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;
}
protected final boolean casHead(long expect, long newValue) {
return UNSAFE.compareAndSwapLong(this, C_INDEX_OFFSET, expect, newValue);
}
final boolean cas(long cmp, long val) {
return UNSAFE.compareAndSwapLong(this, valueOffset, cmp, val);
}
