Package com.lmax.disruptor
Class Sequence
java.lang.Object
com.lmax.disruptor.LhsPadding
com.lmax.disruptor.Value
com.lmax.disruptor.RhsPadding
com.lmax.disruptor.Sequence
- Direct Known Subclasses:
FixedSequenceGroup
,NoOpEventProcessor.SequencerFollowingSequence
,SequenceGroup
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.
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Field Summary
FieldsModifier and TypeFieldDescription(package private) static final long
private static final sun.misc.Unsafe
private static final long
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionlong
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
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.toString()
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Field Details
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INITIAL_VALUE
static final long INITIAL_VALUE- See Also:
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UNSAFE
private static final sun.misc.Unsafe UNSAFE -
VALUE_OFFSET
private static final long VALUE_OFFSET
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Constructor Details
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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.
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Method Details
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get
public long get()Perform a volatile read of this sequence's value.- Returns:
- The current value of the sequence.
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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.
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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.
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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.
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incrementAndGet
public long incrementAndGet()Atomically increment the sequence by one.- Returns:
- The value after the increment
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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.
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toString
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