/**
* Find the index of the previous set bit less than or equal to i, returns -1 if none found.
*
* @param i starting index
* @return index of the previous set bit
*/
public int prevSetBit(final int i) {
int x = i >> 6; // i / 64 with sign extension
long w = bitmap[x];
w <<= 64 - i - 1;
if (w != 0) {
return i - Long.numberOfLeadingZeros(w);
}
for (--x; x >= 0; --x) {
if (bitmap[x] != 0) {
return x * 64 + 63 - Long.numberOfLeadingZeros(bitmap[x]);
}
}
return -1;
}
/**
* Get the encoded length if an integer is stored in a variable-length format
*
* @return the encoded length
*/
public static int getVIntSize(long i) {
if (i >= -112 && i <= 127) {
return 1;
}
if (i < 0) {
i ^= -1L; // take one's complement'
}
// find the number of bytes with non-leading zeros
int dataBits = Long.SIZE - Long.numberOfLeadingZeros(i);
// find the number of data bytes + length byte
return (dataBits + 7) / 8 + 1;
}
private Node makeSiblings(Node node, Node sibling) {
int parentLevel = MAX_BITS - Long.numberOfLeadingZeros(node.bits ^ sibling.bits);
Node parent = createNode(node.bits, parentLevel, 0);
// the branch is given by the bit at the level one below parent
long branch = sibling.bits & parent.getBranchMask();
if (branch == 0) {
parent.left = sibling;
parent.right = node;
} else {
parent.left = node;
parent.right = sibling;
}
return parent;
}