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);
280 ///@name Forward iterators (only for debugging purpose)
284 The forward iterator for lazy list has some features:
285 - it has no post-increment operator
286 - to protect the value, the iterator contains a GC-specific guard + another guard is required locally for increment operator.
287 For some GC (\p gc::HP), a guard is limited resource per thread, so an exception (or assertion) "no free guard"
288 may be thrown if a limit of guard count per thread is exceeded.
289 - The iterator cannot be moved across thread boundary since it contains GC's guard that is thread-private GC data.
290 - Iterator ensures thread-safety even if you delete the item that iterator points to. However, in case of concurrent
291 deleting operations it is no guarantee that you iterate all item in the list.
292 Moreover, a crash is possible when you try to iterate the next element that has been deleted by concurrent thread.
294 @warning Use this iterator on the concurrent container for debugging purpose only.
296 typedef iterator_type<false> iterator;
298 /// Const forward iterator
300 For iterator's features and requirements see \ref iterator
302 typedef iterator_type<true> const_iterator;
304 /// Returns a forward iterator addressing the first element in a list
306 For empty list \code begin() == end() \endcode
310 iterator it( head() );
311 ++it ; // skip dummy head node
315 /// Returns an iterator that addresses the location succeeding the last element in a list
317 Do not use the value returned by <tt>end</tt> function to access any item.
319 The returned value can be used only to control reaching the end of the list.
320 For empty list \code begin() == end() \endcode
324 return iterator( tail() );
327 /// Returns a forward const iterator addressing the first element in a list
328 const_iterator begin() const
330 const_iterator it( head() );
331 ++it ; // skip dummy head node
335 /// Returns a forward const iterator addressing the first element in a list
336 const_iterator cbegin() const
338 const_iterator it( head() );
339 ++it ; // skip dummy head node
343 /// Returns an const iterator that addresses the location succeeding the last element in a list
344 const_iterator end() const
346 return const_iterator( tail() );
349 /// Returns an const iterator that addresses the location succeeding the last element in a list
350 const_iterator cend() const
352 return const_iterator( tail() );
357 /// Default constructor
361 /// Destructor clears the list
369 The function creates a node with copy of \p val value
370 and then inserts the node created into the list.
372 The type \p Q should contain as minimum the complete key of the node.
373 The object of \ref value_type should be constructible from \p val of type \p Q.
374 In trivial case, \p Q is equal to \ref value_type.
376 Returns \p true if inserting successful, \p false otherwise.
378 template <typename Q>
379 bool insert( Q const& val )
381 return insert_at( head(), val );
386 This function inserts new node with default-constructed value and then it calls
387 \p func functor with signature
388 \code void func( value_type& item ) ;\endcode
390 The argument \p item of user-defined functor \p func is the reference
391 to the list's item inserted.
392 When \p func is called it has exclusive access to the item.
393 The user-defined functor is called only if the inserting is success.
395 The type \p Q should contain the complete key of the node.
396 The object of \p value_type should be constructible from \p key of type \p Q.
398 The function allows to split creating of new item into two part:
399 - create item from \p key with initializing key-fields only;
400 - insert new item into the list;
401 - if inserting is successful, initialize non-key fields of item by calling \p func functor
403 This can be useful if complete initialization of object of \p value_type is heavyweight and
404 it is preferable that the initialization should be completed only if inserting is successful.
406 template <typename Q, typename Func>
407 bool insert( Q const& key, Func func )
409 return insert_at( head(), key, func );
412 /// Inserts data of type \p value_type constructed from \p args
414 Returns \p true if inserting successful, \p false otherwise.
416 template <typename... Args>
417 bool emplace( Args&&... args )
419 return emplace_at( head(), std::forward<Args>(args)... );
422 /// Updates data by \p key
424 The operation performs inserting or replacing the element with lock-free manner.
426 If the \p key not found in the list, then the new item created from \p key
427 will be inserted iff \p bAllowInsert is \p true.
428 Otherwise, if \p key is found, the functor \p func is called with item found.
430 The functor \p Func signature is:
433 void operator()( bool bNew, value_type& item, Q const& val );
438 - \p bNew - \p true if the item has been inserted, \p false otherwise
439 - \p item - item of the list
440 - \p val - argument \p key passed into the \p %update() function
442 The functor may change non-key fields of the \p item;
443 during \p func call \p item is locked so it is safe to modify the item in
444 multi-threaded environment.
446 Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
447 \p second is true if new item has been added or \p false if the item with \p key
450 template <typename Q, typename Func>
451 std::pair<bool, bool> update( Q const& key, Func func, bool bAllowInsert = true )
453 return update_at( head(), key, func, bAllowInsert );
456 template <typename Q, typename Func>
457 CDS_DEPRECATED("ensure() is deprecated, use update()")
458 std::pair<bool, bool> ensure( Q const& key, Func f )
460 return update( key, f, true );
464 /// Deletes \p key from the list
465 /** \anchor cds_nonintrusive_LazyList_hp_erase_val
466 Since the key of LazyList's item type \p T is not explicitly specified,
467 template parameter \p Q defines the key type searching in the list.
468 The list item comparator should be able to compare the type \p T of list item
471 Return \p true if key is found and deleted, \p false otherwise
473 template <typename Q>
474 bool erase( Q const& key )
476 return erase_at( head(), key, intrusive_key_comparator(), [](value_type const&){} );
479 /// Deletes the item from the list using \p pred predicate for searching
481 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_val "erase(Q const&)"
482 but \p pred is used for key comparing.
483 \p Less functor has the interface like \p std::less.
484 \p pred must imply the same element order as the comparator used for building the list.
486 template <typename Q, typename Less>
487 bool erase_with( Q const& key, Less pred )
490 return erase_at( head(), key, typename maker::template less_wrapper<Less>::type(), [](value_type const&){} );
493 /// Deletes \p key from the list
494 /** \anchor cds_nonintrusive_LazyList_hp_erase_func
495 The function searches an item with key \p key, calls \p f functor with item found
496 and deletes the item. If \p key is not found, the functor is not called.
498 The functor \p Func interface:
501 void operator()(const value_type& val) { ... }
505 Since the key of LazyList's item type \p T is not explicitly specified,
506 template parameter \p Q defines the key type searching in the list.
507 The list item comparator should be able to compare the type \p T of list item
510 Return \p true if key is found and deleted, \p false otherwise
514 template <typename Q, typename Func>
515 bool erase( Q const& key, Func f )
517 return erase_at( head(), key, intrusive_key_comparator(), f );
520 /// Deletes the item from the list using \p pred predicate for searching
522 The function is an analog of \ref cds_nonintrusive_LazyList_hp_erase_func "erase(Q const&, Func)"
523 but \p pred is used for key comparing.
524 \p Less functor has the interface like \p std::less.
525 \p pred must imply the same element order as the comparator used for building the list.
527 template <typename Q, typename Less, typename Func>
528 bool erase_with( Q const& key, Less pred, Func f )
531 return erase_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
534 /// Extracts the item from the list with specified \p key
535 /** \anchor cds_nonintrusive_LazyList_hp_extract
536 The function searches an item with key equal to \p key,
537 unlinks it from the list, and returns it as \p guarded_ptr.
538 If \p key is not found the function returns an empty guarded pointer.
540 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
542 @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
546 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
550 ord_list::guarded_ptr gp(theList.extract( 5 ));
555 // Destructor of gp releases internal HP guard and frees the item
559 template <typename Q>
560 guarded_ptr extract( Q const& key )
563 extract_at( head(), gp.guard(), key, intrusive_key_comparator() );
567 /// Extracts the item from the list with comparing functor \p pred
569 The function is an analog of \ref cds_nonintrusive_LazyList_hp_extract "extract(Q const&)"
570 but \p pred predicate is used for key comparing.
572 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
574 \p pred must imply the same element order as the comparator used for building the list.
576 template <typename Q, typename Less>
577 guarded_ptr extract_with( Q const& key, Less pred )
581 extract_at( head(), gp.guard(), key, typename maker::template less_wrapper<Less>::type() );
585 /// Checks whether the list contains \p key
587 The function searches the item with key equal to \p key
588 and returns \p true if it is found, and \p false otherwise.
590 template <typename Q>
591 bool contains( Q const& key )
593 return find_at( head(), key, intrusive_key_comparator() );
596 template <typename Q>
597 CDS_DEPRECATED("deprecated, use contains()")
598 bool find( Q const& key )
600 return contains( key );
604 /// Checks whether the list contains \p key using \p pred predicate for searching
606 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
607 \p Less functor has the interface like \p std::less.
608 \p pred must imply the same element order as the comparator used for building the list.
610 template <typename Q, typename Less>
611 bool contains( Q const& key, Less pred )
614 return find_at( head(), key, typename maker::template less_wrapper<Less>::type() );
617 template <typename Q, typename Less>
618 CDS_DEPRECATED("deprecated, use contains()")
619 bool find_with( Q const& key, Less pred )
621 return contains( key, pred );
624 /// Finds the key \p key and performs an action with it
625 /** \anchor cds_nonintrusive_LazyList_hp_find_func
626 The function searches an item with key equal to \p key and calls the functor \p f for the item found.
627 The interface of \p Func functor is:
630 void operator()( value_type& item, Q& key );
633 where \p item is the item found, \p key is the <tt>find</tt> function argument.
635 The functor may change non-key fields of \p item. Note that the function is only guarantee
636 that \p item cannot be deleted during functor is executing.
637 The function does not serialize simultaneous access to the list \p item. If such access is
638 possible you must provide your own synchronization schema to exclude unsafe item modifications.
640 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
641 may modify both arguments.
643 The function returns \p true if \p key is found, \p false otherwise.
645 template <typename Q, typename Func>
646 bool find( Q& key, Func f )
648 return find_at( head(), key, intrusive_key_comparator(), f );
651 template <typename Q, typename Func>
652 bool find( Q const& key, Func f )
654 return find_at( head(), key, intrusive_key_comparator(), f );
658 /// Finds the key \p key using \p pred predicate for searching
660 The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_func "find(Q&, Func)"
661 but \p pred is used for key comparing.
662 \p Less functor has the interface like \p std::less.
663 \p pred must imply the same element order as the comparator used for building the list.
665 template <typename Q, typename Less, typename Func>
666 bool find_with( Q& key, Less pred, Func f )
669 return find_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
672 template <typename Q, typename Less, typename Func>
673 bool find_with( Q const& key, Less pred, Func f )
676 return find_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
680 /// Finds the key \p key and return the item found
681 /** \anchor cds_nonintrusive_LazyList_hp_get
682 The function searches the item with key equal to \p key
683 and returns the item found as \p guarded_ptr.
684 If \p key is not found the function returns an empty guarded pointer.
686 @note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
690 typedef cds::container::LazyList< cds::gc::HP, foo, my_traits > ord_list;
694 ord_list::guarded_ptr gp( theList.get( 5 ));
699 // Destructor of guarded_ptr releases internal HP guard and frees the item
703 Note the compare functor specified for class \p Traits template parameter
704 should accept a parameter of type \p Q that can be not the same as \p value_type.
706 template <typename Q>
707 guarded_ptr get( Q const& key )
710 get_at( head(), gp.guard(), key, intrusive_key_comparator() );
714 /// Finds the key \p key and return the item found
716 The function is an analog of \ref cds_nonintrusive_LazyList_hp_get "get( Q const&)"
717 but \p pred is used for comparing the keys.
719 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
721 \p pred must imply the same element order as the comparator used for building the list.
723 template <typename Q, typename Less>
724 guarded_ptr get_with( Q const& key, Less pred )
728 get_at( head(), gp.guard(), key, typename maker::template less_wrapper<Less>::type() );
732 /// Checks whether the list is empty
735 return base_class::empty();
738 /// Returns list's item count
740 The value returned depends on \p Traits::item_counter type. For \p atomicity::empty_item_counter,
741 this function always returns 0.
743 @note Even if you use real item counter and it returns 0, this fact is not mean that the list
744 is empty. To check list emptyness use \ref empty() method.
748 return base_class::size();
759 bool insert_node_at( head_type& refHead, node_type * pNode )
761 assert( pNode != nullptr );
762 scoped_node_ptr p( pNode );
764 if ( base_class::insert_at( &refHead, *pNode )) {
772 template <typename Q>
773 bool insert_at( head_type& refHead, const Q& val )
775 return insert_node_at( refHead, alloc_node( val ));
778 template <typename... Args>
779 bool emplace_at( head_type& refHead, Args&&... args )
781 return insert_node_at( refHead, alloc_node( std::forward<Args>(args)... ));
784 template <typename Q, typename Func>
785 bool insert_at( head_type& refHead, const Q& key, Func f )
787 scoped_node_ptr pNode( alloc_node( key ));
789 if ( base_class::insert_at( &refHead, *pNode, [&f](node_type& node){ f( node_to_value(node) ); } )) {
796 template <typename Q, typename Compare, typename Func>
797 bool erase_at( head_type& refHead, const Q& key, Compare cmp, Func f )
799 return base_class::erase_at( &refHead, key, cmp, [&f](node_type const& node){ f( node_to_value(node) ); } );
802 template <typename Q, typename Compare>
803 bool extract_at( head_type& refHead, typename guarded_ptr::native_guard& guard, Q const& key, Compare cmp )
805 return base_class::extract_at( &refHead, guard, key, cmp );
808 template <typename Q, typename Func>
809 std::pair<bool, bool> update_at( head_type& refHead, const Q& key, Func f, bool bAllowInsert )
811 scoped_node_ptr pNode( alloc_node( key ));
813 std::pair<bool, bool> ret = base_class::update_at( &refHead, *pNode,
814 [&f, &key](bool bNew, node_type& node, node_type&){f( bNew, node_to_value(node), key );},
816 if ( ret.first && ret.second )
822 template <typename Q, typename Compare>
823 bool find_at( head_type& refHead, Q const& key, Compare cmp )
825 return base_class::find_at( &refHead, key, cmp );
828 template <typename Q, typename Compare, typename Func>
829 bool find_at( head_type& refHead, Q& val, Compare cmp, Func f )
831 return base_class::find_at( &refHead, val, cmp, [&f](node_type& node, Q& val){ f( node_to_value(node), val ); });
834 template <typename Q, typename Compare>
835 bool get_at( head_type& refHead, typename guarded_ptr::native_guard& guard, Q const& key, Compare cmp )
837 return base_class::get_at( &refHead, guard, key, cmp );
843 }} // namespace cds::container
845 #endif // #ifndef CDSLIB_CONTAINER_IMPL_LAZY_LIST_H