/**
* Remove the last element in the vector.
*
* @return element removed
*/
public E pop_back() {
Descriptor<E> desc;
Descriptor<E> newd;
E elem;
do {
desc = descriptor.get();
desc.completeWrite();
int pos = desc.size + FIRST_BUCKET_SIZE - 1;
int bucketInd =
Integer.numberOfLeadingZeros(FIRST_BUCKET_SIZE) - Integer.numberOfLeadingZeros(pos);
int idx = Integer.highestOneBit(pos) ^ pos;
elem = buckets.get(bucketInd).get(idx);
newd = new Descriptor<E>(desc.size - 1, null);
} while (!descriptor.compareAndSet(desc, newd));
return elem;
}
/**
* add e at the end of vector.
*
* @param e element added
*/
public void push_back(E e) {
Descriptor<E> desc;
Descriptor<E> newd;
do {
desc = descriptor.get();
desc.completeWrite();
int pos = desc.size + FIRST_BUCKET_SIZE;
int zeroNumPos = Integer.numberOfLeadingZeros(pos);
int bucketInd = zeroNumFirst - zeroNumPos;
if (buckets.get(bucketInd) == null) {
int newLen = 2 * buckets.get(bucketInd - 1).length();
if (debug) System.out.println("New Length is:" + newLen);
buckets.compareAndSet(bucketInd, null, new AtomicReferenceArray<E>(newLen));
}
int idx = (0x80000000 >>> zeroNumPos) ^ pos;
newd =
new Descriptor<E>(
desc.size + 1, new WriteDescriptor<E>(buckets.get(bucketInd), idx, null, e));
} while (!descriptor.compareAndSet(desc, newd));
descriptor.get().completeWrite();
}