/
autom.NodeNfa.go
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/
autom.NodeNfa.go
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// Copyright 2023 Sneller, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package regexp2
import (
"fmt"
"slices"
"unicode"
"golang.org/x/exp/maps"
)
type nfa struct {
id nodeIDT
edges []edgeT
start bool
accept bool
}
func (n *nfa) addEdgeInternal(e edgeT) {
n.edges = append(n.edges, e)
}
func (n *nfa) addEdgeRune(symbol rune, to nodeIDT, caseSensitive bool) {
n.addEdgeInternal(edgeT{newSymbolRange(symbol, symbol), to})
if !caseSensitive {
for c := unicode.SimpleFold(symbol); c != symbol; c = unicode.SimpleFold(c) {
n.addEdgeInternal(edgeT{newSymbolRange(c, c), to})
}
}
}
func (n *nfa) addEdge(symbolRange symbolRangeT, to nodeIDT) {
n.addEdgeInternal(edgeT{symbolRange, to})
}
func (n *nfa) removeEdge(symbolRange symbolRangeT, to nodeIDT) {
for index, edge := range n.edges {
if (edge.to == to) && (edge.symbolRange == symbolRange) {
n.edges = slices.Delete(n.edges, index, index+1)
return
}
}
}
type NFAStore struct {
nextID nodeIDT
startIDi nodeIDT
startRLZA bool // indicate that the start node has Remaining Length Zero Assertion (RLZ)
data map[nodeIDT]*nfa
maxNodes int
}
func newNFAStore(maxNodes int) NFAStore {
return NFAStore{
nextID: 0,
startIDi: notInitialized,
startRLZA: false,
data: map[nodeIDT]*nfa{},
maxNodes: maxNodes,
}
}
func (store *NFAStore) dot() *Graphviz {
result := newGraphiz()
for _, nodeID := range store.getIDs() {
node, _ := store.get(nodeID)
fromStr := fmt.Sprintf("%v", nodeID)
result.addNode(fromStr, node.start, node.accept, false)
for _, edge := range node.edges {
result.addEdge(fromStr, fmt.Sprintf("%v", edge.to), edge.symbolRange.String())
}
}
return result
}
func (store *NFAStore) newNode() (nodeIDT, error) {
if len(store.data) >= store.maxNodes {
return -1, fmt.Errorf("NFA exceeds max number of nodes %v::newNode", store.maxNodes)
}
nodeID := store.nextID
store.nextID++
node := new(nfa)
node.id = nodeID
node.accept = false
store.data[nodeID] = node
return nodeID, nil
}
func (store *NFAStore) get(nodeID nodeIDT) (*nfa, error) {
if nfa, present := store.data[nodeID]; present {
return nfa, nil
}
return nil, fmt.Errorf("NFAStore.get(%v): nfaId %v not present in map %v", nodeID, nodeID, store.data)
}
func (store *NFAStore) startID() (nodeIDT, error) {
if store.startIDi == notInitialized {
for nodeID, node := range store.data {
if node.start {
store.startIDi = nodeID
return nodeID, nil
}
}
return notInitialized, fmt.Errorf("NFAStore does not have a start node")
}
return store.startIDi, nil
}
// getIDs returns sorted slice of unique ids
func (store *NFAStore) getIDs() vectorT[nodeIDT] {
ids := maps.Keys(store.data)
slices.Sort(ids)
return ids
}
// refactorEdges changes and adds edges such that nodes become choice free
func (store *NFAStore) refactorEdges() (err error) {
// refactor any edges: replaces any-edges (meta edges) with regular edges with ranges
for _, node := range store.data {
for index1, anyEdge := range node.edges {
sr := anyEdge.symbolRange
if (sr == edgeAnyRange) || (sr == edgeAnyNotLfRange) {
symbolRanges := anyEdge.symbolRanges()
for index2, edge2 := range node.edges {
if index1 != index2 { // remove range of regular edges from the range of the any-edge
symbolRanges = symbolRangeSubtract(symbolRanges, edge2.symbolRanges())
}
}
// replace any-edge with new edges in symbolRanges
node.removeEdge(sr, anyEdge.to) // remove the old any-edge
for _, symbolRange := range symbolRanges { // add new regular edge
node.addEdge(symbolRange, anyEdge.to)
}
}
}
}
cg := newCharGroupsRange() // only place where symbol ranges are refactored
for _, node := range store.data {
for _, edge := range node.edges {
if !edge.epsilon() && !edge.rlza() {
cg.add(edge.symbolRange)
}
}
}
toRemove := newVector[edgeT]()
for _, node := range store.data {
for _, edge := range node.edges {
if !edge.epsilon() && !edge.rlza() {
if newSymbolRanges, present := cg.refactor(edge.symbolRange); present {
toRemove.pushBack(edge)
for _, newSymbolRange2 := range *newSymbolRanges {
node.addEdge(newSymbolRange2, edge.to)
}
}
}
}
for _, edge := range toRemove {
node.removeEdge(edge.symbolRange, edge.to)
}
toRemove.clear()
}
return nil
}
// cleanupStaleEdges removes edges that point to removed nodes
func (store *NFAStore) cleanupStaleEdges() {
nodeIDs := newSet[nodeIDT]()
for _, nodeID := range maps.Keys(store.data) {
nodeIDs.insert(nodeID)
}
for _, node := range store.data {
for _, edge := range node.edges {
if !nodeIDs.contains(edge.to) {
node.removeEdge(edge.symbolRange, edge.to)
}
}
}
}
// pruneRLZ removes nodes that are 'after' the RLZA ('$')
// and are thus unreachable
func (store *NFAStore) pruneRLZ() error {
// get the nodeIDs that are eligible for prune
// 1. add all nodes that are reachable from a $-node.
// a $-node is a node that has an incoming $-edge.
// 2. remove all nodes that are reachable from the
// start node, but stop traversing when a $-edge
// is encountered.
// 3. remove all these eligible nodes from the NFA.
eligible := newSet[nodeIDT]()
done := newSet[nodeIDT]()
var reachable1 func(nodeID nodeIDT) error
reachable1 = func(nodeID nodeIDT) error {
if done.contains(nodeID) {
return nil
}
done.insert(nodeID)
node, err := store.get(nodeID)
if err != nil {
return err
}
for _, edge := range node.edges {
if edge.rlza() || edge.epsilon() {
if err := reachable1(edge.to); err != nil {
return err
}
} else {
eligible.insert(edge.to)
}
}
return nil
}
var reachable2 func(nodeID nodeIDT) error
reachable2 = func(nodeID nodeIDT) error {
if done.contains(nodeID) {
return nil
}
done.insert(nodeID)
eligible.erase(nodeID)
node, err := store.get(nodeID)
if err != nil {
return err
}
for _, edge := range node.edges {
if !edge.rlza() {
if err := reachable2(edge.to); err != nil {
return err
}
}
}
return nil
}
// 1. add all nodes that are reachable from a $-node.
for _, node := range store.data {
for _, edge := range node.edges {
if edge.rlza() {
if err := reachable1(edge.to); err != nil {
return err
}
}
}
}
done.clear()
// 2. remove all nodes that are reachable from the
if err := reachable2(store.startIDi); err != nil {
return err
}
// 3. remove all these eligible nodes from the NFA.
changed := false
for nodeID := range eligible {
changed = true
delete(store.data, nodeID)
}
if changed {
store.cleanupStaleEdges()
}
return nil
}