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
144 static CDS_CONSTEXPR const size_t c_nHazardPtrCount = base_class::c_nHazardPtrCount; ///< Count of hazard pointer required for the algorithm
148 typedef typename base_class::value_type node_type;
149 typedef typename maker::cxx_allocator cxx_allocator;
150 typedef typename maker::node_deallocator node_deallocator;
151 typedef typename maker::intrusive_traits::compare intrusive_key_comparator;
153 typedef typename base_class::node_type head_type;
158 typedef typename gc::template guarded_ptr< node_type, value_type, details::guarded_ptr_cast_set<node_type, value_type> > guarded_ptr;
162 static value_type& node_to_value( node_type& n )
166 static value_type const& node_to_value( node_type const& n )
174 template <typename Q>
175 static node_type * alloc_node( Q const& v )
177 return cxx_allocator().New( v );
180 template <typename... Args>
181 static node_type * alloc_node( Args&&... args )
183 return cxx_allocator().MoveNew( std::forward<Args>(args)... );
186 static void free_node( node_type * pNode )
188 cxx_allocator().Delete( pNode );
191 struct node_disposer {
192 void operator()( node_type * pNode )
197 typedef std::unique_ptr< node_type, node_disposer > scoped_node_ptr;
201 return base_class::m_Head;
204 head_type const& head() const
206 return base_class::m_Head;
211 return base_class::m_Tail;
214 head_type const& tail() const
216 return base_class::m_Tail;
222 template <bool IsConst>
223 class iterator_type: protected base_class::template iterator_type<IsConst>
225 typedef typename base_class::template iterator_type<IsConst> iterator_base;
227 iterator_type( head_type const& pNode )
228 : iterator_base( const_cast<head_type *>( &pNode ))
231 iterator_type( head_type const * pNode )
232 : iterator_base( const_cast<head_type *>( pNode ))
235 friend class LazyList;
238 typedef typename cds::details::make_const_type<value_type, IsConst>::pointer value_ptr;
239 typedef typename cds::details::make_const_type<value_type, IsConst>::reference value_ref;
244 iterator_type( const iterator_type& src )
245 : iterator_base( src )
248 value_ptr operator ->() const
250 typename iterator_base::value_ptr p = iterator_base::operator ->();
251 return p ? &(p->m_Value) : nullptr;
254 value_ref operator *() const
256 return (iterator_base::operator *()).m_Value;
260 iterator_type& operator ++()
262 iterator_base::operator ++();
267 bool operator ==(iterator_type<C> const& i ) const
269 return iterator_base::operator ==(i);
272 bool operator !=(iterator_type<C> const& i ) const
274 return iterator_base::operator !=(i);
282 The forward iterator for lazy list has some features:
283 - it has no post-increment operator
284 - to protect the value, the iterator contains a GC-specific guard + another guard is required locally for increment operator.
285 For some GC (\p gc::HP), a guard is limited resource per thread, so an exception (or assertion) "no free guard"
286 may be thrown if a limit of guard count per thread is exceeded.
287 - The iterator cannot be moved across thread boundary since it contains GC's guard that is thread-private GC data.
288 - Iterator ensures thread-safety even if you delete the item that iterator points to. However, in case of concurrent
289 deleting operations it is no guarantee that you iterate all item in the list.
291 @warning Use this iterator on the concurrent container for debugging purpose only.
293 typedef iterator_type<false> iterator;
295 /// Const forward iterator
297 For iterator's features and requirements see \ref iterator
299 typedef iterator_type<true> const_iterator;
301 ///@name Forward iterators (only for debugging purpose)
303 /// Returns a forward iterator addressing the first element in a list
305 For empty list \code begin() == end() \endcode
309 iterator it( head() );
310 ++it ; // skip dummy head node
314 /// Returns an iterator that addresses the location succeeding the last element in a list
316 Do not use the value returned by <tt>end</tt> function to access any item.
318 The returned value can be used only to control reaching the end of the list.
319 For empty list \code begin() == end() \endcode
323 return iterator( tail() );
326 /// Returns a forward const iterator addressing the first element in a list
327 const_iterator begin() const
329 const_iterator it( head() );
330 ++it ; // skip dummy head node
334 /// Returns a forward const iterator addressing the first element in a list
335 const_iterator cbegin() const
337 const_iterator it( head() );
338 ++it ; // skip dummy head node
342 /// Returns an const iterator that addresses the location succeeding the last element in a list
343 const_iterator end() const
345 return const_iterator( tail() );
348 /// Returns an const iterator that addresses the location succeeding the last element in a list
349 const_iterator cend() const
351 return const_iterator( tail() );
356 /// Default constructor
360 /// Destructor clears the list
368 The function creates a node with copy of \p val value
369 and then inserts the node created into the list.
371 The type \p Q should contain as minimum the complete key of the node.
372 The object of \ref value_type should be constructible from \p val of type \p Q.
373 In trivial case, \p Q is equal to \ref value_type.
375 Returns \p true if inserting successful, \p false otherwise.
377 template <typename Q>
378 bool insert( Q const& val )
380 return insert_at( head(), val );
385 This function inserts new node with default-constructed value and then it calls
386 \p func functor with signature
387 \code void func( value_type& item ) ;\endcode
389 The argument \p item of user-defined functor \p func is the reference
390 to the list's item inserted.
391 When \p func is called it has exclusive access to the item.
392 The user-defined functor is called only if the inserting is success.
394 The type \p Q should contain the complete key of the node.
395 The object of \p value_type should be constructible from \p key of type \p Q.
397 The function allows to split creating of new item into two part:
398 - create item from \p key with initializing key-fields only;
399 - insert new item into the list;
400 - if inserting is successful, initialize non-key fields of item by calling \p func functor
402 This can be useful if complete initialization of object of \p value_type is heavyweight and
403 it is preferable that the initialization should be completed only if inserting is successful.
405 template <typename Q, typename Func>
406 bool insert( Q const& key, Func func )
408 return insert_at( head(), key, func );
411 /// Inserts data of type \p value_type constructed from \p args
413 Returns \p true if inserting successful, \p false otherwise.
415 template <typename... Args>
416 bool emplace( Args&&... args )
418 return emplace_at( head(), std::forward<Args>(args)... );
421 /// Updates data by \p key
423 The operation performs inserting or replacing the element with lock-free manner.
425 If the \p key not found in the list, then the new item created from \p key
426 will be inserted iff \p bAllowInsert is \p true.
427 Otherwise, if \p key is found, the functor \p func is called with item found.
429 The functor \p Func signature is:
432 void operator()( bool bNew, value_type& item, Q const& val );
437 - \p bNew - \p true if the item has been inserted, \p false otherwise
438 - \p item - item of the list
439 - \p val - argument \p key passed into the \p %update() function
441 The functor may change non-key fields of the \p item;
442 during \p func call \p item is locked so it is safe to modify the item in
443 multi-threaded environment.
445 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
446 \p second is true if new item has been added or \p false if the item with \p key
449 template <typename Q, typename Func>
450 std::pair<bool, bool> update( Q const& key, Func func, bool bAllowInsert = true )
452 return update_at( head(), key, func, bAllowInsert );
455 template <typename Q, typename Func>
456 CDS_DEPRECATED("ensure() is deprecated, use update()")
457 std::pair<bool, bool> ensure( Q const& key, Func f )
459 return update( key, f, true );
463 /// Deletes \p key from the list
464 /** \anchor cds_nonintrusive_LazyList_hp_erase_val
465 Since the key of LazyList's item type \p T is not explicitly specified,
466 template parameter \p Q defines the key type searching in the list.
467 The list item comparator should be able to compare the type \p T of list item
470 Return \p true if key is found and deleted, \p false otherwise
472 template <typename Q>
473 bool erase( Q const& key )
475 return erase_at( head(), key, intrusive_key_comparator(), [](value_type const&){} );
478 /// Deletes the item from the list using \p pred predicate for searching
480 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_val "erase(Q const&)"
481 but \p pred is used for key comparing.
482 \p Less functor has the interface like \p std::less.
483 \p pred must imply the same element order as the comparator used for building the list.
485 template <typename Q, typename Less>
486 bool erase_with( Q const& key, Less pred )
489 return erase_at( head(), key, typename maker::template less_wrapper<Less>::type(), [](value_type const&){} );
492 /// Deletes \p key from the list
493 /** \anchor cds_nonintrusive_LazyList_hp_erase_func
494 The function searches an item with key \p key, calls \p f functor with item found
495 and deletes the item. If \p key is not found, the functor is not called.
497 The functor \p Func interface:
500 void operator()(const value_type& val) { ... }
504 Since the key of LazyList's item type \p T is not explicitly specified,
505 template parameter \p Q defines the key type searching in the list.
506 The list item comparator should be able to compare the type \p T of list item
509 Return \p true if key is found and deleted, \p false otherwise
513 template <typename Q, typename Func>
514 bool erase( Q const& key, Func f )
516 return erase_at( head(), key, intrusive_key_comparator(), f );
519 /// Deletes the item from the list using \p pred predicate for searching
521 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_func "erase(Q const&, Func)"
522 but \p pred is used for key comparing.
523 \p Less functor has the interface like \p std::less.
524 \p pred must imply the same element order as the comparator used for building the list.
526 template <typename Q, typename Less, typename Func>
527 bool erase_with( Q const& key, Less pred, Func f )
530 return erase_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
533 /// Extracts the item from the list with specified \p key
534 /** \anchor cds_nonintrusive_LazyList_hp_extract
535 The function searches an item with key equal to \p key,
536 unlinks it from the list, and returns it as \p guarded_ptr.
537 If \p key is not found the function returns an empty guarded pointer.
539 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
541 @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
545 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
549 ord_list::guarded_ptr gp(theList.extract( 5 ));
554 // Destructor of gp releases internal HP guard and frees the item
558 template <typename Q>
559 guarded_ptr extract( Q const& key )
562 extract_at( head(), gp.guard(), key, intrusive_key_comparator() );
566 /// Extracts the item from the list with comparing functor \p pred
568 The function is an analog of \ref cds_nonintrusive_LazyList_hp_extract "extract(Q const&)"
569 but \p pred predicate is used for key comparing.
571 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
573 \p pred must imply the same element order as the comparator used for building the list.
575 template <typename Q, typename Less>
576 guarded_ptr extract_with( Q const& key, Less pred )
580 extract_at( head(), gp.guard(), key, typename maker::template less_wrapper<Less>::type() );
584 /// Checks whether the list contains \p key
586 The function searches the item with key equal to \p key
587 and returns \p true if it is found, and \p false otherwise.
589 template <typename Q>
590 bool contains( Q const& key )
592 return find_at( head(), key, intrusive_key_comparator() );
595 template <typename Q>
596 CDS_DEPRECATED("deprecated, use contains()")
597 bool find( Q const& key )
599 return contains( key );
603 /// Checks whether the list contains \p key using \p pred predicate for searching
605 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
606 \p Less functor has the interface like \p std::less.
607 \p pred must imply the same element order as the comparator used for building the list.
609 template <typename Q, typename Less>
610 bool contains( Q const& key, Less pred )
613 return find_at( head(), key, typename maker::template less_wrapper<Less>::type() );
616 template <typename Q, typename Less>
617 CDS_DEPRECATED("deprecated, use contains()")
618 bool find_with( Q const& key, Less pred )
620 return contains( key, pred );
623 /// Finds the key \p key and performs an action with it
624 /** \anchor cds_nonintrusive_LazyList_hp_find_func
625 The function searches an item with key equal to \p key and calls the functor \p f for the item found.
626 The interface of \p Func functor is:
629 void operator()( value_type& item, Q& key );
632 where \p item is the item found, \p key is the <tt>find</tt> function argument.
634 The functor may change non-key fields of \p item. Note that the function is only guarantee
635 that \p item cannot be deleted during functor is executing.
636 The function does not serialize simultaneous access to the list \p item. If such access is
637 possible you must provide your own synchronization schema to exclude unsafe item modifications.
639 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
640 may modify both arguments.
642 The function returns \p true if \p key is found, \p false otherwise.
644 template <typename Q, typename Func>
645 bool find( Q& key, Func f )
647 return find_at( head(), key, intrusive_key_comparator(), f );
650 template <typename Q, typename Func>
651 bool find( Q const& key, Func f )
653 return find_at( head(), key, intrusive_key_comparator(), f );
657 /// Finds the key \p key using \p pred predicate for searching
659 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_func "find(Q&, Func)"
660 but \p pred is used for key comparing.
661 \p Less functor has the interface like \p std::less.
662 \p pred must imply the same element order as the comparator used for building the list.
664 template <typename Q, typename Less, typename Func>
665 bool find_with( Q& key, Less pred, Func f )
668 return find_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
671 template <typename Q, typename Less, typename Func>
672 bool find_with( Q const& key, Less pred, Func f )
675 return find_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
679 /// Finds the key \p key and return the item found
680 /** \anchor cds_nonintrusive_LazyList_hp_get
681 The function searches the item with key equal to \p key
682 and returns the item found as \p guarded_ptr.
683 If \p key is not found the function returns an empty guarded pointer.
685 @note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
689 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
693 ord_list::guarded_ptr gp( theList.get( 5 ));
698 // Destructor of guarded_ptr releases internal HP guard and frees the item
702 Note the compare functor specified for class \p Traits template parameter
703 should accept a parameter of type \p Q that can be not the same as \p value_type.
705 template <typename Q>
706 guarded_ptr get( Q const& key )
709 get_at( head(), gp.guard(), key, intrusive_key_comparator() );
713 /// Finds the key \p key and return the item found
715 The function is an analog of \ref cds_nonintrusive_LazyList_hp_get "get( Q const&)"
716 but \p pred is used for comparing the keys.
718 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
720 \p pred must imply the same element order as the comparator used for building the list.
722 template <typename Q, typename Less>
723 guarded_ptr get_with( Q const& key, Less pred )
727 get_at( head(), gp.guard(), key, typename maker::template less_wrapper<Less>::type() );
731 /// Checks whether the list is empty
734 return base_class::empty();
737 /// Returns list's item count
739 The value returned depends on \p Traits::item_counter type. For \p atomicity::empty_item_counter,
740 this function always returns 0.
742 @note Even if you use real item counter and it returns 0, this fact is not mean that the list
743 is empty. To check list emptyness use \ref empty() method.
747 return base_class::size();
758 bool insert_node_at( head_type& refHead, node_type * pNode )
760 assert( pNode != nullptr );
761 scoped_node_ptr p( pNode );
763 if ( base_class::insert_at( &refHead, *pNode )) {
771 template <typename Q>
772 bool insert_at( head_type& refHead, const Q& val )
774 return insert_node_at( refHead, alloc_node( val ));
777 template <typename... Args>
778 bool emplace_at( head_type& refHead, Args&&... args )
780 return insert_node_at( refHead, alloc_node( std::forward<Args>(args)... ));
783 template <typename Q, typename Func>
784 bool insert_at( head_type& refHead, const Q& key, Func f )
786 scoped_node_ptr pNode( alloc_node( key ));
788 if ( base_class::insert_at( &refHead, *pNode, [&f](node_type& node){ f( node_to_value(node) ); } )) {
795 template <typename Q, typename Compare, typename Func>
796 bool erase_at( head_type& refHead, const Q& key, Compare cmp, Func f )
798 return base_class::erase_at( &refHead, key, cmp, [&f](node_type const& node){ f( node_to_value(node) ); } );
801 template <typename Q, typename Compare>
802 bool extract_at( head_type& refHead, typename guarded_ptr::native_guard& guard, Q const& key, Compare cmp )
804 return base_class::extract_at( &refHead, guard, key, cmp );
807 template <typename Q, typename Func>
808 std::pair<bool, bool> update_at( head_type& refHead, const Q& key, Func f, bool bAllowInsert )
810 scoped_node_ptr pNode( alloc_node( key ));
812 std::pair<bool, bool> ret = base_class::update_at( &refHead, *pNode,
813 [&f, &key](bool bNew, node_type& node, node_type&){f( bNew, node_to_value(node), key );},
815 if ( ret.first && ret.second )
821 template <typename Q, typename Compare>
822 bool find_at( head_type& refHead, Q const& key, Compare cmp )
824 return base_class::find_at( &refHead, key, cmp );
827 template <typename Q, typename Compare, typename Func>
828 bool find_at( head_type& refHead, Q& val, Compare cmp, Func f )
830 return base_class::find_at( &refHead, val, cmp, [&f](node_type& node, Q& val){ f( node_to_value(node), val ); });
833 template <typename Q, typename Compare>
834 bool get_at( head_type& refHead, typename guarded_ptr::native_guard& guard, Q const& key, Compare cmp )
836 return base_class::get_at( &refHead, guard, key, cmp );
842 }} // namespace cds::container
844 #endif // #ifndef CDSLIB_CONTAINER_IMPL_LAZY_LIST_H