add policy checker

Change-Id: I90c50d15b1d9d97832c66ce90e39524729f12a0f
diff --git a/core/conf/checker.hpp b/core/conf/checker.hpp
new file mode 100644
index 0000000..bc253f3
--- /dev/null
+++ b/core/conf/checker.hpp
@@ -0,0 +1,98 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2014,  Regents of the University of California
+ *
+ * This file is part of NSL (NDN Signature Logger).
+ * See AUTHORS.md for complete list of NSL authors and contributors.
+ *
+ * NSL is free software: you can redistribute it and/or modify it under the terms
+ * of the GNU General Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later version.
+ *
+ * NSL is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+ * PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * NSL, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * See AUTHORS.md for complete list of nsl authors and contributors.
+ */
+
+#ifndef NSL_CONF_CHECKER_HPP
+#define NSL_CONF_CHECKER_HPP
+
+#include "common.hpp"
+#include "config.hpp"
+#include "key-locator-checker.hpp"
+
+#include <boost/algorithm/string.hpp>
+#include <boost/filesystem.hpp>
+#include <boost/lexical_cast.hpp>
+
+namespace nsl {
+namespace conf {
+
+class Checker
+{
+public:
+  virtual
+  ~Checker();
+
+  /**
+   * @brief check if data satisfies condition defined in the specific checker implementation
+   *
+   * @param data Data packet
+   * @return false if data cannot pass checking
+   */
+  virtual bool
+  check(const Data& data) = 0;
+};
+
+class CustomizedChecker : public Checker
+{
+public:
+  CustomizedChecker(uint32_t sigType, shared_ptr<KeyLocatorChecker> keyLocatorChecker);
+
+  virtual bool
+  check(const Data& data);
+
+private:
+  uint32_t m_sigType;
+  shared_ptr<KeyLocatorChecker> m_keyLocatorChecker;
+};
+
+class HierarchicalChecker : public CustomizedChecker
+{
+public:
+  explicit
+  HierarchicalChecker(uint32_t sigType);
+};
+
+class CheckerFactory
+{
+public:
+  /**
+   * @brief create a checker from configuration file.
+   *
+   * @param configSection The section containing the definition of checker.
+   * @return a shared pointer to the created checker.
+   */
+  static shared_ptr<Checker>
+  create(const ConfigSection& configSection);
+
+private:
+  static shared_ptr<Checker>
+  createCustomizedChecker(const ConfigSection& configSection);
+
+  static shared_ptr<Checker>
+  createHierarchicalChecker(const ConfigSection& configSection);
+
+  static uint32_t
+  getSigType(const std::string& sigType);
+};
+
+} // namespace conf
+} // namespace nsl
+
+#endif // NSL_CONF_CHECKER_HPP