Unbounded SPSC LAQ cold path

SpscLAQUnbounded.java

@Override
protected boolean offerColdPath(E[] buffer, long mask, E e, long pIndex, long offset) {
  // use a fixed lookahead step based on buffer capacity
  final long lookAheadStep = (mask + 1) / 4;
  long pBufferLimit = pIndex + lookAheadStep;

  // go around the buffer or add a new buffer
  if (null == lvElement(buffer, calcElementOffset(pBufferLimit, mask))) {
    // the element lookAheadStep away is empty, so we can use up to the element before it
    producerBufferLimit = pBufferLimit - 1;
    writeToQueue(buffer, e, pIndex, offset);
  }
  else if (null == lvElement(buffer, calcElementOffset(pIndex + 1, mask))) {
    // the next element is null, so we can write to the current element
    writeToQueue(buffer, e, pIndex, offset);
  }
  else {
    // we got one slot left to write into => need to link new buffer.
    final E[] newBuffer = (E[]) new Object[buffer.length];
    producerBuffer = newBuffer;
    producerBufferLimit = pIndex + mask - 1;

    linkOldToNew(pIndex, buffer, offset, newBuffer, offset, e);
  }
  
  return true;
}

void linkOldToNew(long currIndex,
                  E[] oldBuffer,
                  long offsetInOld,
                  E[] newBuffer,
                  long offsetInNew,
                  E e) {
  soElement(newBuffer, offsetInNew, e); // ordered: newBuffer[index & newMask] = e;
  soNext(oldBuffer, newBuffer); // ordered: oldBuffer[oldBuffer.length - 1] = newBuffer;
  soElement(oldBuffer, offsetInOld, JUMP); // ordered: oldBuffer[index & oldMask] = JUMP;
  soProducerIndex(currIndex + 1);// ordered: producerIndex = currIndex + 1;
}