commit d3ffa844f5a07756009f019e13806e253d1bb119
author Adam Lesinski <adamlesinski@google.com> Thu Sep 28 13:34:35 2017 -0700
committer Adam Lesinski <adamlesinski@google.com> Thu Sep 28 14:08:50 2017 -0700
tree 75ebb146979439d850dd97b9645bae231923c5ca
parent 43ddc05bbdbf8da73da2415b3ab4d68a0180f9b2

AAPT2: Cleanup Visitors for XML and Values

Test: make aapt2_tests
Change-Id: Ib61f64c155a380115610edeaf2d65e60258a2426

tools/aapt2/xml/XmlDom.h

diff --git a/tools/aapt2/xml/XmlDom.h b/tools/aapt2/xml/XmlDom.h
index 9a9151d..063d7b9 100644
--- a/tools/aapt2/xml/XmlDom.h
+++ b/tools/aapt2/xml/XmlDom.h
@@ -35,6 +35,7 @@
 
 class Element;
 class Visitor;
+class ConstVisitor;
 
 // Base class for all XML nodes.
 class Node {
@@ -47,6 +48,7 @@
   std::string comment;
 
   virtual void Accept(Visitor* visitor) = 0;
+  virtual void Accept(ConstVisitor* visitor) const = 0;
 
   using ElementCloneFunc = std::function<void(const Element&, Element*)>;
 
@@ -112,6 +114,7 @@
   std::unique_ptr<Node> Clone(const ElementCloneFunc& el_cloner) const override;
 
   void Accept(Visitor* visitor) override;
+  void Accept(ConstVisitor* visitor) const override;
 };
 
 // A Text (CDATA) XML node. Can not have any children.
@@ -122,6 +125,7 @@
   std::unique_ptr<Node> Clone(const ElementCloneFunc& el_cloner) const override;
 
   void Accept(Visitor* visitor) override;
+  void Accept(ConstVisitor* visitor) const override;
 };
 
 // An XML resource with a source, name, and XML tree.
@@ -180,6 +184,38 @@
   friend class Element;
 };
 
+class ConstVisitor {
+ public:
+  virtual ~ConstVisitor() = default;
+
+  virtual void Visit(const Element* el) {
+    VisitChildren(el);
+  }
+
+  virtual void Visit(const Text* text) {
+  }
+
+ protected:
+  ConstVisitor() = default;
+
+  void VisitChildren(const Element* el) {
+    for (const auto& child : el->children) {
+      child->Accept(this);
+    }
+  }
+
+  virtual void BeforeVisitElement(const Element* el) {
+  }
+
+  virtual void AfterVisitElement(const Element* el) {
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ConstVisitor);
+
+  friend class Element;
+};
+
 // An XML DOM visitor that will record the package name for a namespace prefix.
 class PackageAwareVisitor : public Visitor, public IPackageDeclStack {
  public:
@@ -207,19 +243,19 @@
 namespace internal {
 
 // Base class that overrides the default behaviour and does not descend into child nodes.
-class NodeCastBase : public Visitor {
+class NodeCastBase : public ConstVisitor {
  public:
-  void Visit(Element* el) override {
+  void Visit(const Element* el) override {
   }
-  void Visit(Text* el) override {
+  void Visit(const Text* el) override {
   }
 
  protected:
   NodeCastBase() = default;
 
-  void BeforeVisitElement(Element* el) override {
+  void BeforeVisitElement(const Element* el) override {
   }
-  void AfterVisitElement(Element* el) override {
+  void AfterVisitElement(const Element* el) override {
   }
 
  private:
@@ -233,9 +269,9 @@
 
   NodeCastImpl() = default;
 
-  T* value = nullptr;
+  const T* value = nullptr;
 
-  void Visit(T* v) override {
+  void Visit(const T* v) override {
     value = v;
   }
 
@@ -246,12 +282,17 @@
 }  // namespace internal
 
 template <typename T>
-T* NodeCast(Node* node) {
+const T* NodeCast(const Node* node) {
   internal::NodeCastImpl<T> visitor;
   node->Accept(&visitor);
   return visitor.value;
 }
 
+template <typename T>
+T* NodeCast(Node* node) {
+  return const_cast<T*>(NodeCast<T>(static_cast<const T*>(node)));
+}
+
 }  // namespace xml
 }  // namespace aapt