[GitHub] [lucene] slow-J commented on a diff in pull request #12462: Fix stack overflow in RegExp for long string

[via GitHub]

slow-J commented on code in PR #12462:
URL: https://github.com/apache/lucene/pull/12462#discussion_r1290219209


##########
lucene/core/src/java/org/apache/lucene/util/automaton/RegExp.java:
##########
@@ -1067,22 +1071,44 @@ private boolean check(int flag) {
   }
 
   final RegExp parseUnionExp() throws IllegalArgumentException {
-    RegExp e = parseInterExp();
-    if (match('|')) e = makeUnion(flags, e, parseUnionExp());
-    return e;
+    return iterativeParseExp(this::parseInterExp, () -> match('|'), 
RegExp::makeUnion);
   }
 
   final RegExp parseInterExp() throws IllegalArgumentException {
-    RegExp e = parseConcatExp();
-    if (check(INTERSECTION) && match('&')) e = makeIntersection(flags, e, 
parseInterExp());
-    return e;
+    return iterativeParseExp(
+        this::parseConcatExp, () -> check(INTERSECTION) && match('&'), 
RegExp::makeIntersection);
   }
 
   final RegExp parseConcatExp() throws IllegalArgumentException {
-    RegExp e = parseRepeatExp();
-    if (more() && !peek(")|") && (!check(INTERSECTION) || !peek("&")))
-      e = makeConcatenation(flags, e, parseConcatExp());
-    return e;
+    return iterativeParseExp(
+        this::parseRepeatExp,
+        () -> (more() && !peek(")|") && (!check(INTERSECTION) || !peek("&"))),
+        RegExp::makeConcatenation);
+  }
+
+  /**
+   * Custom Functional Interface for a Supplying methods with signature of 
RegExp(int int1, RegExp
+   * exp1, RegExp exp2)
+   */
+  @FunctionalInterface
+  private interface MakeRegexGroup {
+    RegExp get(int int1, RegExp exp1, RegExp exp2);
+  }
+
+  final RegExp iterativeParseExp(
+      Supplier<RegExp> gather, BooleanSupplier stop, MakeRegexGroup reduce)
+      throws IllegalArgumentException {
+    Deque<RegExp> regExpStack = new ArrayDeque<>();

Review Comment:
   Added a new commit with the changes.



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