/**
* Algorithm of Tarjan for computing the strongly connected components of a graph.
*
* @param v current node
* @throws QueryException if a variable directly calls itself
*/
private void tarjan(final int v) throws QueryException {
final int ixv = 2 * v, llv = ixv + 1, idx = next++;
while (list.size() <= llv) list.add(-1);
list.set(ixv, idx);
list.set(llv, idx);
stack.push(v);
for (final int w : adjacentTo(v)) {
final int ixw = 2 * w, llw = ixw + 1;
if (list.size() <= ixw || list.get(ixw) < 0) {
// Successor w has not yet been visited; recurse on it
tarjan(w);
list.set(llv, Math.min(list.get(llv), list.get(llw)));
} else if (stack.contains(w)) {
// Successor w is in stack S and hence in the current SCC
list.set(llv, Math.min(list.get(llv), list.get(ixw)));
}
}
// If v is a root node, pop the stack and generate an SCC
if (list.get(llv) == list.get(ixv)) {
int w;
Scope[] out = null;
do {
w = stack.pop();
final Scope scp = scopes.get(w);
out = out == null ? new Scope[] {scp} : Array.add(out, scp);
} while (w != v);
result.add(out);
}
}
/**
* Removes values from the index.
*
* @param key key
* @param vals sorted values
*/
void delete(final byte[] key, final int... vals) {
final int id = values.id(key), vl = vals.length, l = lenList.get(id), s = l - vl;
final int[] ids = idsList.get(id);
for (int i = 0, n = 0, v = 0; i < l; i++) {
if (v == vl || ids[i] != vals[v]) ids[n++] = ids[i];
else v++;
}
lenList.set(id, s);
if (s == 0) idsList.set(id, null);
}
/**
* Adds values to the index.
*
* @param key key to be indexed
* @param vals sorted values
*/
void add(final byte[] key, final int... vals) {
// token index: add values. otherwise, reference existing values
final int id = type == IndexType.TOKEN ? values.put(key) : values.id(key), vl = vals.length;
// updatable index: if required, resize existing arrays
while (idsList.size() < id + 1) idsList.add(null);
if (lenList.size() < id + 1) lenList.set(id, 0);
final int len = lenList.get(id), size = len + vl;
int[] ids = idsList.get(id);
if (ids == null) {
ids = vals;
} else {
if (ids.length < size) ids = Arrays.copyOf(ids, Array.newSize(size));
System.arraycopy(vals, 0, ids, len, vl);
if (ids[len - 1] > vals[0]) {
if (reorder == null) reorder = new BoolList(values.size());
reorder.set(id, true);
}
}
idsList.set(id, ids);
lenList.set(id, size);
}
