diff --git a/src/storage/index.hpp b/src/storage/index.hpp
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+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2014,  Regents of the University of California.
+ *
+ * This file is part of NDN repo-ng (Next generation of NDN repository).
+ * See AUTHORS.md for complete list of repo-ng authors and contributors.
+ *
+ * repo-ng 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.
+ *
+ * repo-ng 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
+ * repo-ng, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef REPO_STORAGE_INDEX_HPP
+#define REPO_STORAGE_INDEX_HPP
+
+#include "common.hpp"
+#include "skiplist.hpp"
+#include <queue>
+
+namespace repo {
+
+class Index : noncopyable
+{
+public:
+  class Error : public std::runtime_error
+  {
+  public:
+    explicit
+    Error(const std::string& what)
+      : std::runtime_error(what)
+    {
+    }
+  };
+
+  class Entry
+  {
+  public:
+    class Error : public std::runtime_error
+    {
+    public:
+      explicit
+      Error(const std::string& what)
+        : std::runtime_error(what)
+      {
+      }
+    };
+
+  public:
+
+    /**
+     * @brief used by skiplist to construct node
+     */
+    Entry()
+    {
+    };
+
+    /**
+     * @brief construct Entry by data and id number
+     */
+    Entry(const Data& data, const int64_t id);
+
+    /**
+     * @brief construct Entry by fullName, keyLocator and id number
+     */
+    Entry(const Name& fullName, const KeyLocator& keyLocator, const int64_t id);
+
+    /**
+     * @brief construct Entry by fullName, keyLocatorHash and id number
+     * @param  fullName        full name with digest computed from data
+     * @param  keyLocatorHash  keyLocator hashed by sha256
+     * @param  id              record ID from database
+     */
+    Entry(const Name& fullName, const ndn::ConstBufferPtr& keyLocatorHash, const int64_t id);
+
+    /**
+     *  @brief implicit construct Entry by full name
+     *
+     *  Allow implicit conversion from Name for SkipList lookups by Name
+     */
+    Entry(const Name& name);
+
+    /**
+     *  @brief get the name of entry
+     */
+    const Name&
+    getName() const
+    {
+      return m_name;
+    }
+
+    /**
+     *  @brief get the keyLocator hash value of the entry
+     */
+    const ndn::ConstBufferPtr&
+    getKeyLocatorHash() const
+    {
+      return m_keyLocatorHash;
+    }
+
+    /**
+     *  @brief get record ID from database
+     */
+    const int64_t
+    getId() const
+    {
+      return m_id;
+    }
+
+    bool
+    operator>(const Entry& entry) const
+    {
+      return m_name > entry.getName();
+    }
+
+    bool
+    operator<(const Entry& entry) const
+    {
+      return m_name < entry.getName();
+    }
+
+    bool
+    operator==(const Entry& entry) const
+    {
+      return m_name == entry.getName();
+    }
+
+    bool
+    operator!=(const Entry& entry) const
+    {
+      return m_name != entry.getName();
+    }
+
+  private:
+    Name m_name;
+    ndn::ConstBufferPtr m_keyLocatorHash;
+    int64_t m_id;
+  };
+
+private:
+
+  typedef SkipList<Entry> IndexSkipList;
+
+public:
+  explicit
+  Index(const size_t nMaxPackets);
+
+  /**
+   *  @brief insert entries into index
+   *  @param  data    used to construct entries
+   *  @param  id      obtained from database
+   */
+  bool
+  insert(const Data& data, const int64_t id);
+
+  /**
+   *  @brief insert entries into index
+   *  @param  data    used to construct entries
+   *  @param  id      obtained from database
+   */
+  bool
+  insert(const Name& fullName, const int64_t id,
+         const ndn::ConstBufferPtr& keyLocatorHash);
+
+  /**
+   *  @brief erase the entry in index by its fullname
+   */
+  bool
+  erase(const Name& fullName);
+
+  /** @brief find the Entry for best match of an Interest
+   * @return ID and fullName of the Entry, or (0,ignored) if not found
+   */
+  std::pair<int64_t, Name>
+  find(const Interest& interest) const;
+
+  /** @brief find the first Entry under a Name prefix
+   * @return ID and fullName of the Entry, or (0,ignored) if not found
+   */
+  std::pair<int64_t, Name>
+  find(const Name& name) const;
+
+  /**
+   *  @brief determine whether same Data is already in the index
+   *  @return true if identical Data exists, false otherwise
+   */
+  bool
+  hasData(const Data& data) const;
+
+  /**
+    *  @brief compute the hash value of keyLocator
+    */
+  static const ndn::ConstBufferPtr
+  computeKeyLocatorHash(const KeyLocator& keyLocator);
+
+  const size_t
+  size() const
+  {
+    return m_size;
+  }
+
+private:
+  /**
+   *  @brief select entries which satisfy the selectors in interest and return their name
+   *  @param  interest   used to select entries by comparing the name and checking selectors
+   *  @param  idName    save the id and name of found entries
+   *  @param  startingPoint the entry whose name is equal or larger than the interest name
+   */
+  std::pair<int64_t, Name>
+  selectChild(const Interest& interest,
+              IndexSkipList::const_iterator startingPoint) const;
+
+  /**
+   *  @brief check whether the index is full
+   */
+  bool
+  isFull() const
+  {
+    return m_size >= m_maxPackets;
+  }
+
+  /**
+   *  @brief find the first entry with the prefix
+   *  @param  prefix        used to request the entries
+   *  @param  startingPoint the entry whose name is equal or larger than the interest name
+   *  @return int64_t  the id number of found entry
+   *  @return Name     the name of found entry
+   */
+  std::pair<int64_t, Name>
+  findFirstEntry(const Name& prefix,
+                 IndexSkipList::const_iterator startingPoint) const;
+
+private:
+  IndexSkipList m_skipList;
+  size_t m_maxPackets;
+  size_t m_size;
+};
+
+} // namespace repo
+
+#endif // REPO_STORAGE_INDEX_HPP