org.agrona.concurrent.status

Class AtomicCounter

java.lang.Object

org.agrona.concurrent.status.AtomicCounter

All Implemented Interfaces:

java.lang.AutoCloseable

public class AtomicCounter
extends java.lang.Object
implements java.lang.AutoCloseable

Atomic counter that is backed by an AtomicBuffer that can be read across threads and processes.

Constructor Summary

Constructors

Constructor and Description
AtomicCounter(AtomicBuffer buffer, int counterId) Map a counter over a buffer.
AtomicCounter(AtomicBuffer buffer, int counterId, CountersManager countersManager) Map a counter over a buffer.

Method Summary

Modifier and Type	Method and Description
void	close() Free the counter slot for reuse.
boolean	compareAndSet(long expectedValue, long updateValue) Compare the current value to expected and if true then set to the update value atomically.
long	get() Get the latest value for the counter with volatile semantics.
long	getAndAdd(long increment) Add an increment to the counter that will not lose updates across threads.
long	getAndAddOrdered(long increment) Add an increment to the counter with ordered store semantics.
long	getAndSet(long value) Get the current value of a counter and atomically set it to a new value.
long	getWeak() Get the value of the counter using weak ordering semantics.
int	id() Identity for the counter within the CountersManager.
long	increment() Perform an atomic increment that will not lose updates across threads.
long	incrementOrdered() Perform an atomic increment that is not safe across threads.
boolean	isClosed() Has this counter been closed?
boolean	proposeMax(long proposedValue) Set the value to a new proposedValue if greater than the current value with memory ordering semantics.
boolean	proposeMaxOrdered(long proposedValue) Set the value to a new proposedValue if greater than the current value with memory ordering semantics.
void	set(long value) Set the counter with volatile semantics.
void	setOrdered(long value) Set the counter with ordered semantics.
void	setWeak(long value) Set the counter with normal semantics.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

AtomicCounter

public AtomicCounter(AtomicBuffer buffer,
                     int counterId)

Map a counter over a buffer. This version will NOT free the counter on close.

Parameters:

buffer - containing the counter.

counterId - identifier of the counter.

AtomicCounter

public AtomicCounter(AtomicBuffer buffer,
                     int counterId,
                     CountersManager countersManager)

Map a counter over a buffer. This version will free the counter on close.

Parameters:

buffer - containing the counter.

counterId - identifier for the counter.

countersManager - to be called to free the counter on close.

Method Detail

id

public int id()

Identity for the counter within the CountersManager.

Returns:

identity for the counter within the CountersManager.

isClosed

public boolean isClosed()

Has this counter been closed?

Returns:

true if this counter has already been closed.

increment

public long increment()

Perform an atomic increment that will not lose updates across threads.

Returns:

the previous value of the counter

incrementOrdered

public long incrementOrdered()

Perform an atomic increment that is not safe across threads.

Returns:

the previous value of the counter

set

public void set(long value)

Set the counter with volatile semantics.

Parameters:

value - to be set with volatile semantics.

setOrdered

public void setOrdered(long value)

Set the counter with ordered semantics.

Parameters:

value - to be set with ordered semantics.

setWeak

public void setWeak(long value)

Set the counter with normal semantics.

Parameters:

value - to be set with normal semantics.

getAndAdd

public long getAndAdd(long increment)

Add an increment to the counter that will not lose updates across threads.

Parameters:

increment - to be added.

Returns:

the previous value of the counter

getAndAddOrdered

public long getAndAddOrdered(long increment)

Add an increment to the counter with ordered store semantics.

Parameters:

increment - to be added with ordered store semantics.

Returns:

the previous value of the counter

getAndSet

public long getAndSet(long value)

Get the current value of a counter and atomically set it to a new value.

Parameters:

value - to be set.

Returns:

the previous value of the counter

compareAndSet

public boolean compareAndSet(long expectedValue,
                             long updateValue)

Compare the current value to expected and if true then set to the update value atomically.

Parameters:

expectedValue - for the counter.

updateValue - for the counter.

Returns:

true if successful otherwise false.

get

public long get()

Get the latest value for the counter with volatile semantics.

Returns:

the latest value for the counter.

getWeak

public long getWeak()

Get the value of the counter using weak ordering semantics. This is the same a standard read of a field.

Returns:

the value for the counter.

proposeMax

public boolean proposeMax(long proposedValue)

Set the value to a new proposedValue if greater than the current value with memory ordering semantics.

Parameters:

proposedValue - for the new max.

Returns:

true if a new max as been set otherwise false.

proposeMaxOrdered

public boolean proposeMaxOrdered(long proposedValue)

Set the value to a new proposedValue if greater than the current value with memory ordering semantics.

Parameters:

proposedValue - for the new max.

Returns:

true if a new max as been set otherwise false.

close

public void close()

Free the counter slot for reuse.

Specified by:

close in interface java.lang.AutoCloseable