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Logic useful to read and analyze regular expressions
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/*
* SonarSource Analyzers Regex Parsing Commons
* Copyright (C) 2009-2024 SonarSource SA
* mailto:info AT sonarsource DOT com
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 3 of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
package org.sonarsource.analyzer.commons.regex.helpers;
import java.util.HashSet;
import java.util.Set;
import org.sonarsource.analyzer.commons.regex.ast.AutomatonState;
import org.sonarsource.analyzer.commons.regex.ast.BoundaryTree;
import org.sonarsource.analyzer.commons.regex.ast.FinalState;
import org.sonarsource.analyzer.commons.regex.ast.LookAroundTree;
import static org.sonarsource.analyzer.commons.regex.ast.AutomatonState.TransitionType.EPSILON;
public class RegexTreeHelper {
private RegexTreeHelper() {
// Utils class
}
/**
* If both sub-automata have allowPrefix set to true, this method will check whether auto1 intersects
* the prefix of auto2 or auto2 intersects the prefix of auto1. This is different than checking whether
* the prefix of auto1 intersects the prefix of auto2 (which would always be true because both prefix
* always contain the empty string).
* defaultAnswer will be returned in case of unsupported features or the state limit is exceeded.
* It should be whichever answer does not lead to an issue being reported to avoid false positives.
*/
public static boolean intersects(SubAutomaton auto1, SubAutomaton auto2, boolean defaultAnswer) {
return new IntersectAutomataChecker(defaultAnswer).check(auto1, auto2);
}
/**
* Here auto2.allowPrefix means that if supersetOf(auto1, auto2), then for every string matched by auto2, auto1 can match a prefix of it
* auto1.allowPrefix means that if supersetOf(auto1, auto2), then for every string matched by auto2, auto1 can match a continuation of it
* If both are set, it means either one can be the case.
*/
public static boolean supersetOf(SubAutomaton auto1, SubAutomaton auto2, boolean defaultAnswer) {
return new SupersetAutomataChecker(defaultAnswer).check(auto1, auto2);
}
public static boolean isAnchoredAtEnd(AutomatonState start) {
return isAnchoredAtEnd(start, new HashSet<>());
}
private static boolean isAnchoredAtEnd(AutomatonState start, Set visited) {
if (isEndBoundary(start)) {
return true;
}
if (start instanceof FinalState) {
return false;
}
visited.add(start);
for (AutomatonState successor : start.successors()) {
if (!visited.contains(successor) && !isAnchoredAtEnd(successor, visited)) {
return false;
}
}
return true;
}
public static boolean isEndBoundary(AutomatonState state) {
if (!(state instanceof BoundaryTree)) {
return false;
}
switch (((BoundaryTree) state).type()) {
case LINE_END:
case INPUT_END:
case INPUT_END_FINAL_TERMINATOR:
return true;
default:
return false;
}
}
public static boolean onlyMatchesEmptySuffix(AutomatonState start) {
return onlyMatchesEmptySuffix(start, new HashSet<>());
}
private static boolean onlyMatchesEmptySuffix(AutomatonState start, Set visited) {
if (start instanceof FinalState || visited.contains(start)) {
return true;
}
visited.add(start);
if (start instanceof LookAroundTree) {
return onlyMatchesEmptySuffix(start.continuation(), visited);
}
if (start.incomingTransitionType() != EPSILON) {
return false;
}
for (AutomatonState successor : start.successors()) {
if (!onlyMatchesEmptySuffix(successor, visited)) {
return false;
}
}
return true;
}
}
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