node_to_value(node), val ); });
818 template <typename Q, typename Compare>
819 bool get_at( head_type& refHead, typename gc::Guard& guard, Q const& key, Compare cmp )
821 return base_class::get_at( &refHead, guard, key, cmp );
827 }} // namespace cds::container
829 #endif // #ifndef __CDS_CONTAINER_IMPL_LAZY_LIST_H