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 )
167 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);
278 ///@name Forward iterators (only for debugging purpose)
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.
290 Moreover, a crash is possible when you try to iterate the next element that has been deleted by concurrent thread.
292 @warning Use this iterator on the concurrent container for debugging purpose only.
294 typedef iterator_type<false> iterator;
296 /// Const forward iterator
298 For iterator's features and requirements see \ref iterator
300 typedef iterator_type<true> const_iterator;
302 /// Returns a forward iterator addressing the first element in a list
304 For empty list \code begin() == end() \endcode
308 iterator it( head() );
309 ++it ; // skip dummy head node
313 /// Returns an iterator that addresses the location succeeding the last element in a list
315 Do not use the value returned by <tt>end</tt> function to access any item.
317 The returned value can be used only to control reaching the end of the list.
318 For empty list \code begin() == end() \endcode
322 return iterator( tail() );
325 /// Returns a forward const iterator addressing the first element in a list
326 const_iterator begin() const
328 const_iterator it( head() );
329 ++it ; // skip dummy head node
333 /// Returns a forward const iterator addressing the first element in a list
334 const_iterator cbegin() const
336 const_iterator it( head() );
337 ++it ; // skip dummy head node
341 /// Returns an const iterator that addresses the location succeeding the last element in a list
342 const_iterator end() const
344 return const_iterator( tail() );
347 /// Returns an const iterator that addresses the location succeeding the last element in a list
348 const_iterator cend() const
350 return const_iterator( tail() );
355 /// Default constructor
359 /// Destructor clears the list
367 The function creates a node with copy of \p val value
368 and then inserts the node created into the list.
370 The type \p Q should contain as minimum the complete key of the node.
371 The object of \ref value_type should be constructible from \p val of type \p Q.
372 In trivial case, \p Q is equal to \ref value_type.
374 Returns \p true if inserting successful, \p false otherwise.
376 template <typename Q>
377 bool insert( Q const& val )
379 return insert_at( head(), val );
384 This function inserts new node with default-constructed value and then it calls
385 \p func functor with signature
386 \code void func( value_type& item ) ;\endcode
388 The argument \p item of user-defined functor \p func is the reference
389 to the list's item inserted.
390 When \p func is called it has exclusive access to the item.
391 The user-defined functor is called only if the inserting is success.
393 The type \p Q should contain the complete key of the node.
394 The object of \p value_type should be constructible from \p key of type \p Q.
396 The function allows to split creating of new item into two part:
397 - create item from \p key with initializing key-fields only;
398 - insert new item into the list;
399 - if inserting is successful, initialize non-key fields of item by calling \p func functor
401 This can be useful if complete initialization of object of \p value_type is heavyweight and
402 it is preferable that the initialization should be completed only if inserting is successful.
404 template <typename Q, typename Func>
405 bool insert( Q const& key, Func func )
407 return insert_at( head(), key, func );
410 /// Inserts data of type \p value_type constructed from \p args
412 Returns \p true if inserting successful, \p false otherwise.
414 template <typename... Args>
415 bool emplace( Args&&... args )
417 return emplace_at( head(), std::forward<Args>(args)... );
420 /// Updates data by \p key
422 The operation performs inserting or replacing the element with lock-free manner.
424 If the \p key not found in the list, then the new item created from \p key
425 will be inserted iff \p bAllowInsert is \p true.
426 Otherwise, if \p key is found, the functor \p func is called with item found.
428 The functor \p Func signature is:
431 void operator()( bool bNew, value_type& item, Q const& val );
436 - \p bNew - \p true if the item has been inserted, \p false otherwise
437 - \p item - item of the list
438 - \p val - argument \p key passed into the \p %update() function
440 The functor may change non-key fields of the \p item;
441 during \p func call \p item is locked so it is safe to modify the item in
442 multi-threaded environment.
444 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
445 \p second is true if new item has been added or \p false if the item with \p key
448 template <typename Q, typename Func>
449 std::pair<bool, bool> update( Q const& key, Func func, bool bAllowInsert = true )
451 return update_at( head(), key, func, bAllowInsert );
454 template <typename Q, typename Func>
455 CDS_DEPRECATED("ensure() is deprecated, use update()")
456 std::pair<bool, bool> ensure( Q const& key, Func f )
458 return update( key, f, true );
462 /// Deletes \p key from the list
463 /** \anchor cds_nonintrusive_LazyList_hp_erase_val
464 Since the key of LazyList's item type \p T is not explicitly specified,
465 template parameter \p Q defines the key type searching in the list.
466 The list item comparator should be able to compare the type \p T of list item
469 Return \p true if key is found and deleted, \p false otherwise
471 template <typename Q>
472 bool erase( Q const& key )
474 return erase_at( head(), key, intrusive_key_comparator(), [](value_type const&){} );
477 /// Deletes the item from the list using \p pred predicate for searching
479 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_val "erase(Q const&)"
480 but \p pred is used for key comparing.
481 \p Less functor has the interface like \p std::less.
482 \p pred must imply the same element order as the comparator used for building the list.
484 template <typename Q, typename Less>
485 bool erase_with( Q const& key, Less pred )
488 return erase_at( head(), key, typename maker::template less_wrapper<Less>::type(), [](value_type const&){} );
491 /// Deletes \p key from the list
492 /** \anchor cds_nonintrusive_LazyList_hp_erase_func
493 The function searches an item with key \p key, calls \p f functor with item found
494 and deletes the item. If \p key is not found, the functor is not called.
496 The functor \p Func interface:
499 void operator()(const value_type& val) { ... }
503 Since the key of LazyList's item type \p T is not explicitly specified,
504 template parameter \p Q defines the key type searching in the list.
505 The list item comparator should be able to compare the type \p T of list item
508 Return \p true if key is found and deleted, \p false otherwise
512 template <typename Q, typename Func>
513 bool erase( Q const& key, Func f )
515 return erase_at( head(), key, intrusive_key_comparator(), f );
518 /// Deletes the item from the list using \p pred predicate for searching
520 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_func "erase(Q const&, Func)"
521 but \p pred is used for key comparing.
522 \p Less functor has the interface like \p std::less.
523 \p pred must imply the same element order as the comparator used for building the list.
525 template <typename Q, typename Less, typename Func>
526 bool erase_with( Q const& key, Less pred, Func f )
529 return erase_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
532 /// Extracts the item from the list with specified \p key
533 /** \anchor cds_nonintrusive_LazyList_hp_extract
534 The function searches an item with key equal to \p key,
535 unlinks it from the list, and returns it as \p guarded_ptr.
536 If \p key is not found the function returns an empty guarded pointer.
538 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
540 @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
544 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
548 ord_list::guarded_ptr gp(theList.extract( 5 ));
553 // Destructor of gp releases internal HP guard and frees the item
557 template <typename Q>
558 guarded_ptr extract( Q const& key )
561 extract_at( head(), gp.guard(), key, intrusive_key_comparator() );
565 /// Extracts the item from the list with comparing functor \p pred
567 The function is an analog of \ref cds_nonintrusive_LazyList_hp_extract "extract(Q const&)"
568 but \p pred predicate is used for key comparing.
570 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
572 \p pred must imply the same element order as the comparator used for building the list.
574 template <typename Q, typename Less>
575 guarded_ptr extract_with( Q const& key, Less pred )
579 extract_at( head(), gp.guard(), key, typename maker::template less_wrapper<Less>::type() );
583 /// Checks whether the list contains \p key
585 The function searches the item with key equal to \p key
586 and returns \p true if it is found, and \p false otherwise.
588 template <typename Q>
589 bool contains( Q const& key )
591 return find_at( head(), key, intrusive_key_comparator() );
594 template <typename Q>
595 CDS_DEPRECATED("deprecated, use contains()")
596 bool find( Q const& key )
598 return contains( key );
602 /// Checks whether the list contains \p key using \p pred predicate for searching
604 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
605 \p Less functor has the interface like \p std::less.
606 \p pred must imply the same element order as the comparator used for building the list.
608 template <typename Q, typename Less>
609 bool contains( Q const& key, Less pred )
612 return find_at( head(), key, typename maker::template less_wrapper<Less>::type() );
615 template <typename Q, typename Less>
616 CDS_DEPRECATED("deprecated, use contains()")
617 bool find_with( Q const& key, Less pred )
619 return contains( key, pred );
622 /// Finds the key \p key and performs an action with it
623 /** \anchor cds_nonintrusive_LazyList_hp_find_func
624 The function searches an item with key equal to \p key and calls the functor \p f for the item found.
625 The interface of \p Func functor is:
628 void operator()( value_type& item, Q& key );
631 where \p item is the item found, \p key is the <tt>find</tt> function argument.
633 The functor may change non-key fields of \p item. Note that the function is only guarantee
634 that \p item cannot be deleted during functor is executing.
635 The function does not serialize simultaneous access to the list \p item. If such access is
636 possible you must provide your own synchronization schema to exclude unsafe item modifications.
638 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
639 may modify both arguments.
641 The function returns \p true if \p key is found, \p false otherwise.
643 template <typename Q, typename Func>
644 bool find( Q& key, Func f )
646 return find_at( head(), key, intrusive_key_comparator(), f );
649 template <typename Q, typename Func>
650 bool find( Q const& key, Func f )
652 return find_at( head(), key, intrusive_key_comparator(), f );
656 /// Finds the key \p key using \p pred predicate for searching
658 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_func "find(Q&, Func)"
659 but \p pred is used for key comparing.
660 \p Less functor has the interface like \p std::less.
661 \p pred must imply the same element order as the comparator used for building the list.
663 template <typename Q, typename Less, typename Func>
664 bool find_with( Q& key, Less pred, Func f )
667 return find_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
670 template <typename Q, typename Less, typename Func>
671 bool find_with( Q const& key, Less pred, Func f )
674 return find_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
678 /// Finds the key \p key and return the item found
679 /** \anchor cds_nonintrusive_LazyList_hp_get
680 The function searches the item with key equal to \p key
681 and returns the item found as \p guarded_ptr.
682 If \p key is not found the function returns an empty guarded pointer.
684 @note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
688 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
692 ord_list::guarded_ptr gp( theList.get( 5 ));
697 // Destructor of guarded_ptr releases internal HP guard and frees the item
701 Note the compare functor specified for class \p Traits template parameter
702 should accept a parameter of type \p Q that can be not the same as \p value_type.
704 template <typename Q>
705 guarded_ptr get( Q const& key )
708 get_at( head(), gp.guard(), key, intrusive_key_comparator() );
712 /// Finds the key \p key and return the item found
714 The function is an analog of \ref cds_nonintrusive_LazyList_hp_get "get( Q const&)"
715 but \p pred is used for comparing the keys.
717 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
719 \p pred must imply the same element order as the comparator used for building the list.
721 template <typename Q, typename Less>
722 guarded_ptr get_with( Q const& key, Less pred )
726 get_at( head(), gp.guard(), key, typename maker::template less_wrapper<Less>::type() );
730 /// Checks whether the list is empty
733 return base_class::empty();
736 /// Returns list's item count
738 The value returned depends on \p Traits::item_counter type. For \p atomicity::empty_item_counter,
739 this function always returns 0.
741 @note Even if you use real item counter and it returns 0, this fact is not mean that the list
742 is empty. To check list emptyness use \ref empty() method.
746 return base_class::size();
757 bool insert_node( node_type * pNode )
759 return insert_node_at( head(), pNode );
762 bool insert_node_at( head_type& refHead, node_type * pNode )
764 assert( pNode != nullptr );
765 scoped_node_ptr p( pNode );
767 if ( base_class::insert_at( &refHead, *pNode )) {
775 template <typename Q>
776 bool insert_at( head_type& refHead, const Q& val )
778 return insert_node_at( refHead, alloc_node( val ));
781 template <typename... Args>
782 bool emplace_at( head_type& refHead, Args&&... args )
784 return insert_node_at( refHead, alloc_node( std::forward<Args>(args)... ));
787 template <typename Q, typename Func>
788 bool insert_at( head_type& refHead, const Q& key, Func f )
790 scoped_node_ptr pNode( alloc_node( key ));
792 if ( base_class::insert_at( &refHead, *pNode, [&f](node_type& node){ f( node_to_value(node) ); } )) {
799 template <typename Q, typename Compare, typename Func>
800 bool erase_at( head_type& refHead, const Q& key, Compare cmp, Func f )
802 return base_class::erase_at( &refHead, key, cmp, [&f](node_type const& node){ f( node_to_value(node) ); } );
805 template <typename Q, typename Compare>
806 bool extract_at( head_type& refHead, typename guarded_ptr::native_guard& guard, Q const& key, Compare cmp )
808 return base_class::extract_at( &refHead, guard, key, cmp );
811 template <typename Q, typename Func>
812 std::pair<bool, bool> update_at( head_type& refHead, const Q& key, Func f, bool bAllowInsert )
814 scoped_node_ptr pNode( alloc_node( key ));
816 std::pair<bool, bool> ret = base_class::update_at( &refHead, *pNode,
817 [&f, &key](bool bNew, node_type& node, node_type&){f( bNew, node_to_value(node), key );},
819 if ( ret.first && ret.second )
825 template <typename Q, typename Compare>
826 bool find_at( head_type& refHead, Q const& key, Compare cmp )
828 return base_class::find_at( &refHead, key, cmp );
831 template <typename Q, typename Compare, typename Func>
832 bool find_at( head_type& refHead, Q& val, Compare cmp, Func f )
834 return base_class::find_at( &refHead, val, cmp, [&f](node_type& node, Q& val){ f( node_to_value(node), val ); });
837 template <typename Q, typename Compare>
838 bool get_at( head_type& refHead, typename guarded_ptr::native_guard& guard, Q const& key, Compare cmp )
840 return base_class::get_at( &refHead, guard, key, cmp );
846 }} // namespace cds::container
848 #endif // #ifndef CDSLIB_CONTAINER_IMPL_LAZY_LIST_H