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- protected final boolean offerColdPath(final E[] buffer, final long mask, final E e, final long index,
- final long offset) {
- final long lookAheadStep = this.lookAheadStep;
- // normal case, go around the buffer or resize if full (unless we hit max capacity)
- if (lookAheadStep > 0) {
- long lookAheadElementOffset = calcElementOffset(index + lookAheadStep, mask);
- // Try and look ahead a number of elements so we don't have to do this all the time
- if (null == lvElement(buffer, lookAheadElementOffset)) {
- producerBufferLimit = index + lookAheadStep - 1; // joy, there's plenty of room
- writeToQueue(buffer, e, index, offset);
- return true;
- }
- // we're at max capacity, can use up last element
- final int maxCapacity = maxQueueCapacity;
- if (mask + 1 == maxCapacity) {
- if (null == lvElement(buffer, offset)) {
- writeToQueue(buffer, e, index, offset);
- return true;
- }
- // we're full and can't grow
- return false;
- }
- // not at max capacity, so must allow extra slot for JUMP
- if (null == lvElement(buffer, calcElementOffset(index + 1, mask))) { // buffer is not full
- writeToQueue(buffer, e, index, offset);
- } else {
- // allocate new buffer of same length
- final E[] newBuffer = allocate((int) (2*(mask +1) + 1));
- producerBuffer = newBuffer;
- producerMask = newBuffer.length - 2;
- final long offsetInNew = calcElementOffset(index, producerMask);
- linkOldToNew(index, buffer, offset, newBuffer, offsetInNew, e);
- int newCapacity = (int) (producerMask + 1);
- if (newCapacity == maxCapacity) {
- long currConsumerIndex = lvConsumerIndex();
- // use lookAheadStep to store the consumer distance from final buffer
- this.lookAheadStep = -(index - currConsumerIndex);
- producerBufferLimit = currConsumerIndex + maxCapacity - 1;
- } else {
- producerBufferLimit = index + producerMask - 1;
- adjustLookAheadStep(newCapacity);
- }
- }
- return true;
- }
- // the step is negative (or zero) in the period between allocating the max sized buffer and the
- // consumer starting on it
- else {
- final long prevElementsInOtherBuffers = -lookAheadStep;
- // until the consumer starts using the current buffer we need to check consumer index to
- // verify size
- long currConsumerIndex = lvConsumerIndex();
- int size = (int) (index - currConsumerIndex);
- int maxCapacity = (int) mask+1; // we're on max capacity or we wouldn't be here
- if (size == maxCapacity) {
- // consumer index has not changed since adjusting the lookAhead index, we're full
- return false;
- }
- // if consumerIndex progressed enough so that current size indicates it is on same buffer
- long firstIndexInCurrentBuffer = producerBufferLimit - maxCapacity + prevElementsInOtherBuffers;
- if (currConsumerIndex >= firstIndexInCurrentBuffer) {
- // job done, we've now settled into our final state
- adjustLookAheadStep(maxCapacity);
- }
- // consumer is still on some other buffer
- else {
- // how many elements out of buffer?
- this.lookAheadStep = (int) (currConsumerIndex - firstIndexInCurrentBuffer);
- }
- producerBufferLimit = currConsumerIndex + maxCapacity;
- writeToQueue(buffer, e, index, offset);
- return true;
- }
- }
- private void adjustLookAheadStep(int capacity) {
- lookAheadStep = Math.min(capacity / 4, SpscArrayQueue.MAX_LOOK_AHEAD_STEP);
- }
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