public boolean offer(final E e) {
if (null == e) {
throw new NullPointerException("element cannot be null");
}
long currentTail;
long currentHead = sharedHeadCache;
long bufferLimit = currentHead + capacity;
do {
currentTail = tail;
if (currentTail >= bufferLimit) {
currentHead = head;
bufferLimit = currentHead + capacity;
if (currentTail >= bufferLimit) {
return false;
}
UNSAFE.putOrderedLong(this, SHARED_HEAD_CACHE_OFFSET, currentHead);
}
} while (!UNSAFE.compareAndSwapLong(this, TAIL_OFFSET, currentTail, currentTail + 1));
UNSAFE.putOrderedObject(buffer, sequenceToBufferOffset(currentTail, mask), e);
return true;
}
@SuppressWarnings("unchecked")
public E poll() {
final long currentHead = head;
final long elementOffset = sequenceToBufferOffset(currentHead, mask);
final Object[] buffer = this.buffer;
final Object e = UNSAFE.getObjectVolatile(buffer, elementOffset);
if (null != e) {
UNSAFE.putObject(buffer, elementOffset, null);
UNSAFE.putOrderedLong(this, HEAD_OFFSET, currentHead + 1);
}
return (E) e;
}
@SuppressWarnings("unchecked")
public int drainTo(final Collection<? super E> target, final int limit) {
final Object[] buffer = this.buffer;
final long mask = this.mask;
long nextSequence = head;
int count = 0;
while (count < limit) {
final long elementOffset = sequenceToBufferOffset(nextSequence, mask);
final Object e = UNSAFE.getObjectVolatile(buffer, elementOffset);
if (null == e) {
break;
}
UNSAFE.putOrderedObject(buffer, elementOffset, null);
nextSequence++;
UNSAFE.putOrderedLong(this, HEAD_OFFSET, nextSequence);
count++;
target.add((E) e);
}
return count;
}
@SuppressWarnings("unchecked")
public int drain(final Consumer<E> elementHandler) {
final Object[] buffer = this.buffer;
final long mask = this.mask;
final long currentHead = head;
long nextSequence = currentHead;
final long limit = nextSequence + mask + 1;
while (nextSequence < limit) {
final long elementOffset = sequenceToBufferOffset(nextSequence, mask);
final Object item = UNSAFE.getObjectVolatile(buffer, elementOffset);
if (null == item) {
break;
}
UNSAFE.putOrderedObject(buffer, elementOffset, null);
nextSequence++;
UNSAFE.putOrderedLong(this, HEAD_OFFSET, nextSequence);
elementHandler.accept((E) item);
}
return (int) (nextSequence - currentHead);
}
protected final void soTail(long v) {
UNSAFE.putOrderedLong(this, P_INDEX_OFFSET, v);
}
