[view-compiler] Add layout validation

Layout validation walks over a layout resource and verifies that the layout only
uses features the layout compiler supports.

Currently this means we reject layouts that use any of the following tags:
  * include
  * fragment
  * merge
  * view

In the future, we will extend the layout compiler to handle these, but for now
we want to be liberal in what we reject.

Bug: 111895153
Test: atest view-compiler-tests
Change-Id: I8dca30c035a83b6763497a36fc60c68438fa1b0c

1 files changed, 65 insertions, 0 deletions

diff --git a/startop/view_compiler/tinyxml_layout_parser.h b/startop/view_compiler/tinyxml_layout_parser.h
new file mode 100644
index 000000000000..8f714a2c5a3f
--- /dev/null
+++ b/startop/view_compiler/tinyxml_layout_parser.h
@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#ifndef TINYXML_LAYOUT_PARSER_H_
+#define TINYXML_LAYOUT_PARSER_H_
+
+#include "tinyxml2.h"
+
+#include <codecvt>
+#include <locale>
+#include <string>
+
+namespace startop {
+
+template <typename Visitor>
+class TinyXmlVisitorAdapter : public tinyxml2::XMLVisitor {
+ public:
+  explicit TinyXmlVisitorAdapter(Visitor* visitor) : visitor_{visitor} {}
+
+  bool VisitEnter(const tinyxml2::XMLDocument& /*doc*/) override {
+    visitor_->VisitStartDocument();
+    return true;
+  }
+
+  bool VisitExit(const tinyxml2::XMLDocument& /*doc*/) override {
+    visitor_->VisitEndDocument();
+    return true;
+  }
+
+  bool VisitEnter(const tinyxml2::XMLElement& element,
+                  const tinyxml2::XMLAttribute* /*firstAttribute*/) override {
+    visitor_->VisitStartTag(
+        std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>{}.from_bytes(
+            element.Name()));
+    return true;
+  }
+
+  bool VisitExit(const tinyxml2::XMLElement& /*element*/) override {
+    visitor_->VisitEndTag();
+    return true;
+  }
+
+ private:
+  Visitor* visitor_;
+};
+
+// Returns whether a layout resource represented by a TinyXML document is supported by the layout
+// compiler.
+bool CanCompileLayout(const tinyxml2::XMLDocument& xml, std::string* message = nullptr);
+
+}  // namespace startop
+
+#endif  // TINYXML_LAYOUT_PARSER_H_