cds::sync::lock_array< Lock, SelectPolicy, Alloc > Class Template Reference

Array of locks. More...

#include <cds/sync/lock_array.h>

Public Types
typedef Lock	lock_type
	lock type
typedef SelectPolicy	select_cell_policy
	Cell selection policy functor.

Public Member Functions
	lock_array (size_t nCapacity)
	Constructs array of locks. More...
	lock_array (size_t nCapacity, select_cell_policy const &policy)
	Constructs array of lock and copy cell selection policy. More...
	lock_array (size_t nCapacity, select_cell_policy &&policy)
	Constructs array of lock and move cell selection policy. More...
	~lock_array ()
	Destructs array of locks and frees used memory.
template<typename Q >
size_t	lock (Q const &hint)
	Locks a lock at cell hint. More...
template<typename Q >
size_t	try_lock (Q const &hint)
	Try lock a lock at cell hint. More...
void	unlock (size_t nCell)
	Unlock the lock specified by index nCell.
void	lock_all ()
	Lock all.
void	unlock_all ()
	Unlock all.
lock_type &	at (size_t nCell) const
	Get lock at cell nCell. More...
size_t	size () const
	Size of lock array.

Static Public Attributes
static size_t const	c_nUnspecifiedCell = (size_t) -1
	failed try_lock call result

Protected Attributes
lock_type *	m_arrLocks
	lock array
size_t const	m_nCapacity
	array capacity
select_cell_policy	m_SelectCellPolicy
	Cell selection policy.

Detailed Description

template<typename Lock, typename SelectPolicy = mod_select_policy, class Alloc = CDS_DEFAULT_ALLOCATOR>
class cds::sync::lock_array< Lock, SelectPolicy, Alloc >

Array of locks.

The lock array is useful for building fine-grained lock-based data structure based on striping technique. Instead of locking access to data struct (a hash map, for example) at whole, the striping locks only part of the map (a bucket). So, access to different buckets can be simultaneous.

Template arguments:

• Lock - lock type, for example, std::mutex, cds::sync::spin_lock
• SelectPolicy - array cell selection policy, the default is mod_select_policy Available policies: trivial_select_policy, pow2_select_policy, mod_select_policy.
• Alloc - memory allocator for array

To determine array's cell the selection policy SelectPolicy functor is used. Two arguments are passed to the policy:

size_t operator()( size_t nHint, size_t nCapacity ) const 

• nHint - a hint to calculate cell index in the lock array. Usually, it is a hash value.
• nCapacity - the size of the lock array The functor should return the index in the lock array.

Note that the type of nHint parameter can be any.

Constructor & Destructor Documentation

lock_array() [1/3]

template<typename Lock , typename SelectPolicy = mod_select_policy, class Alloc = CDS_DEFAULT_ALLOCATOR>

cds::sync::lock_array< Lock, SelectPolicy, Alloc >::lock_array ( size_t  nCapacity )

inline

Constructs array of locks.

Allocates the array and initializes all locks as unlocked.

Parameters

[in]

nCapacity

Array size

lock_array() [2/3]

template<typename Lock , typename SelectPolicy = mod_select_policy, class Alloc = CDS_DEFAULT_ALLOCATOR>

cds::sync::lock_array< Lock, SelectPolicy, Alloc >::lock_array ( size_t  nCapacity, select_cell_policy const &  policy  )

inline

Constructs array of lock and copy cell selection policy.

Allocates the array and initializes all locks as unlocked.

Parameters

[in]	nCapacity	Array size
	policy	Cell selection policy (copy-constructible)

lock_array() [3/3]

template<typename Lock , typename SelectPolicy = mod_select_policy, class Alloc = CDS_DEFAULT_ALLOCATOR>

cds::sync::lock_array< Lock, SelectPolicy, Alloc >::lock_array ( size_t  nCapacity, select_cell_policy &&  policy  )

inline

Constructs array of lock and move cell selection policy.

Allocates the array and initializes all locks as unlocked.

Parameters

[in]	nCapacity	Array size
	policy	Cell selection policy (move-constructible)

Member Function Documentation

at()

template<typename Lock , typename SelectPolicy = mod_select_policy, class Alloc = CDS_DEFAULT_ALLOCATOR>

lock_type& cds::sync::lock_array< Lock, SelectPolicy, Alloc >::at ( size_t  nCell ) const

inline

Get lock at cell nCell.

Precondition: nCell < size()

lock()

template<typename Lock , typename SelectPolicy = mod_select_policy, class Alloc = CDS_DEFAULT_ALLOCATOR>

template<typename Q >

size_t cds::sync::lock_array< Lock, SelectPolicy, Alloc >::lock ( Q const &  hint )

inline

Locks a lock at cell hint.

To define real array's cell which should be locked, select_cell_policy is used. The target cell is a result of select_cell_policy( hint, size()).

Returns the index of locked lock.

try_lock()

template<typename Lock , typename SelectPolicy = mod_select_policy, class Alloc = CDS_DEFAULT_ALLOCATOR>

template<typename Q >

size_t cds::sync::lock_array< Lock, SelectPolicy, Alloc >::try_lock ( Q const &  hint )

inline

Try lock a lock at cell hint.

To define real array's cell which should be locked, select_cell_policy is used. The target cell is a result of select_cell_policy( hint, size()).

Returns the index of locked lock if success, c_nUnspecifiedCell constant otherwise.

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

• cds/sync/lock_array.h