Verifies, during deserialization, that the owner/delegate/thisObject references reachable from root do not form a cycle through other closures. Such a cycle cannot arise from normal Groovy code or from the #dehydrate()/#rehydrate round-trip, but it can
(final Closure<?> root)
| 1326 | * @since 6.0.0 |
| 1327 | */ |
| 1328 | protected static void checkForReferenceCycle(final Closure<?> root) throws InvalidObjectException { |
| 1329 | // Iterative depth-first search over the raw owner/delegate/thisObject fields, following only |
| 1330 | // Closure-valued links. "grey" = on the current DFS path, "black" = fully explored. An edge back |
| 1331 | // to a grey node is a genuine cycle; an edge to a black node is a harmless shared reference (e.g. |
| 1332 | // a curried closure whose owner and delegate point at the same wrapped closure). The raw fields |
| 1333 | // are read directly (not via the overridable getters, which would themselves recurse on a cyclic |
| 1334 | // graph); access is permitted as this is the declaring class. |
| 1335 | final Set<Closure<?>> grey = Collections.newSetFromMap(new IdentityHashMap<>()); |
| 1336 | final Set<Closure<?>> black = Collections.newSetFromMap(new IdentityHashMap<>()); |
| 1337 | final Deque<Object> stack = new ArrayDeque<>(); |
| 1338 | stack.push(root); |
| 1339 | while (!stack.isEmpty()) { |
| 1340 | final Object top = stack.peek(); |
| 1341 | if (top instanceof Marker) { |
| 1342 | stack.pop(); |
| 1343 | final Closure<?> done = ((Marker) top).closure; |
| 1344 | grey.remove(done); |
| 1345 | black.add(done); |
| 1346 | continue; |
| 1347 | } |
| 1348 | final Closure<?> node = (Closure<?>) stack.pop(); |
| 1349 | if (black.contains(node) || grey.contains(node)) { |
| 1350 | continue; // already handled via a shared reference |
| 1351 | } |
| 1352 | grey.add(node); |
| 1353 | stack.push(new Marker(node)); |
| 1354 | for (final Object link : new Object[]{node.owner, node.delegate, node.thisObject}) { |
| 1355 | if (link instanceof Closure) { |
| 1356 | final Closure<?> child = (Closure<?>) link; |
| 1357 | if (grey.contains(child)) { |
| 1358 | throw new InvalidObjectException( |
| 1359 | "Closure owner/delegate/thisObject references form a cycle; refusing to deserialize"); |
| 1360 | } |
| 1361 | if (!black.contains(child)) { |
| 1362 | stack.push(child); |
| 1363 | } |
| 1364 | } |
| 1365 | } |
| 1366 | } |
| 1367 | } |
| 1368 | |
| 1369 | /** Sentinel pushed below a node's children during the {@link #checkForReferenceCycle} cycle check. */ |
| 1370 | private static final class Marker { |