2 This file is a part of libcds - Concurrent Data Structures library
4 (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2016
6 Source code repo: http://github.com/khizmax/libcds/
7 Download: http://sourceforge.net/projects/libcds/files/
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31 #ifndef CDSLIB_CONTAINER_IMPL_LAZY_LIST_H
32 #define CDSLIB_CONTAINER_IMPL_LAZY_LIST_H
35 #include <cds/container/details/guarded_ptr_cast.h>
37 namespace cds { namespace container {
40 /** @ingroup cds_nonintrusive_list
41 @anchor cds_nonintrusive_LazyList_gc
43 Usually, ordered single-linked list is used as a building block for the hash table implementation.
44 The complexity of searching is <tt>O(N)</tt>.
47 - [2005] Steve Heller, Maurice Herlihy, Victor Luchangco, Mark Moir, William N. Scherer III, and Nir Shavit
48 "A Lazy Concurrent List-Based Set Algorithm"
50 The lazy list is based on an optimistic locking scheme for inserts and removes,
51 eliminating the need to use the equivalent of an atomically markable
52 reference. It also has a novel wait-free membership \p find() operation
53 that does not need to perform cleanup operations and is more efficient.
55 It is non-intrusive version of \p cds::intrusive::LazyList class.
58 - \p GC - garbage collector: \p gc::HP, \p gp::DHP
59 - \p T - type to be stored in the list.
60 - \p Traits - type traits, default is \p lazy_list::traits.
61 It is possible to declare option-based list with \p lazy_list::make_traits metafunction istead of \p Traits template
62 argument. For example, the following traits-based declaration of \p gc::HP lazy list
64 #include <cds/container/lazy_list_hp.h>
65 // Declare comparator for the item
67 int operator ()( int i1, int i2 )
74 struct my_traits: public cds::container::lazy_list::traits
76 typedef my_compare compare;
79 // Declare traits-based list
80 typedef cds::container::LazyList< cds::gc::HP, int, my_traits > traits_based_list;
82 is equal to the following option-based list:
84 #include <cds/container/lazy_list_hp.h>
86 // my_compare is the same
88 // Declare option-based list
89 typedef cds::container::LazyList< cds::gc::HP, int,
90 typename cds::container::lazy_list::make_traits<
91 cds::container::opt::compare< my_compare > // item comparator option
96 Unlike standard container, this implementation does not divide type \p T into key and value part and
97 may be used as main building block for hash set algorithms.
99 The key is a function (or a part) of type \p T, and the comparing function is specified by \p Traits::compare functor
100 or \p Traits::less predicate.
102 \p LazyKVList is a key-value version of lazy non-intrusive list that is closer to the C++ std library approach.
105 There are different specializations of this template for each garbage collecting schema used.
106 You should include appropriate .h-file depending on GC you are using:
107 - for gc::HP: <tt> <cds/container/lazy_list_hp.h> </tt>
108 - for gc::DHP: <tt> <cds/container/lazy_list_dhp.h> </tt>
109 - for \ref cds_urcu_desc "RCU": <tt> <cds/container/lazy_list_rcu.h> </tt>
110 - for gc::nogc: <tt> <cds/container/lazy_list_nogc.h> </tt>
115 #ifdef CDS_DOXYGEN_INVOKED
116 typename Traits = lazy_list::traits
122 #ifdef CDS_DOXYGEN_INVOKED
123 protected intrusive::LazyList< GC, T, Traits >
125 protected details::make_lazy_list< GC, T, Traits >::type
129 typedef details::make_lazy_list< GC, T, Traits > maker;
130 typedef typename maker::type base_class;
134 typedef GC gc; ///< Garbage collector used
135 typedef T value_type; ///< Type of value stored in the list
136 typedef Traits traits; ///< List traits
138 typedef typename base_class::back_off back_off; ///< Back-off strategy used
139 typedef typename maker::allocator_type allocator_type; ///< Allocator type used for allocate/deallocate the nodes
140 typedef typename base_class::item_counter item_counter; ///< Item counting policy used
141 typedef typename maker::key_comparator key_comparator; ///< key comparison functor
142 typedef typename base_class::memory_model memory_model; ///< Memory ordering. See cds::opt::memory_model option
146 typedef typename base_class::value_type node_type;
147 typedef typename maker::cxx_allocator cxx_allocator;
148 typedef typename maker::node_deallocator node_deallocator;
149 typedef typename maker::intrusive_traits::compare intrusive_key_comparator;
151 typedef typename base_class::node_type head_type;
156 typedef typename gc::template guarded_ptr< node_type, value_type, details::guarded_ptr_cast_set<node_type, value_type> > guarded_ptr;
160 static value_type& node_to_value( node_type& n )
164 static value_type const& node_to_value( node_type const& n )
172 template <typename Q>
173 static node_type * alloc_node( Q const& v )
175 return cxx_allocator().New( v );
178 template <typename... Args>
179 static node_type * alloc_node( Args&&... args )
181 return cxx_allocator().MoveNew( std::forward<Args>(args)... );
184 static void free_node( node_type * pNode )
186 cxx_allocator().Delete( pNode );
189 struct node_disposer {
190 void operator()( node_type * pNode )
195 typedef std::unique_ptr< node_type, node_disposer > scoped_node_ptr;
199 return base_class::m_Head;
202 head_type const& head() const
204 return base_class::m_Head;
209 return base_class::m_Tail;
212 head_type const& tail() const
214 return base_class::m_Tail;
220 template <bool IsConst>
221 class iterator_type: protected base_class::template iterator_type<IsConst>
223 typedef typename base_class::template iterator_type<IsConst> iterator_base;
225 iterator_type( head_type const& pNode )
226 : iterator_base( const_cast<head_type *>( &pNode ))
229 iterator_type( head_type const * pNode )
230 : iterator_base( const_cast<head_type *>( pNode ))
233 friend class LazyList;
236 typedef typename cds::details::make_const_type<value_type, IsConst>::pointer value_ptr;
237 typedef typename cds::details::make_const_type<value_type, IsConst>::reference value_ref;
242 iterator_type( const iterator_type& src )
243 : iterator_base( src )
246 value_ptr operator ->() const
248 typename iterator_base::value_ptr p = iterator_base::operator ->();
249 return p ? &(p->m_Value) : nullptr;
252 value_ref operator *() const
254 return (iterator_base::operator *()).m_Value;
258 iterator_type& operator ++()
260 iterator_base::operator ++();
265 bool operator ==(iterator_type<C> const& i ) const
267 return iterator_base::operator ==(i);
270 bool operator !=(iterator_type<C> const& i ) const
272 return iterator_base::operator !=(i);
280 The forward iterator for lazy list has some features:
281 - it has no post-increment operator
282 - to protect the value, the iterator contains a GC-specific guard + another guard is required locally for increment operator.
283 For some GC (\p gc::HP), a guard is limited resource per thread, so an exception (or assertion) "no free guard"
284 may be thrown if a limit of guard count per thread is exceeded.
285 - The iterator cannot be moved across thread boundary since it contains GC's guard that is thread-private GC data.
286 - Iterator ensures thread-safety even if you delete the item that iterator points to. However, in case of concurrent
287 deleting operations it is no guarantee that you iterate all item in the list.
289 Therefore, the use of iterators in concurrent environment is not good idea. Use the iterator on the concurrent container
290 for debug purpose only.
292 typedef iterator_type<false> iterator;
294 /// Const forward iterator
296 For iterator's features and requirements see \ref iterator
298 typedef iterator_type<true> const_iterator;
300 /// Returns a forward iterator addressing the first element in a list
302 For empty list \code begin() == end() \endcode
306 iterator it( head() );
307 ++it ; // skip dummy head node
311 /// Returns an iterator that addresses the location succeeding the last element in a list
313 Do not use the value returned by <tt>end</tt> function to access any item.
315 The returned value can be used only to control reaching the end of the list.
316 For empty list \code begin() == end() \endcode
320 return iterator( tail() );
323 /// Returns a forward const iterator addressing the first element in a list
325 const_iterator begin() const
327 const_iterator it( head() );
328 ++it ; // skip dummy head node
331 const_iterator cbegin() const
333 const_iterator it( head() );
334 ++it ; // skip dummy head node
339 /// Returns an const iterator that addresses the location succeeding the last element in a list
341 const_iterator end() const
343 return const_iterator( tail() );
345 const_iterator cend() const
347 return const_iterator( tail() );
352 /// Default constructor
356 /// Destructor clears the list
364 The function creates a node with copy of \p val value
365 and then inserts the node created into the list.
367 The type \p Q should contain as minimum the complete key of the node.
368 The object of \ref value_type should be constructible from \p val of type \p Q.
369 In trivial case, \p Q is equal to \ref value_type.
371 Returns \p true if inserting successful, \p false otherwise.
373 template <typename Q>
374 bool insert( Q const& val )
376 return insert_at( head(), val );
381 This function inserts new node with default-constructed value and then it calls
382 \p func functor with signature
383 \code void func( value_type& item ) ;\endcode
385 The argument \p item of user-defined functor \p func is the reference
386 to the list's item inserted.
387 When \p func is called it has exclusive access to the item.
388 The user-defined functor is called only if the inserting is success.
390 The type \p Q should contain the complete key of the node.
391 The object of \p value_type should be constructible from \p key of type \p Q.
393 The function allows to split creating of new item into two part:
394 - create item from \p key with initializing key-fields only;
395 - insert new item into the list;
396 - if inserting is successful, initialize non-key fields of item by calling \p func functor
398 This can be useful if complete initialization of object of \p value_type is heavyweight and
399 it is preferable that the initialization should be completed only if inserting is successful.
401 template <typename Q, typename Func>
402 bool insert( Q const& key, Func func )
404 return insert_at( head(), key, func );
407 /// Inserts data of type \p value_type constructed from \p args
409 Returns \p true if inserting successful, \p false otherwise.
411 template <typename... Args>
412 bool emplace( Args&&... args )
414 return emplace_at( head(), std::forward<Args>(args)... );
417 /// Updates data by \p key
419 The operation performs inserting or replacing the element with lock-free manner.
421 If the \p key not found in the list, then the new item created from \p key
422 will be inserted iff \p bAllowInsert is \p true.
423 Otherwise, if \p key is found, the functor \p func is called with item found.
425 The functor \p Func signature is:
428 void operator()( bool bNew, value_type& item, Q const& 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 %update() function
437 The functor may change non-key fields of the \p item;
438 during \p func call \p item is locked so it is safe to modify the item in
439 multi-threaded environment.
441 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
442 \p second is true if new item has been added or \p false if the item with \p key
445 template <typename Q, typename Func>
446 std::pair<bool, bool> update( Q const& key, Func func, bool bAllowInsert = true )
448 return update_at( head(), key, func, bAllowInsert );
451 template <typename Q, typename Func>
452 CDS_DEPRECATED("ensure() is deprecated, use update()")
453 std::pair<bool, bool> ensure( Q const& key, Func f )
455 return update( key, f, true );
459 /// Deletes \p key from the list
460 /** \anchor cds_nonintrusive_LazyList_hp_erase_val
461 Since the key of LazyList's item type \p T is not explicitly specified,
462 template parameter \p Q defines the key type searching in the list.
463 The list item comparator should be able to compare the type \p T of list item
466 Return \p true if key is found and deleted, \p false otherwise
468 template <typename Q>
469 bool erase( Q const& key )
471 return erase_at( head(), key, intrusive_key_comparator(), [](value_type const&){} );
474 /// Deletes the item from the list using \p pred predicate for searching
476 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_val "erase(Q const&)"
477 but \p pred is used for key comparing.
478 \p Less functor has the interface like \p std::less.
479 \p pred must imply the same element order as the comparator used for building the list.
481 template <typename Q, typename Less>
482 bool erase_with( Q const& key, Less pred )
485 return erase_at( head(), key, typename maker::template less_wrapper<Less>::type(), [](value_type const&){} );
488 /// Deletes \p key from the list
489 /** \anchor cds_nonintrusive_LazyList_hp_erase_func
490 The function searches an item with key \p key, calls \p f functor with item found
491 and deletes the item. If \p key is not found, the functor is not called.
493 The functor \p Func interface:
496 void operator()(const value_type& val) { ... }
500 Since the key of LazyList's item type \p T is not explicitly specified,
501 template parameter \p Q defines the key type searching in the list.
502 The list item comparator should be able to compare the type \p T of list item
505 Return \p true if key is found and deleted, \p false otherwise
509 template <typename Q, typename Func>
510 bool erase( Q const& key, Func f )
512 return erase_at( head(), key, intrusive_key_comparator(), f );
515 /// Deletes the item from the list using \p pred predicate for searching
517 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_func "erase(Q const&, Func)"
518 but \p pred is used for key comparing.
519 \p Less functor has the interface like \p std::less.
520 \p pred must imply the same element order as the comparator used for building the list.
522 template <typename Q, typename Less, typename Func>
523 bool erase_with( Q const& key, Less pred, Func f )
526 return erase_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
529 /// Extracts the item from the list with specified \p key
530 /** \anchor cds_nonintrusive_LazyList_hp_extract
531 The function searches an item with key equal to \p key,
532 unlinks it from the list, and returns it as \p guarded_ptr.
533 If \p key is not found the function returns an empty guarded pointer.
535 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
537 @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
541 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
545 ord_list::guarded_ptr gp(theList.extract( 5 ));
550 // Destructor of gp releases internal HP guard and frees the item
554 template <typename Q>
555 guarded_ptr extract( Q const& key )
558 extract_at( head(), gp.guard(), key, intrusive_key_comparator() );
562 /// Extracts the item from the list with comparing functor \p pred
564 The function is an analog of \ref cds_nonintrusive_LazyList_hp_extract "extract(Q const&)"
565 but \p pred predicate is used for key comparing.
567 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
569 \p pred must imply the same element order as the comparator used for building the list.
571 template <typename Q, typename Less>
572 guarded_ptr extract_with( Q const& key, Less pred )
576 extract_at( head(), gp.guard(), key, typename maker::template less_wrapper<Less>::type() );
580 /// Checks whether the list contains \p key
582 The function searches the item with key equal to \p key
583 and returns \p true if it is found, and \p false otherwise.
585 template <typename Q>
586 bool contains( Q const& key )
588 return find_at( head(), key, intrusive_key_comparator() );
591 template <typename Q>
592 CDS_DEPRECATED("deprecated, use contains()")
593 bool find( Q const& key )
595 return contains( key );
599 /// Checks whether the list contains \p key using \p pred predicate for searching
601 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
602 \p Less functor has the interface like \p std::less.
603 \p pred must imply the same element order as the comparator used for building the list.
605 template <typename Q, typename Less>
606 bool contains( Q const& key, Less pred )
609 return find_at( head(), key, typename maker::template less_wrapper<Less>::type() );
612 template <typename Q, typename Less>
613 CDS_DEPRECATED("deprecated, use contains()")
614 bool find_with( Q const& key, Less pred )
616 return contains( key, pred );
619 /// Finds the key \p key and performs an action with it
620 /** \anchor cds_nonintrusive_LazyList_hp_find_func
621 The function searches an item with key equal to \p key and calls the functor \p f for the item found.
622 The interface of \p Func functor is:
625 void operator()( value_type& item, Q& key );
628 where \p item is the item found, \p key is the <tt>find</tt> function argument.
630 The functor may change non-key fields of \p item. Note that the function is only guarantee
631 that \p item cannot be deleted during functor is executing.
632 The function does not serialize simultaneous access to the list \p item. If such access is
633 possible you must provide your own synchronization schema to exclude unsafe item modifications.
635 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
636 may modify both arguments.
638 The function returns \p true if \p key is found, \p false otherwise.
640 template <typename Q, typename Func>
641 bool find( Q& key, Func f )
643 return find_at( head(), key, intrusive_key_comparator(), f );
646 template <typename Q, typename Func>
647 bool find( Q const& key, Func f )
649 return find_at( head(), key, intrusive_key_comparator(), f );
653 /// Finds the key \p key using \p pred predicate for searching
655 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_func "find(Q&, Func)"
656 but \p pred is used for key comparing.
657 \p Less functor has the interface like \p std::less.
658 \p pred must imply the same element order as the comparator used for building the list.
660 template <typename Q, typename Less, typename Func>
661 bool find_with( Q& key, Less pred, Func f )
664 return find_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
667 template <typename Q, typename Less, typename Func>
668 bool find_with( Q const& key, Less pred, Func f )
671 return find_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
675 /// Finds the key \p key and return the item found
676 /** \anchor cds_nonintrusive_LazyList_hp_get
677 The function searches the item with key equal to \p key
678 and returns the item found as \p guarded_ptr.
679 If \p key is not found the function returns an empty guarded pointer.
681 @note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
685 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
689 ord_list::guarded_ptr gp( theList.get( 5 ));
694 // Destructor of guarded_ptr releases internal HP guard and frees the item
698 Note the compare functor specified for class \p Traits template parameter
699 should accept a parameter of type \p Q that can be not the same as \p value_type.
701 template <typename Q>
702 guarded_ptr get( Q const& key )
705 get_at( head(), gp.guard(), key, intrusive_key_comparator() );
709 /// Finds the key \p key and return the item found
711 The function is an analog of \ref cds_nonintrusive_LazyList_hp_get "get( Q const&)"
712 but \p pred is used for comparing the keys.
714 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
716 \p pred must imply the same element order as the comparator used for building the list.
718 template <typename Q, typename Less>
719 guarded_ptr get_with( Q const& key, Less pred )
723 get_at( head(), gp.guard(), key, typename maker::template less_wrapper<Less>::type() );
727 /// Checks whether the list is empty
730 return base_class::empty();
733 /// Returns list's item count
735 The value returned depends on \p Traits::item_counter type. For \p atomicity::empty_item_counter,
736 this function always returns 0.
738 @note Even if you use real item counter and it returns 0, this fact is not mean that the list
739 is empty. To check list emptyness use \ref empty() method.
743 return base_class::size();
754 bool insert_node_at( head_type& refHead, node_type * pNode )
756 assert( pNode != nullptr );
757 scoped_node_ptr p( pNode );
759 if ( base_class::insert_at( &refHead, *pNode )) {
767 template <typename Q>
768 bool insert_at( head_type& refHead, const Q& val )
770 return insert_node_at( refHead, alloc_node( val ));
773 template <typename... Args>
774 bool emplace_at( head_type& refHead, Args&&... args )
776 return insert_node_at( refHead, alloc_node( std::forward<Args>(args)... ));
779 template <typename Q, typename Func>
780 bool insert_at( head_type& refHead, const Q& key, Func f )
782 scoped_node_ptr pNode( alloc_node( key ));
784 if ( base_class::insert_at( &refHead, *pNode, [&f](node_type& node){ f( node_to_value(node) ); } )) {
791 template <typename Q, typename Compare, typename Func>
792 bool erase_at( head_type& refHead, const Q& key, Compare cmp, Func f )
794 return base_class::erase_at( &refHead, key, cmp, [&f](node_type const& node){ f( node_to_value(node) ); } );
797 template <typename Q, typename Compare>
798 bool extract_at( head_type& refHead, typename guarded_ptr::native_guard& guard, Q const& key, Compare cmp )
800 return base_class::extract_at( &refHead, guard, key, cmp );
803 template <typename Q, typename Func>
804 std::pair<bool, bool> update_at( head_type& refHead, const Q& key, Func f, bool bAllowInsert )
806 scoped_node_ptr pNode( alloc_node( key ));
808 std::pair<bool, bool> ret = base_class::update_at( &refHead, *pNode,
809 [&f, &key](bool bNew, node_type& node, node_type&){f( bNew, node_to_value(node), key );},
811 if ( ret.first && ret.second )
817 template <typename Q, typename Compare>
818 bool find_at( head_type& refHead, Q const& key, Compare cmp )
820 return base_class::find_at( &refHead, key, cmp );
823 template <typename Q, typename Compare, typename Func>
824 bool find_at( head_type& refHead, Q& val, Compare cmp, Func f )
826 return base_class::find_at( &refHead, val, cmp, [&f](node_type& node, Q& val){ f( node_to_value(node), val ); });
829 template <typename Q, typename Compare>
830 bool get_at( head_type& refHead, typename guarded_ptr::native_guard& guard, Q const& key, Compare cmp )
832 return base_class::get_at( &refHead, guard, key, cmp );
838 }} // namespace cds::container
840 #endif // #ifndef CDSLIB_CONTAINER_IMPL_LAZY_LIST_H