/**
* Creates a tree slice from a digit.
*
* @param <N> node type
* @param <E> element type
* @param nodes the digit
* @param from element offset
* @param len number of elements
* @param buffer buffer to insert the node slice into
* @param inBuffer initial number of nodes in the buffer
* @return the slice
*/
private static <N, E> int splitDigit(
final Node<N, E>[] nodes,
final long from,
final long len,
final NodeLike<N, E>[] buffer,
final int inBuffer) {
if (len <= 0) return inBuffer;
// find the first sub-node containing used elements
int firstPos = 0;
long firstOff = from;
Node<N, E> first = nodes[0];
long firstSize = first.size();
while (firstOff >= firstSize) {
firstOff -= firstSize;
first = nodes[++firstPos];
firstSize = first.size();
}
// firstOff < firstSize
final long inFirst = firstSize - firstOff;
if (inFirst >= len) {
// everything in first sub-node
final NodeLike<N, E> part = len == firstSize ? first : first.slice(firstOff, len);
return part.append(buffer, inBuffer);
}
final NodeLike<N, E> firstSlice = firstOff == 0 ? first : first.slice(firstOff, inFirst);
int numMerged = firstSlice.append(buffer, inBuffer);
int pos = firstPos;
long remaining = len - inFirst;
while (remaining > 0) {
final Node<N, E> curr = nodes[++pos];
final long currSize = curr.size();
final NodeLike<N, E> slice = remaining >= currSize ? curr : curr.slice(0, remaining);
numMerged = slice.append(buffer, numMerged);
remaining -= currSize;
}
return numMerged;
}
@Override
public TreeSlice<N, E> slice(final long from, final long len) {
if (from == 0 && len == size) return new TreeSlice<>(this);
final long midSize = middle.size(), rightOff = leftSize + midSize;
final long inLeft = from + len <= leftSize ? len : from < leftSize ? leftSize - from : 0;
final long inRight = from >= rightOff ? len : from + len > rightOff ? from + len - rightOff : 0;
@SuppressWarnings("unchecked")
final NodeLike<N, E>[] buffer = new NodeLike[2 * MAX_DIGIT + 1];
int inBuffer = splitDigit(left, from, inLeft, buffer, 0);
if (inLeft == len) {
if (inBuffer == 1) return new TreeSlice<>(buffer[0]);
final int mid1 = inBuffer / 2;
final Node<N, E>[] ls = slice(buffer, 0, mid1), rs = slice(buffer, mid1, inBuffer);
return new TreeSlice<>(get(ls, rs, len));
}
final long inMiddle = len - inLeft - inRight;
final FingerTree<Node<N, E>, E> mid;
final TreeSlice<Node<N, E>, E> slice;
if (inMiddle == 0) {
mid = EmptyTree.getInstance();
slice = new TreeSlice<>(mid);
} else {
final long midOff = from <= leftSize ? 0 : from - leftSize;
slice = middle.slice(midOff, inMiddle);
if (slice.isTree()) {
mid = slice.getTree();
} else {
final NodeLike<N, E> sub = ((PartialInnerNode<N, E>) slice.getPartial()).sub;
inBuffer = sub.append(buffer, inBuffer);
mid = EmptyTree.getInstance();
}
}
final long rightFrom = from < rightOff ? 0 : from - rightOff;
if (mid.isEmpty()) {
inBuffer = splitDigit(right, rightFrom, inRight, buffer, inBuffer);
return slice.setNodes(buffer, inBuffer, len);
}
final FingerTree<Node<N, E>, E> mid2;
if (inBuffer > 1 || buffer[0] instanceof Node) {
mid2 = mid;
} else {
final InnerNode<N, E> head = (InnerNode<N, E>) mid.head();
final int k = head.arity();
inBuffer = head.getSub(0).append(buffer, inBuffer);
for (int i = 1; i < k; i++) buffer[inBuffer++] = head.getSub(i);
mid2 = mid.tail();
}
if (mid2.isEmpty()) {
inBuffer = splitDigit(right, rightFrom, inRight, buffer, inBuffer);
return slice.setNodes(buffer, inBuffer, len);
}
final Node<N, E>[] newLeft = slice(buffer, 0, inBuffer);
inBuffer = splitDigit(right, rightFrom, inRight, buffer, 0);
final FingerTree<Node<N, E>, E> mid3;
final Node<N, E>[] newRight;
if (inBuffer == 0) {
mid3 = mid2.init();
newRight = ((InnerNode<N, E>) mid2.last()).children;
} else if (inBuffer > 1 || buffer[0] instanceof Node) {
mid3 = mid2;
newRight = slice(buffer, 0, inBuffer);
} else {
final NodeLike<N, E> partial = buffer[0];
final InnerNode<N, E> last = (InnerNode<N, E>) mid2.last();
final int k = last.arity();
for (int i = 0; i < k; i++) buffer[i] = last.getSub(i);
inBuffer = partial.append(buffer, k);
mid3 = mid2.init();
newRight = slice(buffer, 0, inBuffer);
}
return slice.setTree(get(newLeft, mid3, newRight, len));
}
