com.lmax.disruptor

Class Sequence

java.lang.Object

com.lmax.disruptor.Sequence

Direct Known Subclasses:

FixedSequenceGroup, SequenceGroup

public class Sequence
extends java.lang.Object

Concurrent sequence class used for tracking the progress of the ring buffer and event processors. Support a number of concurrent operations including CAS and order writes.

Also attempts to be more efficient with regards to false sharing by adding padding around the volatile field.

Constructor Summary

Constructors

Constructor and Description
Sequence() Create a sequence initialised to -1.
Sequence(long initialValue) Create a sequence with a specified initial value.

Method Summary

Methods

Modifier and Type	Method and Description
long	addAndGet(long increment) Atomically add the supplied value.
boolean	compareAndSet(long expectedValue, long newValue) Perform a compare and set operation on the sequence.
long	get() Perform a volatile read of this sequence's value.
long	incrementAndGet() Atomically increment the sequence by one.
void	set(long value) Perform an ordered write of this sequence.
void	setVolatile(long value) Performs a volatile write of this sequence.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

Sequence

public Sequence()

Create a sequence initialised to -1.

Sequence

public Sequence(long initialValue)

Create a sequence with a specified initial value.

Parameters:

initialValue - The initial value for this sequence.

Method Detail

get

public long get()

Perform a volatile read of this sequence's value.

Returns:

The current value of the sequence.

set

public void set(long value)

Perform an ordered write of this sequence. The intent is a Store/Store barrier between this write and any previous store.

Parameters:

value - The new value for the sequence.

setVolatile

public void setVolatile(long value)

Performs a volatile write of this sequence. The intent is a Store/Store barrier between this write and any previous write and a Store/Load barrier between this write and any subsequent volatile read.

Parameters:

value - The new value for the sequence.

compareAndSet

public boolean compareAndSet(long expectedValue,
                    long newValue)

Perform a compare and set operation on the sequence.

Parameters:

expectedValue - The expected current value.

newValue - The value to update to.

Returns:

true if the operation succeeds, false otherwise.

incrementAndGet

public long incrementAndGet()

Atomically increment the sequence by one.

Returns:

The value after the increment

addAndGet

public long addAndGet(long increment)

Atomically add the supplied value.

Parameters:

increment - The value to add to the sequence.

Returns:

The value after the increment.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object