Package com.lmax.disruptor

Class Sequence

  • Direct Known Subclasses:
    FixedSequenceGroup, SequenceGroup
    public class Sequence
extends 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.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      protected long p1  
      protected long p10  
      protected long p11  
      protected long p12  
      protected long p13  
      protected long p14  
      protected long p15  
      protected long p2  
      protected long p3  
      protected long p4  
      protected long p5  
      protected long p6  
      protected long p7  
      protected long p9  
      protected long value  

    • Constructor Summary

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

    • Field Detail

      • p9

        protected long p9

      • p10

        protected long p10

      • p11

        protected long p11

      • p12

        protected long p12

      • p13

        protected long p13

      • p14

        protected long p14

      • p15

        protected long p15

      • value

        protected volatile long value

      • p1

        protected long p1

      • p2

        protected long p2

      • p3

        protected long p3

      • p4

        protected long p4

      • p5

        protected long p5

      • p6

        protected long p6

      • p7

        protected long p7

    • 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.