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
44 - <tt><cds/container/lazy_list_nogc.h></tt> - for append-only based lazy list
46 LazyKVList is a key-value version of lazy non-intrusive list that is closer to the C++ std library approach.
48 It is possible to declare option-based list with cds::container::lazy_list::make_traits metafunction istead of \p Traits template
49 argument. For example, the following traits-based declaration of gc::HP lazy list
51 #include <cds/container/lazy_list_hp.h>
52 // Declare comparator for the item
54 int operator ()( int i1, int i2 )
60 // Declare type_traits
61 struct my_traits: public cds::container::lazy_list::type_traits
63 typedef my_compare compare;
66 // Declare traits-based list
67 typedef cds::container::LazyList< cds::gc::HP, int, my_traits > traits_based_list;
70 is equivalent for the following option-based list
72 #include <cds/container/lazy_list_hp.h>
74 // my_compare is the same
76 // Declare option-based list
77 typedef cds::container::LazyList< cds::gc::HP, int,
78 typename cds::container::lazy_list::make_traits<
79 cds::container::opt::compare< my_compare > // item comparator option
84 Template argument list \p Options of cds::container::lazy_list::make_traits metafunction are:
85 - opt::lock_type - lock type for per-node locking. Default is cds::lock::Spin. Note that <b>each</b> node
86 of the list has member of type \p lock_type, therefore, heavy-weighted locking primitive is not
87 acceptable as candidate for \p lock_type.
88 - opt::compare - key compare functor. No default functor is provided.
89 If the option is not specified, the opt::less is used.
90 - opt::less - specifies binary predicate used for key compare. Default is \p std::less<T>.
91 - opt::back_off - back-off strategy used. If the option is not specified, the cds::backoff::empty is used.
92 - opt::item_counter - the type of item counting feature. Default is \ref atomicity::empty_item_counter that is no item counting.
93 - opt::allocator - the allocator used for creating and freeing list's item. Default is \ref CDS_DEFAULT_ALLOCATOR macro.
94 - opt::memory_model - C++ memory ordering model. Can be opt::v::relaxed_ordering (relaxed memory model, the default)
95 or opt::v::sequential_consistent (sequentially consisnent memory model).
98 There are different specializations of this template for each garbage collecting schema used.
99 You should include appropriate .h-file depending on GC you are using:
100 - for gc::HP: \code #include <cds/container/lazy_list_hp.h> \endcode
101 - for gc::PTB: \code #include <cds/container/lazy_list_ptb.h> \endcode
102 - for gc::HRC: \code #include <cds/container/lazy_list_hrc.h> \endcode
103 - for \ref cds_urcu_desc "RCU": \code #include <cds/container/lazy_list_rcu.h> \endcode
104 - for gc::nogc: \code #include <cds/container/lazy_list_nogc.h> \endcode
109 #ifdef CDS_DOXYGEN_INVOKED
110 typename Traits = lazy_list::type_traits
116 #ifdef CDS_DOXYGEN_INVOKED
117 protected intrusive::LazyList< GC, T, Traits >
119 protected details::make_lazy_list< GC, T, Traits >::type
123 typedef details::make_lazy_list< GC, T, Traits > options;
124 typedef typename options::type base_class;
128 typedef T value_type ; ///< Type of value stored in the list
129 typedef typename base_class::gc gc ; ///< Garbage collector used
130 typedef typename base_class::back_off back_off ; ///< Back-off strategy used
131 typedef typename options::allocator_type allocator_type ; ///< Allocator type used for allocate/deallocate the nodes
132 typedef typename base_class::item_counter item_counter ; ///< Item counting policy used
133 typedef typename options::key_comparator key_comparator ; ///< key comparison functor
134 typedef typename base_class::memory_model memory_model ; ///< Memory ordering. See cds::opt::memory_model option
138 typedef typename base_class::value_type node_type;
139 typedef typename options::cxx_allocator cxx_allocator;
140 typedef typename options::node_deallocator node_deallocator;
141 typedef typename options::type_traits::compare intrusive_key_comparator;
143 typedef typename base_class::node_type head_type;
148 typedef cds::gc::guarded_ptr< gc, node_type, value_type, details::guarded_ptr_cast_set<node_type, value_type> > guarded_ptr;
152 static value_type& node_to_value( node_type& n )
156 static value_type const& node_to_value( node_type const& n )
164 template <typename Q>
165 static node_type * alloc_node( Q const& v )
167 return cxx_allocator().New( v );
170 template <typename... Args>
171 static node_type * alloc_node( Args&&... args )
173 return cxx_allocator().MoveNew( std::forward<Args>(args)... );
176 static void free_node( node_type * pNode )
178 cxx_allocator().Delete( pNode );
181 struct node_disposer {
182 void operator()( node_type * pNode )
187 typedef std::unique_ptr< node_type, node_disposer > scoped_node_ptr;
191 return *base_class::head();
194 head_type const& head() const
196 return *base_class::head();
201 return *base_class::tail();
204 head_type const& tail() const
206 return *base_class::tail();
212 template <bool IsConst>
213 class iterator_type: protected base_class::template iterator_type<IsConst>
215 typedef typename base_class::template iterator_type<IsConst> iterator_base;
217 iterator_type( head_type const& pNode )
218 : iterator_base( const_cast<head_type *>( &pNode ))
221 iterator_type( head_type const * pNode )
222 : iterator_base( const_cast<head_type *>( pNode ))
225 friend class LazyList;
228 typedef typename cds::details::make_const_type<value_type, IsConst>::pointer value_ptr;
229 typedef typename cds::details::make_const_type<value_type, IsConst>::reference value_ref;
234 iterator_type( const iterator_type& src )
235 : iterator_base( src )
238 value_ptr operator ->() const
240 typename iterator_base::value_ptr p = iterator_base::operator ->();
241 return p ? &(p->m_Value) : nullptr;
244 value_ref operator *() const
246 return (iterator_base::operator *()).m_Value;
250 iterator_type& operator ++()
252 iterator_base::operator ++();
257 bool operator ==(iterator_type<C> const& i ) const
259 return iterator_base::operator ==(i);
262 bool operator !=(iterator_type<C> const& i ) const
264 return iterator_base::operator !=(i);
272 The forward iterator for lazy list has some features:
273 - it has no post-increment operator
274 - to protect the value, the iterator contains a GC-specific guard + another guard is required locally for increment operator.
275 For some GC (gc::HP, gc::HRC), a guard is limited resource per thread, so an exception (or assertion) "no free guard"
276 may be thrown if a limit of guard count per thread is exceeded.
277 - The iterator cannot be moved across thread boundary since it contains GC's guard that is thread-private GC data.
278 - Iterator ensures thread-safety even if you delete the item that iterator points to. However, in case of concurrent
279 deleting operations it is no guarantee that you iterate all item in the list.
281 Therefore, the use of iterators in concurrent environment is not good idea. Use the iterator on the concurrent container
282 for debug purpose only.
284 typedef iterator_type<false> iterator;
286 /// Const forward iterator
288 For iterator's features and requirements see \ref iterator
290 typedef iterator_type<true> const_iterator;
292 /// Returns a forward iterator addressing the first element in a list
294 For empty list \code begin() == end() \endcode
298 iterator it( head() );
299 ++it ; // skip dummy head node
303 /// Returns an iterator that addresses the location succeeding the last element in a list
305 Do not use the value returned by <tt>end</tt> function to access any item.
307 The returned value can be used only to control reaching the end of the list.
308 For empty list \code begin() == end() \endcode
312 return iterator( tail() );
315 /// Returns a forward const iterator addressing the first element in a list
317 const_iterator begin() const
319 const_iterator it( head() );
320 ++it ; // skip dummy head node
323 const_iterator cbegin()
325 const_iterator it( head() );
326 ++it ; // skip dummy head node
331 /// Returns an const iterator that addresses the location succeeding the last element in a list
333 const_iterator end() const
335 return const_iterator( tail() );
337 const_iterator cend()
339 return const_iterator( tail() );
344 /// Default constructor
346 Initializes empty list
362 The function creates a node with copy of \p val value
363 and then inserts the node created into the list.
365 The type \p Q should contain as minimum the complete key of the node.
366 The object of \ref value_type should be constructible from \p val of type \p Q.
367 In trivial case, \p Q is equal to \ref value_type.
369 Returns \p true if inserting successful, \p false otherwise.
371 template <typename Q>
372 bool insert( Q const& val )
374 return insert_at( head(), val );
379 This function inserts new node with default-constructed value and then it calls
380 \p func functor with signature
381 \code void func( value_type& itemValue ) ;\endcode
383 The argument \p itemValue of user-defined functor \p func is the reference
384 to the list's item inserted. User-defined functor \p func should guarantee that during changing
385 item's value no any other changes could be made on this list's item by concurrent threads.
386 The user-defined functor can be passed by reference using <tt>boost::ref</tt>
387 and it is called only if the inserting is success.
389 The type \p Q should contain the complete key of the node.
390 The object of \ref value_type should be constructible from \p key of type \p Q.
392 The function allows to split creating of new item into two part:
393 - create item from \p key with initializing key-fields only;
394 - insert new item into the list;
395 - if inserting is successful, initialize non-key fields of item by calling \p f functor
397 This can be useful if complete initialization of object of \p value_type is heavyweight and
398 it is preferable that the initialization should be completed only if inserting is successful.
400 template <typename Q, typename Func>
401 bool insert( Q const& key, Func func )
403 return insert_at( head(), key, func );
406 /// Inserts data of type \ref value_type constructed with <tt>std::forward<Args>(args)...</tt>
408 Returns \p true if inserting successful, \p false otherwise.
410 template <typename... Args>
411 bool emplace( Args&&... args )
413 return emplace_at( head(), std::forward<Args>(args)... );
416 /// Ensures that the \p key exists in the list
418 The operation performs inserting or changing data with lock-free manner.
420 If the \p key not found in the list, then the new item created from \p key
421 is inserted into the list. Otherwise, the functor \p func is called with the item found.
422 The functor \p Func should be a function with signature:
424 void func( bool bNew, value_type& item, const Q& val );
429 void operator()( bool bNew, value_type& item, const Q& val );
434 - \p bNew - \p true if the item has been inserted, \p false otherwise
435 - \p item - item of the list
436 - \p val - argument \p key passed into the \p ensure function
438 The functor may change non-key fields of the \p item; however, \p func must guarantee
439 that during changing no any other modifications could be made on this item by concurrent threads.
441 You may pass \p func argument by reference using <tt>boost::ref</tt>.
443 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
444 \p second is true if new item has been added or \p false if the item with \p key
445 already is in the list.
447 template <typename Q, typename Func>
448 std::pair<bool, bool> ensure( Q const& key, Func f )
450 return ensure_at( head(), key, f );
453 /// Deletes \p key from the list
454 /** \anchor cds_nonintrusive_LazyList_hp_erase_val
455 Since the key of LazyList's item type \p T is not explicitly specified,
456 template parameter \p Q defines the key type searching in the list.
457 The list item comparator should be able to compare the type \p T of list item
460 Return \p true if key is found and deleted, \p false otherwise
462 template <typename Q>
463 bool erase( Q const& key )
465 return erase_at( head(), key, intrusive_key_comparator(), [](value_type const&){} );
468 /// Deletes the item from the list using \p pred predicate for searching
470 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_val "erase(Q const&)"
471 but \p pred is used for key comparing.
472 \p Less functor has the interface like \p std::less.
473 \p pred must imply the same element order as the comparator used for building the list.
475 template <typename Q, typename Less>
476 bool erase_with( Q const& key, Less pred )
478 return erase_at( head(), key, typename options::template less_wrapper<Less>::type(), [](value_type const&){} );
481 /// Deletes \p key from the list
482 /** \anchor cds_nonintrusive_LazyList_hp_erase_func
483 The function searches an item with key \p key, calls \p f functor with item found
484 and deletes the item. If \p key is not found, the functor is not called.
486 The functor \p Func interface:
489 void operator()(const value_type& val) { ... }
492 The functor may be passed by reference with <tt>boost:ref</tt>
494 Since the key of LazyList's item type \p T is not explicitly specified,
495 template parameter \p Q defines the key type searching in the list.
496 The list item comparator should be able to compare the type \p T of list item
499 Return \p true if key is found and deleted, \p false otherwise
503 template <typename Q, typename Func>
504 bool erase( Q const& key, Func f )
506 return erase_at( head(), key, intrusive_key_comparator(), f );
509 /// Deletes the item from the list using \p pred predicate for searching
511 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_func "erase(Q const&, Func)"
512 but \p pred is used for key comparing.
513 \p Less functor has the interface like \p std::less.
514 \p pred must imply the same element order as the comparator used for building the list.
516 template <typename Q, typename Less, typename Func>
517 bool erase_with( Q const& key, Less pred, Func f )
519 return erase_at( head(), key, typename options::template less_wrapper<Less>::type(), f );
522 /// Extracts the item from the list with specified \p key
523 /** \anchor cds_nonintrusive_LazyList_hp_extract
524 The function searches an item with key equal to \p key,
525 unlinks it from the list, and returns it in \p dest parameter.
526 If the item with key equal to \p key is not found the function returns \p false.
528 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
530 @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
534 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
538 ord_list::guarded_ptr gp;
539 theList.extract( gp, 5 );
543 // Destructor of gp releases internal HP guard and frees the item
547 template <typename Q>
548 bool extract( guarded_ptr& dest, Q const& key )
550 return extract_at( head(), dest.guard(), key, intrusive_key_comparator() );
553 /// Extracts the item from the list with comparing functor \p pred
555 The function is an analog of \ref cds_nonintrusive_LazyList_hp_extract "extract(guarded_ptr&, Q const&)"
556 but \p pred predicate is used for key comparing.
558 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
560 \p pred must imply the same element order as the comparator used for building the list.
562 template <typename Q, typename Less>
563 bool extract_with( guarded_ptr& dest, Q const& key, Less pred )
565 return extract_at( head(), dest.guard(), key, typename options::template less_wrapper<Less>::type() );
568 /// Finds the key \p key
569 /** \anchor cds_nonintrusive_LazyList_hp_find_val
570 The function searches the item with key equal to \p key
571 and returns \p true if it is found, and \p false otherwise
573 template <typename Q>
574 bool find( Q const& key )
576 return find_at( head(), key, intrusive_key_comparator() );
579 /// Finds the key \p val using \p pred predicate for searching
581 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_val "find(Q const&)"
582 but \p pred is used for key comparing.
583 \p Less functor has the interface like \p std::less.
584 \p pred must imply the same element order as the comparator used for building the list.
586 template <typename Q, typename Less>
587 bool find_with( Q const& key, Less pred )
589 return find_at( head(), key, typename options::template less_wrapper<Less>::type() );
592 /// Finds the key \p val and performs an action with it
593 /** \anchor cds_nonintrusive_LazyList_hp_find_func
594 The function searches an item with key equal to \p val and calls the functor \p f for the item found.
595 The interface of \p Func functor is:
598 void operator()( value_type& item, Q& val );
601 where \p item is the item found, \p val is the <tt>find</tt> function argument.
603 You may pass \p f argument by reference using <tt>boost::ref</tt> or cds::ref.
605 The functor may change non-key fields of \p item. Note that the function is only guarantee
606 that \p item cannot be deleted during functor is executing.
607 The function does not serialize simultaneous access to the list \p item. If such access is
608 possible you must provide your own synchronization schema to exclude unsafe item modifications.
610 The \p val argument is non-const since it can be used as \p f functor destination i.e., the functor
611 may modify both arguments.
613 The function returns \p true if \p val is found, \p false otherwise.
615 template <typename Q, typename Func>
616 bool find( Q& val, Func f )
618 return find_at( head(), val, intrusive_key_comparator(), f );
621 /// Finds the key \p val using \p pred predicate for searching
623 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_func "find(Q&, Func)"
624 but \p pred is used for key comparing.
625 \p Less functor has the interface like \p std::less.
626 \p pred must imply the same element order as the comparator used for building the list.
628 template <typename Q, typename Less, typename Func>
629 bool find_with( Q& val, Less pred, Func f )
631 return find_at( head(), val, typename options::template less_wrapper<Less>::type(), f );
634 /// Finds the key \p val and performs an action with it
635 /** \anchor cds_nonintrusive_LazyList_hp_find_cfunc
636 The function searches an item with key equal to \p val and calls the functor \p f for the item found.
637 The interface of \p Func functor is:
640 void operator()( value_type& item, Q const& val );
643 where \p item is the item found, \p val is the <tt>find</tt> function argument.
645 You may pass \p f argument by reference using <tt>boost::ref</tt> or cds::ref.
647 The function does not serialize simultaneous access to the list \p item. If such access is
648 possible you must provide your own synchronization schema to exclude unsafe item modifications.
650 The function returns \p true if \p val is found, \p false otherwise.
652 template <typename Q, typename Func>
653 bool find( Q const& val, Func f )
655 return find_at( head(), val, intrusive_key_comparator(), f );
658 /// Finds the key \p val using \p pred predicate for searching
660 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_cfunc "find(Q&, Func)"
661 but \p pred is used for key comparing.
662 \p Less functor has the interface like \p std::less.
663 \p pred must imply the same element order as the comparator used for building the list.
665 template <typename Q, typename Less, typename Func>
666 bool find_with( Q const& val, Less pred, Func f )
668 return find_at( head(), val, typename options::template less_wrapper<Less>::type(), f );
671 /// Finds the key \p val and return the item found
672 /** \anchor cds_nonintrusive_LazyList_hp_get
673 The function searches the item with key equal to \p val
674 and assigns the item found to guarded pointer \p ptr.
675 The function returns \p true if \p val is found, and \p false otherwise.
676 If \p val is not found the \p ptr parameter is not changed.
678 @note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
682 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
686 ord_list::guarded_ptr gp;
687 if ( theList.get( gp, 5 )) {
691 // Destructor of guarded_ptr releases internal HP guard and frees the item
695 Note the compare functor specified for class \p Traits template parameter
696 should accept a parameter of type \p Q that can be not the same as \p value_type.
698 template <typename Q>
699 bool get( guarded_ptr& ptr, Q const& val )
701 return get_at( head(), ptr.guard(), val, intrusive_key_comparator() );
704 /// Finds the key \p val and return the item found
706 The function is an analog of \ref cds_nonintrusive_LazyList_hp_get "get( guarded_ptr& ptr, Q const&)"
707 but \p pred is used for comparing the keys.
709 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
711 \p pred must imply the same element order as the comparator used for building the list.
713 template <typename Q, typename Less>
714 bool get_with( guarded_ptr& ptr, Q const& val, Less pred )
716 return get_at( head(), ptr.guard(), val, typename options::template less_wrapper<Less>::type() );
719 /// Checks if the list is empty
722 return base_class::empty();
725 /// Returns list's item count
727 The value returned depends on opt::item_counter option. For atomicity::empty_item_counter,
728 this function always returns 0.
730 <b>Warning</b>: even if you use real item counter and it returns 0, this fact is not mean that the list
731 is empty. To check list emptyness use \ref empty() method.
735 return base_class::size();
740 Post-condition: the list is empty
749 bool insert_node_at( head_type& refHead, node_type * pNode )
751 assert( pNode != nullptr );
752 scoped_node_ptr p( pNode );
754 if ( base_class::insert_at( &refHead, *pNode )) {
762 template <typename Q>
763 bool insert_at( head_type& refHead, const Q& val )
765 return insert_node_at( refHead, alloc_node( val ));
768 template <typename... Args>
769 bool emplace_at( head_type& refHead, Args&&... args )
771 return insert_node_at( refHead, alloc_node( std::forward<Args>(args)... ));
774 template <typename Q, typename Func>
775 bool insert_at( head_type& refHead, const Q& key, Func f )
777 scoped_node_ptr pNode( alloc_node( key ));
779 if ( base_class::insert_at( &refHead, *pNode, [&f](node_type& node){ cds::unref(f)( node_to_value(node) ); } )) {
786 template <typename Q, typename Compare, typename Func>
787 bool erase_at( head_type& refHead, const Q& key, Compare cmp, Func f )
789 return base_class::erase_at( &refHead, key, cmp, [&f](node_type const& node){ cds::unref(f)( node_to_value(node) ); } );
792 template <typename Q, typename Compare>
793 bool extract_at( head_type& refHead, typename gc::Guard& dest, Q const& key, Compare cmp )
795 return base_class::extract_at( &refHead, dest, key, cmp );
798 template <typename Q, typename Func>
799 std::pair<bool, bool> ensure_at( head_type& refHead, const Q& key, Func f )
801 scoped_node_ptr pNode( alloc_node( key ));
803 std::pair<bool, bool> ret = base_class::ensure_at( &refHead, *pNode,
804 [&f, &key](bool bNew, node_type& node, node_type&){cds::unref(f)( bNew, node_to_value(node), key ); });
805 if ( ret.first && ret.second )
811 template <typename Q, typename Compare>
812 bool find_at( head_type& refHead, Q const& key, Compare cmp )
814 return base_class::find_at( &refHead, key, cmp );
817 template <typename Q, typename Compare, typename Func>
818 bool find_at( head_type& refHead, Q& val, Compare cmp, Func f )
820 return base_class::find_at( &refHead, val, cmp, [&f](node_type& node, Q& val){ cds::unref(f)( node_to_value(node), val ); });
823 template <typename Q, typename Compare>
824 bool get_at( head_type& refHead, typename gc::Guard& guard, Q const& key, Compare cmp )
826 return base_class::get_at( &refHead, guard, key, cmp );
832 }} // namespace cds::container
834 #endif // #ifndef __CDS_CONTAINER_IMPL_LAZY_LIST_H