A striped Lock/Semaphore/ReadWriteLock. This offers the underlying lock striping similar to that of ConcurrentHashMap in a reusable form, and extends it for semaphores and read-write locks. Conceptually, lock striping is the technique of dividing a lock into many stripes, increasing the granularity of a single lock and allowing independent operations to lock different stripes and proceed concurrently, instead of creating contention for a single lock.

The guarantee provided by this class is that equal keys lead to the same lock (or semaphore), i.e. if (key1.equals(key2)) then striped.get(key1) == striped.get(key2) (assuming Object#hashCode() is correctly implemented for the keys). Note that if key1 is not equal to key2, it is not guaranteed that striped.get(key1) != striped.get(key2); the elements might nevertheless be mapped to the same lock. The lower the number of stripes, the higher the probability of this happening.

There are three flavors of this class: Striped<Lock>, Striped<Semaphore>, and Striped<ReadWriteLock>. For each type, two implementations are offered: strong and weak Striped<Lock>, strong and weak Striped<Semaphore>, and strong and weak Striped<ReadWriteLock>. Strong means that all stripes (locks/semaphores) are initialized eagerly, and are not reclaimed unless Striped itself is reclaimable. Weak means that locks/semaphores are created lazily, and they are allowed to be reclaimed if nobody is holding on to them. This is useful, for example, if one wants to create a Striped<Lock> of many locks, but worries that in most cases only a small portion of these would be in use.

Prior to this class, one might be tempted to use Map<K, Lock>, where K represents the task. This maximizes concurrency by having each unique key mapped to a unique lock, but also maximizes memory footprint. On the other extreme, one could use a single lock for all tasks, which minimizes memory footprint but also minimizes concurrency. Instead of choosing either of these extremes, Striped allows the user to trade between required concurrency and memory footprint. For example, if a set of tasks are CPU-bound, one could easily create a very compact Striped<Lock> of availableProcessors() * 4 stripes, instead of possibly thousands of locks which could be created in a Map<K, Lock> structure.

Nested and Inner Type Summary

Modifier and Type	Class and Description
private static class	Striped.CompactStriped<L> Implementation of Striped where 2^k stripes are represented as an array of the same length, eagerly initialized.
pack-priv static class	Striped.LargeLazyStriped<L> Implementation of Striped where up to 2^k stripes can be represented, using a ConcurrentMap where the key domain is [0..2^k).
private static class	Striped.PaddedLock
private static class	Striped.PaddedSemaphore
private abstract static class	Striped.PowerOfTwoStriped<L>
pack-priv static class	Striped.SmallLazyStriped<L> Implementation of Striped where up to 2^k stripes can be represented, using an AtomicReferenceArray of size 2^k.
private static class	Striped.WeakSafeCondition Condition object that ensures a strong reference is retained to a specified object.
private static class	Striped.WeakSafeLock Lock object that ensures a strong reference is retained to a specified object.
private static class	Striped.WeakSafeReadWriteLock ReadWriteLock implementation whose read and write locks retain a reference back to this lock.

Field Summary

Modifier and Type	Field and Description
private static final int	ALL_SET A bit mask were all bits are set.
private static final int	LARGE_LAZY_CUTOFF If there are at least this many stripes, we assume the memory usage of a ConcurrentMap will be smaller than a large array.

Constructor Summary

Access	Constructor and Description
private	Striped()

Method Summary

Modifier and Type	Method and Description
public Iterable<L>	Returns: the stripes corresponding to the objects (one per each object, derived by delegating to `get(Object)`; may contain duplicates), in an increasing index order. bulkGet(Iterable<? extends Object> arbitrary non-null keys keys) Returns the stripes that correspond to the passed objects, in ascending (as per `getAt(int)`) order.
private static int	ceilToPowerOfTwo(int x)
pack-priv static <L> Striped<L>	Returns: a new `Striped<L>` custom(int the minimum number of stripes (locks) required stripes, Supplier<L> a `Supplier<L>` object to obtain locks from supplier) Creates a `Striped<L>` with eagerly initialized, strongly referenced locks.
public abstract L	Returns: the stripe that the passed key corresponds to get(Object an arbitrary, non-null key key) Returns the stripe that corresponds to the passed key.
public abstract L	Returns: the stripe at the specified index getAt(int the index of the stripe to return; must be in `[0...size())` index) Returns the stripe at the specified index.
pack-priv abstract int	indexFor(Object key) Returns the index to which the given key is mapped, so that getAt(indexFor(key)) == get(key).
private static <L> Striped<L>	lazy(int stripes, Supplier<L> supplier)
public static Striped<Lock>	Returns: a new `Striped<Lock>` lazyWeakLock(int the minimum number of stripes (locks) required stripes) Creates a `Striped<Lock>` with lazily initialized, weakly referenced locks.
public static Striped<ReadWriteLock>	Returns: a new `Striped<ReadWriteLock>` lazyWeakReadWriteLock(int the minimum number of stripes (locks) required stripes) Creates a `Striped<ReadWriteLock>` with lazily initialized, weakly referenced read-write locks.
public static Striped<Semaphore>	Returns: a new `Striped<Semaphore>` lazyWeakSemaphore(int the minimum number of stripes (semaphores) required stripes, int the number of permits in each semaphore permits) Creates a `Striped<Semaphore>` with lazily initialized, weakly referenced semaphores, with the specified number of permits.
public static Striped<Lock>	Returns: a new `Striped<Lock>` lock(int the minimum number of stripes (locks) required stripes) Creates a `Striped<Lock>` with eagerly initialized, strongly referenced locks.
public static Striped<ReadWriteLock>	Returns: a new `Striped<ReadWriteLock>` readWriteLock(int the minimum number of stripes (locks) required stripes) Creates a `Striped<ReadWriteLock>` with eagerly initialized, strongly referenced read-write locks.
public static Striped<Semaphore>	Returns: a new `Striped<Semaphore>` semaphore(int the minimum number of stripes (semaphores) required stripes, int the number of permits in each semaphore permits) Creates a `Striped<Semaphore>` with eagerly initialized, strongly referenced semaphores, with the specified number of permits.
public abstract int	size() Returns the total number of stripes in this instance.
private static int	smear(int hashCode)

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

Field Detail

ALL_SET	back to summary
private static final int ALL_SET A bit mask were all bits are set.

LARGE_LAZY_CUTOFF	back to summary
private static final int LARGE_LAZY_CUTOFF If there are at least this many stripes, we assume the memory usage of a ConcurrentMap will be smaller than a large array. (This assumes that in the lazy case, most stripes are unused. As always, if many stripes are in use, a non-lazy striped makes more sense.)

Constructor Detail

Striped	back to summary
private Striped()

Method Detail

bulkGet back to summary

bulkGet	back to summary
public Iterable<L> bulkGet(Iterable<? extends Object> keys) Returns the stripes that correspond to the passed objects, in ascending (as per `getAt(int)`) order. Thus, threads that use the stripes in the order returned by this method are guaranteed to not deadlock each other. It should be noted that using a `Striped<L>` with relatively few stripes, and `bulkGet(keys)` with a relative large number of keys can cause an excessive number of shared stripes (much like the birthday paradox, where much fewer than anticipated birthdays are needed for a pair of them to match). Please consider carefully the implications of the number of stripes, the intended concurrency level, and the typical number of keys used in a `bulkGet(keys)` operation. See Balls in Bins model for mathematical formulas that can be used to estimate the probability of collisions. Parameters keys:Iterable<? extends Object> arbitrary non-null keys Returns:Iterable<L> the stripes corresponding to the objects (one per each object, derived by delegating to `get(Object)`; may contain duplicates), in an increasing index order.

public Iterable<L> bulkGet(Iterable<? extends Object> keys)

Returns the stripes that correspond to the passed objects, in ascending (as per getAt(int)) order. Thus, threads that use the stripes in the order returned by this method are guaranteed to not deadlock each other.

It should be noted that using a Striped<L> with relatively few stripes, and bulkGet(keys) with a relative large number of keys can cause an excessive number of shared stripes (much like the birthday paradox, where much fewer than anticipated birthdays are needed for a pair of them to match). Please consider carefully the implications of the number of stripes, the intended concurrency level, and the typical number of keys used in a bulkGet(keys) operation. See Balls in Bins model for mathematical formulas that can be used to estimate the probability of collisions.

Parameters

keys:Iterable<? extends Object>: arbitrary non-null keys

Returns:Iterable<L>

the stripes corresponding to the objects (one per each object, derived by delegating to get(Object); may contain duplicates), in an increasing index order.

ceilToPowerOfTwo	back to summary
private static int ceilToPowerOfTwo(int x)

custom back to summary

custom	back to summary
pack-priv static <L> Striped<L> custom(int stripes, Supplier<L> supplier) Creates a `Striped<L>` with eagerly initialized, strongly referenced locks. Every lock is obtained from the passed supplier. Parameters stripes:int the minimum number of stripes (locks) required supplier:Supplier<L> a `Supplier<L>` object to obtain locks from Returns:Striped<L> a new `Striped<L>`

pack-priv static <L> Striped<L> custom(int stripes, Supplier<L> supplier)

Creates a Striped<L> with eagerly initialized, strongly referenced locks. Every lock is obtained from the passed supplier.

Parameters

stripes:int: the minimum number of stripes (locks) required
supplier:Supplier<L>: a Supplier<L> object to obtain locks from

Returns:Striped<L>

a new Striped<L>

get back to summary

get	back to summary
public abstract L get(Object key) Returns the stripe that corresponds to the passed key. It is always guaranteed that if `key1.equals(key2)`, then `get(key1) == get(key2)`. Parameters key:Object an arbitrary, non-null key Returns:L the stripe that the passed key corresponds to

public abstract L get(Object key)

Returns the stripe that corresponds to the passed key. It is always guaranteed that if key1.equals(key2), then get(key1) == get(key2).

Parameters

key:Object: an arbitrary, non-null key

Returns:L

the stripe that the passed key corresponds to

getAt back to summary

getAt	back to summary
public abstract L getAt(int index) Returns the stripe at the specified index. Valid indexes are 0, inclusively, to `size()`, exclusively. Parameters index:int the index of the stripe to return; must be in `[0...size())` Returns:L the stripe at the specified index

public abstract L getAt(int index)

Returns the stripe at the specified index. Valid indexes are 0, inclusively, to size(), exclusively.

Parameters

index:int: the index of the stripe to return; must be in [0...size())

Returns:L

the stripe at the specified index

indexFor	back to summary
pack-priv abstract int indexFor(Object key) Returns the index to which the given key is mapped, so that getAt(indexFor(key)) == get(key).

lazy	back to summary
private static <L> Striped<L> lazy(int stripes, Supplier<L> supplier)

lazyWeakLock back to summary

lazyWeakLock	back to summary
public static Striped<Lock> lazyWeakLock(int stripes) Creates a `Striped<Lock>` with lazily initialized, weakly referenced locks. Every lock is reentrant. Parameters stripes:int the minimum number of stripes (locks) required Returns:Striped<Lock> a new `Striped<Lock>`

public static Striped<Lock> lazyWeakLock(int stripes)

Creates a Striped<Lock> with lazily initialized, weakly referenced locks. Every lock is reentrant.

Parameters

stripes:int: the minimum number of stripes (locks) required

Returns:Striped<Lock>

a new Striped<Lock>

lazyWeakReadWriteLock back to summary

lazyWeakReadWriteLock	back to summary
public static Striped<ReadWriteLock> lazyWeakReadWriteLock(int stripes) Creates a `Striped<ReadWriteLock>` with lazily initialized, weakly referenced read-write locks. Every lock is reentrant. Parameters stripes:int the minimum number of stripes (locks) required Returns:Striped<ReadWriteLock> a new `Striped<ReadWriteLock>`

public static Striped<ReadWriteLock> lazyWeakReadWriteLock(int stripes)

Creates a Striped<ReadWriteLock> with lazily initialized, weakly referenced read-write locks. Every lock is reentrant.

Parameters

stripes:int: the minimum number of stripes (locks) required

Returns:Striped<ReadWriteLock>

a new Striped<ReadWriteLock>

lazyWeakSemaphore back to summary

lazyWeakSemaphore	back to summary
public static Striped<Semaphore> lazyWeakSemaphore(int stripes, int permits) Creates a `Striped<Semaphore>` with lazily initialized, weakly referenced semaphores, with the specified number of permits. Parameters stripes:int the minimum number of stripes (semaphores) required permits:int the number of permits in each semaphore Returns:Striped<Semaphore> a new `Striped<Semaphore>`

public static Striped<Semaphore> lazyWeakSemaphore(int stripes, int permits)

Creates a Striped<Semaphore> with lazily initialized, weakly referenced semaphores, with the specified number of permits.

Parameters

stripes:int: the minimum number of stripes (semaphores) required
permits:int: the number of permits in each semaphore

Returns:Striped<Semaphore>

a new Striped<Semaphore>

lock back to summary

lock	back to summary
public static Striped<Lock> lock(int stripes) Creates a `Striped<Lock>` with eagerly initialized, strongly referenced locks. Every lock is reentrant. Parameters stripes:int the minimum number of stripes (locks) required Returns:Striped<Lock> a new `Striped<Lock>`

public static Striped<Lock> lock(int stripes)

Creates a Striped<Lock> with eagerly initialized, strongly referenced locks. Every lock is reentrant.

Parameters

stripes:int: the minimum number of stripes (locks) required

Returns:Striped<Lock>

a new Striped<Lock>

readWriteLock back to summary

readWriteLock	back to summary
public static Striped<ReadWriteLock> readWriteLock(int stripes) Creates a `Striped<ReadWriteLock>` with eagerly initialized, strongly referenced read-write locks. Every lock is reentrant. Parameters stripes:int the minimum number of stripes (locks) required Returns:Striped<ReadWriteLock> a new `Striped<ReadWriteLock>`

public static Striped<ReadWriteLock> readWriteLock(int stripes)

Creates a Striped<ReadWriteLock> with eagerly initialized, strongly referenced read-write locks. Every lock is reentrant.

Parameters

stripes:int: the minimum number of stripes (locks) required

Returns:Striped<ReadWriteLock>

a new Striped<ReadWriteLock>

semaphore back to summary

semaphore	back to summary
public static Striped<Semaphore> semaphore(int stripes, int permits) Creates a `Striped<Semaphore>` with eagerly initialized, strongly referenced semaphores, with the specified number of permits. Parameters stripes:int the minimum number of stripes (semaphores) required permits:int the number of permits in each semaphore Returns:Striped<Semaphore> a new `Striped<Semaphore>`

public static Striped<Semaphore> semaphore(int stripes, int permits)

Creates a Striped<Semaphore> with eagerly initialized, strongly referenced semaphores, with the specified number of permits.

Parameters

stripes:int: the minimum number of stripes (semaphores) required
permits:int: the number of permits in each semaphore

Returns:Striped<Semaphore>

a new Striped<Semaphore>

size	back to summary
public abstract int size() Returns the total number of stripes in this instance.

smear	back to summary
private static int smear(int hashCode)

com.google.common.util.concurrent back to summary

private Class Striped.CompactStriped<L>

Class Inheritance

extends Striped.PowerOfTwoStriped<L>

java.lang.Object
com.google.common.util.concurrent.Striped
com.google.common.util.concurrent.Striped.PowerOfTwoStriped
com.google.common.util.concurrent.Striped.CompactStriped

Implementation of Striped where 2^k stripes are represented as an array of the same length, eagerly initialized.

Field Summary

Modifier and Type	Field and Description
private final Object[]	array Size is a power of two.

Inherited from com.google.common.util.concurrent.Striped.PowerOfTwoStriped:: mask

Constructor Summary

Access	Constructor and Description
private	CompactStriped(int stripes, Supplier<L> supplier)

Method Summary

Modifier and Type	Method and Description
public L	getAt(int the index of the stripe to return; must be in `[0...size())` index) Implements abstract com.google.common.util.concurrent.Striped.getAt. Returns the stripe at the specified index.
public int	size() Implements abstract com.google.common.util.concurrent.Striped.size. Returns the total number of stripes in this instance.

Inherited from com.google.common.util.concurrent.Striped.PowerOfTwoStriped:: get indexFor

Field Detail

array	back to summary
private final Object[] array Size is a power of two.

Constructor Detail

CompactStriped	back to summary
private CompactStriped(int stripes, Supplier<L> supplier)

Method Detail

getAt back to summary

getAt	back to summary
public L getAt(int index) Implements abstract com.google.common.util.concurrent.Striped.getAt. Doc from com.google.common.util.concurrent.Striped.getAt. Returns the stripe at the specified index. Valid indexes are 0, inclusively, to `size()`, exclusively. Parameters index:int the index of the stripe to return; must be in `[0...size())` Returns:L the stripe at the specified index Annotations @SuppressWarnings:unchecked @Override

public L getAt(int index)

Implements abstract com.google.common.util.concurrent.Striped.getAt.

Doc from com.google.common.util.concurrent.Striped.getAt.

Returns the stripe at the specified index. Valid indexes are 0, inclusively, to size(), exclusively.

Parameters

index:int: the index of the stripe to return; must be in [0...size())

Returns:L

the stripe at the specified index

Annotations

@SuppressWarnings:unchecked
@Override

size	back to summary
public int size() Implements abstract com.google.common.util.concurrent.Striped.size. Doc from com.google.common.util.concurrent.Striped.size. Returns the total number of stripes in this instance. Annotations @Override

size

back to summary

public int size()

Implements abstract com.google.common.util.concurrent.Striped.size.

Doc from com.google.common.util.concurrent.Striped.size.

Returns the total number of stripes in this instance.

Annotations

@Override

com.google.common.util.concurrent back to summary

pack-priv Class Striped.LargeLazyStriped<L>

Class Inheritance

extends Striped.PowerOfTwoStriped<L>

java.lang.Object
com.google.common.util.concurrent.Striped
com.google.common.util.concurrent.Striped.PowerOfTwoStriped
com.google.common.util.concurrent.Striped.LargeLazyStriped

Annotations

@VisibleForTesting

Implementation of Striped where up to 2^k stripes can be represented, using a ConcurrentMap where the key domain is [0..2^k). To map a user key into a stripe, we take a k-bit slice of the user key's (smeared) hashCode(). The stripes are lazily initialized and are weakly referenced.

Field Summary

Modifier and Type	Field and Description
pack-priv final ConcurrentMap<Integer, L>	locks
pack-priv final int	size
pack-priv final Supplier<L>	supplier

Inherited from com.google.common.util.concurrent.Striped.PowerOfTwoStriped:: mask

Constructor Summary

Access	Constructor and Description
pack-priv	LargeLazyStriped(int stripes, Supplier<L> supplier)

Method Summary

Modifier and Type	Method and Description
public L	getAt(int the index of the stripe to return; must be in `[0...size())` index) Implements abstract com.google.common.util.concurrent.Striped.getAt. Returns the stripe at the specified index.
public int	size() Implements abstract com.google.common.util.concurrent.Striped.size. Returns the total number of stripes in this instance.

Inherited from com.google.common.util.concurrent.Striped.PowerOfTwoStriped:: get indexFor

Field Detail

locks	back to summary
pack-priv final ConcurrentMap<Integer, L> locks

size	back to summary
pack-priv final int size

supplier	back to summary
pack-priv final Supplier<L> supplier

Constructor Detail

LargeLazyStriped	back to summary
pack-priv LargeLazyStriped(int stripes, Supplier<L> supplier)

Method Detail

getAt back to summary

getAt	back to summary
public L getAt(int index) Implements abstract com.google.common.util.concurrent.Striped.getAt. Doc from com.google.common.util.concurrent.Striped.getAt. Returns the stripe at the specified index. Valid indexes are 0, inclusively, to `size()`, exclusively. Parameters index:int the index of the stripe to return; must be in `[0...size())` Returns:L the stripe at the specified index Annotations @Override

public L getAt(int index)

Implements abstract com.google.common.util.concurrent.Striped.getAt.

Doc from com.google.common.util.concurrent.Striped.getAt.

Returns the stripe at the specified index. Valid indexes are 0, inclusively, to size(), exclusively.

Parameters

index:int: the index of the stripe to return; must be in [0...size())

Returns:L

the stripe at the specified index

Annotations

@Override

size	back to summary
public int size() Implements abstract com.google.common.util.concurrent.Striped.size. Doc from com.google.common.util.concurrent.Striped.size. Returns the total number of stripes in this instance. Annotations @Override

size

back to summary

public int size()

Implements abstract com.google.common.util.concurrent.Striped.size.

Doc from com.google.common.util.concurrent.Striped.size.

Returns the total number of stripes in this instance.

Annotations

@Override

com.google.common.util.concurrent back to summary

private Class Striped.PaddedLock

Class Inheritance

extends ReentrantLock

java.lang.Object
java.util.concurrent.locks.ReentrantLock
com.google.common.util.concurrent.Striped.PaddedLock

Field Summary

Modifier and Type	Field and Description
pack-priv long	unused1
pack-priv long	unused2
pack-priv long	unused3

Constructor Summary

Access	Constructor and Description
pack-priv	PaddedLock()

Method Summary

Field Detail

unused1	back to summary
pack-priv long unused1

unused2	back to summary
pack-priv long unused2

unused3	back to summary
pack-priv long unused3

Constructor Detail

PaddedLock	back to summary
pack-priv PaddedLock()

com.google.common.util.concurrent back to summary

private Class Striped.PaddedSemaphore

Class Inheritance

extends Semaphore

java.lang.Object
java.util.concurrent.Semaphore
com.google.common.util.concurrent.Striped.PaddedSemaphore

Field Summary

Modifier and Type	Field and Description
pack-priv long	unused1
pack-priv long	unused2
pack-priv long	unused3

Constructor Summary

Access	Constructor and Description
pack-priv	PaddedSemaphore(int permits)

Method Summary

Inherited from java.util.concurrent.Semaphore:: acquire acquire acquireUninterruptibly acquireUninterruptibly availablePermits drainPermits getQueuedThreads getQueueLength hasQueuedThreads isFair reducePermits release release toString tryAcquire tryAcquire tryAcquire tryAcquire

Field Detail

unused1	back to summary
pack-priv long unused1

unused2	back to summary
pack-priv long unused2

unused3	back to summary
pack-priv long unused3

Constructor Detail

PaddedSemaphore	back to summary
pack-priv PaddedSemaphore(int permits)

com.google.common.util.concurrent back to summary

private abstract Class Striped.PowerOfTwoStriped<L>

Class Inheritance

extends Striped<L>

java.lang.Object
com.google.common.util.concurrent.Striped
com.google.common.util.concurrent.Striped.PowerOfTwoStriped

Known Direct Subclasses

com.google.common.util.concurrent.Striped.CompactStriped, com.google.common.util.concurrent.Striped.SmallLazyStriped, com.google.common.util.concurrent.Striped.LargeLazyStriped

Field Summary

Modifier and Type	Field and Description
pack-priv final int	mask Capacity (power of two) minus one, for fast mod evaluation

Constructor Summary

Access	Constructor and Description
pack-priv	PowerOfTwoStriped(int stripes)

Method Summary

Modifier and Type	Method and Description
public final L	get(Object an arbitrary, non-null key key) Implements abstract com.google.common.util.concurrent.Striped.get. Returns the stripe that corresponds to the passed key.
pack-priv final int	indexFor(Object key) Implements abstract com.google.common.util.concurrent.Striped.indexFor. Returns the index to which the given key is mapped, so that getAt(indexFor(key)) == get(key).

Inherited from com.google.common.util.concurrent.Striped:: bulkGet custom getAt lazyWeakLock lazyWeakReadWriteLock lazyWeakSemaphore lock readWriteLock semaphore size

Field Detail

mask	back to summary
pack-priv final int mask Capacity (power of two) minus one, for fast mod evaluation

Constructor Detail

PowerOfTwoStriped	back to summary
pack-priv PowerOfTwoStriped(int stripes)

Method Detail

get back to summary

public final L get(Object key)

Implements abstract com.google.common.util.concurrent.Striped.get.

Doc from com.google.common.util.concurrent.Striped.get.

Returns the stripe that corresponds to the passed key. It is always guaranteed that if key1.equals(key2), then get(key1) == get(key2).

Parameters

key:Object: an arbitrary, non-null key

Returns:L

the stripe that the passed key corresponds to

Annotations

@Override

indexFor

back to summary

pack-priv final int indexFor(Object key)

Implements abstract com.google.common.util.concurrent.Striped.indexFor.

Doc from com.google.common.util.concurrent.Striped.indexFor.

Returns the index to which the given key is mapped, so that getAt(indexFor(key)) == get(key).

Annotations

@Override

com.google.common.util.concurrent back to summary

pack-priv Class Striped.SmallLazyStriped<L>

Class Inheritance

extends Striped.PowerOfTwoStriped<L>

java.lang.Object
com.google.common.util.concurrent.Striped
com.google.common.util.concurrent.Striped.PowerOfTwoStriped
com.google.common.util.concurrent.Striped.SmallLazyStriped

Annotations

@VisibleForTesting

Implementation of Striped where up to 2^k stripes can be represented, using an AtomicReferenceArray of size 2^k. To map a user key into a stripe, we take a k-bit slice of the user key's (smeared) hashCode(). The stripes are lazily initialized and are weakly referenced.

Nested and Inner Type Summary

Modifier and Type	Class and Description
private static class	Striped.SmallLazyStriped.ArrayReference<L>

Field Summary

Modifier and Type	Field and Description
pack-priv final AtomicReferenceArray<@Nullable Striped.SmallLazyStriped.ArrayReference<? extends L>>	locks
pack-priv final ReferenceQueue<L>	queue
pack-priv final int	size
pack-priv final Supplier<L>	supplier

Inherited from com.google.common.util.concurrent.Striped.PowerOfTwoStriped:: mask

Constructor Summary

Access	Constructor and Description
pack-priv	SmallLazyStriped(int stripes, Supplier<L> supplier)

Method Summary

Modifier and Type	Method and Description
private void	drainQueue()
public L	getAt(int the index of the stripe to return; must be in `[0...size())` index) Implements abstract com.google.common.util.concurrent.Striped.getAt. Returns the stripe at the specified index.
public int	size() Implements abstract com.google.common.util.concurrent.Striped.size. Returns the total number of stripes in this instance.

Inherited from com.google.common.util.concurrent.Striped.PowerOfTwoStriped:: get indexFor

Field Detail

locks	back to summary
pack-priv final AtomicReferenceArray<@Nullable Striped.SmallLazyStriped.ArrayReference<? extends L>> locks

queue	back to summary
pack-priv final ReferenceQueue<L> queue

size	back to summary
pack-priv final int size

supplier	back to summary
pack-priv final Supplier<L> supplier

Constructor Detail

SmallLazyStriped	back to summary
pack-priv SmallLazyStriped(int stripes, Supplier<L> supplier)

Method Detail

drainQueue	back to summary
private void drainQueue()

getAt back to summary

public L getAt(int index)

Implements abstract com.google.common.util.concurrent.Striped.getAt.

Doc from com.google.common.util.concurrent.Striped.getAt.

Returns the stripe at the specified index. Valid indexes are 0, inclusively, to size(), exclusively.

Parameters

index:int: the index of the stripe to return; must be in [0...size())

Returns:L

the stripe at the specified index

Annotations

@Override

size

back to summary

public int size()

Implements abstract com.google.common.util.concurrent.Striped.size.

Doc from com.google.common.util.concurrent.Striped.size.

Returns the total number of stripes in this instance.

Annotations

@Override

com.google.common.util.concurrent back to summary

private final Class Striped.SmallLazyStriped.ArrayReference<L>

Class Inheritance

extends WeakReference<L>

java.lang.Object
java.lang.ref.Reference
java.lang.ref.WeakReference
com.google.common.util.concurrent.Striped.SmallLazyStriped.ArrayReference

Field Summary

Modifier and Type	Field and Description
pack-priv final int	index

Constructor Summary

Access	Constructor and Description
pack-priv	ArrayReference(L referent, int index, ReferenceQueue<L> queue)

Field Detail

index	back to summary
pack-priv final int index

Constructor Detail

ArrayReference	back to summary
pack-priv ArrayReference(L referent, int index, ReferenceQueue<L> queue)

com.google.common.util.concurrent back to summary

private final Class Striped.WeakSafeCondition

Class Inheritance

extends ForwardingCondition

java.lang.Object
com.google.common.util.concurrent.ForwardingCondition
com.google.common.util.concurrent.Striped.WeakSafeCondition

Condition object that ensures a strong reference is retained to a specified object.

Field Summary

Modifier and Type	Field and Description
private final Condition	delegate
private final Striped.WeakSafeReadWriteLock	strongReference

Constructor Summary

Access	Constructor and Description
pack-priv	WeakSafeCondition(Condition delegate, Striped.WeakSafeReadWriteLock strongReference)

Method Summary

Modifier and Type	Method and Description
pack-priv Condition	delegate() Implements abstract com.google.common.util.concurrent.ForwardingCondition.delegate.

Inherited from com.google.common.util.concurrent.ForwardingCondition:: await await awaitNanos awaitUninterruptibly awaitUntil signal signalAll

Field Detail

delegate	back to summary
private final Condition delegate

strongReference	back to summary
private final Striped.WeakSafeReadWriteLock strongReference Annotations @SuppressWarnings:unused

Constructor Detail

WeakSafeCondition	back to summary
pack-priv WeakSafeCondition(Condition delegate, Striped.WeakSafeReadWriteLock strongReference)

Method Detail

delegate

back to summary

pack-priv Condition delegate()

Implements abstract com.google.common.util.concurrent.ForwardingCondition.delegate.

Annotations

@Override

com.google.common.util.concurrent back to summary

private final Class Striped.WeakSafeLock

Class Inheritance

extends ForwardingLock

java.lang.Object
com.google.common.util.concurrent.ForwardingLock
com.google.common.util.concurrent.Striped.WeakSafeLock

Lock object that ensures a strong reference is retained to a specified object.

Field Summary

Modifier and Type	Field and Description
private final Lock	delegate
private final Striped.WeakSafeReadWriteLock	strongReference

Constructor Summary

Access	Constructor and Description
pack-priv	WeakSafeLock(Lock delegate, Striped.WeakSafeReadWriteLock strongReference)

Method Summary

Modifier and Type	Method and Description
pack-priv Lock	delegate() Implements abstract com.google.common.util.concurrent.ForwardingLock.delegate.
public Condition	newCondition() Overrides com.google.common.util.concurrent.ForwardingLock.newCondition. Implements java.util.concurrent.locks.Lock.newCondition. Returns a new `Condition` instance that is bound to this `Lock` instance.

Inherited from com.google.common.util.concurrent.ForwardingLock:: lock lockInterruptibly tryLock tryLock unlock

Field Detail

delegate	back to summary
private final Lock delegate

strongReference	back to summary
private final Striped.WeakSafeReadWriteLock strongReference Annotations @SuppressWarnings:unused

Constructor Detail

WeakSafeLock	back to summary
pack-priv WeakSafeLock(Lock delegate, Striped.WeakSafeReadWriteLock strongReference)

Method Detail

delegate

back to summary

pack-priv Lock delegate()

Implements abstract com.google.common.util.concurrent.ForwardingLock.delegate.

Annotations

@Override

newCondition back to summary

public Condition newCondition()

Overrides com.google.common.util.concurrent.ForwardingLock.newCondition.

Implements java.util.concurrent.locks.Lock.newCondition.

Doc from java.util.concurrent.locks.Lock.newCondition.

Returns a new Condition instance that is bound to this Lock instance.

Before waiting on the condition the lock must be held by the current thread. A call to Condition#await() will atomically release the lock before waiting and re-acquire the lock before the wait returns.

Implementation Considerations

The exact operation of the Condition instance depends on the Lock implementation and must be documented by that implementation.

Returns:Condition

A new Condition instance for this Lock instance

Annotations

@Override

com.google.common.util.concurrent back to summary

private final Class Striped.WeakSafeReadWriteLock

Class Inheritance

extends Object
implements ReadWriteLock

java.lang.Object
com.google.common.util.concurrent.Striped.WeakSafeReadWriteLock

All Implemented Interfaces

java.util.concurrent.locks.ReadWriteLock

ReadWriteLock implementation whose read and write locks retain a reference back to this lock. Otherwise, a reference to just the read lock or just the write lock would not suffice to ensure the ReadWriteLock is retained.

Field Summary

Modifier and Type	Field and Description
private final ReadWriteLock	delegate

Constructor Summary

Access	Constructor and Description
pack-priv	WeakSafeReadWriteLock()

Method Summary

Modifier and Type	Method and Description
public Lock	readLock() Implements java.util.concurrent.locks.ReadWriteLock.readLock. Returns the lock used for reading.
public Lock	writeLock() Implements java.util.concurrent.locks.ReadWriteLock.writeLock. Returns the lock used for writing.

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

Field Detail

delegate	back to summary
private final ReadWriteLock delegate

Constructor Detail

WeakSafeReadWriteLock	back to summary
pack-priv WeakSafeReadWriteLock()

Method Detail

readLock

back to summary

public Lock readLock()

Implements java.util.concurrent.locks.ReadWriteLock.readLock.

Doc from java.util.concurrent.locks.ReadWriteLock.readLock.

Returns the lock used for reading.

Returns:Lock

the lock used for reading

Annotations

@Override

writeLock

back to summary

public Lock writeLock()

Implements java.util.concurrent.locks.ReadWriteLock.writeLock.

Doc from java.util.concurrent.locks.ReadWriteLock.writeLock.

Returns the lock used for writing.

Returns:Lock

the lock used for writing

Annotations

@Override

public abstract Class Striped<L>

Nested and Inner Type Summary

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private Class Striped.CompactStriped<L>

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pack-priv Class Striped.LargeLazyStriped<L>

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private Class Striped.PaddedLock

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private Class Striped.PaddedSemaphore

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private abstract Class Striped.PowerOfTwoStriped<L>

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Method Detail

pack-priv Class Striped.SmallLazyStriped<L>

Nested and Inner Type Summary

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Field Detail

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Method Detail

private final Class Striped.SmallLazyStriped.ArrayReference<L>

Field Summary

Constructor Summary

Field Detail

Constructor Detail

private final Class Striped.WeakSafeCondition

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail

private final Class Striped.WeakSafeLock

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail

private final Class Striped.WeakSafeReadWriteLock

Field Summary

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Method Summary

Field Detail

Constructor Detail

Method Detail