static void generateNFAForSubtree(NFA& nfa, unsigned nfaRootId, PrefixTreeVertex& root, size_t maxNFASize)
{
// This recurses the subtree of the prefix tree.
// For each edge that has fixed length (no quantifiers like ?, *, or +) it generates the nfa graph,
// recurses into children, and deletes any processed leaf nodes.
struct ActiveSubtree {
ActiveSubtree(PrefixTreeVertex& vertex, unsigned nfaNodeId, unsigned edgeIndex)
: vertex(vertex)
, nfaNodeId(nfaNodeId)
, edgeIndex(edgeIndex)
{
}
PrefixTreeVertex& vertex;
unsigned nfaNodeId;
unsigned edgeIndex;
};
Vector<ActiveSubtree> stack;
if (!root.edges.isEmpty())
stack.append(ActiveSubtree(root, nfaRootId, 0));
bool nfaTooBig = false;
// Generate graphs for each subtree that does not contain any quantifiers.
while (!stack.isEmpty()) {
PrefixTreeVertex& vertex = stack.last().vertex;
const unsigned edgeIndex = stack.last().edgeIndex;
// Only stop generating an NFA at a leaf to ensure we have a correct NFA. We could go slightly over the maxNFASize.
if (vertex.edges.isEmpty() && nfa.graphSize() > maxNFASize)
nfaTooBig = true;
if (edgeIndex < vertex.edges.size()) {
auto& edge = vertex.edges[edgeIndex];
// Clean up any processed leaves and return early if we are past the maxNFASize.
if (nfaTooBig) {
stack.last().edgeIndex = stack.last().vertex.edges.size();
continue;
}
// Quantified edges in the subtree will be a part of another NFA.
if (!edge.term.hasFixedLength()) {
stack.last().edgeIndex++;
continue;
}
unsigned subtreeRootId = edge.term.generateGraph(nfa, stack.last().nfaNodeId, edge.child->finalActions);
ASSERT(edge.child.get());
stack.append(ActiveSubtree(*edge.child.get(), subtreeRootId, 0));
} else {
ASSERT(edgeIndex == vertex.edges.size());
vertex.edges.removeAllMatching([](PrefixTreeEdge& edge)
{
return edge.term.isDeletedValue();
});
stack.removeLast();
if (!stack.isEmpty()) {
auto& activeSubtree = stack.last();
auto& edge = activeSubtree.vertex.edges[stack.last().edgeIndex];
if (edge.child->edges.isEmpty())
edge.term = Term(Term::DeletedValue); // Mark this leaf for deleting.
activeSubtree.edgeIndex++;
}
}
}
}
