Iterable lock-free ordered single-linked list. More...

#include <cds/intrusive/impl/iterable_list.h>

Inheritance diagram for cds::intrusive::IterableList< GC, T, Traits >:

Public Types
typedef T	value_type
	type of value stored in the list

typedef Traits	traits
	Traits template parameter.

typedef iterable_list::node< value_type >	node_type
	node type

typedef implementation_defined	key_comparator
	key comparison functor based on opt::compare and opt::less option setter.

typedef traits::disposer	disposer
	disposer for `value_type`

typedef GC	gc
	Garbage collector.

typedef traits::back_off	back_off
	back-off strategy

typedef traits::item_counter	item_counter
	Item counting policy used.

typedef traits::memory_model	memory_model
	Memory ordering. See `cds::opt::memory_model` option.

typedef traits::node_allocator	node_allocator
	Node allocator.

typedef traits::stat	stat
	Internal statistics.

typedef gc::template guarded_ptr< value_type >	guarded_ptr
	Guarded pointer.

Public Member Functions
	IterableList ()
	Default constructor initializes empty list.

	~IterableList ()
	Destroys the list object.

bool	insert (value_type &val)
	Inserts new node. More...

template<typename Func >
bool	insert (value_type &val, Func f)
	Inserts new node. More...

template<typename Func >
std::pair< bool, bool >	update (value_type &val, Func func, bool bInsert=true)
	Updates the node. More...

std::pair< bool, bool >	upsert (value_type &val, bool bInsert=true)
	Insert or update. More...

bool	unlink (value_type &val)
	Unlinks the item `val` from the list. More...

template<typename Q >
bool	erase (Q const &key)
	Deletes the item from the list. More...

template<typename Q , typename Less >
bool	erase_with (Q const &key, Less pred)
	Deletes the item from the list using `pred` predicate for searching. More...

template<typename Q , typename Func >
bool	erase (Q const &key, Func func)
	Deletes the item from the list. More...

template<typename Q , typename Less , typename Func >
bool	erase_with (Q const &key, Less pred, Func f)
	Deletes the item from the list using `pred` predicate for searching. More...

bool	erase_at (iterator const &iter)
	Deletes the item pointed by iterator `iter`. More...

template<typename Q >
guarded_ptr	extract (Q const &key)
	Extracts the item from the list with specified `key`. More...

template<typename Q , typename Less >
guarded_ptr	extract_with (Q const &key, Less pred)
	Extracts the item using compare functor `pred`. More...

template<typename Q , typename Func >
bool	find (Q &key, Func f) const
	Finds `key` in the list. More...

template<typename Q >
iterator	find (Q const &key) const
	Finds `key` in the list and returns iterator pointed to the item found. More...

template<typename Q , typename Less , typename Func >
bool	find_with (Q &key, Less pred, Func f) const
	Finds the `key` using `pred` predicate for searching. More...

template<typename Q , typename Less >
iterator	find_with (Q const &key, Less pred) const
	Finds `key` in the list using `pred` predicate for searching and returns iterator pointed to the item found. More...

template<typename Q >
bool	contains (Q const &key) const
	Checks whether the list contains `key`. More...

template<typename Q , typename Less >
bool	contains (Q const &key, Less pred) const
	Checks whether the list contains `key` using `pred` predicate for searching. More...

template<typename Q >
guarded_ptr	get (Q const &key) const
	Finds the `key` and return the item found. More...

template<typename Q , typename Less >
guarded_ptr	get_with (Q const &key, Less pred) const
	Finds the `key` and return the item found. More...

void	clear ()
	Clears the list (thread safe, not atomic)

bool	empty () const
	Checks if the list is empty. More...

size_t	size () const
	Returns list's item count. More...

stat const &	statistics () const
	Returns const reference to internal statistics.

Static Public Attributes
static constexpr const size_t	c_nHazardPtrCount = 4
	Count of hazard pointer required for the algorithm.

Thread-safe forward iterators
typedef iterator_type< false >	iterator
	Forward iterator. More...

typedef iterator_type< true >	const_iterator
	Const forward iterator. More...

iterator	begin ()
	Returns a forward iterator addressing the first element in a list. More...

iterator	end ()
	Returns an iterator that addresses the location succeeding the last element in a list. More...

const_iterator	cbegin () const
	Returns a forward const iterator addressing the first element in a list.

const_iterator	begin () const
	Returns a forward const iterator addressing the first element in a list.

const_iterator	end () const
	Returns an const iterator that addresses the location succeeding the last element in a list.

const_iterator	cend () const
	Returns an const iterator that addresses the location succeeding the last element in a list.

Detailed Description

template<class GC, typename T, class Traits = iterable_list::traits>
class cds::intrusive::IterableList< GC, T, Traits >

Iterable lock-free ordered single-linked list.

This non-blocking list implementation supports thread-safe iterators; searching and removing are lock-free, inserting is non-blocking because it uses a light-weight synchronization based on marked pointers.

Unlike cds::intrusive::MichaelList the iterable list does not require any hook in T to be stored in the list.

Usually, ordered single-linked list is used as a building block for the hash table implementation. Iterable list is suitable for almost append-only hash table because the list doesn't delete its internal node when erasing a key but it is marked them as empty to be reused in the future. However, plenty of empty nodes degrades performance. Separation of internal nodes and user data implies the need for an allocator for internal node so the iterable list is not fully intrusive. Nevertheless, if you need thread-safe iterator, the iterable list is good choice.

The complexity of searching is O(N).

Template arguments:

GC - Garbage collector used.
T - type to be stored in the list.
Traits - type traits, default is iterable_list::traits. It is possible to declare option-based list with cds::intrusive::iterable_list::make_traits metafunction: For example, the following traits-based declaration of gc::HP iterable list
#include <cds/intrusive/iterable_list_hp.h>
// Declare item stored in your list
struct foo
{
int nKey;
// .... other data
};
// Declare comparator for the item
struct my_compare {
int operator()( foo const& i1, foo const& i2 ) const
{
return i1.nKey - i2.nKey;
}
};
// Declare traits
struct my_traits: public cds::intrusive::iterable_list::traits
{
typedef my_compare compare;
};
// Declare list
typedef cds::intrusive::IterableList< cds::gc::HP, foo, my_traits > list_type;
is equivalent for the following option-based list
#include <cds/intrusive/iterable_list_hp.h>
// foo struct and my_compare are the same
// Declare option-based list
typedef cds::intrusive::IterableList< cds::gc::HP, foo,
typename cds::intrusive::iterable_list::make_traits<
cds::intrusive::opt::compare< my_compare > // item comparator option
>::type
> option_list_type;

Usage

There are different specializations of this template for each garbage collecting schema. You should select GC you want and include appropriate .h-file:

for gc::HP: <cds/intrusive/iterable_list_hp.h>
for gc::DHP: <cds/intrusive/iterable_list_dhp.h>

Member Typedef Documentation

◆ const_iterator

template<class GC, typename T, class Traits = iterable_list::traits>

typedef iterator_type<true> cds::intrusive::IterableList< GC, T, Traits >::const_iterator

Const forward iterator.

For iterator's features and requirements see iterator

◆ iterator

template<class GC, typename T, class Traits = iterable_list::traits>

typedef iterator_type<false> cds::intrusive::IterableList< GC, T, Traits >::iterator

Forward iterator.

The forward iterator for iterable list has some features:

it has no post-increment operator
to protect the value, the iterator contains a GC-specific guard. For some GC (like as gc::HP), a guard is a limited resource per thread, so an exception (or assertion) "no free guard" may be thrown if the limit of guard count per thread is exceeded.
The iterator cannot be moved across thread boundary since it contains thread-private GC's guard.
Iterator is thread-safe: even if the element the iterator points to is removed, the iterator stays valid because it contains the guard keeping the value from to be recycled.

The iterator interface:

class iterator {
public:
    // Default constructor
    iterator();
    // Copy construtor
    iterator( iterator const& src );
    // Dereference operator
    value_type * operator ->() const;
    // Dereference operator
    value_type& operator *() const;
    // Preincrement operator
    iterator& operator ++();
    // Assignment operator
    iterator& operator = (iterator const& src);
    // Equality operators
    bool operator ==(iterator const& i ) const;
    bool operator !=(iterator const& i ) const;
};

Note: For two iterators pointed to the same element the value can be different; this code
if ( it1 == it2 )
assert( &(*it1) == &(*it2));
can throw assertion. The point is that the iterator stores the value of element which can be modified later by other thread. The guard inside the iterator prevents recycling that value so the iterator's value remains valid even after changing. Other iterator may observe modified value of the element.

Member Function Documentation

◆ begin()

template<class GC, typename T, class Traits = iterable_list::traits>

iterator cds::intrusive::IterableList< GC, T, Traits >::begin ( )

inline

Returns a forward iterator addressing the first element in a list.

For empty list

begin() == end()

◆ contains() [1/2]

template<class GC, typename T, class Traits = iterable_list::traits>

template<typename Q >

bool cds::intrusive::IterableList< GC, T, Traits >::contains ( Q const & key ) const

inline

Checks whether the list contains key.

The function searches the item with key equal to key and returns true if it is found, and false otherwise.

◆ contains() [2/2]

template<class GC, typename T, class Traits = iterable_list::traits>

template<typename Q , typename Less >

bool cds::intrusive::IterableList< GC, T, Traits >::contains	(	Q const &	key,
		Less	pred
	)		const

inline

Checks whether the list contains key using pred predicate for searching.

The function is an analog of contains( key ) but pred is used for key comparing. Less functor has the interface like std::less. Less must imply the same element order as the comparator used for building the list.

◆ empty()

template<class GC, typename T, class Traits = iterable_list::traits>

bool cds::intrusive::IterableList< GC, T, Traits >::empty ( ) const

inline

Checks if the list is empty.

Emptiness is checked by item counting: if item count is zero then the set is empty. Thus, if you need to use empty() you should provide appropriate (non-empty) iterable_list::traits::item_counter feature.

◆ end()

template<class GC, typename T, class Traits = iterable_list::traits>

iterator cds::intrusive::IterableList< GC, T, Traits >::end ( )

inline

Returns an iterator that addresses the location succeeding the last element in a list.

Do not use the value returned by end function to access any item. Internally, end returning value equals to nullptr.

The returned value can be used only to control reaching the end of the list. For empty list begin() == end()

◆ erase() [1/2]

template<class GC, typename T, class Traits = iterable_list::traits>

template<typename Q >

bool cds::intrusive::IterableList< GC, T, Traits >::erase ( Q const & key )

inline

Deletes the item from the list.

The function searches an item with key equal to key in the list, unlinks it from the list, and returns true. If key is not found the function return false.

disposer specified in Traits is called for deleted item.

◆ erase() [2/2]

template<class GC, typename T, class Traits = iterable_list::traits>

template<typename Q , typename Func >

bool cds::intrusive::IterableList< GC, T, Traits >::erase	(	Q const &	key,
		Func	func
	)

inline

Deletes the item from the list.

The function searches an item with key equal to key in the list, call func functor with item found, unlinks it from the list, and returns true. The Func interface is

struct functor {
    void operator()( value_type const& item );
};

If key is not found the function return false, func is not called.

disposer specified in Traits is called for deleted item.

◆ erase_at()

template<class GC, typename T, class Traits = iterable_list::traits>

bool cds::intrusive::IterableList< GC, T, Traits >::erase_at ( iterator const & iter )

inline

Deletes the item pointed by iterator iter.

Returns true if the operation is successful, false otherwise. The function can return false if the node the iterator points to has already been deleted by other thread.

The function does not invalidate the iterator, it remains valid and can be used for further traversing.

◆ erase_with() [1/2]

template<class GC, typename T, class Traits = iterable_list::traits>

template<typename Q , typename Less >

bool cds::intrusive::IterableList< GC, T, Traits >::erase_with	(	Q const &	key,
		Less	pred
	)

inline

Deletes the item from the list using pred predicate for searching.

The function is an analog of erase(Q const&) but pred is used for key comparing. Less functor has the interface like std::less. pred must imply the same element order as the comparator used for building the list.

disposer specified in Traits is called for deleted item.

◆ erase_with() [2/2]

template<class GC, typename T, class Traits = iterable_list::traits>

template<typename Q , typename Less , typename Func >

bool cds::intrusive::IterableList< GC, T, Traits >::erase_with	(	Q const &	key,
		Less	pred,
		Func	f
	)

inline

Deletes the item from the list using pred predicate for searching.

The function is an analog of erase(Q const&, Func) but pred is used for key comparing. Less functor has the interface like std::less. pred must imply the same element order as the comparator used for building the list.

disposer specified in Traits is called for deleted item.

◆ extract()

template<class GC, typename T, class Traits = iterable_list::traits>

template<typename Q >

guarded_ptr cds::intrusive::IterableList< GC, T, Traits >::extract ( Q const & key )

inline

Extracts the item from the list with specified key.

The function searches an item with key equal to key, unlinks it from the list, and returns it as guarded_ptr. If key is not found returns an empty guarded pointer.

Note the compare functor should accept a parameter of type Q that can be not the same as value_type.

The disposer specified in Traits class template parameter is called automatically by garbage collector GC when returned guarded_ptr object will be destroyed or released.

Note: Each guarded_ptr object uses the GC's guard that can be limited resource.

Usage:

typedef cds::intrusive::IterableList< cds::gc::HP, foo, my_traits >  ord_list;
ord_list theList;
// ...
{
    ord_list::guarded_ptr gp( theList.extract( 5 ));
    if ( gp ) {
        // Deal with gp
        // ...
    }
    // Destructor of gp releases internal HP guard
}

◆ extract_with()

template<class GC, typename T, class Traits = iterable_list::traits>

template<typename Q , typename Less >

guarded_ptr cds::intrusive::IterableList< GC, T, Traits >::extract_with	(	Q const &	key,
		Less	pred
	)

inline

Extracts the item using compare functor pred.

The function is an analog of extract(Q const&) but pred predicate is used for key comparing.

Less functor has the semantics like std::less but should take arguments of type value_type and Q in any order. pred must imply the same element order as the comparator used for building the list.

◆ find() [1/2]

template<class GC, typename T, class Traits = iterable_list::traits>

template<typename Q , typename Func >

bool cds::intrusive::IterableList< GC, T, Traits >::find	(	Q &	key,
		Func	f
	)		const

inline

Finds key in the list.

The function searches the item with key equal to key and calls the functor f for item found. The interface of Func functor is:

struct functor {
    void operator()( value_type& item, Q& key );
};

where item is the item found, key is the find() function argument.

The functor may change non-key fields of item. Note that the function is only guarantee that item cannot be disposed during functor is executing. The function does not serialize simultaneous access to the item. If such access is possible you must provide your own synchronization schema to keep out unsafe item modifications.

The function returns true if val is found, false otherwise.

◆ find() [2/2]

template<class GC, typename T, class Traits = iterable_list::traits>

template<typename Q >

iterator cds::intrusive::IterableList< GC, T, Traits >::find ( Q const & key ) const

inline

Finds key in the list and returns iterator pointed to the item found.

If key is not found the function returns end().

◆ find_with() [1/2]

template<class GC, typename T, class Traits = iterable_list::traits>

template<typename Q , typename Less , typename Func >

bool cds::intrusive::IterableList< GC, T, Traits >::find_with	(	Q &	key,
		Less	pred,
		Func	f
	)		const

inline

Finds the key using pred predicate for searching.

The function is an analog of find(Q&, Func) but pred is used for key comparing. Less functor has the interface like std::less. pred must imply the same element order as the comparator used for building the list.

◆ find_with() [2/2]

template<class GC, typename T, class Traits = iterable_list::traits>

template<typename Q , typename Less >

iterator cds::intrusive::IterableList< GC, T, Traits >::find_with	(	Q const &	key,
		Less	pred
	)		const

inline

Finds key in the list using pred predicate for searching and returns iterator pointed to the item found.

The function is an analog of find(Q&) but pred is used for key comparing. Less functor has the interface like std::less. pred must imply the same element order as the comparator used for building the list.

If key is not found the function returns end().

◆ get()

template<class GC, typename T, class Traits = iterable_list::traits>

template<typename Q >

guarded_ptr cds::intrusive::IterableList< GC, T, Traits >::get ( Q const & key ) const

inline

Finds the key and return the item found.

The function searches the item with key equal to key and returns it as guarded_ptr. If key is not found the function returns an empty guarded pointer.

The disposer specified in Traits class template parameter is called by garbage collector GC automatically when returned guarded_ptr object will be destroyed or released.

Note: Each guarded_ptr object uses one GC's guard which can be limited resource.

Usage:

typedef cds::intrusive::IterableList< cds::gc::HP, foo, my_traits >  ord_list;
ord_list theList;
// ...
{
    ord_list::guarded_ptr gp(theList.get( 5 ));
    if ( gp ) {
        // Deal with gp
        //...
    }
    // Destructor of guarded_ptr releases internal HP guard
}

Note the compare functor specified for Traits template parameter should accept a parameter of type Q that can be not the same as value_type.

◆ get_with()

template<class GC, typename T, class Traits = iterable_list::traits>

template<typename Q , typename Less >

guarded_ptr cds::intrusive::IterableList< GC, T, Traits >::get_with	(	Q const &	key,
		Less	pred
	)		const

inline

Finds the key and return the item found.

The function is an analog of get( Q const&) but pred is used for comparing the keys.

Less functor has the semantics like std::less but should take arguments of type value_type and Q in any order. pred must imply the same element order as the comparator used for building the list.

◆ insert() [1/2]

template<class GC, typename T, class Traits = iterable_list::traits>

bool cds::intrusive::IterableList< GC, T, Traits >::insert ( value_type & val )

inline

Inserts new node.

The function inserts val into the list if the list does not contain an item with key equal to val.

Returns true if val has been linked to the list, false otherwise.

◆ insert() [2/2]

template<class GC, typename T, class Traits = iterable_list::traits>

template<typename Func >

bool cds::intrusive::IterableList< GC, T, Traits >::insert	(	value_type &	val,
		Func	f
	)

inline

Inserts new node.

This function is intended for derived non-intrusive containers.

The function allows to split new item creating into two part:

create item with key only
insert new item into the list
if inserting is success, calls f functor to initialize value-field of val.

The functor signature is:

void func( value_type& val );

where val is the item inserted. User-defined functor f should guarantee that during changing val no any other changes could be made on this list's item by concurrent threads. The user-defined functor is called only if the inserting is success.

Warning: See insert item troubleshooting

◆ size()

template<class GC, typename T, class Traits = iterable_list::traits>

size_t cds::intrusive::IterableList< GC, T, Traits >::size ( ) const

inline

Returns list's item count.

The value returned depends on item counter provided by iterable_list::traits::item_counter. For atomicity::empty_item_counter, this function always returns 0.

◆ unlink()

template<class GC, typename T, class Traits = iterable_list::traits>

bool cds::intrusive::IterableList< GC, T, Traits >::unlink ( value_type & val )

inline

Unlinks the item val from the list.

The function searches the item val in the list and unlinks it from the list if it is found and it is equal to val.

Difference between erase() and unlink(): erase() finds a key and deletes the item found. unlink() finds an item by key and deletes it only if val is an item of the list, i.e. the pointer to item found is equal to &val .

disposer specified in Traits is called for deleted item.

The function returns true if success and false otherwise.

◆ update()

template<class GC, typename T, class Traits = iterable_list::traits>

template<typename Func >

std::pair<bool, bool> cds::intrusive::IterableList< GC, T, Traits >::update	(	value_type &	val,
		Func	func,
		bool	bInsert = `true`
	)

inline

Updates the node.

The operation performs inserting or changing data with lock-free manner.

If the item val is not found in the list, then val is inserted iff bInsert is true. Otherwise, the current element is changed to val, the element will be retired later by call Traits::disposer. The functor func is called after inserting or replacing, it signature is:

void func( value_type& val, value_type * old );

where

val - argument val passed into the update() function
old - old value that will be retired. If new item has been inserted then old is nullptr.

Returns std::pair<bool, bool> where first is true if operation is successful, second is true if val has been added or false if the item with that key already in the list.

◆ upsert()

template<class GC, typename T, class Traits = iterable_list::traits>

std::pair<bool, bool> cds::intrusive::IterableList< GC, T, Traits >::upsert	(	value_type &	val,
		bool	bInsert = `true`
	)

inline

Insert or update.

The operation performs inserting or updating data with lock-free manner.

If the item val is not found in the list, then val is inserted iff bInsert is true. Otherwise, the current element is changed to val, the old element will be retired later by call Traits::disposer.

Returns std::pair<bool, bool> where first is true if operation is successful, second is true if val has been added or false if the item with that key already in the list.

The documentation for this class was generated from the following file:

cds/intrusive/impl/iterable_list.h

Public Types

Public Member Functions

Static Public Attributes

Thread-safe forward iterators

Detailed Description

template<class GC, typename T, class Traits = iterable_list::traits> class cds::intrusive::IterableList< GC, T, Traits >

Member Typedef Documentation

◆ const_iterator

◆ iterator

Member Function Documentation

◆ begin()

◆ contains() [1/2]

◆ contains() [2/2]

◆ empty()

◆ end()

◆ erase() [1/2]

◆ erase() [2/2]

◆ erase_at()

◆ erase_with() [1/2]

◆ erase_with() [2/2]

◆ extract()

◆ extract_with()

◆ find() [1/2]

◆ find() [2/2]

◆ find_with() [1/2]

◆ find_with() [2/2]

◆ get()

◆ get_with()

◆ insert() [1/2]

◆ insert() [2/2]

◆ size()

◆ unlink()

◆ update()

◆ upsert()

template<class GC, typename T, class Traits = iterable_list::traits>
class cds::intrusive::IterableList< GC, T, Traits >