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 You don't need to include <tt><cds/container/impl/lazy_list.h></tt>. Instead, you should do:
41 - <tt><cds/container/lazy_list_hp.h></tt> - for gc::HP-based lazy list
42 - <tt><cds/container/lazy_list_ptb.h></tt> - for gc::PTB-based lazy list
43 - <tt><cds/container/lazy_list_rcu.h></tt> - for @ref cds_urcu_desc "RCU" based lazy list
45 LazyKVList is a key-value version of lazy non-intrusive list that is closer to the C++ std library approach.
47 It is possible to declare option-based list with cds::container::lazy_list::make_traits metafunction istead of \p Traits template
48 argument. For example, the following traits-based declaration of gc::HP lazy list
50 #include <cds/container/lazy_list_hp.h>
51 // Declare comparator for the item
53 int operator ()( int i1, int i2 )
59 // Declare type_traits
60 struct my_traits: public cds::container::lazy_list::type_traits
62 typedef my_compare compare;
65 // Declare traits-based list
66 typedef cds::container::LazyList< cds::gc::HP, int, my_traits > traits_based_list;
69 is equivalent for the following option-based list
71 #include <cds/container/lazy_list_hp.h>
73 // my_compare is the same
75 // Declare option-based list
76 typedef cds::container::LazyList< cds::gc::HP, int,
77 typename cds::container::lazy_list::make_traits<
78 cds::container::opt::compare< my_compare > // item comparator option
83 Template argument list \p Options of cds::container::lazy_list::make_traits metafunction are:
84 - opt::lock_type - lock type for per-node locking. Default is cds::lock::Spin. Note that <b>each</b> node
85 of the list has member of type \p lock_type, therefore, heavy-weighted locking primitive is not
86 acceptable as candidate for \p lock_type.
87 - opt::compare - key compare functor. No default functor is provided.
88 If the option is not specified, the opt::less is used.
89 - opt::less - specifies binary predicate used for key compare. Default is \p std::less<T>.
90 - opt::back_off - back-off strategy used. If the option is not specified, the cds::backoff::empty is used.
91 - opt::item_counter - the type of item counting feature. Default is \ref atomicity::empty_item_counter that is no item counting.
92 - opt::allocator - the allocator used for creating and freeing list's item. Default is \ref CDS_DEFAULT_ALLOCATOR macro.
93 - opt::memory_model - C++ memory ordering model. Can be opt::v::relaxed_ordering (relaxed memory model, the default)
94 or opt::v::sequential_consistent (sequentially consisnent memory model).
97 There are different specializations of this template for each garbage collecting schema used.
98 You should include appropriate .h-file depending on GC you are using:
99 - for gc::HP: \code #include <cds/container/lazy_list_hp.h> \endcode
100 - for gc::PTB: \code #include <cds/container/lazy_list_ptb.h> \endcode
101 - for gc::HRC: \code #include <cds/container/lazy_list_hrc.h> \endcode
102 - for \ref cds_urcu_desc "RCU": \code #include <cds/container/lazy_list_rcu.h> \endcode
103 - for gc::nogc: \code #include <cds/container/lazy_list_nogc.h> \endcode
108 #ifdef CDS_DOXYGEN_INVOKED
109 typename Traits = lazy_list::type_traits
115 #ifdef CDS_DOXYGEN_INVOKED
116 protected intrusive::LazyList< GC, T, Traits >
118 protected details::make_lazy_list< GC, T, Traits >::type
122 typedef details::make_lazy_list< GC, T, Traits > options;
123 typedef typename options::type base_class;
127 typedef T value_type ; ///< Type of value stored in the list
128 typedef typename base_class::gc gc ; ///< Garbage collector used
129 typedef typename base_class::back_off back_off ; ///< Back-off strategy used
130 typedef typename options::allocator_type allocator_type ; ///< Allocator type used for allocate/deallocate the nodes
131 typedef typename base_class::item_counter item_counter ; ///< Item counting policy used
132 typedef typename options::key_comparator key_comparator ; ///< key comparison functor
133 typedef typename base_class::memory_model memory_model ; ///< Memory ordering. See cds::opt::memory_model option
137 typedef typename base_class::value_type node_type;
138 typedef typename options::cxx_allocator cxx_allocator;
139 typedef typename options::node_deallocator node_deallocator;
140 typedef typename options::type_traits::compare intrusive_key_comparator;
142 typedef typename base_class::node_type head_type;
147 typedef cds::gc::guarded_ptr< gc, node_type, value_type, details::guarded_ptr_cast_set<node_type, value_type> > guarded_ptr;
151 static value_type& node_to_value( node_type& n )
155 static value_type const& node_to_value( node_type const& n )
163 template <typename Q>
164 static node_type * alloc_node( Q const& v )
166 return cxx_allocator().New( v );
169 template <typename... Args>
170 static node_type * alloc_node( Args&&... args )
172 return cxx_allocator().MoveNew( std::forward<Args>(args)... );
175 static void free_node( node_type * pNode )
177 cxx_allocator().Delete( pNode );
180 struct node_disposer {
181 void operator()( node_type * pNode )
186 typedef std::unique_ptr< node_type, node_disposer > scoped_node_ptr;
190 return *base_class::head();
193 head_type const& head() const
195 return *base_class::head();
200 return *base_class::tail();
203 head_type const& tail() const
205 return *base_class::tail();
211 template <bool IsConst>
212 class iterator_type: protected base_class::template iterator_type<IsConst>
214 typedef typename base_class::template iterator_type<IsConst> iterator_base;
216 iterator_type( head_type const& pNode )
217 : iterator_base( const_cast<head_type *>( &pNode ))
220 iterator_type( head_type const * pNode )
221 : iterator_base( const_cast<head_type *>( pNode ))
224 friend class LazyList;
227 typedef typename cds::details::make_const_type<value_type, IsConst>::pointer value_ptr;
228 typedef typename cds::details::make_const_type<value_type, IsConst>::reference value_ref;
233 iterator_type( const iterator_type& src )
234 : iterator_base( src )
237 value_ptr operator ->() const
239 typename iterator_base::value_ptr p = iterator_base::operator ->();
240 return p ? &(p->m_Value) : nullptr;
243 value_ref operator *() const
245 return (iterator_base::operator *()).m_Value;
249 iterator_type& operator ++()
251 iterator_base::operator ++();
256 bool operator ==(iterator_type<C> const& i ) const
258 return iterator_base::operator ==(i);
261 bool operator !=(iterator_type<C> const& i ) const
263 return iterator_base::operator !=(i);
271 The forward iterator for lazy list has some features:
272 - it has no post-increment operator
273 - to protect the value, the iterator contains a GC-specific guard + another guard is required locally for increment operator.
274 For some GC (gc::HP, gc::HRC), a guard is limited resource per thread, so an exception (or assertion) "no free guard"
275 may be thrown if a limit of guard count per thread is exceeded.
276 - The iterator cannot be moved across thread boundary since it contains GC's guard that is thread-private GC data.
277 - Iterator ensures thread-safety even if you delete the item that iterator points to. However, in case of concurrent
278 deleting operations it is no guarantee that you iterate all item in the list.
280 Therefore, the use of iterators in concurrent environment is not good idea. Use the iterator on the concurrent container
281 for debug purpose only.
283 typedef iterator_type<false> iterator;
285 /// Const forward iterator
287 For iterator's features and requirements see \ref iterator
289 typedef iterator_type<true> const_iterator;
291 /// Returns a forward iterator addressing the first element in a list
293 For empty list \code begin() == end() \endcode
297 iterator it( head() );
298 ++it ; // skip dummy head node
302 /// Returns an iterator that addresses the location succeeding the last element in a list
304 Do not use the value returned by <tt>end</tt> function to access any item.
306 The returned value can be used only to control reaching the end of the list.
307 For empty list \code begin() == end() \endcode
311 return iterator( tail() );
314 /// Returns a forward const iterator addressing the first element in a list
316 const_iterator begin() const
318 const_iterator it( head() );
319 ++it ; // skip dummy head node
322 const_iterator cbegin()
324 const_iterator it( head() );
325 ++it ; // skip dummy head node
330 /// Returns an const iterator that addresses the location succeeding the last element in a list
332 const_iterator end() const
334 return const_iterator( tail() );
336 const_iterator cend()
338 return const_iterator( tail() );
343 /// Default constructor
345 Initializes empty list
361 The function creates a node with copy of \p val value
362 and then inserts the node created into the list.
364 The type \p Q should contain as minimum the complete key of the node.
365 The object of \ref value_type should be constructible from \p val of type \p Q.
366 In trivial case, \p Q is equal to \ref value_type.
368 Returns \p true if inserting successful, \p false otherwise.
370 template <typename Q>
371 bool insert( Q const& val )
373 return insert_at( head(), val );
378 This function inserts new node with default-constructed value and then it calls
379 \p func functor with signature
380 \code void func( value_type& itemValue ) ;\endcode
382 The argument \p itemValue of user-defined functor \p func is the reference
383 to the list's item inserted. User-defined functor \p func should guarantee that during changing
384 item's value no any other changes could be made on this list's item by concurrent threads.
385 The user-defined functor can be passed by reference using <tt>boost::ref</tt>
386 and it is called only if the inserting is success.
388 The type \p Q should contain the complete key of the node.
389 The object of \ref value_type should be constructible from \p key of type \p Q.
391 The function allows to split creating of new item into two part:
392 - create item from \p key with initializing key-fields only;
393 - insert new item into the list;
394 - if inserting is successful, initialize non-key fields of item by calling \p f functor
396 This can be useful if complete initialization of object of \p value_type is heavyweight and
397 it is preferable that the initialization should be completed only if inserting is successful.
399 template <typename Q, typename Func>
400 bool insert( Q const& key, Func func )
402 return insert_at( head(), key, func );
405 /// Inserts data of type \ref value_type constructed with <tt>std::forward<Args>(args)...</tt>
407 Returns \p true if inserting successful, \p false otherwise.
409 template <typename... Args>
410 bool emplace( Args&&... args )
412 return emplace_at( head(), std::forward<Args>(args)... );
415 /// Ensures that the \p key exists in the list
417 The operation performs inserting or changing data with lock-free manner.
419 If the \p key not found in the list, then the new item created from \p key
420 is inserted into the list. Otherwise, the functor \p func is called with the item found.
421 The functor \p Func should be a function with signature:
423 void func( bool bNew, value_type& item, const Q& val );
428 void operator()( bool bNew, value_type& item, const Q& val );
433 - \p bNew - \p true if the item has been inserted, \p false otherwise
434 - \p item - item of the list
435 - \p val - argument \p key passed into the \p ensure function
437 The functor may change non-key fields of the \p item; however, \p func must guarantee
438 that during changing no any other modifications could be made on this item by concurrent threads.
440 You may pass \p func argument by reference using <tt>boost::ref</tt>.
442 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
443 \p second is true if new item has been added or \p false if the item with \p key
444 already is in the list.
446 template <typename Q, typename Func>
447 std::pair<bool, bool> ensure( Q const& key, Func f )
449 return ensure_at( head(), key, f );
452 /// Deletes \p key from the list
453 /** \anchor cds_nonintrusive_LazyList_hp_erase_val
454 Since the key of LazyList's item type \p T is not explicitly specified,
455 template parameter \p Q defines the key type searching in the list.
456 The list item comparator should be able to compare the type \p T of list item
459 Return \p true if key is found and deleted, \p false otherwise
461 template <typename Q>
462 bool erase( Q const& key )
464 return erase_at( head(), key, intrusive_key_comparator(), [](value_type const&){} );
467 /// Deletes the item from the list using \p pred predicate for searching
469 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_val "erase(Q const&)"
470 but \p pred is used for key comparing.
471 \p Less functor has the interface like \p std::less.
472 \p pred must imply the same element order as the comparator used for building the list.
474 template <typename Q, typename Less>
475 bool erase_with( Q const& key, Less pred )
477 return erase_at( head(), key, typename options::template less_wrapper<Less>::type(), [](value_type const&){} );
480 /// Deletes \p key from the list
481 /** \anchor cds_nonintrusive_LazyList_hp_erase_func
482 The function searches an item with key \p key, calls \p f functor with item found
483 and deletes the item. If \p key is not found, the functor is not called.
485 The functor \p Func interface:
488 void operator()(const value_type& val) { ... }
491 The functor may be passed by reference with <tt>boost:ref</tt>
493 Since the key of LazyList's item type \p T is not explicitly specified,
494 template parameter \p Q defines the key type searching in the list.
495 The list item comparator should be able to compare the type \p T of list item
498 Return \p true if key is found and deleted, \p false otherwise
502 template <typename Q, typename Func>
503 bool erase( Q const& key, Func f )
505 return erase_at( head(), key, intrusive_key_comparator(), f );
508 /// Deletes the item from the list using \p pred predicate for searching
510 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_func "erase(Q const&, Func)"
511 but \p pred is used for key comparing.
512 \p Less functor has the interface like \p std::less.
513 \p pred must imply the same element order as the comparator used for building the list.
515 template <typename Q, typename Less, typename Func>
516 bool erase_with( Q const& key, Less pred, Func f )
518 return erase_at( head(), key, typename options::template less_wrapper<Less>::type(), f );
521 /// Extracts the item from the list with specified \p key
522 /** \anchor cds_nonintrusive_LazyList_hp_extract
523 The function searches an item with key equal to \p key,
524 unlinks it from the list, and returns it in \p dest parameter.
525 If the item with key equal to \p key is not found the function returns \p false.
527 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
529 @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
533 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
537 ord_list::guarded_ptr gp;
538 theList.extract( gp, 5 );
542 // Destructor of gp releases internal HP guard and frees the item
546 template <typename Q>
547 bool extract( guarded_ptr& dest, Q const& key )
549 return extract_at( head(), dest.guard(), key, intrusive_key_comparator() );
552 /// Extracts the item from the list with comparing functor \p pred
554 The function is an analog of \ref cds_nonintrusive_LazyList_hp_extract "extract(guarded_ptr&, Q const&)"
555 but \p pred predicate is used for key comparing.
557 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
559 \p pred must imply the same element order as the comparator used for building the list.
561 template <typename Q, typename Less>
562 bool extract_with( guarded_ptr& dest, Q const& key, Less pred )
564 return extract_at( head(), dest.guard(), key, typename options::template less_wrapper<Less>::type() );
567 /// Finds the key \p key
568 /** \anchor cds_nonintrusive_LazyList_hp_find_val
569 The function searches the item with key equal to \p key
570 and returns \p true if it is found, and \p false otherwise
572 template <typename Q>
573 bool find( Q const& key )
575 return find_at( head(), key, intrusive_key_comparator() );
578 /// Finds the key \p val using \p pred predicate for searching
580 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_val "find(Q const&)"
581 but \p pred is used for key comparing.
582 \p Less functor has the interface like \p std::less.
583 \p pred must imply the same element order as the comparator used for building the list.
585 template <typename Q, typename Less>
586 bool find_with( Q const& key, Less pred )
588 return find_at( head(), key, typename options::template less_wrapper<Less>::type() );
591 /// Finds the key \p val 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 val 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& val );
600 where \p item is the item found, \p val is the <tt>find</tt> function argument.
602 You may pass \p f argument by reference using <tt>boost::ref</tt> or cds::ref.
604 The functor may change non-key fields of \p item. Note that the function is only guarantee
605 that \p item cannot be deleted during functor is executing.
606 The function does not serialize simultaneous access to the list \p item. If such access is
607 possible you must provide your own synchronization schema to exclude unsafe item modifications.
609 The \p val argument is non-const since it can be used as \p f functor destination i.e., the functor
610 may modify both arguments.
612 The function returns \p true if \p val is found, \p false otherwise.
614 template <typename Q, typename Func>
615 bool find( Q& val, Func f )
617 return find_at( head(), val, intrusive_key_comparator(), f );
620 /// Finds the key \p val using \p pred predicate for searching
622 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_func "find(Q&, Func)"
623 but \p pred is used for key comparing.
624 \p Less functor has the interface like \p std::less.
625 \p pred must imply the same element order as the comparator used for building the list.
627 template <typename Q, typename Less, typename Func>
628 bool find_with( Q& val, Less pred, Func f )
630 return find_at( head(), val, typename options::template less_wrapper<Less>::type(), f );
633 /// Finds the key \p val and performs an action with it
634 /** \anchor cds_nonintrusive_LazyList_hp_find_cfunc
635 The function searches an item with key equal to \p val and calls the functor \p f for the item found.
636 The interface of \p Func functor is:
639 void operator()( value_type& item, Q const& val );
642 where \p item is the item found, \p val is the <tt>find</tt> function argument.
644 You may pass \p f argument by reference using <tt>boost::ref</tt> or cds::ref.
646 The function does not serialize simultaneous access to the list \p item. If such access is
647 possible you must provide your own synchronization schema to exclude unsafe item modifications.
649 The function returns \p true if \p val is found, \p false otherwise.
651 template <typename Q, typename Func>
652 bool find( Q const& val, Func f )
654 return find_at( head(), val, intrusive_key_comparator(), f );
657 /// Finds the key \p val using \p pred predicate for searching
659 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_cfunc "find(Q&, Func)"
660 but \p pred is used for key comparing.
661 \p Less functor has the interface like \p std::less.
662 \p pred must imply the same element order as the comparator used for building the list.
664 template <typename Q, typename Less, typename Func>
665 bool find_with( Q const& val, Less pred, Func f )
667 return find_at( head(), val, typename options::template less_wrapper<Less>::type(), f );
670 /// Finds the key \p val and return the item found
671 /** \anchor cds_nonintrusive_LazyList_hp_get
672 The function searches the item with key equal to \p val
673 and assigns the item found to guarded pointer \p ptr.
674 The function returns \p true if \p val is found, and \p false otherwise.
675 If \p val is not found the \p ptr parameter is not changed.
677 @note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
681 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
685 ord_list::guarded_ptr gp;
686 if ( theList.get( gp, 5 )) {
690 // Destructor of guarded_ptr releases internal HP guard and frees the item
694 Note the compare functor specified for class \p Traits template parameter
695 should accept a parameter of type \p Q that can be not the same as \p value_type.
697 template <typename Q>
698 bool get( guarded_ptr& ptr, Q const& val )
700 return get_at( head(), ptr.guard(), val, intrusive_key_comparator() );
703 /// Finds the key \p val and return the item found
705 The function is an analog of \ref cds_nonintrusive_LazyList_hp_get "get( guarded_ptr& ptr, Q const&)"
706 but \p pred is used for comparing the keys.
708 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
710 \p pred must imply the same element order as the comparator used for building the list.
712 template <typename Q, typename Less>
713 bool get_with( guarded_ptr& ptr, Q const& val, Less pred )
715 return get_at( head(), ptr.guard(), val, typename options::template less_wrapper<Less>::type() );
718 /// Checks if the list is empty
721 return base_class::empty();
724 /// Returns list's item count
726 The value returned depends on opt::item_counter option. For atomicity::empty_item_counter,
727 this function always returns 0.
729 <b>Warning</b>: even if you use real item counter and it returns 0, this fact is not mean that the list
730 is empty. To check list emptyness use \ref empty() method.
734 return base_class::size();
739 Post-condition: the list is empty
748 bool insert_node_at( head_type& refHead, node_type * pNode )
750 assert( pNode != nullptr );
751 scoped_node_ptr p( pNode );
753 if ( base_class::insert_at( &refHead, *pNode )) {
761 template <typename Q>
762 bool insert_at( head_type& refHead, const Q& val )
764 return insert_node_at( refHead, alloc_node( val ));
767 template <typename... Args>
768 bool emplace_at( head_type& refHead, Args&&... args )
770 return insert_node_at( refHead, alloc_node( std::forward<Args>(args)... ));
773 template <typename Q, typename Func>
774 bool insert_at( head_type& refHead, const Q& key, Func f )
776 scoped_node_ptr pNode( alloc_node( key ));
778 if ( base_class::insert_at( &refHead, *pNode, [&f](node_type& node){ cds::unref(f)( node_to_value(node) ); } )) {
785 template <typename Q, typename Compare, typename Func>
786 bool erase_at( head_type& refHead, const Q& key, Compare cmp, Func f )
788 return base_class::erase_at( &refHead, key, cmp, [&f](node_type const& node){ cds::unref(f)( node_to_value(node) ); } );
791 template <typename Q, typename Compare>
792 bool extract_at( head_type& refHead, typename gc::Guard& dest, Q const& key, Compare cmp )
794 return base_class::extract_at( &refHead, dest, key, cmp );
797 template <typename Q, typename Func>
798 std::pair<bool, bool> ensure_at( head_type& refHead, const Q& key, Func f )
800 scoped_node_ptr pNode( alloc_node( key ));
802 std::pair<bool, bool> ret = base_class::ensure_at( &refHead, *pNode,
803 [&f, &key](bool bNew, node_type& node, node_type&){cds::unref(f)( bNew, node_to_value(node), key ); });
804 if ( ret.first && ret.second )
810 template <typename Q, typename Compare>
811 bool find_at( head_type& refHead, Q const& key, Compare cmp )
813 return base_class::find_at( &refHead, key, cmp );
816 template <typename Q, typename Compare, typename Func>
817 bool find_at( head_type& refHead, Q& val, Compare cmp, Func f )
819 return base_class::find_at( &refHead, val, cmp, [&f](node_type& node, Q& val){ cds::unref(f)( node_to_value(node), val ); });
822 template <typename Q, typename Compare>
823 bool get_at( head_type& refHead, typename gc::Guard& guard, Q const& key, Compare cmp )
825 return base_class::get_at( &refHead, guard, key, cmp );
831 }} // namespace cds::container
833 #endif // #ifndef __CDS_CONTAINER_IMPL_LAZY_LIST_H