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runtime-linux/antlr4-runtime/tree/IterativeParseTreeWalker.cpp

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+/* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
+ * Use of this file is governed by the BSD 3-clause license that
+ * can be found in the LICENSE.txt file in the project root.
+ */
+
+#include "support/CPPUtils.h"
+
+#include "tree/ParseTreeListener.h"
+#include "tree/ParseTree.h"
+#include "tree/ErrorNode.h"
+
+#include "IterativeParseTreeWalker.h"
+
+using namespace antlr4::tree;
+
+void IterativeParseTreeWalker::walk(ParseTreeListener *listener, ParseTree *t) const {
+
+  std::vector<ParseTree *> nodeStack;
+  std::vector<size_t> indexStack;
+
+  ParseTree *currentNode = t;
+  size_t currentIndex = 0;
+
+  while (currentNode != nullptr) {
+    // pre-order visit
+    if (antlrcpp::is<ErrorNode *>(currentNode)) {
+      listener->visitErrorNode(dynamic_cast<ErrorNode *>(currentNode));
+    } else if (antlrcpp::is<TerminalNode *>(currentNode)) {
+      listener->visitTerminal((TerminalNode *)currentNode);
+    } else {
+      enterRule(listener, currentNode);
+    }
+
+    // Move down to first child, if it exists.
+    if (!currentNode->children.empty()) {
+      nodeStack.push_back(currentNode);
+      indexStack.push_back(currentIndex);
+      currentIndex = 0;
+      currentNode = currentNode->children[0];
+      continue;
+    }
+
+    // No child nodes, so walk tree.
+    do {
+      // post-order visit
+      if (!antlrcpp::is<TerminalNode *>(currentNode)) {
+        exitRule(listener, currentNode);
+      }
+
+      // No parent, so no siblings.
+      if (nodeStack.empty()) {
+        currentNode = nullptr;
+        currentIndex = 0;
+        break;
+      }
+
+      // Move to next sibling if possible.
+      if (nodeStack.back()->children.size() > ++currentIndex) {
+        currentNode = nodeStack.back()->children[currentIndex];
+        break;
+      }
+
+      // No next sibling, so move up.
+      currentNode = nodeStack.back();
+      nodeStack.pop_back();
+      currentIndex = indexStack.back();
+      indexStack.pop_back();
+
+    } while (currentNode != nullptr);
+  }
+}