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::PTB: \code #include <cds/container/lazy_list_ptb.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 (gc::HP, gc::HRC), 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 <tt>boost::ref</tt>
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 template <typename Q, typename Func>
394 bool insert( Q const& key, Func func )
396 return insert_at( head(), key, func );
399 /// Inserts data of type \ref value_type constructed with <tt>std::forward<Args>(args)...</tt>
401 Returns \p true if inserting successful, \p false otherwise.
403 template <typename... Args>
404 bool emplace( Args&&... args )
406 return emplace_at( head(), std::forward<Args>(args)... );
409 /// Ensures that the \p key exists in the list
411 The operation performs inserting or changing data with lock-free manner.
413 If the \p key not found in the list, then the new item created from \p key
414 is inserted into the list. Otherwise, the functor \p func is called with the item found.
415 The functor \p Func should be a function with signature:
417 void func( bool bNew, value_type& item, const Q& val );
422 void operator()( bool bNew, value_type& item, const Q& val );
427 - \p bNew - \p true if the item has been inserted, \p false otherwise
428 - \p item - item of the list
429 - \p val - argument \p key passed into the \p ensure function
431 The functor may change non-key fields of the \p item; however, \p func must guarantee
432 that during changing no any other modifications could be made on this item by concurrent threads.
434 You may pass \p func argument by reference using <tt>boost::ref</tt>.
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 template <typename Q, typename Func>
441 std::pair<bool, bool> ensure( Q const& key, Func f )
443 return ensure_at( head(), key, f );
446 /// Deletes \p key from the list
447 /** \anchor cds_nonintrusive_LazyList_hp_erase_val
448 Since the key of LazyList's item type \p T is not explicitly specified,
449 template parameter \p Q defines the key type searching in the list.
450 The list item comparator should be able to compare the type \p T of list item
453 Return \p true if key is found and deleted, \p false otherwise
455 template <typename Q>
456 bool erase( Q const& key )
458 return erase_at( head(), key, intrusive_key_comparator(), [](value_type const&){} );
461 /// Deletes the item from the list using \p pred predicate for searching
463 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_val "erase(Q const&)"
464 but \p pred is used for key comparing.
465 \p Less functor has the interface like \p std::less.
466 \p pred must imply the same element order as the comparator used for building the list.
468 template <typename Q, typename Less>
469 bool erase_with( Q const& key, Less pred )
471 return erase_at( head(), key, typename options::template less_wrapper<Less>::type(), [](value_type const&){} );
474 /// Deletes \p key from the list
475 /** \anchor cds_nonintrusive_LazyList_hp_erase_func
476 The function searches an item with key \p key, calls \p f functor with item found
477 and deletes the item. If \p key is not found, the functor is not called.
479 The functor \p Func interface:
482 void operator()(const value_type& val) { ... }
485 The functor may be passed by reference with <tt>boost:ref</tt>
487 Since the key of LazyList's item type \p T is not explicitly specified,
488 template parameter \p Q defines the key type searching in the list.
489 The list item comparator should be able to compare the type \p T of list item
492 Return \p true if key is found and deleted, \p false otherwise
496 template <typename Q, typename Func>
497 bool erase( Q const& key, Func f )
499 return erase_at( head(), key, intrusive_key_comparator(), f );
502 /// Deletes the item from the list using \p pred predicate for searching
504 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_func "erase(Q const&, Func)"
505 but \p pred is used for key comparing.
506 \p Less functor has the interface like \p std::less.
507 \p pred must imply the same element order as the comparator used for building the list.
509 template <typename Q, typename Less, typename Func>
510 bool erase_with( Q const& key, Less pred, Func f )
512 return erase_at( head(), key, typename options::template less_wrapper<Less>::type(), f );
515 /// Extracts the item from the list with specified \p key
516 /** \anchor cds_nonintrusive_LazyList_hp_extract
517 The function searches an item with key equal to \p key,
518 unlinks it from the list, and returns it in \p dest parameter.
519 If the item with key equal to \p key is not found the function returns \p false.
521 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
523 @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
527 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
531 ord_list::guarded_ptr gp;
532 theList.extract( gp, 5 );
536 // Destructor of gp releases internal HP guard and frees the item
540 template <typename Q>
541 bool extract( guarded_ptr& dest, Q const& key )
543 return extract_at( head(), dest.guard(), key, intrusive_key_comparator() );
546 /// Extracts the item from the list with comparing functor \p pred
548 The function is an analog of \ref cds_nonintrusive_LazyList_hp_extract "extract(guarded_ptr&, Q const&)"
549 but \p pred predicate is used for key comparing.
551 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
553 \p pred must imply the same element order as the comparator used for building the list.
555 template <typename Q, typename Less>
556 bool extract_with( guarded_ptr& dest, Q const& key, Less pred )
558 return extract_at( head(), dest.guard(), key, typename options::template less_wrapper<Less>::type() );
561 /// Finds the key \p key
562 /** \anchor cds_nonintrusive_LazyList_hp_find_val
563 The function searches the item with key equal to \p key
564 and returns \p true if it is found, and \p false otherwise
566 template <typename Q>
567 bool find( Q const& key )
569 return find_at( head(), key, intrusive_key_comparator() );
572 /// Finds the key \p val using \p pred predicate for searching
574 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_val "find(Q const&)"
575 but \p pred is used for key comparing.
576 \p Less functor has the interface like \p std::less.
577 \p pred must imply the same element order as the comparator used for building the list.
579 template <typename Q, typename Less>
580 bool find_with( Q const& key, Less pred )
582 return find_at( head(), key, typename options::template less_wrapper<Less>::type() );
585 /// Finds the key \p val and performs an action with it
586 /** \anchor cds_nonintrusive_LazyList_hp_find_func
587 The function searches an item with key equal to \p val and calls the functor \p f for the item found.
588 The interface of \p Func functor is:
591 void operator()( value_type& item, Q& val );
594 where \p item is the item found, \p val is the <tt>find</tt> function argument.
596 You may pass \p f argument by reference using <tt>boost::ref</tt> or cds::ref.
598 The functor may change non-key fields of \p item. Note that the function is only guarantee
599 that \p item cannot be deleted during functor is executing.
600 The function does not serialize simultaneous access to the list \p item. If such access is
601 possible you must provide your own synchronization schema to exclude unsafe item modifications.
603 The \p val argument is non-const since it can be used as \p f functor destination i.e., the functor
604 may modify both arguments.
606 The function returns \p true if \p val is found, \p false otherwise.
608 template <typename Q, typename Func>
609 bool find( Q& val, Func f )
611 return find_at( head(), val, intrusive_key_comparator(), f );
614 /// Finds the key \p val using \p pred predicate for searching
616 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_func "find(Q&, Func)"
617 but \p pred is used for key comparing.
618 \p Less functor has the interface like \p std::less.
619 \p pred must imply the same element order as the comparator used for building the list.
621 template <typename Q, typename Less, typename Func>
622 bool find_with( Q& val, Less pred, Func f )
624 return find_at( head(), val, typename options::template less_wrapper<Less>::type(), f );
627 /// Finds the key \p val and performs an action with it
628 /** \anchor cds_nonintrusive_LazyList_hp_find_cfunc
629 The function searches an item with key equal to \p val and calls the functor \p f for the item found.
630 The interface of \p Func functor is:
633 void operator()( value_type& item, Q const& val );
636 where \p item is the item found, \p val is the <tt>find</tt> function argument.
638 You may pass \p f argument by reference using <tt>boost::ref</tt> or cds::ref.
640 The function does not serialize simultaneous access to the list \p item. If such access is
641 possible you must provide your own synchronization schema to exclude unsafe item modifications.
643 The function returns \p true if \p val is found, \p false otherwise.
645 template <typename Q, typename Func>
646 bool find( Q const& val, Func f )
648 return find_at( head(), val, intrusive_key_comparator(), f );
651 /// Finds the key \p val using \p pred predicate for searching
653 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_cfunc "find(Q&, Func)"
654 but \p pred is used for key comparing.
655 \p Less functor has the interface like \p std::less.
656 \p pred must imply the same element order as the comparator used for building the list.
658 template <typename Q, typename Less, typename Func>
659 bool find_with( Q const& val, Less pred, Func f )
661 return find_at( head(), val, typename options::template less_wrapper<Less>::type(), f );
664 /// Finds the key \p val and return the item found
665 /** \anchor cds_nonintrusive_LazyList_hp_get
666 The function searches the item with key equal to \p val
667 and assigns the item found to guarded pointer \p ptr.
668 The function returns \p true if \p val is found, and \p false otherwise.
669 If \p val is not found the \p ptr parameter is not changed.
671 @note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
675 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
679 ord_list::guarded_ptr gp;
680 if ( theList.get( gp, 5 )) {
684 // Destructor of guarded_ptr releases internal HP guard and frees the item
688 Note the compare functor specified for class \p Traits template parameter
689 should accept a parameter of type \p Q that can be not the same as \p value_type.
691 template <typename Q>
692 bool get( guarded_ptr& ptr, Q const& val )
694 return get_at( head(), ptr.guard(), val, intrusive_key_comparator() );
697 /// Finds the key \p val and return the item found
699 The function is an analog of \ref cds_nonintrusive_LazyList_hp_get "get( guarded_ptr& ptr, Q const&)"
700 but \p pred is used for comparing the keys.
702 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
704 \p pred must imply the same element order as the comparator used for building the list.
706 template <typename Q, typename Less>
707 bool get_with( guarded_ptr& ptr, Q const& val, Less pred )
709 return get_at( head(), ptr.guard(), val, typename options::template less_wrapper<Less>::type() );
712 /// Checks if the list is empty
715 return base_class::empty();
718 /// Returns list's item count
720 The value returned depends on opt::item_counter option. For atomicity::empty_item_counter,
721 this function always returns 0.
723 <b>Warning</b>: even if you use real item counter and it returns 0, this fact is not mean that the list
724 is empty. To check list emptyness use \ref empty() method.
728 return base_class::size();
733 Post-condition: the list is empty
742 bool insert_node_at( head_type& refHead, node_type * pNode )
744 assert( pNode != nullptr );
745 scoped_node_ptr p( pNode );
747 if ( base_class::insert_at( &refHead, *pNode )) {
755 template <typename Q>
756 bool insert_at( head_type& refHead, const Q& val )
758 return insert_node_at( refHead, alloc_node( val ));
761 template <typename... Args>
762 bool emplace_at( head_type& refHead, Args&&... args )
764 return insert_node_at( refHead, alloc_node( std::forward<Args>(args)... ));
767 template <typename Q, typename Func>
768 bool insert_at( head_type& refHead, const Q& key, Func f )
770 scoped_node_ptr pNode( alloc_node( key ));
772 if ( base_class::insert_at( &refHead, *pNode, [&f](node_type& node){ cds::unref(f)( node_to_value(node) ); } )) {
779 template <typename Q, typename Compare, typename Func>
780 bool erase_at( head_type& refHead, const Q& key, Compare cmp, Func f )
782 return base_class::erase_at( &refHead, key, cmp, [&f](node_type const& node){ cds::unref(f)( node_to_value(node) ); } );
785 template <typename Q, typename Compare>
786 bool extract_at( head_type& refHead, typename gc::Guard& dest, Q const& key, Compare cmp )
788 return base_class::extract_at( &refHead, dest, key, cmp );
791 template <typename Q, typename Func>
792 std::pair<bool, bool> ensure_at( head_type& refHead, const Q& key, Func f )
794 scoped_node_ptr pNode( alloc_node( key ));
796 std::pair<bool, bool> ret = base_class::ensure_at( &refHead, *pNode,
797 [&f, &key](bool bNew, node_type& node, node_type&){cds::unref(f)( bNew, node_to_value(node), key ); });
798 if ( ret.first && ret.second )
804 template <typename Q, typename Compare>
805 bool find_at( head_type& refHead, Q const& key, Compare cmp )
807 return base_class::find_at( &refHead, key, cmp );
810 template <typename Q, typename Compare, typename Func>
811 bool find_at( head_type& refHead, Q& val, Compare cmp, Func f )
813 return base_class::find_at( &refHead, val, cmp, [&f](node_type& node, Q& val){ cds::unref(f)( node_to_value(node), val ); });
816 template <typename Q, typename Compare>
817 bool get_at( head_type& refHead, typename gc::Guard& guard, Q const& key, Compare cmp )
819 return base_class::get_at( &refHead, guard, key, cmp );
825 }} // namespace cds::container
827 #endif // #ifndef __CDS_CONTAINER_IMPL_LAZY_LIST_H