Disruptor源码分析（四）Sequencer

针对不同的应用场景，为了尽量提高处理性能，Disruptor提供了SingleProducerSequencer和MultiProducerSequencer两种sequencer，分别对应单生产者模式和多生产者模式。

• SingleProducerSequencer

在单生产者模式中，由于只有一个生产者，所以在获取下一个可用序列号时，不会存在多线程竞争的情况，所以直接用一个long类型变量nextSequence，而没有使用Sequence，提高了处理速度。

nextValue变量定义如下：

abstract class SingleProducerSequencerPad extends AbstractSequencer
{
    protected long p1, p2, p3, p4, p5, p6, p7;

    SingleProducerSequencerPad(int bufferSize, WaitStrategy waitStrategy)
    {
        super(bufferSize, waitStrategy);
    }
}

abstract class SingleProducerSequencerFields extends SingleProducerSequencerPad
{
    SingleProducerSequencerFields(int bufferSize, WaitStrategy waitStrategy)
    {
        super(bufferSize, waitStrategy);
    }

    /**
     * Set to -1 as sequence starting point
     */
    long nextValue = Sequence.INITIAL_VALUE;
    long cachedValue = Sequence.INITIAL_VALUE;
}

next方法定义如下：

/**
     * @see Sequencer#next()
     */
    @Override
    public long next()
    {
     &n