cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits > Class Template Reference

Lazy ordered list (template specialization for RCU) More...

#include <cds/container/lazy_list_rcu.h>

Inheritance diagram for cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >:

Public Types
typedef cds::urcu::gc< RCU >	gc
	Garbage collector.
typedef T	value_type
	Type of value stored in the list.
typedef Traits	traits
	List traits.
typedef base_class::back_off	back_off
	Back-off strategy.
typedef maker::allocator_type	allocator_type
	Allocator type used for allocate/deallocate the nodes.
typedef base_class::item_counter	item_counter
	Item counting policy used.
typedef maker::key_comparator	key_comparator
	key compare functor
typedef base_class::memory_model	memory_model
	Memory ordering. See cds::opt::memory_model option.
typedef base_class::stat	stat
	Internal statistics.
typedef base_class::rcu_check_deadlock	rcu_check_deadlock
	Deadlock checking policy.
typedef gc::scoped_lock	rcu_lock
	RCU scoped lock.
using	exempt_ptr = cds::urcu::exempt_ptr< gc, node_type, value_type, typename maker::intrusive_traits::disposer >
typedef value_type *	raw_ptr
	Type of get() member function return value.

Public Member Functions
	LazyList ()
	Default constructor.
	~LazyList ()
	Desctructor clears the list.
template<typename Q >
bool	insert (Q &&val)
	Inserts new node. More...
template<typename Q , typename Func >
bool	insert (Q &&key, Func func)
	Inserts new node. More...
template<typename... Args>
bool	emplace (Args &&...args)
	Inserts data of type value_type constructed from args. More...
template<typename Q , typename Func >
std::pair< bool, bool >	update (Q const &key, Func func, bool bAllowInsert=true)
	Updates data by key. More...
template<typename Q >
bool	erase (Q const &key)
	Deletes key 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 f)
	Deletes key 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...
template<typename Q >
exempt_ptr	extract (Q const &key)
	Extracts an item from the list. More...
template<typename Q , typename Less >
exempt_ptr	extract_with (Q const &key, Less pred)
	Extracts an item from the list using pred predicate for searching. 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 , typename Func >
bool	find (Q &key, Func f) const
	Finds the key key and performs an action with it. More...
template<typename Q , typename Less , typename Func >
bool	find_with (Q &key, Less pred, Func f) const
	Finds the key key using pred predicate for searching. More...
template<typename Q >
value_type *	get (Q const &key) const
	Finds the key key and return the item found. More...
template<typename Q , typename Less >
value_type *	get_with (Q const &key, Less pred) const
	Finds the key key and return the item found. More...
bool	empty () const
	Checks if the list is empty.
size_t	size () const
	Returns list's item count. More...
stat const &	statistics () const
	Returns const reference to internal statistics.
void	clear ()
	Clears the list.

Static Public Attributes
static constexpr const bool	c_bExtractLockExternal = base_class::c_bExtractLockExternal
	Group of extract_xxx functions require external locking.

Forward iterators (only for debugging purpose)
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	begin () const
	Returns a forward const iterator addressing the first element in a list.
const_iterator	cbegin () 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.

Additional Inherited Members
Protected Types inherited from cds::intrusive::LazyList< cds::urcu::gc< RCU >, T, Traits >
typedef cds::urcu::gc< RCU >	gc
	RCU schema.
typedef T	value_type
	type of value stored in the list
typedef Traits	traits
	Traits template parameter.
typedef traits::hook	hook
	hook type
typedef hook::node_type	node_type
	node type
typedef implementation_defined	key_comparator
	key compare functor based on opt::compare and opt::less option setter.
typedef traits::disposer	disposer
	disposer used
typedef get_node_traits< value_type, node_type, hook >::type	node_traits
	node traits
typedef lazy_list::get_link_checker< node_type, traits::link_checker >::type	link_checker
	link checker
typedef traits::back_off	back_off
	back-off strategy (not used)
typedef traits::item_counter	item_counter
	Item counting policy used.
typedef traits::memory_model	memory_model
	C++ memory ordering (see lazy_list::traits::memory_model)
typedef traits::stat	stat
	Internal statistics.
typedef traits::rcu_check_deadlock	rcu_check_deadlock
	Deadlock checking policy.
typedef gc::scoped_lock	rcu_lock
	RCU scoped lock.
using	exempt_ptr = cds::urcu::exempt_ptr< gc, value_type, value_type, clear_and_dispose, void >
	pointer to extracted node
typedef value_type *	raw_ptr
	Type of get() member function return value.
typedef iterator_type< false >	iterator
	Forward iterator. More...
typedef iterator_type< true >	const_iterator
	Const forward iterator.
Protected Member Functions inherited from cds::intrusive::LazyList< cds::urcu::gc< RCU >, T, Traits >
	LazyList ()
	Default constructor initializes empty list.
	~LazyList ()
	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 bAllowInsert=true)
	Updates the item. 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 func)
	Deletes the item from the list using pred predicate for searching. More...
template<typename Q >
exempt_ptr	extract (Q const &key)
	Extracts an item from the list. More...
template<typename Q , typename Less >
exempt_ptr	extract_with (Q const &key, Less pred)
	Extracts an item from the list using pred predicate for searching. More...
template<typename Q , typename Func >
bool	find (Q &key, Func f) const
	Finds the key key. More...
template<typename Q , typename Less , typename Func >
bool	find_with (Q &key, Less pred, Func f) const
	Finds the key key using pred predicate for searching. 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 map contains key using pred predicate for searching. More...
template<typename Q >
value_type *	get (Q const &key) const
	Finds the key key and return the item found. More...
template<typename Q , typename Less >
value_type *	get_with (Q const &key, Less pred) const
	Finds the key key and return the item found. More...
void	clear ()
	Clears the list using default disposer. More...
bool	empty () const
	Checks if the list is empty.
size_t	size () const
	Returns list's item count. More...
stat const &	statistics () const
	Returns const reference to internal statistics.
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	begin () const
	Returns a forward const iterator addressing the first element in a list.
const_iterator	cbegin () 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.
Protected Attributes inherited from cds::intrusive::LazyList< cds::urcu::gc< RCU >, T, Traits >
node_type	m_Head
	List head (dummy node)
node_type	m_Tail
	List tail (dummy node)
item_counter	m_ItemCounter
	Item counter.
stat	m_Stat
	Internal statistics.
Static Protected Attributes inherited from cds::intrusive::LazyList< cds::urcu::gc< RCU >, T, Traits >
static constexpr const bool	c_bExtractLockExternal = true
	Group of extract_xxx functions require external locking.

Detailed Description

template<typename RCU, typename T, typename Traits = lazy_list::traits>
class cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >

Lazy ordered list (template specialization for RCU)

Usually, ordered single-linked list is used as a building block for the hash table implementation. The complexity of searching is O(N).

Source:

• [2005] Steve Heller, Maurice Herlihy, Victor Luchangco, Mark Moir, William N. Scherer III, and Nir Shavit "A Lazy Concurrent List-Based Set Algorithm"

The lazy list is based on an optimistic locking scheme for inserts and removes, eliminating the need to use the equivalent of an atomically markable reference. It also has a novel wait-free membership find operation that does not need to perform cleanup operations and is more efficient.

It is non-intrusive version of cds::intrusive::LazyList class

Template arguments:

• RCU - one of RCU type
• T - type to be stored in the list.
• Traits - type traits, default is lazy_list::traits It is possible to declare option-based list with cds::container::lazy_list::make_traits metafunction istead of Traits template argument. For example, the following traits-based declaration of gc::HP lazy list

  #include <cds/urcu/general_instant.h>
  #include <cds/container/lazy_list_rcu.h>
  // Declare comparator for the item
  struct my_compare {
      int operator ()( int i1, int i2 )
      {
          return i1 - i2;
      }
  };
  
  // Declare traits
  struct my_traits: public cds::container::lazy_list::traits
  {
      typedef my_compare compare;
  };
  
  // Declare traits-based list
  typedef cds::container::LazyList< cds::urcu::gc< cds::urcu::general_instant<> >, int, my_traits > traits_based_list;

  is equal to the following option-based list

  #include <cds/urcu/general_instant.h>
  #include <cds/container/lazy_list_rcu.h>
  
  // my_compare is the same
  
  // Declare option-based list
  typedef cds::container::LazyList< cds::urcu::gc< cds::urcu::general_instant<> >, int,
      typename cds::container::lazy_list::make_traits<
          cds::container::opt::compare< my_compare >     // item comparator option
      >::type
  >     option_based_list;

The implementation does not divide type T into key and value part and may be used as main building block for some hash set containers. The key is a function (or a part) of type T, and this function is specified by Traits::compare functor or Traits::less predicate

LazyKVList is a key-value version of lazy non-intrusive list that is closer to the C++ std library approach.

Note

Before including <cds/container/lazy_list_rcu.h> you should include appropriate RCU header file, see RCU type for list of existing RCU class and corresponding header files.

Member Typedef Documentation

template<typename RCU , typename T , typename Traits = lazy_list::traits>

typedef iterator_type<true> cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >::const_iterator

Const forward iterator.

For iterator's features and requirements see iterator

template<typename RCU , typename T , typename Traits = lazy_list::traits>

using cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >::exempt_ptr = cds::urcu::exempt_ptr< gc, node_type, value_type, typename maker::intrusive_traits::disposer >

pointer to extracted node

template<typename RCU , typename T , typename Traits = lazy_list::traits>

typedef iterator_type<false> cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >::iterator

Forward iterator.

You may safely use iterators in multi-threaded environment only under RCU lock. Otherwise, a crash is possible if another thread deletes the item the iterator points to.

Member Function Documentation

template<typename RCU , typename T , typename Traits = lazy_list::traits>

iterator cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >::begin ( )

inline

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

For empty list

begin() == end() 

template<typename RCU , typename T , typename Traits = lazy_list::traits>

template<typename Q >

bool cds::container::LazyList< cds::urcu::gc< RCU >, 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.

The function applies RCU lock internally.

template<typename RCU , typename T , typename Traits = lazy_list::traits>

template<typename Q , typename Less >

bool cds::container::LazyList< cds::urcu::gc< RCU >, 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. pred must imply the same element order as the comparator used for building the list.

template<typename RCU , typename T , typename Traits = lazy_list::traits>

template<typename... Args>

bool cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >::emplace ( Args &&...  args )

inline

Inserts data of type value_type constructed from args.

Returns true if inserting successful, false otherwise.

The function makes RCU lock internally.

template<typename RCU , typename T , typename Traits = lazy_list::traits>

iterator cds::container::LazyList< cds::urcu::gc< RCU >, 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.

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

begin() == end() 

template<typename RCU , typename T , typename Traits = lazy_list::traits>

template<typename Q >

bool cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >::erase ( Q const &  key )

inline

Deletes key from the list.

Since the key of LazyList's item type T is not explicitly specified, template parameter Q defines the key type searching in the list. The list item comparator should be able to compare the type T of list item and the type Q.

RCU synchronize method can be called. RCU should not be locked.

Return true if key is found and deleted, false otherwise

template<typename RCU , typename T , typename Traits = lazy_list::traits>

template<typename Q , typename Func >

bool cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >::erase ( Q const &  key, Func  f  )

inline

Deletes key from the list.

The function searches an item with key key, calls f functor and deletes the item. If key is not found, the functor is not called.

The functor Func interface:

struct extractor {
    void operator()(value_type const& val) { ... }
};

Since the key of LazyList's item type T is not explicitly specified, template parameter Q defines the key type searching in the list. The list item comparator should be able to compare the type T of list item and the type Q.

RCU synchronize method can be called. RCU should not be locked.

Return true if key is found and deleted, false otherwise

template<typename RCU , typename T , typename Traits = lazy_list::traits>

template<typename Q , typename Less >

bool cds::container::LazyList< cds::urcu::gc< RCU >, 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.

template<typename RCU , typename T , typename Traits = lazy_list::traits>

template<typename Q , typename Less , typename Func >

bool cds::container::LazyList< cds::urcu::gc< RCU >, 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.

template<typename RCU , typename T , typename Traits = lazy_list::traits>

template<typename Q >

exempt_ptr cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >::extract ( Q const &  key )

inline

Extracts an item from the list.

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

Note

The function does NOT call RCU read-side lock or synchronization, and does NOT dispose the item found. It just excludes the item from the list and returns a pointer to item found. You should lock RCU before calling this function.

#include <cds/urcu/general_buffered.h>
#include <cds/container/lazy_list_rcu.h>

typedef cds::urcu::gc< general_buffered<> > rcu;
typedef cds::container::LazyList< rcu, Foo > rcu_lazy_list;

rcu_lazy_list theList;
// ...

rcu_lazy_list::exempt_ptr p;
{
    // first, we should lock RCU
    rcu_lazy_list::rcu_lock sl;

    // Now, you can apply extract function
    // Note that you must not delete the item found inside the RCU lock
    p = theList.extract( 10 );
    if ( p ) {
        // do something with p
        ...
    }
}
// Outside RCU lock section we may safely release extracted pointer.
// release() passes the pointer to RCU reclamation cycle.
p.release();

template<typename RCU , typename T , typename Traits = lazy_list::traits>

template<typename Q , typename Less >

exempt_ptr cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >::extract_with ( Q const &  key, Less  pred  )

inline

Extracts an item from the list using pred predicate for searching.

This function is the analog for extract(Q const&).

The pred is a predicate used for key comparing. Less has the interface like std::less. pred must imply the same element order as key_comparator.

template<typename RCU , typename T , typename Traits = lazy_list::traits>

template<typename Q , typename Func >

bool cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >::find ( Q &  key, Func  f  ) const

inline

Finds the key key and performs an action with it.

The function searches an item with key equal to key and calls the functor f for the 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 deleted during functor is executing. The function does not serialize simultaneous access to the list item. If such access is possible you must provide your own synchronization schema to exclude unsafe item modifications.

The key argument is non-const since it can be used as f functor destination i.e., the functor may modify both arguments.

The function makes RCU lock internally.

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

template<typename RCU , typename T , typename Traits = lazy_list::traits>

template<typename Q , typename Less , typename Func >

bool cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >::find_with ( Q &  key, Less  pred, Func  f  ) const

inline

Finds the key 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.

template<typename RCU , typename T , typename Traits = lazy_list::traits>

template<typename Q >

value_type* cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >::get ( Q const &  key ) const

inline

Finds the key key and return the item found.

The function searches the item with key equal to key and returns the pointer to item found. If key is not found it returns nullptr.

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

RCU should be locked before call of this function. Returned item is valid only while RCU is locked:

typedef cds::container::LazyList< cds::urcu::gc< cds::urcu::general_buffered<> >, foo, my_traits > ord_list;
ord_list theList;
// ...
{
    // Lock RCU
    ord_list::rcu_lock lock;

    foo * pVal = theList.get( 5 );
    if ( pVal ) {
        // Deal with pVal
        //...
    }
    // Unlock RCU by rcu_lock destructor
    // pVal can be freed at any time after RCU has been unlocked
}

template<typename RCU , typename T , typename Traits = lazy_list::traits>

template<typename Q , typename Less >

value_type* cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >::get_with ( Q const &  key, Less  pred  ) const

inline

Finds the key 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.

template<typename RCU , typename T , typename Traits = lazy_list::traits>

template<typename Q >

bool cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >::insert ( Q &&  val )

inline

Inserts new node.

The function creates a node with copy of val value and then inserts the node created into the list.

The type Q should contain as minimum the complete key of the node. The object of value_type should be constructible from val of type Q. In trivial case, Q is equal to value_type.

The function makes RCU lock internally.

Returns true if inserting successful, false otherwise.

template<typename RCU , typename T , typename Traits = lazy_list::traits>

template<typename Q , typename Func >

bool cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >::insert ( Q &&  key, Func  func  )

inline

Inserts new node.

This function inserts new node with default-constructed value and then it calls func functor with signature

void func( value_type& itemValue ) ;

The argument itemValue of user-defined functor func is the reference to the list's item inserted. The user-defined functor is called only if the inserting is success.

The type Q should contain the complete key of the node. The object of value_type should be constructible from key of type Q.

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

• create item from key with initializing key-fields only;
• insert new item into the list;
• if inserting is successful, initialize non-key fields of item by calling f functor

This can be useful if complete initialization of object of value_type is heavyweight and it is preferable that the initialization should be completed only if inserting is successful.

The function makes RCU lock internally.

template<typename RCU , typename T , typename Traits = lazy_list::traits>

size_t cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >::size ( ) const

inline

Returns list's item count.

The value returned depends on Traits::item_counter type. For atomicity::empty_item_counter, this function always returns 0.

Note

Even if you use real item counter and it returns 0, this fact is not mean that the list is empty. To check list emptyness use empty() method.

template<typename RCU , typename T , typename Traits = lazy_list::traits>

template<typename Q , typename Func >

std::pair<bool, bool> cds::container::LazyList< cds::urcu::gc< RCU >, T, Traits >::update ( Q const &  key, Func  func, bool  bAllowInsert = true  )

inline

Updates data by key.

The operation performs inserting or replacing the element with lock-free manner.

If the key not found in the list, then the new item created from key will be inserted iff bAllowInsert is true. Otherwise, if key is found, the functor func is called with item found.

The functor Func signature is:

struct my_functor {
    void operator()( bool bNew, value_type& item, Q const& val );
};

with arguments:

• bNew - true if the item has been inserted, false otherwise
• item - item of the list
• val - argument key passed into the update() function

The functor may change non-key fields of the item; during func call item is locked so it is safe to modify the item in multi-threaded environment.

The function applies RCU lock internally.

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

---

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

• cds/container/lazy_list_rcu.h