diff --git a/tools/versioner/src/DeclarationDatabase.h b/tools/versioner/src/DeclarationDatabase.h
new file mode 100644
index 0000000..057e416
--- /dev/null
+++ b/tools/versioner/src/DeclarationDatabase.h
@@ -0,0 +1,211 @@
+/*
+ * Copyright 2016 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.
+ */
+
+#pragma once
+
+#include <iostream>
+#include <map>
+#include <set>
+#include <string>
+#include <vector>
+
+#include <llvm/ADT/StringRef.h>
+
+#include "Utils.h"
+
+enum class DeclarationType {
+  function,
+  variable,
+  inconsistent,
+};
+
+static const char* declarationTypeName(DeclarationType type) {
+  switch (type) {
+    case DeclarationType::function:
+      return "function";
+    case DeclarationType::variable:
+      return "variable";
+    case DeclarationType::inconsistent:
+      return "inconsistent";
+  }
+}
+
+struct CompilationType {
+  std::string arch;
+  int api_level;
+
+ private:
+  auto tie() const {
+    return std::tie(arch, api_level);
+  }
+
+ public:
+  bool operator<(const CompilationType& other) const {
+    return tie() < other.tie();
+  }
+
+  bool operator==(const CompilationType& other) const {
+    return tie() == other.tie();
+  }
+
+  std::string describe() const {
+    return arch + "-" + std::to_string(api_level);
+  }
+};
+
+struct DeclarationAvailability {
+  int introduced = 0;
+  int deprecated = 0;
+  int obsoleted = 0;
+
+  void dump(std::ostream& out = std::cout) const {
+    bool need_comma = false;
+    auto comma = [&out, &need_comma]() {
+      if (!need_comma) {
+        need_comma = true;
+        return;
+      }
+      out << ", ";
+    };
+
+    if (introduced != 0) {
+      comma();
+      out << "introduced = " << introduced;
+    }
+    if (deprecated != 0) {
+      comma();
+      out << "deprecated = " << deprecated;
+    }
+    if (obsoleted != 0) {
+      comma();
+      out << "obsoleted = " << obsoleted;
+    }
+  }
+
+  bool empty() const {
+    return !(introduced || deprecated || obsoleted);
+  }
+
+  auto tie() const {
+    return std::tie(introduced, deprecated, obsoleted);
+  }
+
+  bool operator==(const DeclarationAvailability& rhs) const {
+    return this->tie() == rhs.tie();
+  }
+
+  bool operator!=(const DeclarationAvailability& rhs) const {
+    return !(*this == rhs);
+  }
+
+  std::string describe() const {
+    return std::string("[") + std::to_string(introduced) + "," + std::to_string(deprecated) + "," +
+           std::to_string(obsoleted) + "]";
+  }
+};
+
+struct DeclarationLocation {
+  std::string filename;
+  unsigned line_number;
+  unsigned column;
+  DeclarationType type;
+  bool is_extern;
+  bool is_definition;
+  DeclarationAvailability availability;
+
+  auto tie() const {
+    return std::tie(filename, line_number, column, type, is_extern, is_definition);
+  }
+
+  bool operator<(const DeclarationLocation& other) const {
+    return tie() < other.tie();
+  }
+
+  bool operator==(const DeclarationLocation& other) const {
+    return tie() == other.tie();
+  }
+};
+
+struct Declaration {
+  std::string name;
+  std::set<DeclarationLocation> locations;
+
+  bool hasDefinition() const {
+    for (const auto& location : locations) {
+      if (location.is_definition) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  DeclarationType type() const {
+    DeclarationType result = locations.begin()->type;
+    for (const DeclarationLocation& location : locations) {
+      if (location.type != result) {
+        result = DeclarationType::inconsistent;
+      }
+    }
+    return result;
+  }
+
+  void dump(const std::string& base_path = "", std::ostream& out = std::cout) const {
+    out << "    " << name << " declared in " << locations.size() << " locations:\n";
+    for (const DeclarationLocation& location : locations) {
+      const char* var_type = declarationTypeName(location.type);
+      const char* declaration_type = location.is_definition ? "definition" : "declaration";
+      const char* linkage = location.is_extern ? "extern" : "static";
+
+      std::string filename;
+      if (llvm::StringRef(location.filename).startswith(base_path)) {
+        filename = location.filename.substr(base_path.size());
+      } else {
+        filename = location.filename;
+      }
+
+      out << "        " << linkage << " " << var_type << " " << declaration_type << " @ "
+          << filename << ":" << location.line_number << ":" << location.column;
+
+      if (!location.availability.empty()) {
+        out << "\t[";
+        location.availability.dump(out);
+        out << "]";
+      } else {
+        out << "\t[no availability]";
+      }
+
+      out << "\n";
+    }
+  }
+};
+
+namespace clang {
+class ASTUnit;
+}
+
+class HeaderDatabase {
+ public:
+  std::map<std::string, Declaration> declarations;
+
+  void parseAST(clang::ASTUnit* ast);
+
+  void dump(const std::string& base_path = "", std::ostream& out = std::cout) const {
+    out << "HeaderDatabase contains " << declarations.size() << " declarations:\n";
+    for (const auto& pair : declarations) {
+      pair.second.dump(base_path, out);
+    }
+  }
+};