3 #ifndef __CDS_CONTAINER_LAZY_LIST_IMPL_H
4 #define __CDS_CONTAINER_LAZY_LIST_IMPL_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 gc::HRC: \code #include <cds/container/lazy_list_hrc.h> \endcode
97 - for \ref cds_urcu_desc "RCU": \code #include <cds/container/lazy_list_rcu.h> \endcode
98 - for gc::nogc: \code #include <cds/container/lazy_list_nogc.h> \endcode
103 #ifdef CDS_DOXYGEN_INVOKED
104 typename Traits = lazy_list::type_traits
110 #ifdef CDS_DOXYGEN_INVOKED
111 protected intrusive::LazyList< GC, T, Traits >
113 protected details::make_lazy_list< GC, T, Traits >::type
117 typedef details::make_lazy_list< GC, T, Traits > options;
118 typedef typename options::type base_class;
122 typedef T value_type ; ///< Type of value stored in the list
123 typedef typename base_class::gc gc ; ///< Garbage collector used
124 typedef typename base_class::back_off back_off ; ///< Back-off strategy used
125 typedef typename options::allocator_type allocator_type ; ///< Allocator type used for allocate/deallocate the nodes
126 typedef typename base_class::item_counter item_counter ; ///< Item counting policy used
127 typedef typename options::key_comparator key_comparator ; ///< key comparison functor
128 typedef typename base_class::memory_model memory_model ; ///< Memory ordering. See cds::opt::memory_model option
132 typedef typename base_class::value_type node_type;
133 typedef typename options::cxx_allocator cxx_allocator;
134 typedef typename options::node_deallocator node_deallocator;
135 typedef typename options::type_traits::compare intrusive_key_comparator;
137 typedef typename base_class::node_type head_type;
142 typedef cds::gc::guarded_ptr< gc, node_type, value_type, details::guarded_ptr_cast_set<node_type, value_type> > guarded_ptr;
146 static value_type& node_to_value( node_type& n )
150 static value_type const& node_to_value( node_type const& n )
158 template <typename Q>
159 static node_type * alloc_node( Q const& v )
161 return cxx_allocator().New( v );
164 template <typename... Args>
165 static node_type * alloc_node( Args&&... args )
167 return cxx_allocator().MoveNew( std::forward<Args>(args)... );
170 static void free_node( node_type * pNode )
172 cxx_allocator().Delete( pNode );
175 struct node_disposer {
176 void operator()( node_type * pNode )
181 typedef std::unique_ptr< node_type, node_disposer > scoped_node_ptr;
185 return *base_class::head();
188 head_type const& head() const
190 return *base_class::head();
195 return *base_class::tail();
198 head_type const& tail() const
200 return *base_class::tail();
206 template <bool IsConst>
207 class iterator_type: protected base_class::template iterator_type<IsConst>
209 typedef typename base_class::template iterator_type<IsConst> iterator_base;
211 iterator_type( head_type const& pNode )
212 : iterator_base( const_cast<head_type *>( &pNode ))
215 iterator_type( head_type const * pNode )
216 : iterator_base( const_cast<head_type *>( pNode ))
219 friend class LazyList;
222 typedef typename cds::details::make_const_type<value_type, IsConst>::pointer value_ptr;
223 typedef typename cds::details::make_const_type<value_type, IsConst>::reference value_ref;
228 iterator_type( const iterator_type& src )
229 : iterator_base( src )
232 value_ptr operator ->() const
234 typename iterator_base::value_ptr p = iterator_base::operator ->();
235 return p ? &(p->m_Value) : nullptr;
238 value_ref operator *() const
240 return (iterator_base::operator *()).m_Value;
244 iterator_type& operator ++()
246 iterator_base::operator ++();
251 bool operator ==(iterator_type<C> const& i ) const
253 return iterator_base::operator ==(i);
256 bool operator !=(iterator_type<C> const& i ) const
258 return iterator_base::operator !=(i);
266 The forward iterator for lazy list has some features:
267 - it has no post-increment operator
268 - to protect the value, the iterator contains a GC-specific guard + another guard is required locally for increment operator.
269 For some GC (gc::HP, gc::HRC), a guard is limited resource per thread, so an exception (or assertion) "no free guard"
270 may be thrown if a limit of guard count per thread is exceeded.
271 - The iterator cannot be moved across thread boundary since it contains GC's guard that is thread-private GC data.
272 - Iterator ensures thread-safety even if you delete the item that iterator points to. However, in case of concurrent
273 deleting operations it is no guarantee that you iterate all item in the list.
275 Therefore, the use of iterators in concurrent environment is not good idea. Use the iterator on the concurrent container
276 for debug purpose only.
278 typedef iterator_type<false> iterator;
280 /// Const forward iterator
282 For iterator's features and requirements see \ref iterator
284 typedef iterator_type<true> const_iterator;
286 /// Returns a forward iterator addressing the first element in a list
288 For empty list \code begin() == end() \endcode
292 iterator it( head() );
293 ++it ; // skip dummy head node
297 /// Returns an iterator that addresses the location succeeding the last element in a list
299 Do not use the value returned by <tt>end</tt> function to access any item.
301 The returned value can be used only to control reaching the end of the list.
302 For empty list \code begin() == end() \endcode
306 return iterator( tail() );
309 /// Returns a forward const iterator addressing the first element in a list
311 const_iterator begin() const
313 const_iterator it( head() );
314 ++it ; // skip dummy head node
317 const_iterator cbegin()
319 const_iterator it( head() );
320 ++it ; // skip dummy head node
325 /// Returns an const iterator that addresses the location succeeding the last element in a list
327 const_iterator end() const
329 return const_iterator( tail() );
331 const_iterator cend()
333 return const_iterator( tail() );
338 /// Default constructor
340 Initializes empty list
356 The function creates a node with copy of \p val value
357 and then inserts the node created into the list.
359 The type \p Q should contain as minimum the complete key of the node.
360 The object of \ref value_type should be constructible from \p val of type \p Q.
361 In trivial case, \p Q is equal to \ref value_type.
363 Returns \p true if inserting successful, \p false otherwise.
365 template <typename Q>
366 bool insert( Q const& val )
368 return insert_at( head(), val );
373 This function inserts new node with default-constructed value and then it calls
374 \p func functor with signature
375 \code void func( value_type& itemValue ) ;\endcode
377 The argument \p itemValue of user-defined functor \p func is the reference
378 to the list's item inserted. User-defined functor \p func should guarantee that during changing
379 item's value no any other changes could be made on this list's item by concurrent threads.
380 The user-defined functor can be passed by reference using <tt>boost::ref</tt>
381 and it is called only if the inserting is success.
383 The type \p Q should contain the complete key of the node.
384 The object of \ref value_type should be constructible from \p key of type \p Q.
386 The function allows to split creating of new item into two part:
387 - create item from \p key with initializing key-fields only;
388 - insert new item into the list;
389 - if inserting is successful, initialize non-key fields of item by calling \p f functor
391 This can be useful if complete initialization of object of \p value_type is heavyweight and
392 it is preferable that the initialization should be completed only if inserting is successful.
394 template <typename Q, typename Func>
395 bool insert( Q const& key, Func func )
397 return insert_at( head(), key, func );
400 /// Inserts data of type \ref value_type constructed with <tt>std::forward<Args>(args)...</tt>
402 Returns \p true if inserting successful, \p false otherwise.
404 template <typename... Args>
405 bool emplace( Args&&... args )
407 return emplace_at( head(), std::forward<Args>(args)... );
410 /// Ensures that the \p key exists in the list
412 The operation performs inserting or changing data with lock-free manner.
414 If the \p key not found in the list, then the new item created from \p key
415 is inserted into the list. Otherwise, the functor \p func is called with the item found.
416 The functor \p Func should be a function with signature:
418 void func( bool bNew, value_type& item, const Q& val );
423 void operator()( bool bNew, value_type& item, const Q& val );
428 - \p bNew - \p true if the item has been inserted, \p false otherwise
429 - \p item - item of the list
430 - \p val - argument \p key passed into the \p ensure function
432 The functor may change non-key fields of the \p item; however, \p func must guarantee
433 that during changing no any other modifications could be made on this item by concurrent threads.
435 You may pass \p func argument by reference using <tt>boost::ref</tt>.
437 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
438 \p second is true if new item has been added or \p false if the item with \p key
439 already is in the list.
441 template <typename Q, typename Func>
442 std::pair<bool, bool> ensure( Q const& key, Func f )
444 return ensure_at( head(), key, f );
447 /// Deletes \p key from the list
448 /** \anchor cds_nonintrusive_LazyList_hp_erase_val
449 Since the key of LazyList's item type \p T is not explicitly specified,
450 template parameter \p Q defines the key type searching in the list.
451 The list item comparator should be able to compare the type \p T of list item
454 Return \p true if key is found and deleted, \p false otherwise
456 template <typename Q>
457 bool erase( Q const& key )
459 return erase_at( head(), key, intrusive_key_comparator(), [](value_type const&){} );
462 /// Deletes the item from the list using \p pred predicate for searching
464 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_val "erase(Q const&)"
465 but \p pred is used for key comparing.
466 \p Less functor has the interface like \p std::less.
467 \p pred must imply the same element order as the comparator used for building the list.
469 template <typename Q, typename Less>
470 bool erase_with( Q const& key, Less pred )
472 return erase_at( head(), key, typename options::template less_wrapper<Less>::type(), [](value_type const&){} );
475 /// Deletes \p key from the list
476 /** \anchor cds_nonintrusive_LazyList_hp_erase_func
477 The function searches an item with key \p key, calls \p f functor with item found
478 and deletes the item. If \p key is not found, the functor is not called.
480 The functor \p Func interface:
483 void operator()(const value_type& val) { ... }
486 The functor may be passed by reference with <tt>boost:ref</tt>
488 Since the key of LazyList's item type \p T is not explicitly specified,
489 template parameter \p Q defines the key type searching in the list.
490 The list item comparator should be able to compare the type \p T of list item
493 Return \p true if key is found and deleted, \p false otherwise
497 template <typename Q, typename Func>
498 bool erase( Q const& key, Func f )
500 return erase_at( head(), key, intrusive_key_comparator(), f );
503 /// Deletes the item from the list using \p pred predicate for searching
505 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_func "erase(Q const&, Func)"
506 but \p pred is used for key comparing.
507 \p Less functor has the interface like \p std::less.
508 \p pred must imply the same element order as the comparator used for building the list.
510 template <typename Q, typename Less, typename Func>
511 bool erase_with( Q const& key, Less pred, Func f )
513 return erase_at( head(), key, typename options::template less_wrapper<Less>::type(), f );
516 /// Extracts the item from the list with specified \p key
517 /** \anchor cds_nonintrusive_LazyList_hp_extract
518 The function searches an item with key equal to \p key,
519 unlinks it from the list, and returns it in \p dest parameter.
520 If the item with key equal to \p key is not found the function returns \p false.
522 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
524 @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
528 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
532 ord_list::guarded_ptr gp;
533 theList.extract( gp, 5 );
537 // Destructor of gp releases internal HP guard and frees the item
541 template <typename Q>
542 bool extract( guarded_ptr& dest, Q const& key )
544 return extract_at( head(), dest.guard(), key, intrusive_key_comparator() );
547 /// Extracts the item from the list with comparing functor \p pred
549 The function is an analog of \ref cds_nonintrusive_LazyList_hp_extract "extract(guarded_ptr&, Q const&)"
550 but \p pred predicate is used for key comparing.
552 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
554 \p pred must imply the same element order as the comparator used for building the list.
556 template <typename Q, typename Less>
557 bool extract_with( guarded_ptr& dest, Q const& key, Less pred )
559 return extract_at( head(), dest.guard(), key, typename options::template less_wrapper<Less>::type() );
562 /// Finds the key \p key
563 /** \anchor cds_nonintrusive_LazyList_hp_find_val
564 The function searches the item with key equal to \p key
565 and returns \p true if it is found, and \p false otherwise
567 template <typename Q>
568 bool find( Q const& key )
570 return find_at( head(), key, intrusive_key_comparator() );
573 /// Finds the key \p val using \p pred predicate for searching
575 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_val "find(Q const&)"
576 but \p pred is used for key comparing.
577 \p Less functor has the interface like \p std::less.
578 \p pred must imply the same element order as the comparator used for building the list.
580 template <typename Q, typename Less>
581 bool find_with( Q const& key, Less pred )
583 return find_at( head(), key, typename options::template less_wrapper<Less>::type() );
586 /// Finds the key \p val and performs an action with it
587 /** \anchor cds_nonintrusive_LazyList_hp_find_func
588 The function searches an item with key equal to \p val and calls the functor \p f for the item found.
589 The interface of \p Func functor is:
592 void operator()( value_type& item, Q& val );
595 where \p item is the item found, \p val is the <tt>find</tt> function argument.
597 You may pass \p f argument by reference using <tt>boost::ref</tt> or cds::ref.
599 The functor may change non-key fields of \p item. Note that the function is only guarantee
600 that \p item cannot be deleted during functor is executing.
601 The function does not serialize simultaneous access to the list \p item. If such access is
602 possible you must provide your own synchronization schema to exclude unsafe item modifications.
604 The \p val argument is non-const since it can be used as \p f functor destination i.e., the functor
605 may modify both arguments.
607 The function returns \p true if \p val is found, \p false otherwise.
609 template <typename Q, typename Func>
610 bool find( Q& val, Func f )
612 return find_at( head(), val, intrusive_key_comparator(), f );
615 /// Finds the key \p val using \p pred predicate for searching
617 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_func "find(Q&, Func)"
618 but \p pred is used for key comparing.
619 \p Less functor has the interface like \p std::less.
620 \p pred must imply the same element order as the comparator used for building the list.
622 template <typename Q, typename Less, typename Func>
623 bool find_with( Q& val, Less pred, Func f )
625 return find_at( head(), val, typename options::template less_wrapper<Less>::type(), f );
628 /// Finds the key \p val and performs an action with it
629 /** \anchor cds_nonintrusive_LazyList_hp_find_cfunc
630 The function searches an item with key equal to \p val and calls the functor \p f for the item found.
631 The interface of \p Func functor is:
634 void operator()( value_type& item, Q const& val );
637 where \p item is the item found, \p val is the <tt>find</tt> function argument.
639 You may pass \p f argument by reference using <tt>boost::ref</tt> or cds::ref.
641 The function does not serialize simultaneous access to the list \p item. If such access is
642 possible you must provide your own synchronization schema to exclude unsafe item modifications.
644 The function returns \p true if \p val is found, \p false otherwise.
646 template <typename Q, typename Func>
647 bool find( Q const& val, Func f )
649 return find_at( head(), val, intrusive_key_comparator(), f );
652 /// Finds the key \p val using \p pred predicate for searching
654 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_cfunc "find(Q&, Func)"
655 but \p pred is used for key comparing.
656 \p Less functor has the interface like \p std::less.
657 \p pred must imply the same element order as the comparator used for building the list.
659 template <typename Q, typename Less, typename Func>
660 bool find_with( Q const& val, Less pred, Func f )
662 return find_at( head(), val, typename options::template less_wrapper<Less>::type(), f );
665 /// Finds the key \p val and return the item found
666 /** \anchor cds_nonintrusive_LazyList_hp_get
667 The function searches the item with key equal to \p val
668 and assigns the item found to guarded pointer \p ptr.
669 The function returns \p true if \p val is found, and \p false otherwise.
670 If \p val is not found the \p ptr parameter is not changed.
672 @note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
676 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
680 ord_list::guarded_ptr gp;
681 if ( theList.get( gp, 5 )) {
685 // Destructor of guarded_ptr releases internal HP guard and frees the item
689 Note the compare functor specified for class \p Traits template parameter
690 should accept a parameter of type \p Q that can be not the same as \p value_type.
692 template <typename Q>
693 bool get( guarded_ptr& ptr, Q const& val )
695 return get_at( head(), ptr.guard(), val, intrusive_key_comparator() );
698 /// Finds the key \p val and return the item found
700 The function is an analog of \ref cds_nonintrusive_LazyList_hp_get "get( guarded_ptr& ptr, Q const&)"
701 but \p pred is used for comparing the keys.
703 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
705 \p pred must imply the same element order as the comparator used for building the list.
707 template <typename Q, typename Less>
708 bool get_with( guarded_ptr& ptr, Q const& val, Less pred )
710 return get_at( head(), ptr.guard(), val, typename options::template less_wrapper<Less>::type() );
713 /// Checks if the list is empty
716 return base_class::empty();
719 /// Returns list's item count
721 The value returned depends on opt::item_counter option. For atomicity::empty_item_counter,
722 this function always returns 0.
724 <b>Warning</b>: even if you use real item counter and it returns 0, this fact is not mean that the list
725 is empty. To check list emptyness use \ref empty() method.
729 return base_class::size();
734 Post-condition: the list is empty
743 bool insert_node_at( head_type& refHead, node_type * pNode )
745 assert( pNode != nullptr );
746 scoped_node_ptr p( pNode );
748 if ( base_class::insert_at( &refHead, *pNode )) {
756 template <typename Q>
757 bool insert_at( head_type& refHead, const Q& val )
759 return insert_node_at( refHead, alloc_node( val ));
762 template <typename... Args>
763 bool emplace_at( head_type& refHead, Args&&... args )
765 return insert_node_at( refHead, alloc_node( std::forward<Args>(args)... ));
768 template <typename Q, typename Func>
769 bool insert_at( head_type& refHead, const Q& key, Func f )
771 scoped_node_ptr pNode( alloc_node( key ));
773 if ( base_class::insert_at( &refHead, *pNode, [&f](node_type& node){ cds::unref(f)( node_to_value(node) ); } )) {
780 template <typename Q, typename Compare, typename Func>
781 bool erase_at( head_type& refHead, const Q& key, Compare cmp, Func f )
783 return base_class::erase_at( &refHead, key, cmp, [&f](node_type const& node){ cds::unref(f)( node_to_value(node) ); } );
786 template <typename Q, typename Compare>
787 bool extract_at( head_type& refHead, typename gc::Guard& dest, Q const& key, Compare cmp )
789 return base_class::extract_at( &refHead, dest, key, cmp );
792 template <typename Q, typename Func>
793 std::pair<bool, bool> ensure_at( head_type& refHead, const Q& key, Func f )
795 scoped_node_ptr pNode( alloc_node( key ));
797 std::pair<bool, bool> ret = base_class::ensure_at( &refHead, *pNode,
798 [&f, &key](bool bNew, node_type& node, node_type&){cds::unref(f)( bNew, node_to_value(node), key ); });
799 if ( ret.first && ret.second )
805 template <typename Q, typename Compare>
806 bool find_at( head_type& refHead, Q const& key, Compare cmp )
808 return base_class::find_at( &refHead, key, cmp );
811 template <typename Q, typename Compare, typename Func>
812 bool find_at( head_type& refHead, Q& val, Compare cmp, Func f )
814 return base_class::find_at( &refHead, val, cmp, [&f](node_type& node, Q& val){ cds::unref(f)( node_to_value(node), val ); });
817 template <typename Q, typename Compare>
818 bool get_at( head_type& refHead, typename gc::Guard& guard, Q const& key, Compare cmp )
820 return base_class::get_at( &refHead, guard, key, cmp );
826 }} // namespace cds::container
828 #endif // #ifndef __CDS_CONTAINER_LAZY_LIST_IMPL_H